chore: Remove unused warning in api integration test

Resolve a warning of unused `output` variable.

Fixes: 0745019 docs(cli): Create commented config file

Signed-off-by: Paul Spooren <mail@aparcar.org>

Cargo.lock

@@ -403,9 +403,9 @@ dependencies = [
 
 [[package]]
 name = "clap_complete"
-version = "4.5.38"
+version = "4.5.40"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d9647a559c112175f17cf724dc72d3645680a883c58481332779192b0d8e7a01"
+checksum = "ac2e663e3e3bed2d32d065a8404024dad306e699a04263ec59919529f803aee9"
 dependencies = [
  "clap 4.5.23",
 ]
@@ -815,12 +815,12 @@ checksum = "5443807d6dff69373d433ab9ef5378ad8df50ca6298caf15de6e52e24aaf54d5"
 
 [[package]]
 name = "errno"
-version = "0.3.9"
+version = "0.3.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "534c5cf6194dfab3db3242765c03bbe257cf92f22b38f6bc0c58d59108a820ba"
+checksum = "33d852cb9b869c2a9b3df2f71a3074817f01e1844f839a144f5fcef059a4eb5d"
 dependencies = [
  "libc",
- "windows-sys 0.52.0",
+ "windows-sys 0.59.0",
 ]
 
 [[package]]
@@ -1204,9 +1204,9 @@ checksum = "830d08ce1d1d941e6b30645f1a0eb5643013d835ce3779a5fc208261dbe10f55"
 
 [[package]]
 name = "libc"
-version = "0.2.167"
+version = "0.2.168"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "09d6582e104315a817dff97f75133544b2e094ee22447d2acf4a74e189ba06fc"
+checksum = "5aaeb2981e0606ca11d79718f8bb01164f1d6ed75080182d3abf017e6d244b6d"
 
 [[package]]
 name = "libcrux"
@@ -1865,6 +1865,11 @@ dependencies = [
 [[package]]
 name = "rosenpass-cipher-traits"
 version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "rosenpass-oqs",
+ "rosenpass-secret-memory",
+]
 
 [[package]]
 name = "rosenpass-ciphers"
@@ -2054,15 +2059,15 @@ dependencies = [
 
 [[package]]
 name = "rustix"
-version = "0.38.41"
+version = "0.38.42"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d7f649912bc1495e167a6edee79151c84b1bad49748cb4f1f1167f459f6224f6"
+checksum = "f93dc38ecbab2eb790ff964bb77fa94faf256fd3e73285fd7ba0903b76bedb85"
 dependencies = [
  "bitflags 2.6.0",
  "errno",
  "libc",
  "linux-raw-sys",
- "windows-sys 0.52.0",
+ "windows-sys 0.59.0",
 ]
 
 [[package]]
@@ -2109,18 +2114,18 @@ checksum = "61697e0a1c7e512e84a621326239844a24d8207b4669b41bc18b32ea5cbf988b"
 
 [[package]]
 name = "serde"
-version = "1.0.215"
+version = "1.0.216"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6513c1ad0b11a9376da888e3e0baa0077f1aed55c17f50e7b2397136129fb88f"
+checksum = "0b9781016e935a97e8beecf0c933758c97a5520d32930e460142b4cd80c6338e"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.215"
+version = "1.0.216"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ad1e866f866923f252f05c889987993144fb74e722403468a4ebd70c3cd756c0"
+checksum = "46f859dbbf73865c6627ed570e78961cd3ac92407a2d117204c49232485da55e"
 dependencies = [
  "proc-macro2",
  "quote",

Cargo.toml

@@ -49,8 +49,8 @@ typenum = "1.17.0"
 log = { version = "0.4.22" }
 clap = { version = "4.5.23", features = ["derive"] }
 clap_mangen = "0.2.24"
-clap_complete = "4.5.38"
-serde = { version = "1.0.215", features = ["derive"] }
+clap_complete = "4.5.40"
+serde = { version = "1.0.216", features = ["derive"] }
 arbitrary = { version = "1.4.1", features = ["derive"] }
 anyhow = { version = "1.0.94", features = ["backtrace", "std"] }
 mio = { version = "1.0.3", features = ["net", "os-poll"] }
@@ -90,4 +90,4 @@ procspawn = { version = "1.0.1", features = ["test-support"] }
 #Broker dependencies (might need cleanup or changes)
 wireguard-uapi = { version = "3.0.0", features = ["xplatform"] }
 command-fds = "0.2.3"
-rustix = { version = "0.38.41", features = ["net", "fs", "process"] }
+rustix = { version = "0.38.42", features = ["net", "fs", "process"] }

cipher-traits/Cargo.toml

@@ -10,3 +10,8 @@ repository = "https://github.com/rosenpass/rosenpass"
 readme = "readme.md"
 
 [dependencies]
+
+[dev-dependencies]
+rosenpass-oqs = { workspace = true }
+rosenpass-secret-memory = { workspace = true }
+anyhow = {workspace = true}

cipher-traits/readme.md

@@ -2,4 +2,4 @@
 
 Rosenpass internal library providing traits for cryptographic primitives.
 
-This is an internal library; not guarantee is made about its API at this point in time.
+This is an internal library; no guarantee is made about its API at this point in time.

cipher-traits/src/kem.rs

@@ -5,10 +5,128 @@
 //!
 //! Conceptually KEMs are akin to public-key encryption, but instead of encrypting
 //! arbitrary data, KEMs are limited to the transmission of keys, randomly chosen during
-//!
 //! encapsulation.
-//! The [KEM] Trait describes the basic API offered by a Key Encapsulation
-//! Mechanism. Two implementations for it are provided, [StaticKEM] and [EphemeralKEM].
+//!
+//! The [Kem] Trait describes the basic API offered by a Key Encapsulation
+//! Mechanism. Two implementations for it are provided:
+//! [Kyber512](../../rosenpass_oqs/kyber_512/enum.Kyber512.html) and
+//! [ClassicMceliece460896](../../rosenpass_oqs/classic_mceliece_460896/enum.ClassicMceliece460896.html).
+//!
+//! An example where Alice generates a keypair and gives her public key to Bob, for Bob to
+//! encapsulate a symmetric key and Alice to decapsulate it would look as follows.
+//! In the example, we are using Kyber512, but any KEM that correctly implements the [Kem]
+//! trait could be used as well.
+//!```rust
+//! use rosenpass_cipher_traits::Kem;
+//! use rosenpass_oqs::Kyber512;
+//! # use rosenpass_secret_memory::{secret_policy_use_only_malloc_secrets, Secret};
+//!
+//! type MyKem = Kyber512;
+//! secret_policy_use_only_malloc_secrets();
+//! let mut alice_sk: Secret<{ MyKem::SK_LEN }> = Secret::zero();
+//! let mut alice_pk: [u8; MyKem::PK_LEN] = [0; MyKem::PK_LEN];
+//! MyKem::keygen(alice_sk.secret_mut(), &mut alice_pk)?;
+//!
+//! let mut bob_shk: Secret<{ MyKem::SHK_LEN }> = Secret::zero();
+//! let mut bob_ct: [u8; MyKem::CT_LEN] = [0; MyKem::CT_LEN];
+//! MyKem::encaps(bob_shk.secret_mut(), &mut bob_ct, &mut alice_pk)?;
+//!
+//! let mut alice_shk: Secret<{ MyKem::SHK_LEN }> = Secret::zero();
+//! MyKem::decaps(alice_shk.secret_mut(), alice_sk.secret_mut(), &mut bob_ct)?;
+//!
+//! # assert_eq!(alice_shk.secret(), bob_shk.secret());
+//! # Ok::<(), anyhow::Error>(())
+//!```
+//!
+//! Implementing the [Kem]-trait for a KEM is easy. Mostly, you must format the KEM's
+//! keys, and ciphertext as `u8` slices. Below, we provide an example for how the trait can
+//! be implemented using a **HORRIBLY INSECURE** DummyKem that only uses static values for keys
+//! and ciphertexts as an example.  
+//!```rust
+//!# use rosenpass_cipher_traits::Kem;
+//!
+//! struct DummyKem {}
+//! impl Kem for DummyKem {
+//!
+//!     // For this DummyKem, using String for errors is sufficient.
+//!     type Error = String;
+//!
+//!     // For this DummyKem, we will use a single `u8` for everything
+//!     const SK_LEN: usize = 1;
+//!     const PK_LEN: usize = 1;
+//!     const CT_LEN: usize = 1;
+//!     const SHK_LEN: usize = 1;
+//!
+//!     fn keygen(sk: &mut [u8], pk: &mut [u8]) -> Result<(), Self::Error> {
+//!         if sk.len() != Self::SK_LEN {
+//!             return Err("sk does not have the correct length!".to_string());
+//!         }
+//!         if pk.len() != Self::PK_LEN {
+//!             return Err("pk does not have the correct length!".to_string());
+//!         }
+//!         sk[0] = 42;
+//!         pk[0] = 21;
+//!         Ok(())
+//!     }
+//!
+//!     fn encaps(shk: &mut [u8], ct: &mut [u8], pk: &[u8]) -> Result<(), Self::Error> {
+//!         if pk.len() != Self::PK_LEN {
+//!             return Err("pk does not have the correct length!".to_string());
+//!         }
+//!         if ct.len() != Self::CT_LEN {
+//!             return Err("ct does not have the correct length!".to_string());
+//!         }
+//!         if shk.len() != Self::SHK_LEN {
+//!             return Err("shk does not have the correct length!".to_string());
+//!         }
+//!         if pk[0] != 21 {
+//!             return Err("Invalid public key!".to_string());
+//!         }
+//!         ct[0] = 7;
+//!         shk[0] = 17;
+//!         Ok(())
+//!     }
+//!
+//!     fn decaps(shk: &mut [u8], sk: &[u8], ct: &[u8]) -> Result<(), Self::Error> {
+//!         if sk.len() != Self::SK_LEN {
+//!             return Err("sk does not have the correct length!".to_string());
+//!         }
+//!         if ct.len() != Self::CT_LEN {
+//!             return Err("ct does not have the correct length!".to_string());
+//!         }
+//!         if shk.len() != Self::SHK_LEN {
+//!             return Err("shk does not have the correct length!".to_string());
+//!         }
+//!         if sk[0] != 42 {
+//!             return Err("Invalid public key!".to_string());
+//!         }
+//!         if ct[0] != 7 {
+//!             return Err("Invalid ciphertext!".to_string());
+//!         }
+//!         shk[0] = 17;
+//!         Ok(())
+//!     }
+//! }
+//! # use rosenpass_secret_memory::{secret_policy_use_only_malloc_secrets, Secret};
+//! #
+//! # type MyKem = DummyKem;
+//! # secret_policy_use_only_malloc_secrets();
+//! # let mut alice_sk: Secret<{ MyKem::SK_LEN }> = Secret::zero();
+//! # let mut alice_pk: [u8; MyKem::PK_LEN] = [0; MyKem::PK_LEN];
+//! # MyKem::keygen(alice_sk.secret_mut(), &mut alice_pk)?;
+//!
+//! # let mut bob_shk: Secret<{ MyKem::SHK_LEN }> = Secret::zero();
+//! # let mut bob_ct: [u8; MyKem::CT_LEN] = [0; MyKem::CT_LEN];
+//! # MyKem::encaps(bob_shk.secret_mut(), &mut bob_ct, &mut alice_pk)?;
+//! #
+//! # let mut alice_shk: Secret<{ MyKem::SHK_LEN }> = Secret::zero();
+//! # MyKem::decaps(alice_shk.secret_mut(), alice_sk.secret_mut(), &mut bob_ct)?;
+//! #
+//! # assert_eq!(alice_shk.secret(), bob_shk.secret());
+//! #
+//! # Ok::<(), String>(())
+//!```
+//!
 
 /// Key Encapsulation Mechanism
 ///

ciphers/src/hash_domain.rs

@@ -13,7 +13,6 @@ pub use hash::KEY_LEN;
 /// # rosenpass_secret_memory::secret_policy_use_only_malloc_secrets();
 ///
 /// const PROTOCOL_IDENTIFIER: &str = "MY_PROTOCOL:IDENTIFIER";
-/// # fn do_doc_test() -> Result<(), Box<dyn std::error::Error>> {
 /// // create use once hash domain for the protocol identifier
 /// let mut hash_domain = HashDomain::zero();
 /// hash_domain = hash_domain.mix(PROTOCOL_IDENTIFIER.as_bytes())?;
@@ -31,10 +30,7 @@ pub use hash::KEY_LEN;
 /// let new_key_identifier = "my_new_key_identifier".as_bytes();
 /// let new_key = secret_hash_domain.mix(new_key_identifier)?.into_secret();
 ///
-/// # Ok(())
-/// # }
-/// # do_doc_test().unwrap();
-///
+/// # Ok::<(), anyhow::Error>(())
 ///```
 ///
 

ciphers/src/lib.rs

@@ -41,10 +41,11 @@ pub mod xaead {
 pub mod hash_domain;
 
 /// This crate includes two key encapsulation mechanisms.
-/// Namely ClassicMceliece460896 (as [StaticKem]) and Kyber512 (as [EphemeralKem]).
+/// Namely ClassicMceliece460896 (also referred to as `StaticKem` sometimes) and
+/// Kyber512 (also referred to as  `EphemeralKem` sometimes).
 ///
-/// See [rosenpass_oqs::ClassicMceliece460896](rosenpass_oqs::ClassicMceliece460896)
-/// and [rosenpass_oqs::Kyber512](rosenpass_oqs::Kyber512) for more details on the specific KEMS.
+/// See [rosenpass_oqs::ClassicMceliece460896]
+/// and [rosenpass_oqs::Kyber512] for more details on the specific KEMS.
 ///
 pub mod kem {
     pub use rosenpass_oqs::ClassicMceliece460896 as StaticKem;

ciphers/src/subtle/blake2b.rs

@@ -10,7 +10,7 @@ use rosenpass_to::{ops::copy_slice, with_destination, To};
 use rosenpass_util::typenum2const;
 
 /// Specify that the used implementation of BLAKE2b is the MAC version of BLAKE2b
-/// with output and key length of 32 bytes (see [Blake2bMac<U32>]).
+/// with output and key length of 32 bytes (see [Blake2bMac]).
 type Impl = Blake2bMac<U32>;
 
 type KeyLen = <Impl as KeySizeUser>::KeySize;
@@ -21,17 +21,17 @@ const KEY_LEN: usize = typenum2const! { KeyLen };
 /// The output length for BLAKE2b supported by this API. Currently 32 Bytes.
 const OUT_LEN: usize = typenum2const! { OutLen };
 
-/// Minimal key length supported by this API (identical to [KEY_LEN])
+/// Minimal key length supported by this API.
 pub const KEY_MIN: usize = KEY_LEN;
-/// maximal key length supported by this API (identical to [KEY_LEN])
+/// maximal key length supported by this API.
 pub const KEY_MAX: usize = KEY_LEN;
-/// minimal output length supported by this API (identical [OUT_LEN])
+/// minimal output length supported by this API.
 pub const OUT_MIN: usize = OUT_LEN;
-/// maximal output length supported by this API (identical [OUT_LEN])
+/// maximal output length supported by this API.
 pub const OUT_MAX: usize = OUT_LEN;
 
-/// Hashes the given `data` with the [Blake2bMac<U32>] hash function under the given `key`.
-/// The [KEY_LEN] and [OUT_LEN] are both set to 32 bytes (or 256 bits).  
+/// Hashes the given `data` with the [Blake2bMac] hash function under the given `key`.
+/// The both the length of the output the length of the key 32 bytes (or 256 bits).  
 ///
 /// # Examples
 ///

ciphers/src/subtle/mod.rs

@@ -1,7 +1,7 @@
 /// This module provides the following cryptographic schemes:
 /// - [blake2b]: The blake2b hash function
-/// - [chacha20poly1305_ietf]: The Chacha20Poly1305 AEAD as implemented in [RustCrypto](https://crates.io/crates/chacha20poly1305) (only used when the feature `experiment_libcrux` is disabled.
-/// - [chacha20poly1305_ietf_libcrux]: The Chacha20Poly1305 AEAD as implemented in [libcrux](https://github.com/cryspen/libcrux) (only used when the feature `experiment_libcrux` is enabled.
+/// - [chacha20poly1305_ietf]: The Chacha20Poly1305 AEAD as implemented in [RustCrypto](https://crates.io/crates/chacha20poly1305) (only used when the feature `experiment_libcrux` is disabled).
+/// - [chacha20poly1305_ietf_libcrux]: The Chacha20Poly1305 AEAD as implemented in [libcrux](https://github.com/cryspen/libcrux) (only used when the feature `experiment_libcrux` is enabled).
 /// - [incorrect_hmac_blake2b]: An (incorrect) hmac based on [blake2b].
 /// - [xchacha20poly1305_ietf] The Chacha20Poly1305 AEAD as implemented in [RustCrypto](https://crates.io/crates/chacha20poly1305)
 pub mod blake2b;

constant-time/Cargo.toml

@@ -20,3 +20,6 @@ memsec = { workspace = true }
 
 [dev-dependencies]
 rand = "0.8.5"
+
+[lints.rust]
+unexpected_cfgs = { level = "allow", check-cfg = ['cfg(coverage)'] }

constant-time/src/compare.rs

@@ -2,14 +2,29 @@
 
 use core::ptr;
 
-/// Little endian memcmp version of quinier/memsec
-/// https://github.com/quininer/memsec/blob/bbc647967ff6d20d6dccf1c85f5d9037fcadd3b0/src/lib.rs#L30
+/// Little endian memcmp version of [quinier/memsec](https://github.com/quininer/memsec/blob/bbc647967ff6d20d6dccf1c85f5d9037fcadd3b0/src/lib.rs#L30)
 ///
 /// # Panic & Safety
 ///
 /// Both input arrays must be at least of the indicated length.
 ///
 /// See [std::ptr::read_volatile] on safety.
+///
+/// # Examples
+/// ```
+/// let a = [1, 2, 3, 4];
+/// let b = [1, 2, 3, 4];
+/// let c = [1, 2, 2, 5];
+/// let d = [1, 2, 2, 4];
+///
+/// unsafe {
+///     use rosenpass_constant_time::memcmp_le;
+///     assert_eq!(memcmp_le(a.as_ptr(), b.as_ptr(), 4), 0);
+///     assert!(memcmp_le(a.as_ptr(), c.as_ptr(), 4) < 0);
+///     assert!(memcmp_le(a.as_ptr(), d.as_ptr(), 4) > 0);
+///     assert_eq!(memcmp_le(a.as_ptr(), b.as_ptr(), 2), 0);
+/// }
+/// ```
 #[inline(never)]
 pub unsafe fn memcmp_le(b1: *const u8, b2: *const u8, len: usize) -> i32 {
     let mut res = 0;
@@ -77,3 +92,23 @@ pub fn compare(a: &[u8], b: &[u8]) -> i32 {
     assert!(a.len() == b.len());
     unsafe { memcmp_le(a.as_ptr(), b.as_ptr(), a.len()) }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::compare::memcmp_le;
+
+    #[test]
+    fn memcmp_le_test() {
+        let a = [1, 2, 3, 4];
+        let b = [1, 2, 3, 4];
+        let c = [1, 2, 2, 5];
+        let d = [1, 2, 2, 4];
+
+        unsafe {
+            assert_eq!(memcmp_le(a.as_ptr(), b.as_ptr(), 4), 0);
+            assert!(memcmp_le(a.as_ptr(), c.as_ptr(), 4) < 0);
+            assert!(memcmp_le(a.as_ptr(), d.as_ptr(), 4) > 0);
+            assert_eq!(memcmp_le(a.as_ptr(), b.as_ptr(), 2), 0);
+        }
+    }
+}

constant-time/src/increment.rs

@@ -6,8 +6,16 @@ use core::hint::black_box;
 /// and increment that integer.
 ///
 /// # Leaks
-/// TODO: mention here if this function leaks any information, see
-/// <https://github.com/rosenpass/rosenpass/issues/232>
+/// This function may leak timing information in the following ways:
+///
+/// - The function execution time is linearly proportional to the input length
+/// - The number of carry operations that occur may affect timing slightly
+/// - Memory access patterns are sequential and predictable
+///
+/// The carry operation timing variation is mitigated through the use of black_box,
+/// but the linear scaling with input size is inherent to the operation.
+/// These timing characteristics are generally considered acceptable for most
+/// cryptographic counter implementations.
 ///
 /// ## Tests
 /// For discussion on how to ensure the constant-time execution of this function, see

constant-time/src/lib.rs

@@ -7,6 +7,32 @@
 //! ## TODO
 //! Figure out methodology to ensure that code is actually constant time, see
 //! <https://github.com/rosenpass/rosenpass/issues/232>
+//!
+//! # Examples
+//!
+//! ```rust
+//! use rosenpass_constant_time::{memcmp, compare};
+//!
+//! let a = [1, 2, 3, 4];
+//! let b = [1, 2, 3, 4];
+//! let c = [1, 2, 3, 5];
+//!
+//! // Compare for equality
+//! assert!(memcmp(&a, &b));
+//! assert!(!memcmp(&a, &c));
+//!
+//! // Compare lexicographically
+//! assert_eq!(compare(&a, &c), -1); // a < c
+//! assert_eq!(compare(&c, &a), 1);  // c > a
+//! assert_eq!(compare(&a, &b), 0);  // a == b
+//! ```
+//!
+//! # Security Notes
+//!
+//! While these functions aim to be constant-time, they may leak timing information in some cases:
+//!
+//! - Length mismatches between inputs are immediately detectable
+//! - Execution time scales linearly with input size
 
 mod compare;
 mod increment;
@@ -14,6 +40,7 @@ mod memcmp;
 mod xor;
 
 pub use compare::compare;
+pub use compare::memcmp_le;
 pub use increment::increment;
 pub use memcmp::memcmp;
 pub use xor::xor;

constant-time/src/memcmp.rs

@@ -113,9 +113,10 @@ mod tests {
         // Pearson correlation
         let correlation = cv / (sd_x * sd_y);
         println!("correlation: {:.6?}", correlation);
+        #[cfg(not(coverage))]
         assert!(
             correlation.abs() < 0.01,
             "execution time correlates with result"
-        )
+        );
     }
 }

constant-time/src/xor.rs

@@ -5,12 +5,23 @@ use rosenpass_to::{with_destination, To};
 
 /// Xors the source into the destination
 ///
+/// Performs a constant-time XOR operation between two byte slices
+///
+/// Takes a source slice and XORs it with the destination slice in-place using the
+/// rosenpass_to trait for destination management.
+///
 /// # Panics
 /// If source and destination are of different sizes.
 ///
 /// # Leaks
-/// TODO: mention here if this function leaks any information, see
-/// <https://github.com/rosenpass/rosenpass/issues/232>
+/// This function may leak timing information in the following ways:
+///
+/// - The function execution time is linearly proportional to the input length
+/// - Length mismatches between source and destination are immediately detectable via panic
+/// - Memory access patterns follow a predictable sequential pattern
+///
+/// These leaks are generally considered acceptable in most cryptographic contexts
+/// as they don't reveal information about the actual content being XORed.
 ///
 /// ## Tests
 /// For discussion on how to ensure the constant-time execution of this function, see

coverage_report.sh

@@ -21,8 +21,9 @@ main() {
     open="1"
   fi
 
-  exc cargo llvm-cov --all-features --workspace --doctests
+  exc cargo llvm-cov --all-features --workspace --doctests --branch
 
