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Auto merge of #31876 - ollie27:win_fill_bytes, r=brson

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CryptGenRandom takes a DWORD (u32) for the length so it only supports
writing u32::MAX bytes at a time.

Casting the length from a usize caused truncation meaning the whole
buffer was not always filled.

cc #31841

This is the same as rust-lang-nursery/rand#99. I think it's a good idea to keep the implementations in sync.

r? @alexcrichton
This commit is contained in:
bors 2016-02-26 22:21:59 +00:00
commit 98a8a71236
1 changed files with 11 additions and 7 deletions
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18
src/libstd/sys/windows/rand.rs
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@ -48,13 +48,17 @@ impl Rng for OsRng {
unsafe { mem::transmute(v) }
}
fn fill_bytes(&mut self, v: &mut [u8]) {
let ret = unsafe {
c::CryptGenRandom(self.hcryptprov, v.len() as c::DWORD,
v.as_mut_ptr())
};
if ret == 0 {
panic!("couldn't generate random bytes: {}",
io::Error::last_os_error());
// CryptGenRandom takes a DWORD (u32) for the length so we need to
// split up the buffer.
for slice in v.chunks_mut(<c::DWORD>::max_value() as usize) {
let ret = unsafe {
c::CryptGenRandom(self.hcryptprov, slice.len() as c::DWORD,
slice.as_mut_ptr())
};
if ret == 0 {
panic!("couldn't generate random bytes: {}",
io::Error::last_os_error());
}
}
}
}