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Auto merge of #31825 - ollie27:win_lfs, r=alexcrichton

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`ReadFile` and `WriteFile` take a DWORD (u32) for the length argument
which was erroneously cast from a usize causing truncation. This meant
methods like `write_all` and `read_exact` would unexpectedly fail if
given a buffer 4 GiB or larger.

We can instead just ask for `u32::MAX` bytes if the given buffer is too
big.
This commit is contained in:
bors 2016-02-23 14:09:35 +00:00
commit 0de3cace0a
1 changed files with 11 additions and 5 deletions
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16
src/libstd/sys/windows/handle.rs
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@ -8,6 +8,7 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use cmp;
use io::ErrorKind;
use io;
use mem;
@ -15,6 +16,7 @@ use ops::Deref;
use ptr;
use sys::c;
use sys::cvt;
use u32;
/// An owned container for `HANDLE` object, closing them on Drop.
///
@ -64,10 +66,12 @@ impl RawHandle {
pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
let mut read = 0;
// ReadFile takes a DWORD (u32) for the length so it only supports
// reading u32::MAX bytes at a time.
let len = cmp::min(buf.len(), u32::MAX as usize) as c::DWORD;
let res = cvt(unsafe {
c::ReadFile(self.0, buf.as_ptr() as c::LPVOID,
buf.len() as c::DWORD, &mut read,
ptr::null_mut())
c::ReadFile(self.0, buf.as_mut_ptr() as c::LPVOID,
len, &mut read, ptr::null_mut())
});
match res {
@ -85,10 +89,12 @@ impl RawHandle {
pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
let mut amt = 0;
// WriteFile takes a DWORD (u32) for the length so it only supports
// writing u32::MAX bytes at a time.
let len = cmp::min(buf.len(), u32::MAX as usize) as c::DWORD;
try!(cvt(unsafe {
c::WriteFile(self.0, buf.as_ptr() as c::LPVOID,
buf.len() as c::DWORD, &mut amt,
ptr::null_mut())
len, &mut amt, ptr::null_mut())
}));
Ok(amt as usize)
}