+  exc cp -rv target/llvm-cov-target/doctestbins target/llvm-cov-target/debug/deps/doctestbins
   exc rm -rf "${OUTPUT_DIR}"
   exc mkdir -p "${OUTPUT_DIR}"
   exc grcov target/llvm-cov-target/ --llvm  -s . --branch \

rosenpass/Cargo.toml

@@ -91,3 +91,6 @@ experiment_api = [
 internal_signal_handling_for_coverage_reports = ["signal-hook"]
 internal_testing = []
 internal_bin_gen_ipc_msg_types = ["hex", "heck"]
+
+[lints.rust]
+unexpected_cfgs = { level = "allow", check-cfg = ['cfg(coverage)'] }

rosenpass/src/app_server.rs

@@ -167,6 +167,8 @@ const EVENT_CAPACITY: usize = 20;
 // TODO add user control via unix domain socket and stdin/stdout
 #[derive(Debug)]
 pub struct AppServer {
+    #[cfg(feature = "internal_signal_handling_for_coverage_reports")]
+    pub term_signal: terminate::TerminateRequested,
     pub crypto_site: ConstructionSite<BuildCryptoServer, CryptoServer>,
     pub sockets: Vec<mio::net::UdpSocket>,
     pub events: mio::Events,
@@ -633,6 +635,8 @@ impl AppServer {
         };
 
         Ok(Self {
+            #[cfg(feature = "internal_signal_handling_for_coverage_reports")]
+            term_signal: terminate::TerminateRequested::new()?,
             crypto_site,
             peers: Vec::new(),
             verbosity,
@@ -754,18 +758,35 @@ impl AppServer {
         Ok(AppPeerPtr(pn))
     }
 
-    pub fn listen_loop(&mut self) -> anyhow::Result<()> {
+    pub fn event_loop(&mut self) -> anyhow::Result<()> {
         const INIT_SLEEP: f64 = 0.01;
         const MAX_FAILURES: i32 = 10;
         let mut failure_cnt = 0;
 
         loop {
             let msgs_processed = 0usize;
-            let err = match self.event_loop() {
+            let err = match self.event_loop_without_error_handling() {
                 Ok(()) => return Ok(()),
                 Err(e) => e,
             };
 
+            #[cfg(feature = "internal_signal_handling_for_coverage_reports")]
+            {
+                let terminated_by_signal = err
+                    .downcast_ref::<std::io::Error>()
+                    .filter(|e| e.kind() == std::io::ErrorKind::Interrupted)
+                    .filter(|_| self.term_signal.value())
+                    .is_some();
+                if terminated_by_signal {
+                    log::warn!(
+                        "\
+                        Terminated by signal; this signal handler is correct during coverage testing \
+                        but should be otherwise disabled"
+                    );
+                    return Ok(());
+                }
+            }
+
             // This should not happen…
             failure_cnt = if msgs_processed > 0 {
                 0
@@ -790,7 +811,7 @@ impl AppServer {
         }
     }
 
-    pub fn event_loop(&mut self) -> anyhow::Result<()> {
+    pub fn event_loop_without_error_handling(&mut self) -> anyhow::Result<()> {
         let (mut rx, mut tx) = (MsgBuf::zero(), MsgBuf::zero());
 
         /// if socket address for peer is known, call closure
@@ -1288,3 +1309,48 @@ impl crate::api::mio::MioManagerContext for MioManagerFocus<'_> {
         self.0
     }
 }
+
+/// These signal handlers are used exclusively used during coverage testing
+/// to ensure that the llvm-cov can produce reports during integration tests
+/// with multiple processes where subprocesses are terminated via kill(2).
+///
+/// llvm-cov does not support producing coverage reports when the process exits
+/// through a signal, so this is necessary.
+///
+/// The functionality of exiting gracefully upon reception of a terminating signal
+/// is desired for the production variant of Rosenpass, but we should make sure
+/// to use a higher quality implementation; in particular, we should use signalfd(2).
+///
+#[cfg(feature = "internal_signal_handling_for_coverage_reports")]
+mod terminate {
+    use signal_hook::flag::register as sig_register;
+    use std::sync::{
+        atomic::{AtomicBool, Ordering},
+        Arc,
+    };
+
+    /// Automatically register a signal handler for common termination signals;
+    /// whether one of these signals was issued can be polled using [Self::value].
+    ///
+    /// The signal handler is not removed when this struct goes out of scope.
+    #[derive(Debug)]
+    pub struct TerminateRequested {
+        value: Arc<AtomicBool>,
+    }
+
+    impl TerminateRequested {
+        /// Register signal handlers watching for common termination signals
+        pub fn new() -> anyhow::Result<Self> {
+            let value = Arc::new(AtomicBool::new(false));
+            for sig in signal_hook::consts::TERM_SIGNALS.iter().copied() {
+                sig_register(sig, Arc::clone(&value))?;
+            }
+            Ok(Self { value })
+        }
+
+        /// Check whether a termination signal has been set
+        pub fn value(&self) -> bool {
+            self.value.load(Ordering::Relaxed)
+        }
+    }
+}

rosenpass/src/main.rs

@@ -5,7 +5,6 @@ use clap::Parser;
 use clap_mangen::roff::{roman, Roff};
 use log::error;
 use rosenpass::cli::CliArgs;
-use rosenpass_util::functional::run;
 use std::process::exit;
 
 /// Printing custom man sections when generating the man page
@@ -78,40 +77,13 @@ pub fn main() {
         // error!("error dummy");
     }
 
-    let res = run(|| {
-        #[cfg(feature = "internal_signal_handling_for_coverage_reports")]
-        let term_signal = terminate::TerminateRequested::new()?;
-
-        let broker_interface = args.get_broker_interface();
-        let err = match args.run(broker_interface, None) {
-            Ok(()) => return Ok(()),
-            Err(err) => err,
-        };
-
-        // This is very very hacky and just used for coverage measurement
-        #[cfg(feature = "internal_signal_handling_for_coverage_reports")]
-        {
-            let terminated_by_signal = err
-                .downcast_ref::<std::io::Error>()
-                .filter(|e| e.kind() == std::io::ErrorKind::Interrupted)
-                .filter(|_| term_signal.value())
-                .is_some();
-            if terminated_by_signal {
-                log::warn!(
-                    "\
-                    Terminated by signal; this signal handler is correct during coverage testing \
-                    but should be otherwise disabled"
-                );
-                return Ok(());
-            }
+    let broker_interface = args.get_broker_interface();
+    match args.run(broker_interface, None) {
+        Ok(_) => {}
+        Err(e) => {
+            error!("{e:?}");
+            exit(1);
         }
-
-        Err(err)
-    });
-
-    if let Err(e) = res {
-        error!("{e:?}");
-        exit(1);
     }
 }
 
@@ -138,47 +110,3 @@ Peischl, Stephan Ajuvo, and Lisa Schmidt.";
 /// Custom main page section: Bugs.
 static BUGS_MAN: &str = r"
 The bugs are tracked at https://github.com/rosenpass/rosenpass/issues.";
-
-/// These signal handlers are used exclusively used during coverage testing
-/// to ensure that the llvm-cov can produce reports during integration tests
-/// with multiple processes where subprocesses are terminated via kill(2).
-///
-/// llvm-cov does not support producing coverage reports when the process exits
-/// through a signal, so this is necessary.
-///
-/// The functionality of exiting gracefully upon reception of a terminating signal
-/// is desired for the production variant of Rosenpass, but we should make sure
-/// to use a higher quality implementation; in particular, we should use signalfd(2).
-///
-#[cfg(feature = "internal_signal_handling_for_coverage_reports")]
-mod terminate {
-    use signal_hook::flag::register as sig_register;
-    use std::sync::{
-        atomic::{AtomicBool, Ordering},
-        Arc,
-    };
-
-    /// Automatically register a signal handler for common termination signals;
-    /// whether one of these signals was issued can be polled using [Self::value].
-    ///
-    /// The signal handler is not removed when this struct goes out of scope.
-    pub struct TerminateRequested {
-        value: Arc<AtomicBool>,
-    }
-
-    impl TerminateRequested {
-        /// Register signal handlers watching for common termination signals
-        pub fn new() -> anyhow::Result<Self> {
-            let value = Arc::new(AtomicBool::new(false));
-            for sig in signal_hook::consts::TERM_SIGNALS.iter().copied() {
-                sig_register(sig, Arc::clone(&value))?;
-            }
-            Ok(Self { value })
-        }
-
-        /// Check whether a termination signal has been set
-        pub fn value(&self) -> bool {
-            self.value.load(Ordering::Relaxed)
-        }
-    }
-}

rosenpass/src/protocol/mod.rs

@@ -16,7 +16,11 @@
 //! # Example Handshake
 //!
 //! This example illustrates a minimal setup for a key-exchange between two
-//! [CryptoServer].
+//! [CryptoServer]s; this is what we use for some testing purposes but it is not
+//! what should be used in a real world application, as timing-based events
+//! are handled by [CryptoServer::poll].
+//!
+//! See [CryptoServer::poll] on how to use crypto server in polling mode for production usage.
 //!
 //! ```
 //! use std::ops::DerefMut;

rosenpass/tests/api-integration-tests-api-setup.rs

@@ -35,8 +35,15 @@ impl Drop for KillChild {
     fn drop(&mut self) {
         use rustix::process::{kill_process, Pid, Signal::Term};
         let pid = Pid::from_child(&self.0);
-        rustix::process::kill_process(pid, Term).discard_result();
-        self.0.wait().discard_result();
+        // We seriously need to start handling signals with signalfd, our current signal handling
+        // system is a bit broken; there is probably a few functions that just restart on EINTR
+        // so the signal is absorbed
+        loop {
+            kill_process(pid, Term).discard_result();
+            if self.0.try_wait().unwrap().is_some() {
+                break;
+            }
+        }
     }
 }
 

rosenpass/tests/integration_test.rs

@@ -160,6 +160,9 @@ fn check_example_config() {
         .output()
         .expect("EXAMPLE_CONFIG not valid");
 
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert_eq!(stderr, "");
+
     fs::copy(
         tmp_dir.path().join("rp-public-key"),
         tmp_dir.path().join("rp-peer-public-key"),

rosenpass/tests/poll_example.rs

@@ -0,0 +1,642 @@
+/// This file contains a correct simulation of a two-party key exchange using Poll
+use std::{
+    borrow::{Borrow, BorrowMut},
+    collections::VecDeque,
+    ops::DerefMut,
+};
+
+use rosenpass_cipher_traits::Kem;
+use rosenpass_ciphers::kem::StaticKem;
+use rosenpass_util::result::OkExt;
+
+use rosenpass::protocol::{
+    testutils::time_travel_forward, CryptoServer, HostIdentification, MsgBuf, PeerPtr, PollResult,
+    SPk, SSk, SymKey, Timing, UNENDING,
+};
+
+// TODO: Most of the utility functions in here should probably be moved to
+// rosenpass::protocol::testutils;
+
+#[test]
+fn test_successful_exchange_with_poll() -> anyhow::Result<()> {
+    // Set security policy for storing secrets; choose the one that is faster for testing
+    rosenpass_secret_memory::policy::secret_policy_use_only_malloc_secrets();
+
+    let mut sim = RosenpassSimulator::new()?;
+    sim.poll_loop(150)?; // Poll 75 times
+    let transcript = sim.transcript;
+
+    let _completions: Vec<_> = transcript
+        .iter()
+        .filter(|elm| matches!(elm, (_, TranscriptEvent::CompletedExchange(_))))
+        .collect();
+
+    #[cfg(not(coverage))]
+    assert!(
+        !_completions.is_empty(),
+        "\
+        Should have performed a successful key exchanged!\n\
+          Transcript: {transcript:?}\n\
+          Completions: {_completions:?}\
+        "
+    );
+    #[cfg(not(coverage))]
+    assert!(
+        _completions[0].0 < 20.0,
+        "\
+        First key exchange should happen in under twenty seconds!\n\
+          Transcript: {transcript:?}\n\
+          Completions: {_completions:?}\
+        "
+    );
+
+    #[cfg(not(coverage))]
+    assert!(
+        _completions.len() >= 3,
+        "\
+        Should have at least two renegotiations!\n\
+          Transcript: {transcript:?}\n\
+          Completions: {_completions:?}\
+        "
+    );
+    #[cfg(not(coverage))]
+    assert!(
+        (110.0..175.0).contains(&_completions[1].0),
+        "\
+        First renegotiation should happen in between two and three minutes!\n\
+          Transcript: {transcript:?}\n\
+          Completions: {_completions:?}\
+        "
+    );
+    #[cfg(not(coverage))]
+    assert!((110.0..175.0).contains(&(_completions[2].0 - _completions[1].0)), "\
+        First renegotiation should happen in between two and three minutes after the first renegotiation!\n\
+          Transcript: {transcript:?}\n\
+          Completions: {_completions:?}\
+        ");
+
+    Ok(())
+}
+
+#[test]
+fn test_successful_exchange_under_packet_loss() -> anyhow::Result<()> {
+    // Set security policy for storing secrets; choose the one that is faster for testing
+    rosenpass_secret_memory::policy::secret_policy_use_only_malloc_secrets();
+
+    // Create the simulator
+    let mut sim = RosenpassSimulator::new()?;
+
+    // Make sure the servers are set to under load condition
+    sim.srv_a.under_load = true;
+    sim.srv_b.under_load = false; // See Issue #539 -- https://github.com/rosenpass/rosenpass/issues/539
+
+    // Perform the key exchanges
+    let mut pkg_counter = 0usize;
+    for _ in 0..300 {
+        let ev = sim.poll()?;
+        if let TranscriptEvent::ServerEvent {
+            source,
+            event: ServerEvent::Transmit(_, _),
+        } = ev
+        {
+            // Drop every fifth package
+            if pkg_counter % 10 == 0 {
+                source.drop_outgoing_packet(&mut sim);
+            }
+
+            pkg_counter += 1;
+        }
+    }
+
+    let transcript = sim.transcript;
+    let _completions: Vec<_> = transcript
+        .iter()
+        .filter(|elm| matches!(elm, (_, TranscriptEvent::CompletedExchange(_))))
+        .collect();
+
+    #[cfg(not(coverage))]
+    assert!(
+        !_completions.is_empty(),
+        "\
+        Should have performed a successful key exchanged!\n\
+          Transcript: {transcript:?}\n\
+          Completions: {_completions:?}\
+        "
+    );
+    #[cfg(not(coverage))]
+    assert!(
+        _completions[0].0 < 10.0,
+        "\
+          First key exchange should happen in under twenty seconds!\n\
+          Transcript: {transcript:?}\n\
+          Completions: {_completions:?}\
+        "
+    );
+
+    #[cfg(not(coverage))]
+    assert!(
+        _completions.len() >= 3,
+        "\
+        Should have at least two renegotiations!\n\
+          Transcript: {transcript:?}\n\
+          Completions: {_completions:?}\
+        "
+    );
+    #[cfg(not(coverage))]
+    assert!(
+        (110.0..175.0).contains(&_completions[1].0),
+        "\
+        First renegotiation should happen in between two and three minutes!\n\
+          Transcript: {transcript:?}\n\
+          Completions: {_completions:?}\
+        "
+    );
+    #[cfg(not(coverage))]
+    assert!((110.0..175.0).contains(&(_completions[2].0 - _completions[1].0)), "\
+        First renegotiation should happen in between two and three minutes after the first renegotiation!\n\
+          Transcript: {transcript:?}\n\
+          Completions: {_completions:?}\
+        ");
+
+    Ok(())
+}
+
+type MessageType = u8;
+
+/// Lets record the events that are produced by Rosenpass
+#[derive(Debug)]
+#[allow(unused)]
+enum TranscriptEvent {
+    Wait(Timing),
+    ServerEvent {
+        source: ServerPtr,
+        event: ServerEvent,
+    },
+    CompletedExchange(SymKey),
+}
+
+#[derive(Debug)]
+#[allow(unused)]
+enum ServerEvent {
+    DeleteKey,
+    SendInitiationRequested,
+    SendRetransmissionRequested,
+    Exchanged(SymKey),
+    DiscardInvalidMessage(anyhow::Error),
+    Transmit(MessageType, SendMsgReason),
+    Receive(Option<MessageType>),
+    DroppedPackage,
+}
+
+#[derive(Debug, Clone, Copy)]
+enum SendMsgReason {
+    Initiation,
+    Response,
+    Retransmission,
+}
+
+impl TranscriptEvent {
+    fn hibernate() -> Self {
+        Self::Wait(UNENDING)
+    }
+
+    fn begin_poll() -> Self {
+        Self::hibernate()
+    }
+
+    fn transmit(source: ServerPtr, buf: &[u8], reason: SendMsgReason) -> Self {
+        assert!(!buf.is_empty());
+        let msg_type = buf[0];
+        ServerEvent::Transmit(msg_type, reason).into_transcript_event(source)
+    }
+
+    fn receive(source: ServerPtr, buf: &[u8]) -> Self {
+        let msg_type = (!buf.is_empty()).then(|| buf[0]);
+        ServerEvent::Receive(msg_type).into_transcript_event(source)
+    }
+
+    pub fn try_fold_with<F: FnOnce() -> anyhow::Result<TranscriptEvent>>(
+        self,
+        f: F,
+    ) -> anyhow::Result<TranscriptEvent> {
+        let wait_time_a = match self {
+            Self::Wait(wait_time_a) => wait_time_a,
+            els => return (els).ok(),
+        };
+
+        let wait_time_b = match f()? {
+            Self::Wait(wait_time_b) => wait_time_b,
+            els => return els.ok(),
+        };
+
+        let min_wt = if wait_time_a <= wait_time_b {
+            wait_time_a
+        } else {
+            wait_time_b
+        };
+        Self::Wait(min_wt).ok()
+    }
+}
+
+impl ServerEvent {
+    fn into_transcript_event(self, source: ServerPtr) -> TranscriptEvent {
+        let event = self;
+        TranscriptEvent::ServerEvent { source, event }
+    }
+}
+
+#[derive(Debug)]
+struct RosenpassSimulator {
+    transcript: Vec<(Timing, TranscriptEvent)>,
+    srv_a: SimulatorServer,
+    srv_b: SimulatorServer,
+    poll_focus: ServerPtr,
+}
+
+#[derive(Debug)]
+enum UpcomingPollResult {
+    IssueEvent(TranscriptEvent),
+    SendMessage(Vec<u8>, TranscriptEvent),
+}
+
+#[derive(Debug)]
+struct SimulatorServer {
+    /// We sometimes return multiple multiple events in one call,
+    /// but [ServerPtr::poll] should return just one event per call
+    upcoming_poll_results: VecDeque<UpcomingPollResult>,
+    srv: CryptoServer,
+    rx_queue: VecDeque<Vec<u8>>,
+    other_peer: PeerPtr,
+    under_load: bool,
+}
+
+impl RosenpassSimulator {
+    /// Set up the simulator
+    fn new() -> anyhow::Result<Self> {
+        // Set up the first server
+        let (mut peer_a_sk, mut peer_a_pk) = (SSk::zero(), SPk::zero());
+        StaticKem::keygen(peer_a_sk.secret_mut(), peer_a_pk.deref_mut())?;
+        let mut srv_a = CryptoServer::new(peer_a_sk, peer_a_pk.clone());
+
+        // …and the second server.
+        let (mut peer_b_sk, mut peer_b_pk) = (SSk::zero(), SPk::zero());
+        StaticKem::keygen(peer_b_sk.secret_mut(), peer_b_pk.deref_mut())?;
+        let mut srv_b = CryptoServer::new(peer_b_sk, peer_b_pk.clone());
+
+        // Generate a PSK and introduce the Peers to each other.
+        let psk = SymKey::random();
+        let peer_a = srv_a.add_peer(Some(psk.clone()), peer_b_pk)?;
+        let peer_b = srv_b.add_peer(Some(psk), peer_a_pk)?;
+
+        // Set up the individual server data structures
+        let srv_a = SimulatorServer::new(srv_a, peer_b);
+        let srv_b = SimulatorServer::new(srv_b, peer_a);
+
+        // Initialize transcript and polling state
+        let transcript = Vec::new();
+        let poll_focus = ServerPtr::A;
+
+        // Construct the simulator itself
+        Self {
+            transcript,
+            poll_focus,
+            srv_a,
+            srv_b,
+        }
+        .ok()
+    }
+
+    /// Call [poll] a fixed number of times
+    fn poll_loop(&mut self, times: u64) -> anyhow::Result<()> {
+        for _ in 0..times {
+            self.poll()?;
+        }
+        Ok(())
+    }
+
+    /// Every call to poll produces one [TranscriptEvent] and
+    /// and implicitly adds it to [Self:::transcript]
+    fn poll(&mut self) -> anyhow::Result<&TranscriptEvent> {
+        let ev = TranscriptEvent::begin_poll()
+            .try_fold_with(|| self.poll_focus.poll(self))?
+            .try_fold_with(|| {
+                self.poll_focus = self.poll_focus.other();
+                self.poll_focus.poll(self)
+            })?;
+
+        // Generate up a time stamp
+        let now = self.srv_a.srv.timebase.now();
+
+        // Push the event onto the transcript
+        self.transcript.push((now, ev));
+        // We can unwrap; we just pushed the event ourselves
+        let ev = self.transcript.last().unwrap().1.borrow();
+
+        // Time travel instead of waiting
+        if let TranscriptEvent::Wait(secs) = ev {
+            time_travel_forward(&mut self.srv_a.srv, *secs);
+            time_travel_forward(&mut self.srv_b.srv, *secs);
+        }
+
+        ev.ok()
+    }
+}
+
+impl SimulatorServer {
+    fn new(srv: CryptoServer, other_peer: PeerPtr) -> Self {
+        let upcoming_poll_results = VecDeque::new();
+        let rx_queue = VecDeque::new();
+        let under_load = false;
+        Self {
+            upcoming_poll_results,
+            srv,
+            rx_queue,
+            other_peer,
+            under_load,
+        }
+    }
+}
+
+/// Straightforward way of accessing either of the two servers
+/// with associated data
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+enum ServerPtr {
+    A,
+    B,
+}
+
+impl std::fmt::Display for ServerPtr {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_fmt(format_args!("{:?}", self))
+    }
+}
+
+impl HostIdentification for ServerPtr {
+    fn encode(&self) -> &[u8] {
+        match *self {
+            Self::A => b"ServerPtr::A",
+            Self::B => b"ServerPtr::B",
+        }
+    }
+}
+
+impl ServerPtr {
+    fn poll(self, sim: &mut RosenpassSimulator) -> anyhow::Result<TranscriptEvent> {
+        TranscriptEvent::begin_poll()
+            .try_fold_with(|| self.flush_upcoming_events(sim).ok())?
+            .try_fold_with(|| self.poll_for_timed_events(sim))?
+            .try_fold_with(|| self.process_incoming_messages(sim))
+    }
+
+    /// Returns and applies the first upcoming event
+    fn flush_upcoming_events(self, sim: &mut RosenpassSimulator) -> TranscriptEvent {
+        use UpcomingPollResult as R;
+        match self.get_mut(sim).upcoming_poll_results.pop_front() {
+            None => TranscriptEvent::hibernate(),
+            Some(R::IssueEvent(ev)) => ev,
+            Some(R::SendMessage(msg, ev)) => {
+                self.transmit(sim, msg);
+                ev
+            }
+        }
+    }
+
+    fn poll_for_timed_events(
+        self,
+        sim: &mut RosenpassSimulator,
+    ) -> anyhow::Result<TranscriptEvent> {
+        use PollResult as P;
+        use ServerEvent as SE;
+        use TranscriptEvent as TE;
+
+        let other_peer = self.peer(sim);
+
+        // Check if there are events to process from poll()
+        loop {
+            match self.srv_mut(sim).poll()? {
+                // Poll just told us to immediately call poll again
+                P::Sleep(0.0) => continue,
+
+                // No event to handle immediately. We can now check to see if there are some
+                // messages to be handled
+                P::Sleep(wait_time) => {
+                    return TE::Wait(wait_time).ok();
+                }
+
+                // Not deleting any keys in practice here, since we just push events to the
+                // transcript
+                P::DeleteKey(_) => {
+                    return SE::DeleteKey.into_transcript_event(self).ok();
+                }
+
+                P::SendInitiation(_) => {
+                    self.enqueue_upcoming_poll_event(
+                        sim,
+                        SE::SendInitiationRequested.into_transcript_event(self),
+                    );
+
+                    let mut buf = MsgBuf::zero();
+                    let len = self
+                        .srv_mut(sim)
+                        .initiate_handshake(other_peer, &mut buf[..])?;
+                    self.enqueue_upcoming_poll_transmission(
+                        sim,
+                        buf[..len].to_vec(),
+                        SendMsgReason::Initiation,
+                    );
+
+                    return self.flush_upcoming_events(sim).ok(); // Just added them
+                }
+
+                P::SendRetransmission(_) => {
+                    self.enqueue_upcoming_poll_event(
+                        sim,
+                        SE::SendRetransmissionRequested.into_transcript_event(self),
+                    );
+
+                    let mut buf = MsgBuf::zero();
+                    let len = self
+                        .srv_mut(sim)
+                        .retransmit_handshake(other_peer, &mut buf[..])?;
+                    self.enqueue_upcoming_poll_transmission(
+                        sim,
+                        buf[..len].to_vec(),
+                        SendMsgReason::Retransmission,
+                    );
+
+                    return self.flush_upcoming_events(sim).ok(); // Just added them
+                }
+            };
+        }
+    }
+
+    fn process_incoming_messages(
+        self,
+        sim: &mut RosenpassSimulator,
+    ) -> anyhow::Result<TranscriptEvent> {
+        use ServerEvent as SE;
+        use TranscriptEvent as TE;
+
+        // Check for a message or exit
+        let rx_msg = match self.recv(sim) {
+            None => return TE::hibernate().ok(),
+            // Actually received a message
+            Some(rx_msg) => rx_msg,
+        };
+
+        // Add info that a message was received into the transcript
+        self.enqueue_upcoming_poll_event(sim, TE::receive(self, rx_msg.borrow()));
+
+        // Let the crypto server handle the message now
+        let mut tx_buf = MsgBuf::zero();
+        let handle_msg_result = if self.get(sim).under_load {
+            self.srv_mut(sim)
+                .handle_msg_under_load(rx_msg.borrow(), tx_buf.borrow_mut(), &self)
+        } else {
+            self.srv_mut(sim)
+                .handle_msg(rx_msg.borrow(), tx_buf.borrow_mut())
+        };
+
+        // Handle bad messages
+        let handle_msg_result = match handle_msg_result {
+            Ok(res) => res,
+            Err(e) => {
+                self.enqueue_upcoming_poll_event(
+                    sim,
+                    SE::DiscardInvalidMessage(e).into_transcript_event(self),
+                );
+                return self.flush_upcoming_events(sim).ok(); // Just added them
+            }
+        };
+
+        // Successful key exchange; emit the appropriate event
+        if handle_msg_result.exchanged_with.is_some() {
+            self.enqueue_on_exchanged_events(sim)?;
+        }
+
+        // Handle message responses
+        if let Some(len) = handle_msg_result.resp {
+            let resp = &tx_buf[..len];
+            self.enqueue_upcoming_poll_transmission(sim, resp.to_vec(), SendMsgReason::Response);
+        };
+
+        // Return the first of the events we just enqueued
+        self.flush_upcoming_events(sim).ok()
+    }
+
+    fn enqueue_on_exchanged_events(self, sim: &mut RosenpassSimulator) -> anyhow::Result<()> {
+        use ServerEvent as SE;
+        use TranscriptEvent as TE;
+
+        // Retrieve the key exchanged; this function will panic if the OSK is missing
+        let osk = self.osk(sim).unwrap();
+
+        // Issue the `Exchanged`
+        self.enqueue_upcoming_poll_event(
+            sim,
+            SE::Exchanged(osk.clone()).into_transcript_event(self),
+        );
+
+        // Retrieve the other osk
+        let other_osk = match self.other().try_osk(sim) {
+            Some(other_osk) => other_osk,
+            None => return Ok(()),
+        };
+
+        // Issue the successful exchange event if the OSKs are equal;
+        // be careful to use constant time comparison for things like this!
+        if rosenpass_constant_time::memcmp(osk.secret(), other_osk.secret()) {
+            self.enqueue_upcoming_poll_event(sim, TE::CompletedExchange(osk));
+        }
+
+        Ok(())
+    }
+
+    fn enqueue_upcoming_poll_event(self, sim: &mut RosenpassSimulator, ev: TranscriptEvent) {
+        let upcoming = UpcomingPollResult::IssueEvent(ev);
+        self.get_mut(sim).upcoming_poll_results.push_back(upcoming);
+    }
+
+    fn enqueue_upcoming_poll_transmission(
+        self,
+        sim: &mut RosenpassSimulator,
+        msg: Vec<u8>,
+        reason: SendMsgReason,
+    ) {
+        let ev = TranscriptEvent::transmit(self, msg.borrow(), reason);
+        let upcoming = UpcomingPollResult::SendMessage(msg, ev);
+        self.get_mut(sim).upcoming_poll_results.push_back(upcoming);
+    }
+
+    fn try_osk(self, sim: &RosenpassSimulator) -> Option<SymKey> {
+        let peer = self.peer(sim);
+        let has_osk = peer.session().get(self.srv(sim)).is_some();
+
+        has_osk.then(|| {
+            // We already checked whether the OSK is present; there should be no other errors
+            self.osk(sim).unwrap()
+        })
+    }
+
+    fn osk(self, sim: &RosenpassSimulator) -> anyhow::Result<SymKey> {
+        self.srv(sim).osk(self.peer(sim))
+    }
+
+    fn drop_outgoing_packet(self, sim: &mut RosenpassSimulator) -> Option<Vec<u8>> {
+        let pkg = self.tx_queue_mut(sim).pop_front();
+        self.enqueue_upcoming_poll_event(
+            sim,
+            ServerEvent::DroppedPackage.into_transcript_event(self),
+        );
+        pkg
+    }
+
+    fn other(self) -> Self {
+        match self {
+            Self::A => Self::B,
+            Self::B => Self::A,
+        }
+    }
+
+    fn get(self, sim: &RosenpassSimulator) -> &SimulatorServer {
+        match self {
+            ServerPtr::A => sim.srv_a.borrow(),
+            ServerPtr::B => sim.srv_b.borrow(),
+        }
+    }
+
+    fn get_mut(self, sim: &mut RosenpassSimulator) -> &mut SimulatorServer {
+        match self {
+            ServerPtr::A => sim.srv_a.borrow_mut(),
+            ServerPtr::B => sim.srv_b.borrow_mut(),
+        }
+    }
+
+    fn srv(self, sim: &RosenpassSimulator) -> &CryptoServer {
+        self.get(sim).srv.borrow()
+    }
+
+    fn srv_mut(self, sim: &mut RosenpassSimulator) -> &mut CryptoServer {
+        self.get_mut(sim).srv.borrow_mut()
+    }
+
+    fn peer(self, sim: &RosenpassSimulator) -> PeerPtr {
+        self.get(sim).other_peer
+    }
+
+    fn recv(self, sim: &mut RosenpassSimulator) -> Option<Vec<u8>> {
+        self.rx_queue_mut(sim).pop_front()
+    }
+
+    fn transmit(self, sim: &mut RosenpassSimulator, msg: Vec<u8>) {
+        self.tx_queue_mut(sim).push_back(msg);
+    }
+
+    fn rx_queue_mut(self, sim: &mut RosenpassSimulator) -> &mut VecDeque<Vec<u8>> {
+        self.get_mut(sim).rx_queue.borrow_mut()
+    }
+
+    fn tx_queue_mut(self, sim: &mut RosenpassSimulator) -> &mut VecDeque<Vec<u8>> {
+        self.other().rx_queue_mut(sim)
+    }
+}

