chore: Add a few comments about unsafe usage

swf/src/string.rs

@@ -19,11 +19,12 @@ pub struct SwfStr {
 }
 
 impl SwfStr {
-    /// Create a new `SwfStr` from a byte slice with a given encoding.
-    /// The string will be truncated if a null byte is encountered.
+    /// Create a new `SwfStr` from a byte slice.
     /// The data is not required to be valid for the given encoding.
     #[inline]
     pub fn from_bytes(string: &[u8]) -> &Self {
+        // SAFETY: Casting is safe because internal representations are
+        // the same, see repr(transparent).
         unsafe { &*(string as *const [u8] as *const Self) }
     }
 

web/src/audio.rs

@@ -689,11 +689,18 @@ impl WebAudioBackend {
             .unwrap();
         let audio_buffer = Rc::new(RefCell::new(audio_buffer));
 
-        let data_array = unsafe { js_sys::Uint8Array::view(&audio_data[..]) };
-        let array_buffer = data_array.buffer().slice_with_end(
+        // Clone the audio data into an ArrayBuffer
+        // SAFETY: (compare with the docs for `Uint8Array::view`)
+        // - We don't resize WASMs backing buffer before the view is cloned
+        // - We don't mutate `data_array`
+        // - Since we clone the buffer, its lifetime is correctly disconnected from `audio_data`
+        let array_buffer = {
+            let data_array = unsafe { js_sys::Uint8Array::view(audio_data) };
+            data_array.buffer().slice_with_end(
                 data_array.byte_offset(),
                 data_array.byte_offset() + data_array.byte_length(),
-        );
+            )
+        };
 
         NUM_SOUNDS_LOADING.with(|n| n.set(n.get() + 1));