feat: Rosenpass-to for nicely handling destination parameters

to/src/ops.rs

@@ -0,0 +1,80 @@
+//! Functions with destination copying data between slices and arrays.
+
+use crate::{with_destination, To};
+
+/// Function with destination that copies data from
+/// origin into the destination.
+///
+/// # Panics
+///
+/// This function will panic if the two slices have different lengths.
+pub fn copy_slice<'a, T>(origin: &'a [T]) -> impl To<[T], ()> + 'a
+where
+    T: Copy,
+{
+    with_destination(|out: &mut [T]| out.copy_from_slice(origin))
+}
+
+/// Function with destination that copies all data from
+/// origin into the destination.
+///
+/// Destination may be longer than origin.
+///
+/// # Panics
+///
+/// This function will panic if destination is shorter than origin.
+pub fn copy_slice_least_src<'a, T>(origin: &'a [T]) -> impl To<[T], ()> + 'a
+where
+    T: Copy,
+{
+    with_destination(|out: &mut [T]| copy_slice(origin).to(&mut out[..origin.len()]))
+}
+
+/// Function with destination that copies as much data as possible from origin to the
+/// destination.
+///
+/// Copies as much data as is present in the shorter slice.
+pub fn copy_slice_least<'a, T>(origin: &'a [T]) -> impl To<[T], ()> + 'a
+where
+    T: Copy,
+{
+    with_destination(|out: &mut [T]| {
+        let len = std::cmp::min(origin.len(), out.len());
+        copy_slice(&origin[..len]).to(&mut out[..len])
+    })
+}
+
+/// Function with destination that attempts to copy data from origin into the destination.
+///
+/// Will return None if the slices are of different lengths.
+pub fn try_copy_slice<'a, T>(origin: &'a [T]) -> impl To<[T], Option<()>> + 'a
+where
+    T: Copy,
+{
+    with_destination(|out: &mut [T]| {
+        (origin.len() == out.len()).then(|| copy_slice(origin).to(out))
+    })
+}
+
+/// Function with destination that tries to copy all data from
+/// origin into the destination.
+///
+/// Destination may be longer than origin.
+///
+/// Will return None if the destination is shorter than origin.
+pub fn try_copy_slice_least_src<'a, T>(origin: &'a [T]) -> impl To<[T], Option<()>> + 'a
+where
+    T: Copy,
+{
+    with_destination(|out: &mut [T]| {
+        (origin.len() <= out.len()).then(|| copy_slice_least_src(origin).to(out))
+    })
+}
+
+/// Function with destination that copies all data between two array references.
+pub fn copy_array<'a, T, const N: usize>(origin: &'a [T; N]) -> impl To<[T; N], ()> + 'a
+where
+    T: Copy,
+{
+    with_destination(|out: &mut [T; N]| out.copy_from_slice(origin))
+}