rp/src/cli.rs

@@ -3,6 +3,11 @@ use std::{iter::Peekable, net::SocketAddr};
 
 use crate::exchange::{ExchangeOptions, ExchangePeer};
 
+/// The different commands supported by the `rp` binary.
+/// [GenKey](crate::cli::Command::GenKey), [PubKey](crate::cli::Command::PubKey),
+/// [Exchange](crate::cli::Command::Exchange) and
+/// [ExchangeConfig](crate::cli::Command::ExchangeConfig)
+/// contain information specific to the respective command.  
 pub enum Command {
     GenKey {
         private_keys_dir: PathBuf,
@@ -18,6 +23,10 @@ pub enum Command {
     Help,
 }
 
+/// The different command types supported by the `rp` binary.
+/// This enum is exclusively used in [fatal] and when calling [fatal] and is therefore
+/// limited to the command types that can fail. E.g., the help command can not fail and is therefore
+/// not part of the [CommandType]-enum.
 enum CommandType {
     GenKey,
     PubKey,
@@ -25,12 +34,24 @@ enum CommandType {
     ExchangeConfig,
 }
 
+/// This structure captures the result of parsing the  arguments to the `rp` binary.
+/// A new [Cli] is created by calling [Cli::parse] with the appropriate arguments.
 #[derive(Default)]
 pub struct Cli {
+    /// Whether the output should be verbose.
     pub verbose: bool,
+    /// The command specified by the given arguments.
     pub command: Option<Command>,
 }
 
+/// Processes a fatal error when parsing cli arguments.
+/// It *always* returns an [Err(String)], where such that the contained [String] explains
+/// the parsing error, including the provided `note`.
+///
+/// # Generic Parameters
+/// the generic parameter `T` is given to make the [Result]-type compatible with the respective
+/// return type of the calling function.
+///
 fn fatal<T>(note: &str, command: Option<CommandType>) -> Result<T, String> {
     match command {
         Some(command) => match command {
@@ -44,6 +65,9 @@ fn fatal<T>(note: &str, command: Option<CommandType>) -> Result<T, String> {
 }
 
 impl ExchangePeer {
+    /// Parses peer parameters given to the `rp` binary in the context of an `exchange` operation.
+    /// It returns a result with either [ExchangePeer] that contains the parameters of the peer
+    /// or an error describing why the arguments could not be parsed.
     pub fn parse(args: &mut &mut Peekable<impl Iterator<Item = String>>) -> Result<Self, String> {
         let mut peer = ExchangePeer::default();
 
@@ -126,6 +150,9 @@ impl ExchangePeer {
 }
 
 impl ExchangeOptions {
+    /// Parses the arguments given to the `rp` binary *if the `exchange` operation is given*.
+    /// It returns a result with either [ExchangeOptions] that contains the result of parsing the
+    /// arguments or an error describing why the arguments could not be parsed.
     pub fn parse(mut args: &mut Peekable<impl Iterator<Item = String>>) -> Result<Self, String> {
         let mut options = ExchangeOptions::default();
 
@@ -191,6 +218,9 @@ impl ExchangeOptions {
 }
 
 impl Cli {
+    /// Parses the arguments given to the `rp` binary. It returns a result with either
+    /// a [Cli] that contains the result of parsing the arguments or an error describing
+    /// why the arguments could not be parsed.
     pub fn parse(mut args: Peekable<impl Iterator<Item = String>>) -> Result<Self, String> {
         let mut cli = Cli::default();
 

rp/src/exchange.rs

@@ -11,21 +11,37 @@ use anyhow::Result;
 #[cfg(any(target_os = "linux", target_os = "freebsd"))]
 use crate::key::WG_B64_LEN;
 
+/// Used to define a peer for the rosenpass connection that consists of
+/// a directory for storing public keys and optionally an IP address and port of the endpoint,
+/// for how long the connection should be kept alive and a list of allowed IPs for the peer.
 #[derive(Default, Deserialize)]
 pub struct ExchangePeer {
+    /// Directory where public keys are stored
     pub public_keys_dir: PathBuf,
+    /// The IP address of the endpoint
     pub endpoint: Option<SocketAddr>,
+    /// For how long to keep the connection alive
     pub persistent_keepalive: Option<u32>,
+    /// The IPs that are allowed for this peer.
     pub allowed_ips: Option<String>,
 }
 
+/// Options for the exchange operation of the `rp` binary.
 #[derive(Default, Deserialize)]
 pub struct ExchangeOptions {
+    /// Whether the cli output should be verbose.
     pub verbose: bool,
+    /// path to the directory where private keys are stored.
     pub private_keys_dir: PathBuf,
+    /// The link rosenpass should run as. If None is given [exchange] will use `"rosenpass0"`
+    /// instead.
     pub dev: Option<String>,
+    /// The IP-address rosenpass should run under.
     pub ip: Option<String>,
+    /// The IP-address and port that the rosenpass [AppServer](rosenpass::app_server::AppServer)
+    /// should use.
     pub listen: Option<SocketAddr>,
+    /// Other peers a connection should be initialized to
     pub peers: Vec<ExchangePeer>,
 }
 
@@ -48,8 +64,11 @@ mod netlink {
     use netlink_packet_wireguard::nlas::WgDeviceAttrs;
     use rtnetlink::Handle;
 
+    /// Creates a netlink named `link_name` and changes the state to up. It returns the index
+    /// of the interface in the list of interfaces as the result or an error if any of the
+    /// operations of creating the link or changing its state to up fails.
     pub async fn link_create_and_up(rtnetlink: &Handle, link_name: String) -> Result<u32> {
-        // add the link
+        // Add the link, equivalent to `ip link add <link_name> type wireguard`.
         rtnetlink
             .link()
             .add()
@@ -57,7 +76,8 @@ mod netlink {
             .execute()
             .await?;
 
-        // retrieve the link to be able to up it
+        // Retrieve the link to be able to up it, equivalent to `ip link show` and then
+        // using the link shown that is identified by `link_name`.
         let link = rtnetlink
             .link()
             .get()
@@ -69,7 +89,7 @@ mod netlink {
             .0
             .unwrap()?;
 
-        // up the link
+        // Up the link, equivalent to `ip link set dev <DEV> up`.
         rtnetlink
             .link()
             .set(link.header.index)
@@ -80,12 +100,16 @@ mod netlink {
         Ok(link.header.index)
     }
 
+    /// Deletes a link using rtnetlink. The link is specified using its index in the list of links.
     pub async fn link_cleanup(rtnetlink: &Handle, index: u32) -> Result<()> {
         rtnetlink.link().del(index).execute().await?;
 
         Ok(())
     }
 
+    /// Deletes a link using rtnetlink. The link is specified using its index in the list of links.
+    /// In contrast to [link_cleanup], this function create a new socket connection to netlink and
+    /// *ignores errors* that occur during deletion.
     pub async fn link_cleanup_standalone(index: u32) -> Result<()> {
         let (connection, rtnetlink, _) = rtnetlink::new_connection()?;
         tokio::spawn(connection);
@@ -111,7 +135,7 @@ mod netlink {
         use netlink_packet_generic::GenlMessage;
         use netlink_packet_wireguard::{Wireguard, WireguardCmd};
 
-        // Scope our `set` command to only the device of the specified index
+        // Scope our `set` command to only the device of the specified index.
         attr.insert(0, WgDeviceAttrs::IfIndex(index));
 
         // Construct the WireGuard-specific netlink packet
@@ -120,12 +144,12 @@ mod netlink {
             nlas: attr,
         };
 
-        // Construct final message
+        // Construct final message.
         let genl = GenlMessage::from_payload(wgc);
         let mut nlmsg = NetlinkMessage::from(genl);
         nlmsg.header.flags = NLM_F_REQUEST | NLM_F_ACK;
 
-        // Send and wait for the ACK or error
+        // Send and wait for the ACK or error.
         let (res, _) = genetlink.request(nlmsg).await?.into_future().await;
         if let Some(res) = res {
             let res = res?;
@@ -138,6 +162,9 @@ mod netlink {
     }
 }
 
+/// A wrapper for a list of cleanup handlers that can be used in an asynchronous context
+/// to clean up after the usage of rosenpass or if the `rp` binary is interrupted with ctrl+c
+/// or a `SIGINT` signal in general.
 #[derive(Clone)]
 #[cfg(any(target_os = "linux", target_os = "freebsd"))]
 struct CleanupHandlers(
@@ -146,19 +173,27 @@ struct CleanupHandlers(
 
 #[cfg(any(target_os = "linux", target_os = "freebsd"))]
 impl CleanupHandlers {
+    /// Creates a new list of [CleanupHandlers].
     fn new() -> Self {
         CleanupHandlers(Arc::new(::futures::lock::Mutex::new(vec![])))
     }
 
+    /// Enqueues a new cleanup handler in the form of a [Future].
     async fn enqueue(&self, handler: Pin<Box<dyn Future<Output = Result<(), Error>> + Send>>) {
         self.0.lock().await.push(Box::pin(handler))
     }
 
+    /// Runs all cleanup handlers. Following the documentation of [futures::future::try_join_all]:
+    /// If any cleanup handler returns an error then all other cleanup handlers will be canceled and
+    /// an error will be returned immediately. If all cleanup handlers complete successfully,
+    /// however, then the returned future will succeed with a Vec of all the successful results.
     async fn run(self) -> Result<Vec<()>, Error> {
         futures::future::try_join_all(self.0.lock().await.deref_mut()).await
     }
 }
 
+/// Sets up the rosenpass link and wireguard and configures both with the configuration specified by
+/// `options`.
 #[cfg(any(target_os = "linux", target_os = "freebsd"))]
 pub async fn exchange(options: ExchangeOptions) -> Result<()> {
     use std::fs;
@@ -182,6 +217,8 @@ pub async fn exchange(options: ExchangeOptions) -> Result<()> {
     let link_name = options.dev.clone().unwrap_or("rosenpass0".to_string());
     let link_index = netlink::link_create_and_up(&rtnetlink, link_name.clone()).await?;
 
+    // Set up a list of (initiallc empty) cleanup handlers that are to be run if
+    // ctrl-c is hit or generally a `SIGINT` signal is received and always in the end.
     let cleanup_handlers = CleanupHandlers::new();
     let final_cleanup_handlers = (&cleanup_handlers).clone();
 
@@ -198,6 +235,7 @@ pub async fn exchange(options: ExchangeOptions) -> Result<()> {
             .expect("Failed to clean up");
     })?;
 
+    // Run `ip address add <ip> dev <dev>` and enqueue `ip address del <ip> dev <dev>` as a cleanup.
     if let Some(ip) = options.ip {
         let dev = options.dev.clone().unwrap_or("rosenpass0".to_string());
         Command::new("ip")
@@ -223,7 +261,7 @@ pub async fn exchange(options: ExchangeOptions) -> Result<()> {
             .await;
     }
 
-    // Deploy the classic wireguard private key
+    // Deploy the classic wireguard private key.
     let (connection, mut genetlink, _) = genetlink::new_connection()?;
     tokio::spawn(connection);
 
@@ -244,6 +282,7 @@ pub async fn exchange(options: ExchangeOptions) -> Result<()> {
 
     netlink::wg_set(&mut genetlink, link_index, attr).await?;
 
+    // set up the rosenpass AppServer
     let pqsk = options.private_keys_dir.join("pqsk");
     let pqpk = options.private_keys_dir.join("pqpk");
 
@@ -271,6 +310,7 @@ pub async fn exchange(options: ExchangeOptions) -> Result<()> {
         anyhow::Error::msg(format!("NativeUnixBrokerConfigBaseBuilderError: {:?}", e))
     }
 
+    // Configure everything per peer.
     for peer in options.peers {
         let wgpk = peer.public_keys_dir.join("wgpk");
         let pqpk = peer.public_keys_dir.join("pqpk");
@@ -318,7 +358,8 @@ pub async fn exchange(options: ExchangeOptions) -> Result<()> {
             peer.endpoint.map(|x| x.to_string()),
         )?;
 
-        // Configure routes
+        // Configure routes, equivalent to `ip route replace <allowed_ips> dev <dev>` and set up
+        // the cleanup as `ip route del <allowed_ips>`.
         if let Some(allowed_ips) = peer.allowed_ips {
             Command::new("ip")
                 .arg("route")
@@ -349,7 +390,8 @@ pub async fn exchange(options: ExchangeOptions) -> Result<()> {
     match out {
         Ok(_) => Ok(()),
         Err(e) => {
-            // Check if the returned error is actually EINTR, in which case, the run actually succeeded.
+            // Check if the returned error is actually EINTR, in which case, the run actually
+            // succeeded.
             let is_ok = if let Some(e) = e.root_cause().downcast_ref::<std::io::Error>() {
                 matches!(e.kind(), std::io::ErrorKind::Interrupted)
             } else {

rp/src/key.rs

@@ -14,6 +14,7 @@ use rosenpass_cipher_traits::Kem;
 use rosenpass_ciphers::kem::StaticKem;
 use rosenpass_secret_memory::{file::StoreSecret as _, Public, Secret};
 
+/// The length of wireguard keys as a length in base 64 encoding.
 pub const WG_B64_LEN: usize = 32 * 5 / 3;
 
 #[cfg(not(target_family = "unix"))]
@@ -24,6 +25,14 @@ pub fn genkey(_: &Path) -> Result<()> {
     ))
 }
 
+/// Generates a new symmetric keys for wireguard and asymmetric keys for rosenpass
+/// in the provided `private_keys_dir`.
+///  
+/// It checks whether the directory `private_keys_dir` points to exists and creates it otherwise.
+/// If it exists, it ensures that the permission is set to 0700 and aborts otherwise. If the
+/// directory is newly created, the appropriate permissions are set.
+///
+/// Already existing keys are not overwritten.
 #[cfg(target_family = "unix")]
 pub fn genkey(private_keys_dir: &Path) -> Result<()> {
     if private_keys_dir.exists() {
@@ -70,6 +79,11 @@ pub fn genkey(private_keys_dir: &Path) -> Result<()> {
     Ok(())
 }
 
+/// Creates a new directory under `public_keys_dir` and stores the public keys for rosenpass and for
+/// wireguard that correspond to the private keys in `private_keys_dir` in `public_keys_dir`.
+///
+/// If `public_keys_dir` already exists, the wireguard private key or the rosenpass public key
+/// are not present in `private_keys_dir`, an error is returned.
 pub fn pubkey(private_keys_dir: &Path, public_keys_dir: &Path) -> Result<()> {
     if public_keys_dir.exists() {
         return Err(anyhow!("Directory {:?} already exists", public_keys_dir));
@@ -90,9 +104,11 @@ pub fn pubkey(private_keys_dir: &Path, public_keys_dir: &Path) -> Result<()> {
         Public::from_slice(public.as_bytes())
     };
 
+    // Store the wireguard public key.
     wgpk.store_b64::<WG_B64_LEN, _>(public_wgpk)?;
     wgpk.zeroize();
 
+    // Copy the pq-public key to the public directory.
     fs::copy(private_pqpk, public_pqpk)?;
 
     Ok(())

to/README.md

@@ -17,13 +17,14 @@ use rosenpass_to::{to, with_destination, To};
 use std::ops::BitXorAssign;
 
 // Destination functions return some value that implements the To trait.
-// Unfortunately dealing with lifetimes is a bit more finicky than it would#
+// Unfortunately dealing with lifetimes is a bit more finicky than it would
 // be without destination parameters
 fn xor_slice<'a, T>(src: &'a [T]) -> impl To<[T], ()> + 'a
 where
     T: BitXorAssign + Clone,
 {
     // Custom implementations of the to trait can be created, but the easiest
+    // way to create them is to use the provided helper functions like with_destination.
     with_destination(move |dst: &mut [T]| {
         assert!(src.len() == dst.len());
         for (d, s) in dst.iter_mut().zip(src.iter()) {

to/src/ops.rs

@@ -1,4 +1,5 @@
-//! Functions with destination copying data between slices and arrays.
+//! Functions that make it easy to copy data between arrays and slices using functions with
+//! destinations. See the specific functions for examples and more explanations.
 
 use crate::{with_destination, To};
 
