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use raw ptr for racy load and add comment (#289)

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Ralf Jung
2019-08-28 14:41:04 -07:00
committed by Carl Lerche
parent 4f5ed82b3c
commit 425432ba6c
1 changed files with 5 additions and 2 deletions
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src/bytes.rs
+5 -2
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@@ -1940,8 +1940,11 @@ impl Inner {
#[inline] #[inline]
fn inline_len(&self) -> usize { fn inline_len(&self) -> usize {
let p: &usize = unsafe { mem::transmute(&self.arc) }; // This is undefind behavior due to a data race, but experimental
(p & INLINE_LEN_MASK) >> INLINE_LEN_OFFSET // evidence shows that it works in practice (discussion:
// https://internals.rust-lang.org/t/bit-wise-reasoning-for-atomic-accesses/8853).
let p: *const usize = unsafe { mem::transmute(&self.arc) };
(unsafe { *p } & INLINE_LEN_MASK) >> INLINE_LEN_OFFSET
} }
/// Set the length of the inline buffer. This is done by writing to the /// Set the length of the inline buffer. This is done by writing to the