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std: minor simplification to sync::deque. #14378

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May 24, 2014
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std: minor simplification to sync::deque. #14378

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10 changes: 5 additions & 5 deletions src/libstd/sync/deque.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -54,7 +54,7 @@ use clone::Clone;
use iter::{range, Iterator};
use kinds::Send;
use kinds::marker;
use mem::{forget, min_align_of, size_of, transmute};
use mem::{forget, min_align_of, size_of, transmute, overwrite};
use ops::Drop;
use option::{Option, Some, None};
use owned::Box;
Expand Down Expand Up @@ -371,20 +371,20 @@ impl<T: Send> Buffer<T> {
// Apparently LLVM cannot optimize (foo % (1 << bar)) into this implicitly
fn mask(&self) -> int { (1 << self.log_size) - 1 }

unsafe fn elem(&self, i: int) -> *T { self.storage.offset(i & self.mask()) }
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This diverges slightly from the original paper, but it's so small there's no need to revert it.


// This does not protect against loading duplicate values of the same cell,
// nor does this clear out the contents contained within. Hence, this is a
// very unsafe method which the caller needs to treat specially in case a
// race is lost.
unsafe fn get(&self, i: int) -> T {
ptr::read(self.storage.offset(i & self.mask()))
ptr::read(self.elem(i))
}

// Unsafe because this unsafely overwrites possibly uninitialized or
// initialized data.
unsafe fn put(&self, i: int, t: T) {
let ptr = self.storage.offset(i & self.mask());
ptr::copy_nonoverlapping_memory(ptr as *mut T, &t as *T, 1);
forget(t);
overwrite(self.elem(i) as *mut T, t);
}

// Again, unsafe because this has incredibly dubious ownership violations.
Expand Down