@@ -8,6 +9,17 @@ use crate::{with_destination, To};
 /// # Panics
 ///
 /// This function will panic if the two slices have different lengths.
+///
+/// # Example
+/// ```
+/// use rosenpass_to::To;
+/// # use crate::rosenpass_to::ops::copy_slice;
+/// let to_function = copy_slice(&[0; 16]);
+/// let mut dst = [255; 16];
+/// to_function.to(&mut dst);
+/// // After the operation `dst` will hold the same data as the original slice.
+/// assert!(dst.iter().all(|b| *b == 0));
+/// ```
 pub fn copy_slice<T>(origin: &[T]) -> impl To<[T], ()> + '_
 where
     T: Copy,
@@ -23,6 +35,19 @@ where
 /// # Panics
 ///
 /// This function will panic if destination is shorter than origin.
+///
+/// # Example
+/// ```
+/// use rosenpass_to::To;
+/// # use crate::rosenpass_to::ops::copy_slice_least_src;
+/// let to_function = copy_slice_least_src(&[0; 16]);
+/// let mut dst = [255; 32];
+/// to_function.to(&mut dst);
+/// // After the operation the first half of `dst` will hold the same data as the original slice.
+/// assert!(dst[0..16].iter().all(|b| *b == 0));
+/// // The second half will have remained the same
+/// assert!(dst[16..32].iter().all(|b| *b == 255));
+/// ```
 pub fn copy_slice_least_src<T>(origin: &[T]) -> impl To<[T], ()> + '_
 where
     T: Copy,
@@ -34,6 +59,18 @@ where
 /// destination.
 ///
 /// Copies as much data as is present in the shorter slice.
+/// # Example
+/// ```
+/// use rosenpass_to::To;
+/// # use crate::rosenpass_to::ops::copy_slice_least;
+/// let to_function = copy_slice_least(&[0; 16]);
+/// let mut dst = [255; 32];
+/// to_function.to(&mut dst);
+/// // After the operation the first half of `dst` will hold the same data as the original slice.
+/// assert!(dst[0..16].iter().all(|b| *b == 0));
+/// // The second half will have remained the same.
+/// assert!(dst[16..32].iter().all(|b| *b == 255));
+/// ```
 pub fn copy_slice_least<T>(origin: &[T]) -> impl To<[T], ()> + '_
 where
     T: Copy,
@@ -47,6 +84,24 @@ where
 /// Function with destination that attempts to copy data from origin into the destination.
 ///
 /// Will return None if the slices are of different lengths.
+/// # Example
+/// ```
+/// use rosenpass_to::To;
+/// # use crate::rosenpass_to::ops::try_copy_slice;
+/// let to_function = try_copy_slice(&[0; 16]);
+/// let mut dst = [255; 32];
+/// let result = to_function.to(&mut dst);
+/// // This will return None because the slices do not have the same length.
+/// assert!(result.is_none());
+///
+/// let to_function = try_copy_slice(&[0; 16]);
+/// let mut dst = [255; 16];
+/// let result = to_function.to(&mut dst);
+/// // This time it works:
+/// assert!(result.is_some());
+/// // After the operation `dst` will hold the same data as the original slice.
+/// assert!(dst.iter().all(|b| *b == 0));
+/// ```
 pub fn try_copy_slice<T>(origin: &[T]) -> impl To<[T], Option<()>> + '_
 where
     T: Copy,
@@ -62,6 +117,26 @@ where
 /// Destination may be longer than origin.
 ///
 /// Will return None if the destination is shorter than origin.
+/// # Example
+/// ```rust
+/// use rosenpass_to::To;
+/// # use crate::rosenpass_to::ops::try_copy_slice_least_src;
+/// let to_function = try_copy_slice_least_src(&[0; 16]);
+/// let mut dst = [255; 15];
+/// let result = to_function.to(&mut dst);
+/// // This will return None because the destination is to short.
+/// assert!(result.is_none());
+///
+/// let to_function = try_copy_slice_least_src(&[0; 16]);
+/// let mut dst = [255; 32];
+/// let result = to_function.to(&mut dst);
+/// // This time it works:
+/// assert!(result.is_some());
+/// // After the operation, the first half of `dst` will hold the same data as the original slice.
+/// assert!(dst[0..16].iter().all(|b| *b == 0));
+/// // The second half will have remained the same.
+/// assert!(dst[16..32].iter().all(|b| *b == 255));
+/// ```
 pub fn try_copy_slice_least_src<T>(origin: &[T]) -> impl To<[T], Option<()>> + '_
 where
     T: Copy,
@@ -72,6 +147,18 @@ where
 }
 
 /// Function with destination that copies all data between two array references.
+///
+/// # Example
+/// ```rust
+/// use rosenpass_to::ops::copy_array;
+/// use rosenpass_to::To;
+/// let my_arr: [u8; 32] = [0; 32];
+/// let to_function = copy_array(&my_arr);
+/// let mut dst = [255; 32];
+/// to_function.to(&mut dst);
+/// // After the operation `dst` will hold the same data as the original slice.
+/// assert!(dst.iter().all(|b| *b == 0));
+/// ```
 pub fn copy_array<T, const N: usize>(origin: &[T; N]) -> impl To<[T; N], ()> + '_
 where
     T: Copy,

to/src/to/beside.rs

@@ -1,6 +1,11 @@
+//! This module provides the [Beside] struct. In the context of functions with targets,
+//! [Beside] structures the destination value and the return value unmistakably and offers useful
+//! helper functions to work with them.
+
 use crate::CondenseBeside;
 
-/// Named tuple holding the return value and the output from a function with destinations.
+/// Named tuple holding the return value and the destination from a function with destinations.
+/// See the respective functions for usage examples.
 #[derive(Debug, PartialEq, Eq, Default, PartialOrd, Ord, Copy, Clone)]
 pub struct Beside<Val, Ret>(pub Val, pub Ret);
 
@@ -59,7 +64,7 @@ impl<Val, Ret> Beside<Val, Ret> {
         &mut self.1
     }
 
-    /// Perform beside condensation. See [CondenseBeside]
+    /// Perform beside condensation. See [CondenseBeside] for more details.
     ///
     /// # Example
     /// ```
@@ -90,3 +95,25 @@ impl<Val, Ret> From<Beside<Val, Ret>> for (Val, Ret) {
         (val, ret)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::Beside;
+
+    #[test]
+    fn from_tuple() {
+        let tuple = (21u8, 42u16);
+        let beside: Beside<u8, u16> = Beside::from(tuple);
+        assert_eq!(beside.dest(), &21u8);
+        assert_eq!(beside.ret(), &42u16);
+    }
+
+    #[test]
+    fn from_beside() {
+        let beside: Beside<u8, u16> = Beside(21u8, 42u16);
+        type U8u16 = (u8, u16);
+        let tuple = U8u16::from(beside);
+        assert_eq!(tuple.0, 21u8);
+        assert_eq!(tuple.1, 42u16);
+    }
+}

to/src/to/condense.rs

@@ -1,4 +1,11 @@
-/// Beside condensation.
+//! This module provides condensation for values that stand side by side,
+//! which is often useful when working with destination parameters. See [CondenseBeside]
+//! for more details.
+
+/// Condenses two values that stand beside each other into one value.
+/// For example, a blanked implementation for [Result<(), Error>](Result) is provided. If
+/// `condense(val)` is called on such an object, a [Result<Val, Error>](Result) will
+/// be returned, if `val` is of type `Val`.
 ///
 /// This trait can be used to enable the use of [to_this(|| ...)](crate::To::to_this),
 /// [to_value()](crate::To::to_value), and [collect::<...>()](crate::To::collect) with custom
@@ -6,6 +13,19 @@
 ///
 /// The function [Beside::condense()](crate::Beside::condense) is a shorthand for using the
 /// condense trait.
+///
+/// # Example
+/// As an example implementation, we take a look at the blanket implementation for [Option]
+/// ```ignore
+/// impl<Val> CondenseBeside<Val> for Option<()> {
+///     type Condensed = Option<Val>;
+///
+///     /// Replaces the empty tuple inside this [Option] with `ret`.
+///     fn condense(self, ret: Val) -> Option<Val> {
+///         self.map(|()| ret)
+///     }
+/// }
+/// ```
 pub trait CondenseBeside<Val> {
     /// The type that results from condensation.
     type Condensed;
@@ -17,6 +37,7 @@ pub trait CondenseBeside<Val> {
 impl<Val> CondenseBeside<Val> for () {
     type Condensed = Val;
 
+    /// Replaces this empty tuple with `ret`.
     fn condense(self, ret: Val) -> Val {
         ret
     }
@@ -25,6 +46,7 @@ impl<Val> CondenseBeside<Val> for () {
 impl<Val, Error> CondenseBeside<Val> for Result<(), Error> {
     type Condensed = Result<Val, Error>;
 
+    /// Replaces the empty tuple inside this [Result] with `ret`.
     fn condense(self, ret: Val) -> Result<Val, Error> {
         self.map(|()| ret)
     }
@@ -33,6 +55,7 @@ impl<Val, Error> CondenseBeside<Val> for Result<(), Error> {
 impl<Val> CondenseBeside<Val> for Option<()> {
     type Condensed = Option<Val>;
 
+    /// Replaces the empty tuple inside this [Option] with `ret`.
     fn condense(self, ret: Val) -> Option<Val> {
         self.map(|()| ret)
     }

to/src/to/dst_coercion.rs

@@ -1,5 +1,28 @@
-/// Helper performing explicit unsized coercion.
-/// Used by the [to](crate::to()) function.
+//! This module provides explicit type coercion from [Sized] types to [?Sized][core::marker::Sized]
+//! types. See [DstCoercion] for more details.
+
+/// Helper Trait for performing explicit coercion from [Sized] types to
+/// [?Sized][core::marker::Sized] types. It's used by the [to](crate::to()) function.
+///
+/// We provide blanket implementations for any [Sized] type and for any array of [Sized] types.
+///
+/// # Example
+/// It can be used as follows:
+/// ```
+/// # use rosenpass_to::DstCoercion;
+/// // Consider a sized type like this example:
+/// struct SizedStruct {
+///     x: u32
+/// }
+/// // Then we can coerce it to be unsized:
+/// let mut sized = SizedStruct { x: 42 };
+/// assert_eq!(42, sized.coerce_dest().x);
+///
+/// // Analogously, we can coerce arrays to slices:
+/// let mut sized_array = [1, 2, 3, 4, 5, 6, 7, 8, 9];
+/// let un_sized: &[i32] = sized_array.coerce_dest();
+/// assert_eq!(un_sized, un_sized);
+/// ```
 pub trait DstCoercion<Dst: ?Sized> {
     /// Performs an explicit coercion to the destination type.
     fn coerce_dest(&mut self) -> &mut Dst;

to/src/to/mod.rs

@@ -6,11 +6,16 @@
 //! - `Dst: ?Sized`; (e.g. [u8]) – The target to write to
 //! - `Out: Sized = &mut Dst`; (e.g. &mut [u8]) – A reference to the target to write to
 //! - `Coercable: ?Sized + DstCoercion<Dst>`; (e.g. `[u8]`, `[u8; 16]`) – Some value that
-//!   destination coercion can be applied to. Usually either `Dst` itself (e.g. `[u8]` or some sized variant of
+//!   destination coercion can be applied to. Usually either `Dst` itself (e.g. `[u8]` or
+//!   some sized variant of
 //!   `Dst` (e.g. `[u8; 64]`).
-//! - `Ret: Sized`; (anything) – must be `CondenseBeside<_>` if condensing is to be applied. The ordinary return value of a function with an output
-//! - `Val: Sized + BorrowMut<Dst>`; (e.g. [u8; 16]) – Some owned storage that can be borrowed as `Dst`
-//! - `Condensed: Sized = CondenseBeside<Val>::Condensed`; (e.g. [u8; 16], Result<[u8; 16]>) – The combiation of Val and Ret after condensing was applied (`Beside<Val, Ret>::condense()`/`Ret::condense(v)` for all `v : Val`).
+//! - `Ret: Sized`; (anything) – must be `CondenseBeside<_>` if condensing is to be applied. The
+//!    ordinary return value of a function with an output
+//! - `Val: Sized + BorrowMut<Dst>`; (e.g. [u8; 16]) – Some owned storage that can be borrowed as
+//!   `Dst`
+//! - `Condensed: Sized = CondenseBeside<Val>::Condensed`; (e.g. [u8; 16], Result<[u8; 16]>)
+//! – The combiation of Val and Ret after condensing was applied
+//!   (`Beside<Val, Ret>::condense()`/`Ret::condense(v)` for all `v : Val`).
 
 pub mod beside;
 pub mod condense;

to/src/to/to_function.rs

@@ -1,9 +1,23 @@
+//! This module provides the [To::to] function which allows to use functions with destination in
+//! a manner akin to that of a variable assignment. See [To::to] for more details.
+
 use crate::{DstCoercion, To};
 
 /// Alias for [To::to] moving the destination to the left.
 ///
 /// This provides similar haptics to the let assignment syntax is rust, which also keeps
 /// the variable to assign to on the left and the generating function on the right.
+///
+/// # Example
+/// ```rust
+/// // Using the to function to have data flowing from the right to the left,
+/// // performing something akin to a variable assignment.
+/// use rosenpass_to::ops::copy_slice_least;
+/// # use rosenpass_to::to;
+/// let mut dst = b"           ".to_vec();
+/// to(&mut dst[..], copy_slice_least(b"Hello World"));
+/// assert_eq!(&dst[..], b"Hello World");
+/// ```
 pub fn to<Coercable, Src, Dst, Ret>(dst: &mut Coercable, src: Src) -> Ret
 where
     Coercable: ?Sized + DstCoercion<Dst>,

to/src/to/to_trait.rs

@@ -1,12 +1,46 @@
+//! Module that contains the [To] crate which is the container used to
+//! implement the core functionality of this crate.
+
 use crate::{Beside, CondenseBeside};
 use std::borrow::BorrowMut;
 
 /// The To trait is the core of the to crate; most functions with destinations will either return
-/// an object that is an instance of this trait or they will return `-> impl To<Destination,
-/// Return_value`.
+/// an object that is an instance of this trait, or they will return `-> impl To<Destination,
+/// Return_value>`.
 ///
 /// A quick way to implement a function with destination is to use the
-/// [with_destination(|param: &mut Type| ...)] higher order function.
+/// [with_destination(|param: &mut Type| ...)](crate::with_destination) higher order function.
+///
+/// # Example
+/// Below, we provide a very simple example for how the Trait can be implemented. More examples for
+/// how this Trait is best implemented can be found in the overall [crate documentation](crate).
+/// ```
+/// use rosenpass_to::To;
+///
+/// // This is a simple wrapper around a String that can be written into a byte array using to.
+/// struct StringToBytes {
+///    inner: String
+/// }
+///
+/// impl To<[u8], Result<(), String>> for StringToBytes {
+///     fn to(self, out: &mut [u8]) -> Result<(), String> {
+///         let bytes = self.inner.as_bytes();
+///         if bytes.len() > out.len() {
+///             return Err("out is to short".to_string());
+///         }
+///         for i in 0..bytes.len() {
+///             (*out)[i] = bytes[i];
+///         }
+///         Ok(())
+///     }
+/// }
+///
+/// let string_to_bytes = StringToBytes { inner: "my message".to_string() };
+/// let mut buffer: [u8; 10] = [0; 10];
+/// let result = string_to_bytes.to(&mut buffer);
+/// assert_eq!(buffer, [109, 121, 32, 109, 101, 115, 115, 97, 103, 101]);
+/// assert!(result.is_ok());
+/// ```
 pub trait To<Dst: ?Sized, Ret>: Sized {
     /// Writes self to the destination `out` and returns a value of type `Ret`.
     ///
@@ -19,6 +53,36 @@ pub trait To<Dst: ?Sized, Ret>: Sized {
     /// calls [crate::to()] to evaluate the function and finally
     /// returns a [Beside] instance containing the generated destination value and the return
     /// value.
+    ///
+    /// # Example
+    /// Below, we rewrite the example for the overall [To]-Trait and simplify it by using
+    /// [self.to_this_beside]. We refer to the overall [crate documentation](crate)
+    /// for more examples and general explanations.
+    /// ```
+    /// # use rosenpass_to::To;
+    /// use rosenpass_to::Beside;
+    /// # struct StringToBytes {
+    /// #   inner: String
+    /// # }
+    ///
+    /// # impl To<[u8], Result<(), String>> for StringToBytes {
+    /// #    fn to(self, out: &mut [u8]) -> Result<(), String> {
+    /// #        let bytes = self.inner.as_bytes();
+    /// #        if bytes.len() > out.len() {
+    /// #            return Err("out is to short".to_string());
+    /// #        }
+    /// #        for i in 0..bytes.len() {
+    /// #            (*out)[i] = bytes[i];
+    /// #        }
+    /// #        Ok(())
+    /// #    }
+    /// # }
+    /// // StringToBytes is taken from the overall Trait example.
+    /// let string_to_bytes = StringToBytes { inner: "my message".to_string() };
+    /// let Beside(dst, result) = string_to_bytes.to_this_beside(|| [0; 10]);
+    /// assert_eq!(dst, [109, 121, 32, 109, 101, 115, 115, 97, 103, 101]);
+    /// assert!(result.is_ok());
+    /// ```
     fn to_this_beside<Val, Fun>(self, fun: Fun) -> Beside<Val, Ret>
     where
         Val: BorrowMut<Dst>,
@@ -31,10 +95,21 @@ pub trait To<Dst: ?Sized, Ret>: Sized {
 
     /// Generate a destination on the fly using default.
     ///
-    /// Uses [Default] to create a value,
-    /// calls [crate::to()] to evaluate the function and finally
+    /// Uses [Default] to create a value, calls [crate::to()] to evaluate the function and finally
     /// returns a [Beside] instance containing the generated destination value and the return
     /// value.
+    ///
+    /// # Example
+    /// Below, we provide a simple example for the usage of [to_value_beside](To::to_value_beside).
+    /// We refer to the overall [crate documentation](crate) for more examples and general
+    /// explanations.
+    /// ```
+    /// use rosenpass_to::Beside;
+    /// use rosenpass_to::To;
+    /// use rosenpass_to::ops::*;
+    /// let Beside(dst, ret) = copy_array(&[42u8; 16]).to_value_beside();
+    /// assert_eq!(dst, [42u8; 16]);
+    /// ```
     fn to_value_beside(self) -> Beside<Dst, Ret>
     where
         Dst: Sized + Default,
@@ -53,6 +128,19 @@ pub trait To<Dst: ?Sized, Ret>: Sized {
     /// when the Destination is unsized.
     ///
     /// This could be the case when the destination is an `[u8]` for instance.
+    ///
+    /// # Example
+    /// Below, we provide a simple example for the usage of [collect_beside](To::collect_beside).
+    /// We refer to the overall [crate documentation](crate) for more examples and general
+    /// explanations.
+    /// ```
+    /// use rosenpass_to::Beside;
+    /// use rosenpass_to::To;
+    /// use rosenpass_to::ops::*;
+    ///
+    /// let Beside(dst, ret) = copy_slice(&[42u8; 16]).collect_beside::<[u8; 16]>();
+    /// assert_eq!(dst, [42u8; 16]);
+    /// ```
     fn collect_beside<Val>(self) -> Beside<Val, Ret>
     where
         Val: Default + BorrowMut<Dst>,
@@ -64,6 +152,36 @@ pub trait To<Dst: ?Sized, Ret>: Sized {
     /// return value into one.
     ///
     /// This is like using [Self::to_this_beside] followed by calling [Beside::condense].
+    /// # Example
+    /// Below, we rewrite the example for the overall [To]-Trait and simplify it by using
+    /// [Self::to_this]. We refer to the overall [crate documentation](crate)
+    /// for more examples and general explanations.
+    /// ```
+    /// # use rosenpass_to::To;
+    /// use rosenpass_to::Beside;
+    /// # struct StringToBytes {
+    /// #   inner: String
+    /// # }
+    ///
+    /// # impl To<[u8], Result<(), String>> for StringToBytes {
+    /// #    fn to(self, out: &mut [u8]) -> Result<(), String> {
+    /// #        let bytes = self.inner.as_bytes();
+    /// #        if bytes.len() > out.len() {
+    /// #            return Err("out is to short".to_string());
+    /// #        }
+    /// #        for i in 0..bytes.len() {
+    /// #            (*out)[i] = bytes[i];
+    /// #        }
+    /// #        Ok(())
+    /// #    }
+    /// # }
+    /// // StringToBytes is taken from the overall Trait example.
+    /// let string_to_bytes = StringToBytes { inner: "my message".to_string() };
+    /// let result = string_to_bytes.to_this_beside(|| [0; 10]).condense();
+    /// assert!(result.is_ok());
+    /// assert_eq!(result.unwrap(), [109, 121, 32, 109, 101, 115, 115, 97, 103, 101]);
+    ///
+    /// ```
     fn to_this<Val, Fun>(self, fun: Fun) -> <Ret as CondenseBeside<Val>>::Condensed
     where
         Ret: CondenseBeside<Val>,
@@ -77,6 +195,18 @@ pub trait To<Dst: ?Sized, Ret>: Sized {
     /// return value into one.
     ///
     /// This is like using [Self::to_value_beside] followed by calling [Beside::condense].
+    ///
+    /// # Example
+    /// Below, we provide a simple example for the usage of [to_value](To::to_value).
+    /// We refer to the overall [crate documentation](crate) for more examples and general
+    /// explanations.
+    /// ```
+    /// use rosenpass_to::Beside;
+    /// use rosenpass_to::To;
+    /// use rosenpass_to::ops::*;
+    /// let dst = copy_array(&[42u8; 16]).to_value_beside().condense();
+    /// assert_eq!(dst, [42u8; 16]);
+    /// ```
     fn to_value(self) -> <Ret as CondenseBeside<Dst>>::Condensed
     where
         Dst: Sized + Default,
@@ -89,6 +219,19 @@ pub trait To<Dst: ?Sized, Ret>: Sized {
     /// return value into one.
     ///
     /// This is like using [Self::collect_beside] followed by calling [Beside::condense].
+    ///
+    /// # Example
+    /// Below, we provide a simple example for the usage of [collect](To::collect).
+    /// We refer to the overall [crate documentation](crate) for more examples and general
+    /// explanations.
+    /// ```
+    /// use rosenpass_to::Beside;
+    /// use rosenpass_to::To;
+    /// use rosenpass_to::ops::*;
+    ///
+    /// let dst = copy_slice(&[42u8; 16]).collect_beside::<[u8; 16]>().condense();
+    /// assert_eq!(dst, [42u8; 16]);
+    /// ```
     fn collect<Val>(self) -> <Ret as CondenseBeside<Val>>::Condensed
     where
         Val: Default + BorrowMut<Dst>,

to/src/to/with_destination.rs

@@ -1,15 +1,19 @@
+//! The module provides the [with_destination] function, which makes it easy to create
+//! a [To] from a lambda function. See [with_destination] and the [crate documentation](crate)
+//! for more details and examples.
+
 use crate::To;
 use std::marker::PhantomData;
 
-/// A struct that wraps a closure and implements the `To` trait
+/// A struct that wraps a closure and implements the `To` trait.
 ///
 /// This allows passing closures that operate on a destination type `Dst`
-/// and return `Ret`.
+/// and return `Ret`. It is only internally used to implement [with_destination].
 ///
 /// # Type Parameters
-/// * `Dst` - The destination type the closure operates on
-/// * `Ret` - The return type of the closure
-/// * `Fun` - The closure type that implements `FnOnce(&mut Dst) -> Ret`
+/// * `Dst` - The destination type the closure operates on.
+/// * `Ret` - The return type of the closure.
+/// * `Fun` - The closure type that implements `FnOnce(&mut Dst) -> Ret`.
 struct ToClosure<Dst, Ret, Fun>
 where
     Dst: ?Sized,
@@ -17,11 +21,11 @@ where
 {
     /// The function to call.
     fun: Fun,
-    /// Phantom data to hold the destination type
+    /// Phantom data to hold the destination type.
     _val: PhantomData<Box<Dst>>,
 }
 
