feat(mobile): free native core buffers through a dedicated export

mobile/integration_test/native_core_test.dart

@@ -86,7 +86,7 @@ void main() {
         expect(pixels[i], 255, reason: 'alpha at $i');
       }
       expect(pixels.toSet().length, greaterThan(2));
-      malloc.free(ptr);
+      immich_core_free(ptr);
 
       expect(immich_core_thumbhash_decode(hashPtr, 4, info), equals(nullptr));
     } finally {

mobile/lib/utils/hooks/blurhash_hook.dart

@@ -35,7 +35,7 @@ Uint8List? decodeDriftThumbHash(String? thumbHash) {
     try {
       return _rgbaToBmp(rgba, info[0], info[1], info[2]);
     } finally {
-      malloc.free(rgba);
+      immich_core_free(rgba);
     }
   } finally {
     malloc.free(hashPtr);

native/crates/immich_core_ffi/include/immich_core.h

@@ -20,6 +20,15 @@ char *immich_core_version(void);
  */
 void immich_core_free_string(char *ptr);
 
+/**
+ * Release a buffer returned by this library, such as a decoded ThumbHash.
+ *
+ * # Safety
+ * `ptr` must be a buffer previously returned by this library, or null, and
+ * must not be released twice.
+ */
+void immich_core_free(uint8_t *ptr);
+
 /**
  * Returns whether an EXIF orientation swaps width and height.
  */
@@ -55,8 +64,8 @@ bool immich_core_rgba1010102_to_rgba8888(const uint8_t *src,
                                          uintptr_t dst_len);
 
 /**
- * Decodes a ThumbHash into a libc buffer and writes width, height, and row bytes to `out_info`.
- * Free the buffer with `free`; malformed hashes return null.
+ * Decodes a ThumbHash into a new buffer and writes width, height, and row bytes to `out_info`.
+ * Free the buffer with `immich_core_free`; malformed hashes return null.
  *
  * # Safety
  * `hash` must be valid for `hash_len` bytes and `out_info` for three u32 writes.

native/crates/immich_core_ffi/src/capi/mod.rs

@@ -28,6 +28,17 @@ pub unsafe extern "C" fn immich_core_free_string(ptr: *mut c_char) {
     });
 }
 
+/// Release a buffer returned by this library, such as a decoded ThumbHash.
+///
+/// # Safety
+/// `ptr` must be a buffer previously returned by this library, or null, and
+/// must not be released twice.
+#[no_mangle]
+pub unsafe extern "C" fn immich_core_free(ptr: *mut u8) {
+    // SAFETY: the buffer came from this library's libc allocation; free accepts null.
+    unsafe { libc::free(ptr as *mut core::ffi::c_void) };
+}
+
 fn guard<T>(sentinel: T, f: impl FnOnce() -> T + std::panic::UnwindSafe) -> T {
     crate::log::ensure_panic_hook();
     std::panic::catch_unwind(f).unwrap_or(sentinel)

native/crates/immich_core_ffi/src/capi/thumbhash.rs

@@ -22,8 +22,8 @@ pub(crate) fn decode_malloc(hash: &[u8]) -> Option<(*mut u8, u32, u32)> {
     Some((dst, w, h))
 }
 
-/// Decodes a ThumbHash into a libc buffer and writes width, height, and row bytes to `out_info`.
-/// Free the buffer with `free`; malformed hashes return null.
+/// Decodes a ThumbHash into a new buffer and writes width, height, and row bytes to `out_info`.
+/// Free the buffer with `immich_core_free`; malformed hashes return null.
 ///
 /// # Safety
 /// `hash` must be valid for `hash_len` bytes and `out_info` for three u32 writes.

native/crates/immich_core_ffi/src/lib.rs

@@ -18,4 +18,4 @@ pub use capi::image::{
     immich_core_rotate_rgba8888,
 };
 pub use capi::thumbhash::immich_core_thumbhash_decode;
-pub use capi::{immich_core_free_string, immich_core_version};
+pub use capi::{immich_core_free, immich_core_free_string, immich_core_version};

native/crates/immich_core_ffi/tests/c_abi.rs

@@ -4,7 +4,7 @@ use std::ffi::CStr;
 use std::ptr;
 
 use immich_core_ffi::{
-    immich_core_free_string, immich_core_orientation_swaps_dims,
+    immich_core_free, immich_core_free_string, immich_core_orientation_swaps_dims,
     immich_core_rgba1010102_to_rgba8888, immich_core_rotate_rgba8888, immich_core_thumbhash_decode,
     immich_core_version,
 };
@@ -186,7 +186,12 @@ fn thumbhash_decodes_into_a_malloc_buffer() {
     let pixels = unsafe { std::slice::from_raw_parts(ptr, len) };
     assert!(pixels.chunks_exact(4).all(|px| px[3] == 255));
     assert!(pixels.chunks_exact(4).any(|px| px[0] != pixels[0]));
-    unsafe { libc::free(ptr as *mut libc::c_void) };
+    unsafe { immich_core_free(ptr) };
+}
+
+#[test]
+fn free_accepts_null() {
+    unsafe { immich_core_free(ptr::null_mut()) };
 }
 
 #[test]

native/immich_native_core/lib/src/ffi/bindings.g.dart

@@ -18,6 +18,14 @@ external ffi.Pointer<ffi.Char> immich_core_version();
 @ffi.Native<ffi.Void Function(ffi.Pointer<ffi.Char>)>()
 external void immich_core_free_string(ffi.Pointer<ffi.Char> ptr);
 
+/// Release a buffer returned by this library, such as a decoded ThumbHash.
+///
+/// # Safety
+/// `ptr` must be a buffer previously returned by this library, or null, and
+/// must not be released twice.
+@ffi.Native<ffi.Void Function(ffi.Pointer<ffi.Uint8>)>()
+external void immich_core_free(ffi.Pointer<ffi.Uint8> ptr);
+
 /// Returns whether an EXIF orientation swaps width and height.
 @ffi.Native<ffi.Bool Function(ffi.Int32)>()
 external bool immich_core_orientation_swaps_dims(int orientation);
@@ -74,8 +82,8 @@ external bool immich_core_rgba1010102_to_rgba8888(
   int dst_len,
 );
 
-/// Decodes a ThumbHash into a libc buffer and writes width, height, and row bytes to `out_info`.
-/// Free the buffer with `free`; malformed hashes return null.
+/// Decodes a ThumbHash into a new buffer and writes width, height, and row bytes to `out_info`.
+/// Free the buffer with `immich_core_free`; malformed hashes return null.
 ///
 /// # Safety
 /// `hash` must be valid for `hash_len` bytes and `out_info` for three u32 writes.

native/immich_native_core/test/native_core_test.dart

@@ -125,7 +125,7 @@ void main() {
         expect(pixels[i], 255, reason: 'alpha at $i');
       }
       expect(pixels.toSet().length, greaterThan(2));
-      malloc.free(ptr);
+      immich_core_free(ptr);
 
       expect(immich_core_thumbhash_decode(hashPtr, 4, info), equals(nullptr));
     } finally {