Skip to content

Commit

Permalink
Auto merge of rust-lang#116438 - ChrisDenton:truncate, r=thomcc
Browse files Browse the repository at this point in the history
Windows: Allow `File::create` to work on hidden files

This makes `OpenOptions::new().write(true).create(true).truncate(true).open(&path)` work if the path exists and is a hidden file. Previously it would fail with access denied.

This makes it consistent with `OpenOptions::new().write(true).truncate(true).open(&path)` (note the lack of `create`) which does not have this restriction. It's also more consistent with other platforms.

Fixes rust-lang#115745 (see that issue for more details).
  • Loading branch information
bors committed Dec 13, 2023
2 parents 3340d49 + c6f7aa0 commit 77d1699
Show file tree
Hide file tree
Showing 2 changed files with 53 additions and 7 deletions.
27 changes: 26 additions & 1 deletion library/std/src/fs/tests.rs
Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,7 @@ use crate::os::unix::fs::symlink as symlink_file;
#[cfg(unix)]
use crate::os::unix::fs::symlink as symlink_junction;
#[cfg(windows)]
use crate::os::windows::fs::{symlink_dir, symlink_file};
use crate::os::windows::fs::{symlink_dir, symlink_file, OpenOptionsExt};
#[cfg(windows)]
use crate::sys::fs::symlink_junction;
#[cfg(target_os = "macos")]
Expand Down Expand Up @@ -1793,3 +1793,28 @@ fn windows_unix_socket_exists() {
assert_eq!(socket_path.try_exists().unwrap(), true);
assert_eq!(socket_path.metadata().is_ok(), true);
}

#[cfg(windows)]
#[test]
fn test_hidden_file_truncation() {
// Make sure that File::create works on an existing hidden file. See #115745.
let tmpdir = tmpdir();
let path = tmpdir.join("hidden_file.txt");

// Create a hidden file.
const FILE_ATTRIBUTE_HIDDEN: u32 = 2;
let mut file = OpenOptions::new()
.write(true)
.create_new(true)
.attributes(FILE_ATTRIBUTE_HIDDEN)
.open(&path)
.unwrap();
file.write("hidden world!".as_bytes()).unwrap();
file.flush().unwrap();
drop(file);

// Create a new file by truncating the existing one.
let file = File::create(&path).unwrap();
let metadata = file.metadata().unwrap();
assert_eq!(metadata.len(), 0);
}
33 changes: 27 additions & 6 deletions library/std/src/sys/windows/fs.rs
Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
use crate::os::windows::prelude::*;

use crate::borrow::Cow;
use crate::ffi::OsString;
use crate::ffi::{c_void, OsString};
use crate::fmt;
use crate::io::{self, BorrowedCursor, Error, IoSlice, IoSliceMut, SeekFrom};
use crate::mem::{self, MaybeUninit};
Expand All @@ -16,8 +16,6 @@ use crate::sys::{c, cvt, Align8};
use crate::sys_common::{AsInner, FromInner, IntoInner};
use crate::thread;

use core::ffi::c_void;

use super::path::maybe_verbatim;
use super::{api, to_u16s, IoResult};

Expand Down Expand Up @@ -273,7 +271,9 @@ impl OpenOptions {
(false, false, false) => c::OPEN_EXISTING,
(true, false, false) => c::OPEN_ALWAYS,
(false, true, false) => c::TRUNCATE_EXISTING,
(true, true, false) => c::CREATE_ALWAYS,
// `CREATE_ALWAYS` has weird semantics so we emulate it using
// `OPEN_ALWAYS` and a manual truncation step. See #115745.
(true, true, false) => c::OPEN_ALWAYS,
(_, _, true) => c::CREATE_NEW,
})
}
Expand All @@ -289,19 +289,40 @@ impl OpenOptions {
impl File {
pub fn open(path: &Path, opts: &OpenOptions) -> io::Result<File> {
let path = maybe_verbatim(path)?;
let creation = opts.get_creation_mode()?;
let handle = unsafe {
c::CreateFileW(
path.as_ptr(),
opts.get_access_mode()?,
opts.share_mode,
opts.security_attributes,
opts.get_creation_mode()?,
creation,
opts.get_flags_and_attributes(),
ptr::null_mut(),
)
};
let handle = unsafe { HandleOrInvalid::from_raw_handle(handle) };
if let Ok(handle) = handle.try_into() {
if let Ok(handle) = OwnedHandle::try_from(handle) {
// Manual truncation. See #115745.
if opts.truncate
&& creation == c::OPEN_ALWAYS
&& unsafe { c::GetLastError() } == c::ERROR_ALREADY_EXISTS
{
unsafe {
// Setting the allocation size to zero also sets the
// EOF position to zero.
let alloc = c::FILE_ALLOCATION_INFO { AllocationSize: 0 };
let result = c::SetFileInformationByHandle(
handle.as_raw_handle(),
c::FileAllocationInfo,
ptr::addr_of!(alloc).cast::<c_void>(),
mem::size_of::<c::FILE_ALLOCATION_INFO>() as u32,
);
if result == 0 {
return Err(io::Error::last_os_error());
}
}
}
Ok(File { handle: Handle::from_inner(handle) })
} else {
Err(Error::last_os_error())
Expand Down

0 comments on commit 77d1699

Please sign in to comment.