-/// Implementation of the `To` trait for ToClosure
+/// Implementation of the `To` trait for ToClosure.
 ///
 /// This enables calling the wrapped closure with a destination reference.
 impl<Dst, Ret, Fun> To<Dst, Ret> for ToClosure<Dst, Ret, Fun>
@@ -33,6 +37,7 @@ where
     ///
     /// # Arguments
     /// * `out` - Mutable reference to the destination
+    /// See the tutorial in [readme.md] for examples and more explanations.
     fn to(self, out: &mut Dst) -> Ret {
         (self.fun)(out)
     }
@@ -48,7 +53,24 @@ where
 /// * `Ret` - The return type of the closure
 /// * `Fun` - The closure type that implements `FnOnce(&mut Dst) -> Ret`
 ///
-/// See the tutorial in [readme.me]..
+/// See the tutorial in the [crate documentation](crate) for more examples and more explanations.
+/// # Example
+/// ```
+/// # use rosenpass_to::with_destination;
+/// use crate::rosenpass_to::To;
+/// let my_origin_data: [u8; 16]= [2; 16];
+/// let times_two = with_destination( move |dst: &mut [u8; 16]| {
+///     for (dst, org) in dst.iter_mut().zip(my_origin_data.iter()) {
+///         *dst = dst.clone() * org;
+///     }
+/// });
+/// let mut dst: [u8; 16] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
+/// times_two.to(&mut dst);
+/// for i in 0..16 {
+///     assert_eq!(dst[i], (2 * i) as u8);
+/// }
+///
+/// ```
 pub fn with_destination<Dst, Ret, Fun>(fun: Fun) -> impl To<Dst, Ret>
 where
     Dst: ?Sized,

util/src/build.rs

@@ -78,8 +78,8 @@ pub trait Build<T>: Sized {
 
 /// A type that can be incrementally built from a type that can [Build] it
 ///
-/// This is similar to an option, where [Self::Void] is [std::Option::None],
-/// [Self::Product] is [std::Option::Some], except that there is a third
+/// This is similar to an option, where [Self::Void] is [std::option::Option::None],
+/// [Self::Product] is [std::option::Option::Some], except that there is a third
 /// intermediate state [Self::Builder] that represents a Some/Product value
 /// in the process of being made.
 ///
@@ -508,9 +508,9 @@ where
         matches!(self, Self::Void)
     }
 
-    /// Returns `true` if the construction site is [`InProgress`].
+    /// Returns `true` if the construction site is in the [`Builder`] phase.
     ///
-    /// [`InProgress`]: ConstructionSite::InProgress
+    /// [`Builder`]: ConstructionSite::Builder
     ///
     /// # Examples
     ///
@@ -541,9 +541,10 @@ where
         matches!(self, Self::Builder(..))
     }
 
-    /// Returns `true` if the construction site is [`Done`].
+    /// Returns `true` if the construction site is in the [`Product`] phase and
+    /// is therefore done.
     ///
-    /// [`Done`]: ConstructionSite::Done
+    /// [`Product`]: ConstructionSite::Product
     ///
     /// # Examples
     ///

util/src/controlflow.rs

@@ -1,4 +1,4 @@
-/// A collection of control flow utility macros
+//! A collection of control flow utility macros
 
 #[macro_export]
 /// A simple for loop to repeat a $body a number of times
@@ -33,7 +33,7 @@ macro_rules! repeat {
 ///     0
 /// }
 /// assert_eq!(test_fn(), 0);
-
+///
 /// fn test_fn2() -> i32 {
 ///     return_unless!(false, 1);
 ///     0
@@ -65,7 +65,7 @@ macro_rules! return_unless {
 ///     0
 /// }
 /// assert_eq!(test_fn(), 1);
-
+///
 /// fn test_fn2() -> i32 {
 ///     return_if!(false, 1);
 ///     0
@@ -98,7 +98,7 @@ macro_rules! return_if {
 ///     sum += 1;
 /// }
 /// assert_eq!(sum, 5);
-
+///
 /// let mut sum = 0;
 /// 'one: for _ in 0..10 {
 ///     for j in 0..20 {
@@ -134,7 +134,7 @@ macro_rules! break_if {
 ///     sum += 1;
 /// }
 /// assert_eq!(sum, 9);
-
+///
 /// let mut sum = 0;
 /// 'one: for i in 0..10 {
 ///     continue_if!(i == 5, 'one);

util/src/fd.rs

@@ -89,6 +89,30 @@ pub fn claim_fd_inplace(fd: RawFd) -> rustix::io::Result<OwnedFd> {
 ///
 /// Will panic if the given file descriptor is negative of or larger than
 /// the file descriptor numbers permitted by the operating system.
+///
+/// # Example
+/// ```
+/// # use std::fs::File;
+/// # use std::io::Read;
+/// # use std::os::unix::io::{AsRawFd, FromRawFd};
+/// # use std::os::fd::IntoRawFd;
+/// # use rustix::fd::AsFd;
+/// # use rosenpass_util::fd::mask_fd;
+///
+/// // Open a temporary file
+/// let fd = tempfile::tempfile().unwrap().into_raw_fd();
+/// assert!(fd >= 0);
+///
+/// // Mask the file descriptor
+/// mask_fd(fd).unwrap();
+///
+/// // Verify the file descriptor now points to `/dev/null`
+/// // Reading from `/dev/null` always returns 0 bytes
+/// let mut replaced_file = unsafe { File::from_raw_fd(fd) };
+/// let mut buffer = [0u8; 4];
+/// let bytes_read = replaced_file.read(&mut buffer).unwrap();
+/// assert_eq!(bytes_read, 0);
+/// ```
 pub fn mask_fd(fd: RawFd) -> rustix::io::Result<()> {
     // Safety: because the OwnedFd resulting from OwnedFd::from_raw_fd is wrapped in a Forgetting,
     // it never gets dropped, meaning that fd is never closed and thus outlives the OwnedFd
@@ -286,14 +310,14 @@ where
     }
 }
 
-/// Distinguish different socket address familys; e.g. IP and unix sockets
+/// Distinguish different socket address families; e.g. IP and unix sockets
 #[cfg(target_os = "linux")]
 pub trait GetSocketDomain {
     /// Error type returned by operations in this trait
     type Error;
     /// Retrieve the socket domain (address family)
     fn socket_domain(&self) -> Result<rustix::net::AddressFamily, Self::Error>;
-    /// Alias for [socket_domain]
+    /// Alias for [Self::socket_domain]
     fn socket_address_family(&self) -> Result<rustix::net::AddressFamily, Self::Error> {
         self.socket_domain()
     }
@@ -320,9 +344,67 @@ where
 pub trait GetUnixSocketType {
     /// Error type returned by operations in this trait
     type Error;
-    /// Check if the socket is a unix stream socket
+
+    /// Checks whether the socket is a Unix stream socket.
+    ///
+    /// # Returns
+    /// - `Ok(true)` if the socket is a Unix stream socket.
+    /// - `Ok(false)` if the socket is not a Unix stream socket.
+    /// - `Err(Self::Error)` if there is an error while performing the check.
+    ///
+    /// # Examples
+    /// ```
+    /// # use std::fs::File;
+    /// # use std::os::fd::{AsFd, BorrowedFd};
+    /// # use std::os::unix::net::UnixListener;
+    /// # use tempfile::NamedTempFile;
+    /// # use rosenpass_util::fd::GetUnixSocketType;
+    /// let f = {
+    ///     // Generate a temp file and take its path
+    ///     // Remove the temp file
+    ///     // Create a unix socket on the temp path that is not unused
+    ///     let temp_file = NamedTempFile::new().unwrap();
+    ///     let socket_path = temp_file.path().to_owned();
+    ///     std::fs::remove_file(&socket_path).unwrap();
+    ///     UnixListener::bind(socket_path).unwrap()
+    /// };
+    /// assert!(matches!(f.as_fd().is_unix_stream_socket(), Ok(true)));
+    /// ```
     fn is_unix_stream_socket(&self) -> Result<bool, Self::Error>;
     /// Returns Ok(()) only if the underlying socket is a unix stream socket
+    /// # Examples
+    /// ```
+    /// # use std::fs::File;
+    /// # use std::os::fd::{AsFd, BorrowedFd};
+    /// # use std::os::unix::net::{UnixDatagram, UnixListener};
+    /// # use tempfile::NamedTempFile;
+    /// # use rosenpass_util::fd::GetUnixSocketType;
+    /// let f = {
+    ///     // Generate a temp file and take its path
+    ///     // Remove the temp file
+    ///     // Create a unix socket on the temp path that is not unused
+    ///     let temp_file = NamedTempFile::new().unwrap();
+    ///     let socket_path = temp_file.path().to_owned();
+    ///     std::fs::remove_file(&socket_path).unwrap();
+    ///     UnixListener::bind(socket_path).unwrap()
+    /// };
+    /// assert!(matches!(f.as_fd().demand_unix_stream_socket(), Ok(())));
+    /// // Error if the FD is a file
+    /// let temp_file = NamedTempFile::new().unwrap();
+    /// assert_eq!(temp_file.as_fd().demand_unix_stream_socket().err().unwrap().to_string(),
+    ///  "Socket operation on non-socket (os error 88)"
+    /// );
+    /// // Error if the FD is a Unix stream with a wrong mode (e.g. Datagram)
+    /// let f = {
+    ///     let temp_file = NamedTempFile::new().unwrap();
+    ///     let socket_path = temp_file.path().to_owned();
+    ///     std::fs::remove_file(&socket_path).unwrap();
+    ///     UnixDatagram::bind(socket_path).unwrap()
+    /// };
+    /// assert_eq!(f.as_fd().demand_unix_stream_socket().err().unwrap().to_string(),
+    ///  "Expected unix socket in stream mode, but mode is SocketType(2)"
+    /// );
+    /// ```
     fn demand_unix_stream_socket(&self) -> anyhow::Result<()>;
 }
 
@@ -352,16 +434,65 @@ where
 #[cfg(target_os = "linux")]
 /// Distinguish between different network socket protocols (e.g. tcp, udp)
 pub trait GetSocketProtocol {
-    /// Retrieve the socket protocol
+    /// Retrieves the socket's protocol.
+    ///
+    /// # Returns
+    /// - `Ok(Some(Protocol))`: The protocol of the socket if available.
+    /// - `Ok(None)`: If the protocol information is unavailable.
+    /// - `Err(rustix::io::Errno)`: If an error occurs while retrieving the protocol.
+    ///
+    /// # Examples
+    /// ```
+    /// # use std::net::UdpSocket;
+    /// # use std::os::fd::{AsFd, AsRawFd};
+    /// # use rosenpass_util::fd::GetSocketProtocol;
+    /// let socket = UdpSocket::bind("127.0.0.1:0")?;
+    /// assert_eq!(socket.as_fd().socket_protocol().unwrap().unwrap(), rustix::net::ipproto::UDP);
+    /// # Ok::<(), std::io::Error>(())
+    /// ```
     fn socket_protocol(&self) -> Result<Option<rustix::net::Protocol>, rustix::io::Errno>;
     /// Check if the socket is a udp socket
+    ///
+    /// # Examples
+    /// ```
+    /// # use std::net::UdpSocket;
+    /// # use std::net::TcpListener;
+    /// # use std::os::fd::{AsFd, AsRawFd};
+    /// # use rosenpass_util::fd::GetSocketProtocol;
+    /// let socket = UdpSocket::bind("127.0.0.1:0")?;
+    /// assert!(socket.as_fd().is_udp_socket().unwrap());
+    ///
+    /// let socket = TcpListener::bind("127.0.0.1:0")?;
+    /// assert!(!socket.as_fd().is_udp_socket().unwrap());
+    /// # Ok::<(), std::io::Error>(())
+    /// ```
     fn is_udp_socket(&self) -> Result<bool, rustix::io::Errno> {
         self.socket_protocol()?
             .map(|p| p == rustix::net::ipproto::UDP)
             .unwrap_or(false)
             .ok()
     }
-    /// Return Ok(()) only if the socket is a udp socket
+
+    /// Ensures that the socket is a UDP socket, returning an error otherwise.
+    ///
+    /// # Returns
+    /// - `Ok(())` if the socket is a UDP socket.
+    /// - `Err(anyhow::Error)` if the socket is not a UDP socket or if an error occurs retrieving the socket protocol.
+    ///
+    /// # Examples
+    /// ```
+    /// # use std::net::UdpSocket;
+    /// # use std::net::TcpListener;
+    /// # use std::os::fd::{AsFd, AsRawFd};
+    /// # use rosenpass_util::fd::GetSocketProtocol;
+    /// let socket = UdpSocket::bind("127.0.0.1:0")?;
+    /// assert!(matches!(socket.as_fd().demand_udp_socket(), Ok(())));
+    ///
+    /// let socket = TcpListener::bind("127.0.0.1:0")?;
+    /// assert_eq!(socket.as_fd().demand_udp_socket().unwrap_err().to_string(),
+    ///     "Not a udp socket, instead socket protocol is: Protocol(6)");
+    /// # Ok::<(), std::io::Error>(())
+    /// ```
     fn demand_udp_socket(&self) -> anyhow::Result<()> {
         match self.socket_protocol() {
             Ok(Some(rustix::net::ipproto::UDP)) => Ok(()),

util/src/io.rs

@@ -244,7 +244,6 @@
 use std::{borrow::Borrow, io};
 
 use anyhow::ensure;
-use zerocopy::AsBytes;
 
 /// Generic trait for accessing [std::io::Error::kind]
 ///

util/src/length_prefix_encoding/decoder.rs

@@ -1,3 +1,16 @@
+//! This module provides utilities for decoding length-prefixed messages from I/O streams.
+//!
+//! Messages are prefixed with an unsigned 64-bit little-endian length header, followed by the
+//! message payload. The [`decoder::LengthPrefixDecoder`] is a central component here, maintaining
+//! internal buffers and state for partial reads and boundary checks.
+//!
+//! The module defines errors to handle size mismatches, I/O issues, and boundary violations
+//! that may occur during decoding.
+//!
+//! The abstractions provided in this module enable safe and convenient reading
+//! of structured data from streams, including handling unexpected EOFs and ensuring messages
+//! fit within allocated buffers.
+
 use std::{borrow::BorrowMut, cmp::min, io};
 
 use thiserror::Error;
@@ -8,54 +21,79 @@ use crate::{
     result::ensure_or,
 };
 
-/// Size in bytes of a message header carrying length information
+/// Size in bytes of the message header carrying length information.
+/// Currently, HEADER_SIZE is always 8 bytes and encodes a 64-bit little-endian number.
 pub const HEADER_SIZE: usize = std::mem::size_of::<u64>();
 
+/// Error enum representing sanity check failures when accessing buffer regions.
+///
+/// This error is triggered when internal offsets point outside allowable regions.
 #[derive(Error, Debug)]
-/// Error enum to represent various boundary sanity check failures during buffer operations
 pub enum SanityError {
+    /// The given offset exceeded the read buffer bounds.
     #[error("Offset is out of read buffer bounds")]
-    /// Error indicating that the given offset exceeds the bounds of the read buffer
     OutOfBufferBounds,
+
+    /// The given offset exceeded the message buffer bounds.
     #[error("Offset is out of message buffer bounds")]
-    /// Error indicating that the given offset exceeds the bounds of the message buffer
     OutOfMessageBounds,
 }
 
+/// Error indicating that the message size is larger than the available buffer space.
 #[derive(Error, Debug)]
 #[error("Message too large ({msg_size} bytes) for buffer ({buf_size} bytes)")]
-/// Error indicating that message exceeds available buffer space
 pub struct MessageTooLargeError {
     msg_size: usize,
     buf_size: usize,
 }
 
 impl MessageTooLargeError {
-    /// Creates a new MessageTooLargeError with the given message and buffer sizes
+    /// Creates a new `MessageTooLargeError` with the given message and buffer sizes.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use rosenpass_util::length_prefix_encoding::decoder::MessageTooLargeError;
+    /// let err = MessageTooLargeError::new(1024, 512);
+    /// assert_eq!(format!("{}", err), "Message too large (1024 bytes) for buffer (512 bytes)");
+    /// ```
     pub fn new(msg_size: usize, buf_size: usize) -> Self {
         Self { msg_size, buf_size }
     }
 
-    /// Ensures that the message size fits within the buffer size
+    /// Ensures the message fits within the given buffer.
     ///
-    /// Returns Ok(()) if the message fits, otherwise returns an error with size details
+    /// Returns `Ok(())` if `msg_size <= buf_size`, otherwise returns a `MessageTooLargeError`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use rosenpass_util::length_prefix_encoding::decoder::MessageTooLargeError;
+    /// let result = MessageTooLargeError::ensure(100, 200);
+    /// assert!(result.is_ok());
+    ///
+    /// let err = MessageTooLargeError::ensure(300, 200).unwrap_err();
+    /// assert_eq!(format!("{}", err), "Message too large (300 bytes) for buffer (200 bytes)");
+    /// ```
     pub fn ensure(msg_size: usize, buf_size: usize) -> Result<(), Self> {
         let err = MessageTooLargeError { msg_size, buf_size };
         ensure_or(msg_size <= buf_size, err)
     }
 }
 
+/// Return type for `ReadFromIo` operations, containing the number of bytes read and an optional message slice.
 #[derive(Debug)]
-/// Return type for ReadFromIo operations that contains the number of bytes read and an optional message slice
 pub struct ReadFromIoReturn<'a> {
-    /// Number of bytes read from the input
+    /// Number of bytes read.
     pub bytes_read: usize,
-    /// Optional slice containing the complete message, if one was read
+    /// The complete message slice if fully read, otherwise `None`.
     pub message: Option<&'a mut [u8]>,
 }
 
 impl<'a> ReadFromIoReturn<'a> {
-    /// Creates a new ReadFromIoReturn with the given number of bytes read and optional message slice.
+    /// Creates a new `ReadFromIoReturn`.
+    ///
+    /// Generally used internally to represent partial or complete read results.
     pub fn new(bytes_read: usize, message: Option<&'a mut [u8]>) -> Self {
         Self {
             bytes_read,
@@ -64,13 +102,17 @@ impl<'a> ReadFromIoReturn<'a> {
     }
 }
 
+/// An error that may occur when reading from an I/O source.
+///
+/// This enum wraps I/O errors and message-size errors, allowing higher-level logic to determine
+/// if the error is a fundamental I/O problem or a size mismatch issue.
 #[derive(Debug, Error)]
-/// An enum representing errors that can occur during read operations from I/O
 pub enum ReadFromIoError {
-    /// Error occurred while reading from the underlying I/O stream
+    /// Error reading from the underlying I/O stream.
     #[error("Error reading from the underlying stream")]
     IoError(#[from] io::Error),
-    /// Error occurred because message size exceeded buffer capacity
+
+    /// The message size exceeded the capacity of the available buffer.
     #[error("Message size out of buffer bounds")]
     MessageTooLargeError(#[from] MessageTooLargeError),
 }
@@ -84,11 +126,31 @@ impl TryIoErrorKind for ReadFromIoError {
     }
 }
 
-#[derive(Debug, Default, Clone)]
-/// A decoder for length-prefixed messages
+/// A decoder for length-prefixed messages.
 ///
-/// This struct provides functionality to decode messages that are prefixed with their length.
-/// It maintains internal state for header information, the message buffer, and current offset.
+/// This decoder reads a 64-bit little-endian length prefix followed by the message payload.
+/// It maintains state so that partial reads from a non-blocking or streaming source can
+/// accumulate until a full message is available.
+///
+/// # Examples
+///
+/// ```
+/// # use std::io::Cursor;
+/// # use rosenpass_util::length_prefix_encoding::decoder::LengthPrefixDecoder;
+/// let data: Vec<u8> = {
+///     let mut buf = Vec::new();
+///     buf.extend_from_slice(&(5u64.to_le_bytes())); // message length = 5
+///     buf.extend_from_slice(b"hello");
+///     buf
+/// };
+///
+/// let mut decoder = LengthPrefixDecoder::new(vec![0; 64]);
+/// let mut cursor = Cursor::new(data);
+///
+/// let message = decoder.read_all_from_stdio(&mut cursor).expect("read failed");
+/// assert_eq!(message, b"hello");
+/// ```
+#[derive(Debug, Default, Clone)]
 pub struct LengthPrefixDecoder<Buf: BorrowMut<[u8]>> {
     header: [u8; HEADER_SIZE],
     buf: Buf,
@@ -96,33 +158,102 @@ pub struct LengthPrefixDecoder<Buf: BorrowMut<[u8]>> {
 }
 
 impl<Buf: BorrowMut<[u8]>> LengthPrefixDecoder<Buf> {
-    /// Creates a new LengthPrefixDecoder with the given buffer
+    /// Creates a new `LengthPrefixDecoder` with the provided buffer.
+    ///
+    /// The provided buffer must be large enough to hold the expected maximum message size.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use rosenpass_util::length_prefix_encoding::decoder::LengthPrefixDecoder;
+    /// let decoder = LengthPrefixDecoder::new(vec![0; 1024]);
+    /// assert_eq!(*decoder.bytes_read(), 0);
+    /// ```
     pub fn new(buf: Buf) -> Self {
         let header = Default::default();
         let off = 0;
         Self { header, buf, off }
     }
 
-    /// Clears and zeroes all internal state
+    /// Clears and zeroes all internal state.
+    ///
+    /// This zeroizes the header and the buffer, as well as resets the offset to zero.
     pub fn clear(&mut self) {
         self.zeroize()
     }
 
-    /// Creates a new LengthPrefixDecoder from its component parts
+    /// Creates a decoder from parts.
+    ///
+    /// Typically used for low-level reconstruction of a decoder state.
     pub fn from_parts(header: [u8; HEADER_SIZE], buf: Buf, off: usize) -> Self {
         Self { header, buf, off }
     }
 
-    /// Consumes the decoder and returns its component parts
+    /// Consumes the decoder and returns its internal parts.
+    ///
+    /// Returns the header, the underlying buffer, and the current offset.
     pub fn into_parts(self) -> ([u8; HEADER_SIZE], Buf, usize) {
         let Self { header, buf, off } = self;
         (header, buf, off)
     }
 
-    /// Reads a complete message from the given reader into the decoder.
+    /// Reads a complete message from the given reader.
     ///
-    /// Retries on interrupts and returns the decoded message buffer on success.
-    /// Returns an error if the read fails or encounters an unexpected EOF.
+    /// Will retry on interrupts and fails if EOF is encountered prematurely. On success,
+    /// returns a mutable slice of the fully read message.
+    ///
+    /// # Examples
+    ///
+    /// ## Successful read
+    /// ```
+    /// # use std::io::Cursor;
+    /// # use rosenpass_util::length_prefix_encoding::decoder::{LengthPrefixDecoder, ReadFromIoError, MessageTooLargeError};
+    /// let mut data: Cursor<Vec<u8>> = {
+    ///     let mut buf = Vec::new();
+    ///     buf.extend_from_slice(&(3u64.to_le_bytes()));
+    ///     // The buffer can also be larger than the message size:
+    ///     // Here `cats` is 4 bytes and 1 byte longer than the message size defined in the header
+    ///     buf.extend_from_slice(b"cats");
+    ///     Cursor::new(buf)
+    /// };
+    /// let mut decoder = LengthPrefixDecoder::new(vec![0; 8]);
+    /// let msg = decoder.read_all_from_stdio(&mut data).expect("read failed");
+    /// assert_eq!(msg, b"cat");
+    /// ```
+    ///
+    /// ## MessageTooLargeError
+    ///
+    /// Buffer of the `LengthPrefixDecoder` configured to be too small:
+    /// ```
+    /// # use std::io::Cursor;
+    /// # use rosenpass_util::length_prefix_encoding::decoder::{LengthPrefixDecoder, ReadFromIoError, MessageTooLargeError};
+    /// let mut data: Cursor<Vec<u8>> = {
+    ///     let mut buf = Vec::new();
+    ///     buf.extend_from_slice(&(7u64.to_le_bytes()));
+    ///     buf.extend_from_slice(b"giraffe");
+    ///     Cursor::new(buf)
+    /// };
+    /// // Buffer is too small, should be at least 7 bytes (defined in the header)
+    /// let mut decoder = LengthPrefixDecoder::new(vec![0; 5]);
+    /// let err = decoder.read_all_from_stdio(&mut data).expect_err("read should have failed");
+    /// assert!(matches!(err, ReadFromIoError::MessageTooLargeError(_)));
+    /// ```
+    ///
+    /// ## IOError (EOF)
+    /// ```
+    /// # use std::io::Cursor;
+    /// # use rosenpass_util::length_prefix_encoding::decoder::{LengthPrefixDecoder, ReadFromIoError, MessageTooLargeError};
+    /// let mut data: Cursor<Vec<u8>> = {
+    ///     let mut buf = Vec::new();
+    ///     // Message size set to 10 bytes, but the message is only 7 bytes long
+    ///     buf.extend_from_slice(&(10u64.to_le_bytes()));
+    ///     buf.extend_from_slice(b"giraffe");
+    ///     Cursor::new(buf)
+    /// };
+    /// let mut decoder = LengthPrefixDecoder::new(vec![0; 10]);
+    /// let err = decoder.read_all_from_stdio(&mut data).expect_err("read should have failed");
+    /// assert!(matches!(err, ReadFromIoError::IoError(_)));
+    /// ```
     pub fn read_all_from_stdio<R: io::Read>(
         &mut self,
         mut r: R,
@@ -153,7 +284,19 @@ impl<Buf: BorrowMut<[u8]>> LengthPrefixDecoder<Buf> {
         }
     }
 
