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chore(serde_v8): V8Slice SAFETY (#14493)

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Aaron O'Mullan 2022-05-05 09:16:39 -03:00 committed by GitHub
parent 45a4d75296
commit a58afc098d
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1 changed files with 16 additions and 2 deletions
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18
serde_v8/magic/v8slice.rs
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@ -41,12 +41,26 @@ impl V8Slice {
}
fn as_slice(&self) -> &[u8] {
// SAFETY: v8::SharedRef<v8::BackingStore> is similar to Arc<[u8]>,
// it points to a fixed continuous slice of bytes on the heap.
// We assume it's initialized and thus safe to read (though may not contain meaningful data)
unsafe { &*(&self.store[self.range.clone()] as *const _ as *const [u8]) }
}
#[allow(clippy::cast_ref_to_mut)]
fn as_slice_mut(&mut self) -> &mut [u8] {
unsafe { &mut *(&self.store[self.range.clone()] as *const _ as *mut [u8]) }
// SAFETY: v8::SharedRef<v8::BackingStore> is similar to Arc<[u8]>,
// it points to a fixed continuous slice of bytes on the heap.
// It's safe-ish to mutate concurrently because it can not be
// shrunk/grown/moved/reallocated, thus avoiding dangling refs (unlike a Vec).
// Concurrent writes can't lead to meaningful structural invalidation
// since we treat them as opaque buffers / "bags of bytes",
// concurrent mutation is simply an accepted fact of life.
// And in practice V8Slices also do not have overallping read/write phases.
// TLDR: permissive interior mutability on slices of bytes is "fine"
#[allow(clippy::cast_ref_to_mut)]
unsafe {
&mut *(&self.store[self.range.clone()] as *const _ as *mut [u8])
}
}
}