-    /// Reads from the given reader into the decoder's internal buffers
+    /// Attempts to read from the given `Read` source into the decoder.
+    ///
+    /// On success, returns how many bytes were read and a mutable slice of the complete message if fully available.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use std::io::Cursor;
+    /// # use rosenpass_util::length_prefix_encoding::decoder::{LengthPrefixDecoder, ReadFromIoReturn};
+    /// let mut data = Cursor::new([4u64.to_le_bytes().as_slice(), b"cats"].concat());
+    /// let mut decoder = LengthPrefixDecoder::new(vec![0; 8]);
+    /// decoder.read_from_stdio(&mut data).expect("read failed");
+    /// ```
     pub fn read_from_stdio<R: io::Read>(
         &mut self,
         mut r: R,
@@ -179,7 +322,12 @@ impl<Buf: BorrowMut<[u8]>> LengthPrefixDecoder<Buf> {
         })
     }
 
-    /// Gets the next buffer slice that can be written to
+    /// Returns the next slice of internal buffer that needs data.
+    ///
+    /// If the header is not yet fully read, returns the remaining part of the header buffer.
+    /// Otherwise, returns the remaining part of the message buffer if the message size is known.
+    ///
+    /// If no more data is needed (message fully read), returns `Ok(None)`.
     pub fn next_slice_to_write_to(&mut self) -> Result<Option<&mut [u8]>, MessageTooLargeError> {
         fn some_if_nonempty(buf: &mut [u8]) -> Option<&mut [u8]> {
             match buf.is_empty() {
@@ -202,7 +350,9 @@ impl<Buf: BorrowMut<[u8]>> LengthPrefixDecoder<Buf> {
         Ok(None)
     }
 
-    /// Advances the internal offset by the specified number of bytes
+    /// Advances the internal offset by `count` bytes.
+    ///
+    /// This checks that the offset does not exceed buffer or message limits.
     pub fn advance(&mut self, count: usize) -> Result<(), SanityError> {
         let off = self.off + count;
         let msg_off = off.saturating_sub(HEADER_SIZE);
@@ -220,7 +370,9 @@ impl<Buf: BorrowMut<[u8]>> LengthPrefixDecoder<Buf> {
         Ok(())
     }
 
-    /// Ensures that the internal message buffer is large enough for the message size in the header
+    /// Checks that the allocated message buffer is large enough for the message length.
+    ///
+    /// If the header is not fully read, this does nothing. If it is, ensures the buffer fits the message.
     pub fn ensure_sufficient_msg_buffer(&self) -> Result<(), MessageTooLargeError> {
         let buf_size = self.message_buffer().len();
         let msg_size = match self.get_header() {
@@ -230,53 +382,64 @@ impl<Buf: BorrowMut<[u8]>> LengthPrefixDecoder<Buf> {
         MessageTooLargeError::ensure(msg_size, buf_size)
     }
 
-    /// Returns a reference to the header buffer
+    /// Returns a reference to the header buffer.
     pub fn header_buffer(&self) -> &[u8] {
         &self.header[..]
     }
 
-    /// Returns a mutable reference to the header buffer
+    /// Returns a mutable reference to the header buffer.
     pub fn header_buffer_mut(&mut self) -> &mut [u8] {
         &mut self.header[..]
     }
 
-    /// Returns a reference to the message buffer
+    /// Returns a reference to the underlying message buffer.
     pub fn message_buffer(&self) -> &[u8] {
         self.buf.borrow()
     }
 
-    /// Returns a mutable reference to the message buffer
+    /// Returns a mutable reference to the underlying message buffer.
     pub fn message_buffer_mut(&mut self) -> &mut [u8] {
         self.buf.borrow_mut()
     }
 
-    /// Returns the number of bytes read so far
+    /// Returns a reference to the total number of bytes read so far.
     pub fn bytes_read(&self) -> &usize {
         &self.off
     }
 
-    /// Consumes the decoder and returns just the message buffer
+    /// Consumes the decoder and returns the underlying buffer.
+    ///
+    /// # Examples
+    /// ```
+    /// # use std::io::Cursor;
+    /// # use rosenpass_util::length_prefix_encoding::decoder::{LengthPrefixDecoder, ReadFromIoReturn};
+    /// let mut data = Cursor::new([4u64.to_le_bytes().as_slice(), b"cats"].concat());
+    /// let mut decoder = LengthPrefixDecoder::new(vec![0; 8]);
+    /// decoder.read_all_from_stdio(&mut data).expect("read failed");
+    /// let buffer: Vec<u8> = decoder.into_message_buffer();
+    /// assert_eq!(buffer, vec![99, 97, 116, 115, 0, 0, 0, 0]);
+    /// ```
     pub fn into_message_buffer(self) -> Buf {
         let Self { buf, .. } = self;
         buf
     }
 
-    /// Returns the current offset into the header buffer
+    /// Returns the current offset into the header buffer.
     pub fn header_buffer_offset(&self) -> usize {
         min(self.off, HEADER_SIZE)
     }
 
-    /// Returns the current offset into the message buffer
+    /// Returns the current offset into the message buffer.
     pub fn message_buffer_offset(&self) -> usize {
         self.off.saturating_sub(HEADER_SIZE)
     }
 
-    /// Returns whether a complete header has been read
+    /// Returns whether the header has been fully read.
     pub fn has_header(&self) -> bool {
         self.header_buffer_offset() == HEADER_SIZE
     }
 
-    /// Returns whether a complete message has been read
+    /// Returns `true` if the entire message has been read, `false` otherwise.
     pub fn has_message(&self) -> Result<bool, MessageTooLargeError> {
         self.ensure_sufficient_msg_buffer()?;
         let msg_size = match self.get_header() {
@@ -286,55 +449,55 @@ impl<Buf: BorrowMut<[u8]>> LengthPrefixDecoder<Buf> {
         Ok(self.message_buffer_avail().len() == msg_size)
     }
 
-    /// Returns a slice of the available data in the header buffer
+    /// Returns the currently read portion of the header.
     pub fn header_buffer_avail(&self) -> &[u8] {
         let off = self.header_buffer_offset();
         &self.header_buffer()[..off]
     }
 
-    /// Returns a mutable slice of the available data in the header buffer
+    /// Returns a mutable slice of the currently read portion of the header.
     pub fn header_buffer_avail_mut(&mut self) -> &mut [u8] {
         let off = self.header_buffer_offset();
         &mut self.header_buffer_mut()[..off]
     }
 
-    /// Returns a slice of the remaining space in the header buffer
+    /// Returns the remaining unread portion of the header.
     pub fn header_buffer_left(&self) -> &[u8] {
         let off = self.header_buffer_offset();
         &self.header_buffer()[off..]
     }
 
-    /// Returns a mutable slice of the remaining space in the header buffer
+    /// Returns a mutable slice of the remaining unread portion of the header.
     pub fn header_buffer_left_mut(&mut self) -> &mut [u8] {
         let off = self.header_buffer_offset();
         &mut self.header_buffer_mut()[off..]
     }
 
-    /// Returns a slice of the available data in the message buffer
+    /// Returns the currently read portion of the message.
     pub fn message_buffer_avail(&self) -> &[u8] {
         let off = self.message_buffer_offset();
         &self.message_buffer()[..off]
     }
 
-    /// Returns a mutable slice of the available data in the message buffer
+    /// Returns a mutable slice of the currently read portion of the message.
     pub fn message_buffer_avail_mut(&mut self) -> &mut [u8] {
         let off = self.message_buffer_offset();
         &mut self.message_buffer_mut()[..off]
     }
 
-    /// Returns a slice of the remaining space in the message buffer
+    /// Returns the remaining unread portion of the message buffer.
     pub fn message_buffer_left(&self) -> &[u8] {
         let off = self.message_buffer_offset();
         &self.message_buffer()[off..]
     }
 
-    /// Returns a mutable slice of the remaining space in the message buffer
+    /// Returns a mutable slice of the remaining unread portion of the message buffer.
     pub fn message_buffer_left_mut(&mut self) -> &mut [u8] {
         let off = self.message_buffer_offset();
         &mut self.message_buffer_mut()[off..]
     }
 
-    /// Returns the message size from the header if available
+    /// Returns the message size from the header if fully read.
     pub fn get_header(&self) -> Option<usize> {
         match self.header_buffer_offset() == HEADER_SIZE {
             false => None,
@@ -342,23 +505,23 @@ impl<Buf: BorrowMut<[u8]>> LengthPrefixDecoder<Buf> {
         }
     }
 
-    /// Returns the size of the message if header is available
+    /// Returns the message size if known (i.e., if the header is fully read).
     pub fn message_size(&self) -> Option<usize> {
         self.get_header()
     }
 
-    /// Returns the total size of the encoded message including header
+    /// Returns the total size of the encoded message (header + payload) if known.
     pub fn encoded_message_bytes(&self) -> Option<usize> {
         self.message_size().map(|sz| sz + HEADER_SIZE)
     }
 
-    /// Returns a slice of the message fragment if available
+    /// Returns the complete message fragment if the header is known and buffer is sufficient.
     pub fn message_fragment(&self) -> Result<Option<&[u8]>, MessageTooLargeError> {
         self.ensure_sufficient_msg_buffer()?;
         Ok(self.message_size().map(|sz| &self.message_buffer()[..sz]))
     }
 
-    /// Returns a mutable slice of the message fragment if available
+    /// Returns a mutable reference to the complete message fragment.
     pub fn message_fragment_mut(&mut self) -> Result<Option<&mut [u8]>, MessageTooLargeError> {
         self.ensure_sufficient_msg_buffer()?;
         Ok(self
@@ -366,14 +529,14 @@ impl<Buf: BorrowMut<[u8]>> LengthPrefixDecoder<Buf> {
             .map(|sz| &mut self.message_buffer_mut()[..sz]))
     }
 
-    /// Returns a slice of the available data in the message fragment
+    /// Returns the portion of the message fragment that has been filled so far.
     pub fn message_fragment_avail(&self) -> Result<Option<&[u8]>, MessageTooLargeError> {
         let off = self.message_buffer_avail().len();
         self.message_fragment()
             .map(|frag| frag.map(|frag| &frag[..off]))
     }
 
-    /// Returns a mutable slice of the available data in the message fragment
+    /// Returns a mutable portion of the message fragment that has been filled so far.
     pub fn message_fragment_avail_mut(
         &mut self,
     ) -> Result<Option<&mut [u8]>, MessageTooLargeError> {
@@ -382,28 +545,32 @@ impl<Buf: BorrowMut<[u8]>> LengthPrefixDecoder<Buf> {
             .map(|frag| frag.map(|frag| &mut frag[..off]))
     }
 
-    /// Returns a slice of the remaining space in the message fragment
+    /// Returns the remaining portion of the message fragment that still needs to be read.
     pub fn message_fragment_left(&self) -> Result<Option<&[u8]>, MessageTooLargeError> {
         let off = self.message_buffer_avail().len();
         self.message_fragment()
             .map(|frag| frag.map(|frag| &frag[off..]))
     }
 
-    /// Returns a mutable slice of the remaining space in the message fragment
+    /// Returns a mutable slice of the remaining portion of the message fragment that still needs to be read.
     pub fn message_fragment_left_mut(&mut self) -> Result<Option<&mut [u8]>, MessageTooLargeError> {
         let off = self.message_buffer_avail().len();
         self.message_fragment_mut()
             .map(|frag| frag.map(|frag| &mut frag[off..]))
     }
 
-    /// Returns a slice of the complete message if available
+    /// If the entire message is available, returns a reference to it.
+    ///
+    /// Otherwise returns `Ok(None)`.
     pub fn message(&self) -> Result<Option<&[u8]>, MessageTooLargeError> {
         let sz = self.message_size();
         self.message_fragment_avail()
             .map(|frag_opt| frag_opt.and_then(|frag| (frag.len() == sz?).then_some(frag)))
     }
 
-    /// Returns a mutable slice of the complete message if available
+    /// If the entire message is available, returns a mutable reference to it.
+    ///
+    /// Otherwise returns `Ok(None)`.
     pub fn message_mut(&mut self) -> Result<Option<&mut [u8]>, MessageTooLargeError> {
         let sz = self.message_size();
         self.message_fragment_avail_mut()
@@ -418,3 +585,107 @@ impl<Buf: BorrowMut<[u8]>> Zeroize for LengthPrefixDecoder<Buf> {
         self.off.zeroize();
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_read_from_stdio() {
+        use std::io::Cursor;
+        let mut data = {
+            let mut buf = Vec::new();
+            buf.extend_from_slice(&(8u64.to_le_bytes()));
+            buf.extend_from_slice(b"cats"); // provide only half of the message
+            Cursor::new(buf)
+        };
+
+        let mut decoder = LengthPrefixDecoder::new(vec![0; 9]);
+
+        fn loop_read(decoder: &mut LengthPrefixDecoder<Vec<u8>>, data: &mut Cursor<Vec<u8>>) {
+            // Read until the buffer is fully read
+            let data_len = data.get_ref().len();
+            loop {
+                let result: ReadFromIoReturn =
+                    decoder.read_from_stdio(&mut *data).expect("read failed");
+                if data.position() as usize == data_len {
+                    // the entire data was read
+                    break;
+                }
+                assert!(result.message.is_none());
+                assert!(result.bytes_read > 0); // at least 1 byte was read (or all data was read)
+            }
+        }
+
+        loop_read(&mut decoder, &mut data);
+
+        // INSERT HERE A TEST FOR EACH INTERNAL METHOD OF LengthPrefixDecoder (decoder)
+        assert_eq!(decoder.message_size(), Some(8));
+
+        // Header-related assertions
+        assert!(decoder.has_header());
+        assert_eq!(decoder.has_message().ok(), Some(false));
+        assert_eq!(decoder.header_buffer_offset(), HEADER_SIZE);
+        assert_eq!(decoder.header_buffer_avail().len(), HEADER_SIZE);
+        assert_eq!(decoder.header_buffer_left().len(), 0);
+        {
+            let header_buffer_mut: &mut [u8] = decoder.header_buffer_avail_mut();
+            assert_eq!(header_buffer_mut, &[8, 0, 0, 0, 0, 0, 0, 0]);
+            let header_buffer_ref: &[u8] = decoder.header_buffer_avail();
+            assert_eq!(header_buffer_ref, &[8, 0, 0, 0, 0, 0, 0, 0]);
+        }
+        assert_eq!(decoder.get_header(), Some(8));
+        assert_eq!(decoder.message_size(), Some(8));
+        assert_eq!(decoder.encoded_message_bytes(), Some(8 + HEADER_SIZE));
+
+        // Message-related assertions
+        assert_eq!(*decoder.bytes_read(), 12);
+        assert_eq!(decoder.message_buffer_offset(), 4); // "cats" is 4 bytes
+        assert_eq!(decoder.message_buffer_avail(), b"cats");
+        assert_eq!(decoder.message_buffer_avail_mut(), b"cats");
+        assert_eq!(decoder.message_buffer_left().len(), 5); // buffer size is 9, 4 read -> 5 left
+        assert_eq!(decoder.message_buffer_left_mut().len(), 5);
+        assert!(!decoder.has_message().unwrap()); // not fully read
+
+        // Message fragment assertions
+        let frag = decoder.message_fragment().unwrap().unwrap();
+        assert_eq!(frag.len(), 8); // full message fragment slice (not fully filled)
+        let frag_avail = decoder.message_fragment_avail().unwrap().unwrap();
+        assert_eq!(frag_avail, b"cats"); // available portion matches what's read
+        let frag_left = decoder.message_fragment_left().unwrap().unwrap();
+        assert_eq!(frag_left.len(), 4); // 4 bytes remain to complete the message
+        assert_eq!(decoder.message().unwrap(), None); // full message not yet available
+
+        // disassemble the decoder and reassemble it
+        let (header, buf, off) = decoder.clone().into_parts();
+        let mut decoder = LengthPrefixDecoder::from_parts(header, buf, off);
+
+        let mut data = Cursor::new(Vec::from(b"dogs"));
+        loop_read(&mut decoder, &mut data);
+
+        // After providing the remaining "dogs" data, the message should now be fully available.
+        assert!(decoder.has_message().unwrap());
+        assert_eq!(decoder.message().unwrap().unwrap(), b"catsdogs");
+
+        // At this point:
+        // - The entire message (8 bytes) plus the header (8 bytes for the length) should be accounted for.
+        assert_eq!(
+            decoder.message_fragment_avail().unwrap().unwrap(),
+            b"catsdogs"
+        );
+        assert!(decoder.message_fragment_left().unwrap().unwrap().is_empty());
+
+        // The offsets and buffers should reflect that everything is read.
+        assert_eq!(decoder.message_buffer_offset(), 8); // all 8 message bytes are now read
+        assert_eq!(decoder.message_buffer_avail(), b"catsdogs");
+        assert_eq!(decoder.message_buffer_left().len(), 1); // buffer size was 9, 8 read -> 1 left unused
+
+        // No more data needed to complete the message.
+        assert!(decoder.next_slice_to_write_to().unwrap().is_none());
+
+        // clear the decoder
+        decoder.clear();
+        assert_eq!(decoder.buf, vec![0; 9]);
+        assert_eq!(decoder.off, 0);
+        assert_eq!(decoder.header, [0; HEADER_SIZE]);
+    }
+}

util/src/lib.rs

@@ -22,7 +22,7 @@ pub mod io;
 pub mod length_prefix_encoding;
 /// Memory manipulation and allocation utilities.
 pub mod mem;
-/// MIO integration utilities.
+/// [MIO (Metal I/O)](https://docs.rs/crate/mio/) integration utilities.
 pub mod mio;
 /// Extended Option type functionality.
 pub mod option;

util/src/mem.rs

@@ -1,10 +1,33 @@
+//!
+//! This module provides functions for copying data, concatenating byte arrays,
+//! and various traits and types that help manage values, including preventing
+//! drops, discarding results, and swapping values.
+
 use std::borrow::{Borrow, BorrowMut};
 use std::cmp::min;
 use std::mem::{forget, swap};
 use std::ops::{Deref, DerefMut};
 
-/// Concatenate two byte arrays
 // TODO: Zeroize result?
+/// Concatenate multiple byte slices into a fixed-size byte array.
+///
+/// # Panics
+///
+/// Panics if the concatenated length does not match the declared length.
+///
+/// # Examples
+///
+/// ```rust
+/// use rosenpass_util::cat;
+/// let arr = cat!(6; b"abc", b"def");
+/// assert_eq!(&arr, b"abcdef");
+///
+/// let err = std::panic::catch_unwind(|| cat!(5; b"abc", b"def"));
+/// assert!(matches!(err, Err(_)));
+///
+/// let err = std::panic::catch_unwind(|| cat!(7; b"abc", b"def"));
+/// assert!(matches!(err, Err(_)));
+/// ```
 #[macro_export]
 macro_rules! cat {
     ($len:expr; $($toks:expr),+) => {{
@@ -22,12 +45,37 @@ macro_rules! cat {
 }
 
 // TODO: consistent inout ordering
-/// Copy all bytes from `src` to `dst`. The lengths must match.
+/// Copy bytes from `src` to `dst`, requiring equal lengths.
+///
+/// # Panics
+///
+/// Panics if lengths differ.
+///
+/// # Examples
+///
+/// ```rust
+/// use rosenpass_util::mem::cpy;
+/// let src = [1, 2, 3];
+/// let mut dst = [0; 3];
+/// cpy(&src, &mut dst);
+/// assert_eq!(dst, [1, 2, 3]);
+/// ```
 pub fn cpy<T: BorrowMut<[u8]> + ?Sized, F: Borrow<[u8]> + ?Sized>(src: &F, dst: &mut T) {
     dst.borrow_mut().copy_from_slice(src.borrow());
 }
 
-/// Copy from `src` to `dst`. If `src` and `dst` are not of equal length, copy as many bytes as possible.
+/// Copy from `src` to `dst`. If `src` and `dst` are not of equal length,
+/// copy as many bytes as possible.
+///
+/// # Examples
+///
+/// ```rust
+/// use rosenpass_util::mem::cpy_min;
+/// let src = [1, 2, 3, 4];
+/// let mut dst = [0; 2];
+/// cpy_min(&src, &mut dst);
+/// assert_eq!(dst, [1, 2]);
+/// ```
 pub fn cpy_min<T: BorrowMut<[u8]> + ?Sized, F: Borrow<[u8]> + ?Sized>(src: &F, dst: &mut T) {
     let src = src.borrow();
     let dst = dst.borrow_mut();
@@ -35,20 +83,30 @@ pub fn cpy_min<T: BorrowMut<[u8]> + ?Sized, F: Borrow<[u8]> + ?Sized>(src: &F, d
     dst[..len].copy_from_slice(&src[..len]);
 }
 
-/// Wrapper type to inhibit calling [std::mem::Drop] when the underlying variable is freed
+/// Wrapper type to inhibit calling [std::mem::Drop] when the underlying
+/// variable is freed
+///
+/// # Examples
+///
+/// ```rust
+/// use rosenpass_util::mem::Forgetting;
+/// let f = Forgetting::new(String::from("hello"));
+/// assert_eq!(&*f, "hello");
+/// let val = f.extract();
+/// assert_eq!(val, "hello");
+/// ```
 #[derive(PartialEq, Eq, PartialOrd, Ord, Debug, Clone, Default)]
 pub struct Forgetting<T> {
     value: Option<T>,
 }
 
 impl<T> Forgetting<T> {
-    /// Creates a new `Forgetting<T>` instance containing the given value.
+    /// Create a new `Forgetting` wrapping `value`.
     pub fn new(value: T) -> Self {
-        let value = Some(value);
-        Self { value }
+        Self { value: Some(value) }
     }
 
-    /// Extracts and returns the contained value, consuming self.
+    /// Consume and return the inner value.
     pub fn extract(mut self) -> T {
         let mut value = None;
         swap(&mut value, &mut self.value);
@@ -97,6 +155,13 @@ impl<T> Drop for Forgetting<T> {
 }
 
 /// A trait that provides a method to discard a value without explicitly handling its results.
+///
+/// # Examples
+///
+/// ```rust
+/// # use rosenpass_util::mem::DiscardResultExt;
+/// let result: () = (|| { return 42 })().discard_result(); // Just discard
+/// ```
 pub trait DiscardResultExt {
     /// Consumes and discards a value without doing anything with it.
     fn discard_result(self);
@@ -107,8 +172,16 @@ impl<T> DiscardResultExt for T {
 }
 
 /// Trait that provides a method to explicitly forget values.
+///
+/// # Examples
+///
+/// ```rust
+/// # use rosenpass_util::mem::ForgetExt;
+/// let s = String::from("no drop");
+/// s.forget(); // destructor not run
+/// ```
 pub trait ForgetExt {
-    /// Consumes and forgets a value, preventing its destructor from running.
+    /// Forget the value.
     fn forget(self);
 }
 
@@ -119,10 +192,23 @@ impl<T> ForgetExt for T {
 }
 
 /// Extension trait that provides methods for swapping values.
+///
+/// # Examples
+///
+/// ```rust
+/// use rosenpass_util::mem::SwapWithExt;
+/// let mut x = 10;
+/// let mut y = x.swap_with(20);
+/// assert_eq!(x, 20);
+/// assert_eq!(y, 10);
+/// y.swap_with_mut(&mut x);
+/// assert_eq!(x, 10);
+/// assert_eq!(y, 20);
+/// ```
 pub trait SwapWithExt {
-    /// Takes ownership of `other` and swaps its value with `self`, returning the original value.
+    /// Swap values and return the old value of `self`.
     fn swap_with(&mut self, other: Self) -> Self;
-    /// Swaps the values between `self` and `other` in place.
+    /// Swap values in place with another mutable reference.
     fn swap_with_mut(&mut self, other: &mut Self);
 }
 
@@ -138,8 +224,18 @@ impl<T> SwapWithExt for T {
 }
 
 /// Extension trait that provides methods for swapping values with default values.
+///
+/// # Examples
+///
+/// ```rust
+/// # use rosenpass_util::mem::SwapWithDefaultExt;
+/// let mut s = String::from("abc");
+/// let old = s.swap_with_default();
+/// assert_eq!(old, "abc");
+/// assert_eq!(s, "");
+/// ```
 pub trait SwapWithDefaultExt {
-    /// Takes the current value and replaces it with the default value, returning the original.
+    /// Swap with `Self::default()`.
     fn swap_with_default(&mut self) -> Self;
 }
 
@@ -150,6 +246,26 @@ impl<T: Default> SwapWithDefaultExt for T {
 }
 
 /// Extension trait that provides a method to explicitly move values.
+///
+/// # Examples
+///
+/// ```rust
+/// # use std::rc::Rc;
+/// use rosenpass_util::mem::MoveExt;
+/// let val = 42;
+/// let another_val = val.move_here();
+/// assert_eq!(another_val, 42);
+/// // val is now inaccessible
+///
+/// let value = Rc::new(42);
+/// let clone = Rc::clone(&value);
+///
+/// assert_eq!(Rc::strong_count(&value), 2);
+///
+/// clone.move_here(); // this will drop the second reference
+///
+/// assert_eq!(Rc::strong_count(&value), 1);
+/// ```
 pub trait MoveExt {
     /// Deliberately move the value
     ///
@@ -163,3 +279,29 @@ impl<T: Sized> MoveExt for T {
         self
     }
 }
+
+#[cfg(test)]
+mod test_forgetting {
+    use crate::mem::Forgetting;
+    use std::sync::atomic::AtomicBool;
+    use std::sync::atomic::Ordering::SeqCst;
+    use std::sync::Arc;
+
+    #[test]
+    fn test_forgetting() {
+        let drop_was_called = Arc::new(AtomicBool::new(false));
+        struct SetFlagOnDrop(Arc<AtomicBool>);
+        impl Drop for SetFlagOnDrop {
+            fn drop(&mut self) {
+                self.0.store(true, SeqCst);
+            }
+        }
+        drop(SetFlagOnDrop(drop_was_called.clone()));
+        assert!(drop_was_called.load(SeqCst));
+        // reset flag and use Forgetting
+        drop_was_called.store(false, SeqCst);
+        let forgetting = Forgetting::new(SetFlagOnDrop(drop_was_called.clone()));
+        drop(forgetting);
+        assert_eq!(drop_was_called.load(SeqCst), false);
+    }
+}

util/src/mio/mio.rs

@@ -6,7 +6,7 @@ use crate::{
     result::OkExt,
 };
 
-/// Module containing I/O interest flags for Unix operations
+/// Module containing I/O interest flags for Unix operations (see also: [mio::Interest])
 pub mod interest {
     use mio::Interest;
 
@@ -20,9 +20,48 @@ pub mod interest {
     pub const RW: Interest = R.add(W);
 }
 
-/// Extension trait providing additional functionality for Unix listener
+/// Extension trait providing additional functionality for a Unix listener
+///
+/// # Example
+///
+/// ```rust
+/// use mio::net::{UnixListener, UnixStream};
+/// use rosenpass_util::mio::{UnixListenerExt, UnixStreamExt};
+///
+/// use std::os::unix::io::{AsRawFd, IntoRawFd, RawFd};
+/// use std::path::Path;
+///
+/// // This would be the UDS created by an external source
+/// let socket_path = "/tmp/rp_mio_uds_test_socket";
+/// if Path::new(socket_path).exists() {
+///     std::fs::remove_file(socket_path).expect("Failed to remove existing socket");
+/// }
+///
+/// // An extended MIO listener can then be created by claiming the existing socket
+/// // Note that the original descriptor is not reused, but copied before claiming it here
+/// let listener = UnixListener::bind(socket_path).unwrap();
+/// let listener_fd: RawFd = listener.as_raw_fd();
+/// let ext_listener = <UnixListener as UnixListenerExt>
+///     ::claim_fd(listener_fd).expect("Failed to claim_fd for ext_listener socket");
+///
+/// // Similarly, "client" connections can be established by claiming existing sockets
+/// // Note that in this case, the file descriptor will be reused (safety implications!)
+/// let stream = UnixStream::connect(socket_path).unwrap();
+/// let stream_fd = stream.into_raw_fd();
+/// let ext_stream = <UnixStream as UnixStreamExt>
+///     ::claim_fd_inplace(stream_fd).expect("Failed to claim_fd_inplace for ext_stream socket");
+///
+/// // Handle accepted connections...
+/// ext_listener.accept().expect("Failed to accept incoming connection");
+///
+/// // Send or receive messages ...
+///
+/// // Cleanup, shutdown etc. goes here ...
+/// std::fs::remove_file(socket_path).unwrap();
+/// ```
 pub trait UnixListenerExt: Sized {
     /// Creates a new Unix listener by claiming ownership of a raw file descriptor
+    /// (see [fd::claim_fd](crate::fd::claim_fd))
     fn claim_fd(fd: RawFd) -> anyhow::Result<Self>;
 }
 
@@ -36,15 +75,17 @@ impl UnixListenerExt for UnixListener {
     }
 }
 
-/// Extension trait providing additional functionality for Unix streams
+/// Extension trait providing additional functionality for a Unix stream
 pub trait UnixStreamExt: Sized {
     /// Creates a new Unix stream from an owned file descriptor
     fn from_fd(fd: OwnedFd) -> anyhow::Result<Self>;
 
     /// Claims ownership of a raw file descriptor and creates a new Unix stream
+    /// (see [fd::claim_fd](crate::fd::claim_fd))
     fn claim_fd(fd: RawFd) -> anyhow::Result<Self>;
 
     /// Claims ownership of a raw file descriptor in place and creates a new Unix stream
+    ///  (see [fd::claim_fd_inplace](crate::fd::claim_fd_inplace))
     fn claim_fd_inplace(fd: RawFd) -> anyhow::Result<Self>;
 }
 

util/src/mio/uds_recv_fd.rs

@@ -12,6 +12,58 @@ use crate::fd::{claim_fd_inplace, IntoStdioErr};
 /// A wrapper around a socket that combines reading from the socket with tracking
 /// received file descriptors. Limits the maximum number of file descriptors that
 /// can be received in a single read operation via the `MAX_FDS` parameter.
+///
+/// # Example
+///
+/// ```rust
+/// use std::collections::VecDeque;
+/// use std::io::Cursor;
+/// use std::io::Read;
+/// use std::os::fd::AsRawFd;
+/// use std::os::fd::OwnedFd;
+///
+/// use mio::net::UnixStream;
+/// use rosenpass_util::mio::ReadWithFileDescriptors;
+/// use rosenpass_util::io::TryIoResultKindHintExt;
+///
+/// const MAX_REQUEST_FDS : usize = 2; // Limit to 2 descriptors per read operation
+/// let mut read_fd_buffer = VecDeque::<OwnedFd>::new(); // File descriptor queue
+///
+/// // In this case, the unused writable end of the connection can be ignored
+/// let (io_stream, _) = UnixStream::pair().expect("failed to create socket pair");
+///
+/// // Wait until the output stream is writable...
+///
+/// // Wrap the socket to start tracking received file descriptors
+/// let mut fd_passing_sock = ReadWithFileDescriptors::<MAX_REQUEST_FDS, UnixStream, _, _>::new(
+///	&io_stream,
+///	&mut read_fd_buffer,
+/// );
+////
+/// // Simulated reads; the actual operations will depend on the protocol (implementation details)
+/// let mut recv_buffer = Vec::<u8>::new();
+/// let bytes_read = fd_passing_sock.read(&mut recv_buffer[..]).expect("error reading from socket");
+/// assert_eq!(bytes_read, 0);
+/// assert_eq!(&recv_buffer[..bytes_read], []);
+///
+/// // Alternatively, it's possible to use the try_io_err_kind_hint utility provided by this crate
+/// match fd_passing_sock.read(&mut recv_buffer).try_io_err_kind_hint() {
+///     Err(_) => {
+///         // Handle errors here ...
+///     }
+///     Ok(result) => {
+///         // Process messages here ...
+///         assert_eq!(0, result); // Nothing to read in this example
+///     }
+/// };
+///
+/// // The wrapped components can still be accessed
+/// assert_eq!(fd_passing_sock.socket().as_raw_fd(), io_stream.as_raw_fd());
+/// let (socket, fd_queue) = fd_passing_sock.into_parts();
+/// assert_eq!(socket.as_raw_fd(), io_stream.as_raw_fd());
+///
+/// // Shutdown, cleanup, etc. goes here ...
+/// ```
 pub struct ReadWithFileDescriptors<const MAX_FDS: usize, Sock, BorrowSock, BorrowFds>
 where
     Sock: FdPassingExt,

util/src/result.rs

@@ -1,6 +1,24 @@
 use std::convert::Infallible;
 
 /// Try block basically…returns a result and allows the use of the question mark operator inside
+///
+/// # Examples
+/// ```rust
+/// # use anyhow::Result;
+/// # use rosenpass_util::attempt;
+/// let result: Result<i32> = attempt!({
+///     let x = 42;
+///     Ok(x)
+/// });
+///
+/// assert_eq!(result.unwrap(), 42);
+///
+/// let error_result: Result<()> = attempt!({
+///     Err(anyhow::anyhow!("some error"))
+/// });
+///
+/// assert!(error_result.is_err());
+/// ```
 #[macro_export]
 macro_rules! attempt {
     ($block:expr) => {
@@ -9,6 +27,19 @@ macro_rules! attempt {
 }
 
 /// Trait for the ok operation, which provides a way to convert a value into a Result
+/// # Examples
+/// ```rust
+/// # use rosenpass_util::result::OkExt;
+/// let value: i32 = 42;
+/// let result: Result<i32, &str> = value.ok();
+///
+/// assert_eq!(result, Ok(42));
+///
+/// let value = "hello";
+/// let result: Result<&str, &str> = value.ok();
+///
+/// assert_eq!(result, Ok("hello"));
+/// ```
 pub trait OkExt<E>: Sized {
     /// Wraps a value in a Result::Ok variant
     fn ok(self) -> Result<Self, E>;
@@ -26,6 +57,11 @@ impl<T, E> OkExt<E> for T {
 /// the function will not panic.
 ///
 /// Implementations must not panic.
+/// # Examples
+/// ```
+/// # use rosenpass_util::result::GuaranteedValue;
+/// let x:u32 = 10u8.try_into().guaranteed();
+/// ```
 pub trait GuaranteedValue {
     /// The value type that will be returned by guaranteed()
     type Value;

util/src/typenum.rs

@@ -3,7 +3,23 @@ use typenum::int::{NInt, PInt, Z0};
 use typenum::marker_traits as markers;
 use typenum::uint::{UInt, UTerm};
 
-/// Convenience macro to convert type numbers to constant integers
+/// Convenience macro to convert [`typenum`] type numbers to constant integers.
+///
+/// This macro takes a [`typenum`] type-level integer (like `U5`, `P3`, or `N7`)
+/// and converts it into its equivalent constant integer value at compile time.
+/// By default, it converts to a suitable unsigned integer type, but you can
+/// specify a target type explicitly using `typenum2const!(Type as i32)`,
+/// for example.
+///
+/// # Examples
+///
+/// ```rust
+/// # use typenum::consts::U10;
+/// # use rosenpass_util::typenum2const;
+///
+/// const TEN: u32 = typenum2const!(U10 as u32);
+/// assert_eq!(TEN, 10);
+/// ```
 #[macro_export]
 macro_rules! typenum2const {
     ($val:ty) => {
@@ -14,35 +30,80 @@ macro_rules! typenum2const {
     };
 }
 
-/// Trait implemented by constant integers to facilitate conversion to constant integers
+/// A trait implemented by type-level integers to facilitate their conversion
+/// into constant values.
+///
+/// Types from the [`typenum`] crate (like `U5`, `P3`, or `N7`) can implement
+/// `IntoConst` to produce a compile-time constant integer of the specified
+/// type. This trait is part of the underlying mechanism used by the
+/// [`crate::typenum2const`] macro.
+///
+/// # Examples
+///
+/// ```rust
+/// use rosenpass_util::typenum2const;
+/// use typenum::consts::U42;
+/// use rosenpass_util::typenum::IntoConst;
+///
+/// // Directly using IntoConst:
+/// const VALUE: u64 = <U42 as IntoConst<u64>>::VALUE;
+/// assert_eq!(VALUE, 42);
+///
+/// // Or via the macro:
+/// const VALUE_MACRO: u64 = typenum2const!(U42 as u64);
+/// assert_eq!(VALUE_MACRO, 42);
+/// ```
 pub trait IntoConst<T> {
-    /// The constant value after conversion
+    /// The constant value after conversion.
     const VALUE: T;
 }
 
 #[allow(dead_code)]
+/// Internal struct for applying a negative sign to an unsigned type-level integer during conversion.
+///
+/// This is part of the implementation detail for signed conversions. It uses
+/// [`AssociatedUnsigned`] to determine the underlying unsigned type and negates its value.
 struct ConstApplyNegSign<T: AssociatedUnsigned, Param: IntoConst<<T as AssociatedUnsigned>::Type>>(
     *const T,
     *const Param,
 );
 
 #[allow(dead_code)]
+/// Internal struct for applying a positive sign to an unsigned type-level integer during conversion.
+///
+/// This is used as part of converting a positive signed type-level integer to its runtime integer
+/// value, ensuring that the correct unsigned representation is known via [`AssociatedUnsigned`].
 struct ConstApplyPosSign<T: AssociatedUnsigned, Param: IntoConst<<T as AssociatedUnsigned>::Type>>(
     *const T,
     *const Param,
 );
 
 #[allow(dead_code)]
-struct ConstLshift<T, Param: IntoConst<T>, const SHIFT: i32>(*const T, *const Param); // impl IntoConst<T>
+/// Internal struct representing a left-shift operation on a type-level integer.
+///
+/// Used as part of compile-time computations. `SHIFT` determines how many bits the value will be
+/// shifted to the left.
+struct ConstLshift<T, Param: IntoConst<T>, const SHIFT: i32>(*const T, *const Param);
 
 #[allow(dead_code)]
-struct ConstAdd<T, Lhs: IntoConst<T>, Rhs: IntoConst<T>>(*const T, *const Lhs, *const Rhs); // impl IntoConst<T>
+/// Internal struct representing an addition operation between two type-level integers.
+///
+/// `ConstAdd` is another building block for compile-time arithmetic on type-level integers before
+/// their conversion to runtime constants.
+struct ConstAdd<T, Lhs: IntoConst<T>, Rhs: IntoConst<T>>(*const T, *const Lhs, *const Rhs);
 
-/// Assigns an unsigned type to a signed type
+/// Associates an unsigned type with a signed type, enabling conversions between signed and unsigned
+/// representations of compile-time integers.
+///
+/// This trait is used internally to facilitate the conversion of signed [`typenum`] integers by
+/// referencing their underlying unsigned representation.
 trait AssociatedUnsigned {
+    /// The associated unsigned type.
     type Type;
 }
 
+/// Internal macro implementing the [`IntoConst`] trait for a given mapping from a type-level integer
+/// to a concrete integer type.
 macro_rules! impl_into_const {
     ( $from:ty as $to:ty := $impl:expr) => {
         impl IntoConst<$to> for $from {
@@ -51,6 +112,10 @@ macro_rules! impl_into_const {
     };
 }
 
+/// Internal macro implementing common `IntoConst` logic for various numeric types.
+///
+/// It sets up `Z0`, `B0`, `B1`, `UTerm`, and also provides default implementations for
+/// `ConstLshift` and `ConstAdd`.
 macro_rules! impl_numeric_into_const_common {
     ($type:ty) => {
         impl_into_const! { Z0 as $type := 0 }
@@ -73,6 +138,10 @@ macro_rules! impl_numeric_into_const_common {
     };
 }
 
+/// Internal macro implementing `IntoConst` for unsigned integer types.
+///
+/// It sets up conversions for multiple unsigned integer target types and
+/// provides the positive sign application implementation.
 macro_rules! impl_numeric_into_const_unsigned {
     ($($to_list:ty),*) =>  {
         $( impl_numeric_into_const_unsigned! { @impl $to_list } )*
@@ -91,6 +160,9 @@ macro_rules! impl_numeric_into_const_unsigned {
     };
 }
 
+/// Internal macro implementing `IntoConst` for signed integer types.
+///
+/// It uses their associated unsigned types to handle positive and negative conversions correctly.
 macro_rules! impl_numeric_into_const_signed {
     ($($to_list:ty : $unsigned_list:ty),*) =>  {
         $( impl_numeric_into_const_signed! { @impl $to_list : $unsigned_list} )*
@@ -110,9 +182,8 @@ macro_rules! impl_numeric_into_const_signed {
         impl<Param: IntoConst<$unsigned>> IntoConst<$type> for ConstApplyNegSign<$type, Param> {
             const VALUE : $type =
                 if Param::VALUE == (1 as $unsigned).rotate_right(1) {
-                    // Handle the negative value without an associated positive value (e.g. -128
-                    // for i8)
-                    < $type >::MIN
+                    // Handling negative values at boundaries, such as i8::MIN
+                    <$type>::MIN
                 } else {
                     -(Param::VALUE as $type)
                 };
@@ -122,10 +193,10 @@ macro_rules! impl_numeric_into_const_signed {
 
 impl_into_const! { B0 as bool := false }
 impl_into_const! { B1 as bool := true }
+
 impl_numeric_into_const_unsigned! { usize, u8, u16, u32, u64, u128 }
 impl_numeric_into_const_signed! { isize : usize, i8 : u8, i16 : u16, i32 : u32, i64 : u64, i128 : u128 }
 
-// Unsigned type numbers to const integers
 impl<Ret, Rest, Bit> IntoConst<Ret> for UInt<Rest, Bit>
 where
     Rest: IntoConst<Ret>,
@@ -133,26 +204,28 @@ where
     ConstLshift<Ret, Rest, 1>: IntoConst<Ret>,
     ConstAdd<Ret, ConstLshift<Ret, Rest, 1>, Bit>: IntoConst<Ret>,
 {
+    /// Converts an unsigned [`UInt`] typenum into its corresponding constant integer by
+    /// decomposing it into shifts and additions on its subparts.
     const VALUE: Ret = <ConstAdd<Ret, ConstLshift<Ret, Rest, 1>, Bit> as IntoConst<Ret>>::VALUE;
 }
 
-// Signed type numbers with positive sign to const integers
 impl<Ret, Unsigned> IntoConst<Ret> for PInt<Unsigned>
 where
     Ret: AssociatedUnsigned,
     Unsigned: markers::Unsigned + markers::NonZero + IntoConst<<Ret as AssociatedUnsigned>::Type>,
     ConstApplyPosSign<Ret, Unsigned>: IntoConst<Ret>,
 {
+    /// Converts a positive signed [`PInt`] typenum into its corresponding constant integer.
     const VALUE: Ret = <ConstApplyPosSign<Ret, Unsigned> as IntoConst<Ret>>::VALUE;
 }
 
-// Signed type numbers with negative sign to const integers
 impl<Ret, Unsigned> IntoConst<Ret> for NInt<Unsigned>
 where
     Ret: AssociatedUnsigned,
     Unsigned: markers::Unsigned + markers::NonZero + IntoConst<<Ret as AssociatedUnsigned>::Type>,
     ConstApplyNegSign<Ret, Unsigned>: IntoConst<Ret>,
 {
+    /// Converts a negative signed [`NInt`] typenum into its corresponding constant integer.
     const VALUE: Ret = <ConstApplyNegSign<Ret, Unsigned> as IntoConst<Ret>>::VALUE;
 }
 

util/src/zerocopy/mod.rs

@@ -1,3 +1,20 @@
+//! This module provides utilities for working with zero-copy references
+//! and slices.
+//!
+//! It offers the following primary abstractions and traits:
+//!
+//! - [`RefMaker`](crate::zerocopy::RefMaker): A helper structure for safely
+//! creating `zerocopy::Ref` references from byte slices.
+//! - [`ZerocopyEmancipateExt`](crate::zerocopy::ZerocopyEmancipateExt):
+//! A trait to convert `Ref<B, T>` into a borrowed `Ref<&[u8], T>`.
+//! - [`ZerocopyEmancipateMutExt`](crate::zerocopy::ZerocopyEmancipateMutExt):
+//! A trait to convert `Ref<B, T>` into a borrowed mutable `Ref<&mut [u8], T>`.
+//! - [`ZerocopySliceExt`](crate::zerocopy::ZerocopySliceExt): Extension methods
+//! for parsing byte slices into zero-copy references.
+//! - [`ZerocopyMutSliceExt`](crate::zerocopy::ZerocopyMutSliceExt):
+//! Extension methods for parsing and zeroizing byte slices into zero-copy
+//! references.
+
 mod ref_maker;
 mod zerocopy_ref_ext;
 mod zerocopy_slice_ext;

util/src/zerocopy/ref_maker.rs

@@ -1,74 +1,206 @@
-use std::marker::PhantomData;
+//! A module providing the [`RefMaker`] type and its associated methods for constructing
+//! [`zerocopy::Ref`] references from byte buffers.
 
 use anyhow::{ensure, Context};
+use std::marker::PhantomData;
 use zerocopy::{ByteSlice, ByteSliceMut, Ref};
 use zeroize::Zeroize;
 
 use crate::zeroize::ZeroizedExt;
 
+/// A convenience type for working with buffers and extracting [`zerocopy::Ref`]
+/// references.
+///
+/// `RefMaker` holds a buffer and a target type parameter `T`. Using `RefMaker`,
+/// you can validate that the provided buffer is large enough for `T` and then
+/// parse out a strongly-typed reference (`Ref`) to that data. It also provides
+/// methods for extracting prefixes and suffixes from the buffer.
+///
+/// # Example
+///
+/// ```
+/// # use zerocopy::{AsBytes, FromBytes, FromZeroes, Ref};///
+/// # use rosenpass_util::zerocopy::RefMaker;
+///
+/// #[derive(FromBytes, FromZeroes, AsBytes)]
+/// #[repr(C)]
+/// struct Header {
+///     field1: u32,
+///     field2: u16,
+///     field3: u16,
+/// }
+/// #[repr(align(4))]
+/// struct AlignedBuf([u8; 8]);
+/// let bytes = AlignedBuf([0xAA, 0xBB, 0xCC, 0xDD,
+/// 0x00, 0x10, 0x20, 0x30]);
+/// let rm = RefMaker::<&[u8], Header>::new(&bytes.0);
+/// let header_ref: Ref<&[u8], Header> = rm.parse().unwrap();
+/// assert_eq!(header_ref.field1, 0xDDCCBBAA);
+/// assert_eq!(header_ref.field2, 0x1000);
+/// assert_eq!(header_ref.field3, 0x3020);
+/// ```
 #[derive(Clone, Copy, Debug)]
-/// A convenience type for working with mutable references to a buffer and an
-/// expected target type.
 pub struct RefMaker<B: Sized, T> {
     buf: B,
     _phantom_t: PhantomData<T>,
 }
 
 impl<B, T> RefMaker<B, T> {
-    /// Creates a new RefMaker with the given buffer
+    /// Creates a new `RefMaker` with the given buffer.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use rosenpass_util::zerocopy::RefMaker;
+    /// let buffer = [0u8; 10];
+    /// let rm: RefMaker<_, u32> = RefMaker::new(buffer);
+    /// ```
     pub fn new(buf: B) -> Self {
         let _phantom_t = PhantomData;
         Self { buf, _phantom_t }
     }
 
-    /// Returns the size in bytes needed for target type T
+    /// Returns the size in bytes required by the target type `T`.
+    /// This is currently defined as [`std::mem::size_of::<T>`] of `T`.
     pub const fn target_size() -> usize {
         std::mem::size_of::<T>()
     }
 
-    /// Consumes this RefMaker and returns the inner buffer
+    /// Consumes this `RefMaker` and returns the inner buffer.
     pub fn into_buf(self) -> B {
         self.buf
     }
 
-    /// Returns a reference to the inner buffer
+    /// Returns a reference to the inner buffer.
     pub fn buf(&self) -> &B {
         &self.buf
     }
 
-    /// Returns a mutable reference to the inner buffer
+    /// Returns a mutable reference to the inner buffer.
     pub fn buf_mut(&mut self) -> &mut B {
         &mut self.buf
     }
 }
 
 impl<B: ByteSlice, T> RefMaker<B, T> {
-    /// Parses the buffer into a reference of type T
+    /// Parses the buffer into a [`zerocopy::Ref<B, T>`].
+    ///
+    /// This will fail if the buffer is smaller than `size_of::<T>`.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the buffer is undersized or if parsing fails.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use zerocopy::{AsBytes, FromBytes, FromZeroes, Ref};
+    /// # use rosenpass_util::zerocopy::RefMaker;
+    ///
+    /// #[derive(FromBytes, FromZeroes, AsBytes, Debug)]
+    /// #[repr(C)]
+    /// struct Data(u32);
+    ///
+    /// let bytes: &[u8] = &[0x01, 0x00, 0x00, 0x00];
+    /// let data_ref: Ref<&[u8], Data> = RefMaker::<_, Data>::new(bytes).parse().unwrap();
+    /// assert_eq!(data_ref.0, 1);
+    ///
+    /// // errors if buffer is undersized
+    /// let bytes: &[u8] = &[0x01, 0x02, 0x03];
+    /// let parse_error = RefMaker::<_, Data>::new(bytes).parse()
+    ///     .expect_err("Should error");
+    /// assert_eq!(parse_error.to_string(),
+    ///     "Buffer is undersized at 3 bytes (need 4 bytes)!");
+    ///
+    /// // errors if the byte buffer is misaligned
+    /// let bytes = [1u8, 2, 3, 4, 5, 6, 7, 8];
+    /// let parse_error = RefMaker::<_, Data>::new(&bytes[1..5]).parse()
+    ///     .expect_err("Should error");
+    /// assert_eq!(parse_error.to_string(), "Parser error!");
+    /// ```
     pub fn parse(self) -> anyhow::Result<Ref<B, T>> {
         self.ensure_fit()?;
         Ref::<B, T>::new(self.buf).context("Parser error!")
     }
 
-    /// Splits the buffer into a RefMaker containing the first `target_size` bytes and the remaining tail
+    /// Splits the internal buffer into a `RefMaker` containing a buffer with
+    /// exactly `size_of::<T>()` bytes and the remaining tail of the previous
+    /// internal buffer.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the buffer is undersized.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use rosenpass_util::zerocopy::RefMaker;
+    /// let bytes: &[u8] = &[1,2,3,4,5,6,7,8];
+    /// let (prefix_rm, tail) = RefMaker::<_, u32>::new(bytes).from_prefix_with_tail().unwrap();
+    /// assert_eq!(prefix_rm.bytes(), &[1,2,3,4]);
+    /// assert_eq!(tail, &[5,6,7,8]);
+    /// ```
     pub fn from_prefix_with_tail(self) -> anyhow::Result<(Self, B)> {
         self.ensure_fit()?;
         let (head, tail) = self.buf.split_at(Self::target_size());
         Ok((Self::new(head), tail))
     }
 
-    /// Splits the buffer into two RefMakers, with the first containing the first `target_size` bytes
+    /// Splits the buffer into two `RefMaker`s, with the first containing the
+    /// first `size_of::<T>()` bytes and the second containing the remaining
+    /// tail buffer.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the buffer is undersized.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use rosenpass_util::zerocopy::RefMaker;
+    /// let bytes: &[u8] = &[1,2,3,4,5,6,7,8,9,10];
+    /// let (prefix_rm, tail) = RefMaker::<_, u32>::new(bytes).split_prefix().unwrap();
+    /// assert_eq!(prefix_rm.bytes(), &[1,2,3,4]);
+    /// assert_eq!(tail.bytes(), &[5,6,7,8,9,10]);
+    /// ```
     pub fn split_prefix(self) -> anyhow::Result<(Self, Self)> {
         self.ensure_fit()?;
         let (head, tail) = self.buf.split_at(Self::target_size());
         Ok((Self::new(head), Self::new(tail)))
     }
 
-    /// Returns a RefMaker containing only the first `target_size` bytes
+    /// Returns a `RefMaker` containing only the first `size_of::<T>()` bytes.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the buffer is undersized.
+    ///
+    /// # Example
+    /// ```
+    /// # use rosenpass_util::zerocopy::RefMaker;
+    /// let bytes: &[u8] = &[1,2,3,4,5,6,7,8,9,10];
+    /// let prefix_rm = RefMaker::<_, u32>::new(bytes).from_prefix().unwrap();
+    /// assert_eq!(prefix_rm.bytes(), &[1,2,3,4]);
+    /// ```
     pub fn from_prefix(self) -> anyhow::Result<Self> {
         Ok(Self::from_prefix_with_tail(self)?.0)
     }
 
-    /// Splits the buffer into a RefMaker containing the last `target_size` bytes and the preceding head
+    /// Splits the buffer into a `RefMaker` containing the last `size_of::<T>()`
+    /// bytes as [RefMaker] and the preceding bytes as a buffer.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the buffer is undersized.
+    ///
+    /// # Example
+    /// ```
+    /// # use rosenpass_util::zerocopy::RefMaker;
+    /// let bytes: &[u8] = &[1,2,3,4,5,6,7,8,9,10];
+    /// let (suffix_rm, head) = RefMaker::<_, u32>::new(bytes).from_suffix_with_head().unwrap();
+    /// assert_eq!(suffix_rm.bytes(), &[7,8,9,10]);
+    /// assert_eq!(head, &[1,2,3,4,5,6]);
+    /// ```
     pub fn from_suffix_with_head(self) -> anyhow::Result<(Self, B)> {
         self.ensure_fit()?;
         let point = self.bytes().len() - Self::target_size();
@@ -76,7 +208,22 @@ impl<B: ByteSlice, T> RefMaker<B, T> {
         Ok((Self::new(tail), head))
     }
 
-    /// Splits the buffer into two RefMakers, with the second containing the last `target_size` bytes
+    /// Splits the buffer into two `RefMaker`s, with the second containing the
+    /// last `size_of::<T>()` bytes, and the first containing the remaining
+    /// preceding bytes.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the buffer is undersized.
+    ///
+    /// # Example
+    /// ```
+    /// # use rosenpass_util::zerocopy::RefMaker;
+    /// let bytes: &[u8] = &[1,2,3,4,5,6,7,8,9,10];
+    /// let (head, tail) = RefMaker::<_, u32>::new(bytes).split_suffix().unwrap();
+    /// assert_eq!(head.bytes(), &[1,2,3,4,5,6]);
+    /// assert_eq!(tail.bytes(), &[7,8,9,10]);
+    /// ```
     pub fn split_suffix(self) -> anyhow::Result<(Self, Self)> {
         self.ensure_fit()?;
         let point = self.bytes().len() - Self::target_size();
@@ -84,17 +231,46 @@ impl<B: ByteSlice, T> RefMaker<B, T> {
         Ok((Self::new(head), Self::new(tail)))
     }
 
-    /// Returns a RefMaker containing only the last `target_size` bytes
+    /// Returns a `RefMaker` containing only the last `target_size()` bytes.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the buffer is undersized.
+    ///
+    /// # Example
+    /// ```
+    /// # use rosenpass_util::zerocopy::RefMaker;
+    /// let bytes: &[u8] = &[1,2,3,4,5,6,7,8,9,10];
+    /// let suffix_rm = RefMaker::<_, u32>::new(bytes).from_suffix().unwrap();
+    /// assert_eq!(suffix_rm.bytes(), &[7,8,9,10]);
+    /// ```
     pub fn from_suffix(self) -> anyhow::Result<Self> {
         Ok(Self::from_suffix_with_head(self)?.0)
     }
 
-    /// Returns a reference to the underlying bytes
+    /// Returns a reference to the underlying bytes.
     pub fn bytes(&self) -> &[u8] {
         self.buf().deref()
     }
 
-    /// Ensures the buffer is large enough to hold type T
+    /// Ensures that the buffer is large enough to hold a `T`.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the buffer is undersized.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use rosenpass_util::zerocopy::RefMaker;
+    /// let bytes: &[u8] = &[1,2,3,4,5,6,7,8,9,10];
+    /// let rm = RefMaker::<_, u32>::new(bytes);
+    /// rm.ensure_fit().unwrap();
+    ///
+    /// let bytes: &[u8] = &[1,2,3];
+    /// let rm = RefMaker::<_, u32>::new(bytes);
+    /// assert!(rm.ensure_fit().is_err());
+    /// ```
     pub fn ensure_fit(&self) -> anyhow::Result<()> {
         let have = self.bytes().len();
         let need = Self::target_size();
@@ -107,12 +283,30 @@ impl<B: ByteSlice, T> RefMaker<B, T> {
 }
 
 impl<B: ByteSliceMut, T> RefMaker<B, T> {
-    /// Creates a zeroed reference of type T from the buffer
+    /// Creates a zeroized reference of type `T` from the buffer.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the buffer is undersized.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use zerocopy::{AsBytes, FromBytes, FromZeroes, Ref};    ///
+    /// # use rosenpass_util::zerocopy::RefMaker;
+    /// #[derive(FromBytes, FromZeroes, AsBytes)]
+    /// #[repr(C)]
+    /// struct Data([u8; 4]);
+    ///
+    /// let mut bytes = [0xFF; 4];
+    /// let data_ref: Ref<&mut [u8], Data> = RefMaker::<_, Data>::new(&mut bytes[..]).make_zeroized().unwrap();
+    /// assert_eq!(data_ref.0, [0,0,0,0]);
+    /// ```
     pub fn make_zeroized(self) -> anyhow::Result<Ref<B, T>> {
         self.zeroized().parse()
     }
 
-    /// Returns a mutable reference to the underlying bytes
+    /// Returns a mutable reference to the underlying bytes.
     pub fn bytes_mut(&mut self) -> &mut [u8] {
         self.buf_mut().deref_mut()
     }

util/src/zerocopy/zerocopy_ref_ext.rs

@@ -1,14 +1,64 @@
+//! Extension traits for converting `Ref<B, T>` into references backed by
+//! standard slices.
+
 use zerocopy::{ByteSlice, ByteSliceMut, Ref};
 
 /// A trait for converting a `Ref<B, T>` into a `Ref<&[u8], T>`.
+///
+/// This can be useful when you need a reference that is tied to a slice rather
+/// than the original buffer type `B`.
+///
+/// Note: This trait is implemented to [`Ref`] of byte slices (`&[u8]`).
 pub trait ZerocopyEmancipateExt<B, T> {
-    /// Converts this reference into a reference backed by a byte slice.
+    /// Converts this reference into a reference backed by a plain byte slice.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use std::ops::Deref;
+    /// # use zerocopy::{AsBytes, ByteSlice, FromBytes, FromZeroes, Ref};
+    /// # use rosenpass_util::zerocopy::ZerocopyEmancipateExt;
+    /// #[derive(FromBytes, FromZeroes, AsBytes)]
+    /// #[repr(C)]
+    /// struct Data(u32);
+    /// #[repr(align(4))]
+    /// struct AlignedBuf([u8; 4]);
+    /// let bytes = AlignedBuf([0xAA, 0xBB, 0xCC, 0xDD]);
+    /// let r = Ref::<&[u8], Data>::new(&bytes.0).unwrap();
+    /// let emancipated: Ref<&[u8], Data> = r.emancipate(); // same data, but guaranteed &[u8] backing
+    /// assert_eq!(emancipated.0, 0xDDCCBBAA);
+    /// ```
     fn emancipate(&self) -> Ref<&[u8], T>;
 }
 
 /// A trait for converting a `Ref<B, T>` into a mutable `Ref<&mut [u8], T>`.
+///
+/// Similar to [`ZerocopyEmancipateExt`], but for mutable references.
+///
+/// Note: this trait is implemented to [`Ref`] of mutable byte
+/// slices (`&mut [u8]`).
 pub trait ZerocopyEmancipateMutExt<B, T> {
-    /// Converts this reference into a mutable reference backed by a byte slice.
+    /// Converts this reference into a mutable reference backed by a plain
+    /// mutable byte slice.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use zerocopy::{AsBytes, FromBytes, FromZeroes, Ref};
+    /// # use rosenpass_util::zerocopy::{ZerocopyEmancipateMutExt};
+    /// #[derive(FromBytes, FromZeroes, AsBytes)]
+    /// #[repr(C)]
+    /// struct Data(u32);
+    /// #[repr(align(4))]
+    /// struct AlignedBuf([u8; 4]);
+    /// let mut bytes = AlignedBuf([0xAA, 0xBB, 0xCC, 0xDD]);
+    /// let mut r = Ref::<&mut [u8], Data>::new(&mut bytes.0).unwrap();
+    /// let mut emancipated: Ref<&mut [u8], Data> = r.emancipate_mut(); // same data, but guaranteed &[u8] backing
+    /// assert_eq!(emancipated.0, 0xDDCCBBAA);
+    /// emancipated.0 = 0x33221100;
+    /// drop(emancipated);
+    /// assert_eq!(bytes.0, [0x00, 0x11, 0x22, 0x33]);
+    /// ```
     fn emancipate_mut(&mut self) -> Ref<&mut [u8], T>;
 }
 

util/src/zerocopy/zerocopy_slice_ext.rs

@@ -1,25 +1,113 @@
+//! Extension traits for parsing slices into [`zerocopy::Ref`] values using the
+//! [`RefMaker`] abstraction.
+
 use zerocopy::{ByteSlice, ByteSliceMut, Ref};
 
 use super::RefMaker;
 
-/// Extension trait for zero-copy slice operations.
+/// Extension trait for performing zero-copy parsing operations on byte slices.
+///
+/// This trait adds methods for creating [`Ref`] references from
+/// slices by using the [`RefMaker`] type internally.
 pub trait ZerocopySliceExt: Sized + ByteSlice {
     /// Creates a new `RefMaker` for the given slice.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use zerocopy::{AsBytes, FromBytes, FromZeroes};
+    /// # use rosenpass_util::zerocopy::{RefMaker, ZerocopySliceExt};
+    ///
+    /// #[derive(FromBytes, FromZeroes, AsBytes)]
+    /// #[repr(C)]
+    /// struct Data(u32);
+    ///
+    /// let rm: RefMaker<&[u8], Data> = [3,0,0,0].zk_ref_maker();
+    /// assert_eq!(rm.bytes(), &[3,0,0,0]);
+    /// assert_eq!(rm.parse().unwrap().0, 3);
+    /// ```
     fn zk_ref_maker<T>(self) -> RefMaker<Self, T> {
         RefMaker::<Self, T>::new(self)
     }
 
-    /// Parses the slice into a zero-copy reference.
+    /// Parses the given slice into a zero-copy reference of the given type `T`.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the slice is too small.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use zerocopy::{AsBytes, FromBytes, FromZeroes};
+    /// # use rosenpass_util::zerocopy::ZerocopySliceExt;
+    ///
+    /// #[derive(FromBytes, FromZeroes, AsBytes)]
+    /// #[repr(C)]
+    /// struct Data(u16, u16);
+    /// #[repr(align(4))]
+    /// struct AlignedBuf([u8; 4]);
+    /// let bytes = AlignedBuf([0x01,0x02,0x03,0x04]);
+    /// let data_ref = bytes.0.zk_parse::<Data>().unwrap();
+    /// assert_eq!(data_ref.0, 0x0201);
+    /// assert_eq!(data_ref.1, 0x0403);
+    /// ```
     fn zk_parse<T>(self) -> anyhow::Result<Ref<Self, T>> {
         self.zk_ref_maker().parse()
     }
 
     /// Parses a prefix of the slice into a zero-copy reference.
+    ///
+    /// Uses only the first [`std::mem::size_of::<T>()`] bytes of `T`.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the slice is too small.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use zerocopy::{AsBytes, FromBytes, FromZeroes};
+    /// # use rosenpass_util::zerocopy::ZerocopySliceExt;
+    /// #[derive(FromBytes, FromZeroes, AsBytes)]
+    /// #[repr(C)]
+    /// struct Header(u32);
+    /// #[repr(align(4))]
+    /// struct AlignedBuf([u8; 8]);
+    /// let bytes = AlignedBuf([0xAA, 0xBB, 0xCC, 0xDD,
+    /// 0x00, 0x10, 0x20, 0x30]);
+    ///
+    /// let header_ref = bytes.0.zk_parse_prefix::<Header>().unwrap();
+    /// assert_eq!(header_ref.0, 0xDDCCBBAA);
+    /// ```
     fn zk_parse_prefix<T>(self) -> anyhow::Result<Ref<Self, T>> {
         self.zk_ref_maker().from_prefix()?.parse()
     }
 
     /// Parses a suffix of the slice into a zero-copy reference.
+    ///
+    /// Uses only the last [`std::mem::size_of::<T>()`] bytes of `T`.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the slice is too small.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use zerocopy::{AsBytes, FromBytes, FromZeroes};
+    /// # use rosenpass_util::zerocopy::ZerocopySliceExt;
+    /// #[derive(FromBytes, FromZeroes, AsBytes)]
+    /// #[repr(C)]
+    /// struct Header(u32);
+    /// #[repr(align(4))]
+    /// struct AlignedBuf([u8; 8]);
+    /// let bytes = AlignedBuf([0xAA, 0xBB, 0xCC, 0xDD,
+    /// 0x00, 0x10, 0x20, 0x30]);
+    ///
+    /// let header_ref = bytes.0.zk_parse_suffix::<Header>().unwrap();
+    /// assert_eq!(header_ref.0, 0x30201000);
+    /// ```
     fn zk_parse_suffix<T>(self) -> anyhow::Result<Ref<Self, T>> {
         self.zk_ref_maker().from_suffix()?.parse()
     }
@@ -27,19 +115,90 @@ pub trait ZerocopySliceExt: Sized + ByteSlice {
 
 impl<B: ByteSlice> ZerocopySliceExt for B {}
 
-/// Extension trait for zero-copy slice operations with mutable slices.
+/// Extension trait for zero-copy parsing of mutable slices with zeroization
+/// capabilities.
+///
+/// Provides convenience methods to create zero-initialized references.
 pub trait ZerocopyMutSliceExt: ZerocopySliceExt + Sized + ByteSliceMut {
-    /// Creates a new zeroed reference from the entire slice.
+    /// Creates a new zeroized reference from the entire slice.
+    ///
+    /// This zeroizes the slice first, then provides a `Ref`.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the slice is too small.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use zerocopy::{AsBytes, FromBytes, FromZeroes};
+    /// # use rosenpass_util::zerocopy::ZerocopyMutSliceExt;
+    /// #[derive(FromBytes, FromZeroes, AsBytes)]
+    /// #[repr(C)]
+    /// struct Data([u8; 4]);
+    /// #[repr(align(4))]
+    /// struct AlignedBuf([u8; 4]);
+    /// let mut bytes = AlignedBuf([0xFF; 4]);
+    /// let data_ref = bytes.0.zk_zeroized::<Data>().unwrap();
+    /// assert_eq!(data_ref.0, [0,0,0,0]);
+    /// assert_eq!(bytes.0, [0, 0, 0, 0]);
+    /// ```
     fn zk_zeroized<T>(self) -> anyhow::Result<Ref<Self, T>> {
         self.zk_ref_maker().make_zeroized()
     }
 
-    /// Creates a new zeroed reference from a prefix of the slice.
+    /// Creates a new zeroized reference from the prefix of the slice.
+    ///
+    /// Zeroizes the first `target_size()` bytes of the slice, then returns a
+    /// `Ref`.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the slice is too small.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use zerocopy::{AsBytes, FromBytes, FromZeroes};
+    /// # use rosenpass_util::zerocopy::ZerocopyMutSliceExt;
+    /// #[derive(FromBytes, FromZeroes, AsBytes)]
+    /// #[repr(C)]
+    /// struct Data([u8; 4]);
+    /// #[repr(align(4))]
+    /// struct AlignedBuf([u8; 6]);
+    /// let mut bytes = AlignedBuf([0xFF; 6]);
+    /// let data_ref = bytes.0.zk_zeroized_from_prefix::<Data>().unwrap();
+    /// assert_eq!(data_ref.0, [0,0,0,0]);
+    /// assert_eq!(bytes.0, [0, 0, 0, 0, 0xFF, 0xFF]);
+    /// ```
     fn zk_zeroized_from_prefix<T>(self) -> anyhow::Result<Ref<Self, T>> {
         self.zk_ref_maker().from_prefix()?.make_zeroized()
     }
 
-    /// Creates a new zeroed reference from a suffix of the slice.
+    /// Creates a new zeroized reference from the suffix of the slice.
+    ///
+    /// Zeroizes the last `target_size()` bytes of the slice, then returns a
+    /// `Ref`.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the slice is too small.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use zerocopy::{AsBytes, FromBytes, FromZeroes};
+    /// # use rosenpass_util::zerocopy::ZerocopyMutSliceExt;
+    /// #[derive(FromBytes, FromZeroes, AsBytes)]
+    /// #[repr(C)]
+    /// struct Data([u8; 4]);
+    /// #[repr(align(4))]
+    /// struct AlignedBuf([u8; 6]);
+    /// let mut bytes = AlignedBuf([0xFF; 6]);
+    /// let data_ref = bytes.0.zk_zeroized_from_suffix::<Data>().unwrap();
+    /// assert_eq!(data_ref.0, [0,0,0,0]);
+    /// assert_eq!(bytes.0, [0xFF, 0xFF, 0, 0, 0, 0]);
+    /// ```
     fn zk_zeroized_from_suffix<T>(self) -> anyhow::Result<Ref<Self, T>> {
         self.zk_ref_maker().from_suffix()?.make_zeroized()
     }

util/src/zeroize/mod.rs

@@ -1,2 +1,23 @@
+//!
+//! This module provides an extension trait,
+//! [`ZeroizedExt`](crate::zeroize::ZeroizedExt), for all types implementing the
+//! `zeroize::Zeroize` trait.
+//! It introduces the [`zeroized`](crate::zeroize::ZeroizedExt::zeroized)
+//! method, which zeroizes a value in place and returns it, making it convenient
+//! for chaining operations and ensuring sensitive data is securely erased.
+//!
+//! # Examples
+//!
+//! ```rust
+//! use zeroize::Zeroize;
+//! use rosenpass_util::zeroize::ZeroizedExt;
+//!
+//! let mut value = String::from("hello");
+//! value.zeroize(); // Zeroizes in place
+//! assert_eq!(value, "");
+//!
+//! assert_eq!(String::from("hello").zeroized(), "");
+//! ```
+
 mod zeroized_ext;
 pub use zeroized_ext::*;

wireguard-broker/Cargo.toml

@@ -28,7 +28,7 @@ derive_builder = { workspace = true }
 postcard = { workspace = true }
 # Problem in CI, unknown reasons: dependency (libc) specified without providing a local path, Git repository, version, or workspace dependency to use
 # Maybe something about the combination of features and optional crates?
-rustix = { version = "0.38.41", optional = true }
+rustix = { version = "0.38.42", optional = true }
 libc = { version = "0.2", optional = true }
 
 # Mio broker client