nordic-dev.net/rust
nordic-dev.net/rust
2
0
Fork 0
mirror of https://github.com/rust-lang/rust.git synced 2025-04-28 11:07:42 +00:00
Code Issues Packages Projects Releases Wiki Activity

Rollup merge of #101236 - thomcc:winfs-nozero, r=ChrisDenton

Browse Source 
Avoid needless buffer zeroing in `std::sys::windows::fs`

Followup to https://github.com/rust-lang/rust/pull/101171 and https://github.com/rust-lang/rust/pull/101193. This finishes up avoiding buffer zeroing pointed out in https://github.com/rust-lang/rust/pull/100729#issuecomment-1220055311 (thanks!)

r? `@ChrisDenton`
This commit is contained in:
Matthias Krüger 2022-08-31 21:30:17 +02:00 committed by GitHub
commit 3da66f0353
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 24 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
library/std/src/sys/windows/fs.rs
View File

@ -3,7 +3,7 @@ use crate::os::windows::prelude::*;
use crate::ffi::OsString; use crate::ffi::OsString;
use crate::fmt; use crate::fmt;
use crate::io::{self, BorrowedCursor, Error, IoSlice, IoSliceMut, SeekFrom}; use crate::io::{self, BorrowedCursor, Error, IoSlice, IoSliceMut, SeekFrom};
use crate::mem; use crate::mem::{self, MaybeUninit};
use crate::os::windows::io::{AsHandle, BorrowedHandle}; use crate::os::windows::io::{AsHandle, BorrowedHandle};
use crate::path::{Path, PathBuf}; use crate::path::{Path, PathBuf};
use crate::ptr; use crate::ptr;
@ -326,7 +326,8 @@ impl File {
cvt(c::GetFileInformationByHandle(self.handle.as_raw_handle(), &mut info))?; cvt(c::GetFileInformationByHandle(self.handle.as_raw_handle(), &mut info))?;
let mut reparse_tag = 0; let mut reparse_tag = 0;
if info.dwFileAttributes & c::FILE_ATTRIBUTE_REPARSE_POINT != 0 { if info.dwFileAttributes & c::FILE_ATTRIBUTE_REPARSE_POINT != 0 {
let mut b = Align8([0u8; c::MAXIMUM_REPARSE_DATA_BUFFER_SIZE]); let mut b =
Align8([MaybeUninit::<u8>::uninit(); c::MAXIMUM_REPARSE_DATA_BUFFER_SIZE]);
if let Ok((_, buf)) = self.reparse_point(&mut b) { if let Ok((_, buf)) = self.reparse_point(&mut b) {
reparse_tag = (*buf).ReparseTag; reparse_tag = (*buf).ReparseTag;
} }
@ -389,7 +390,8 @@ impl File {
attr.file_size = info.AllocationSize as u64; attr.file_size = info.AllocationSize as u64;
attr.number_of_links = Some(info.NumberOfLinks); attr.number_of_links = Some(info.NumberOfLinks);
if attr.file_type().is_reparse_point() { if attr.file_type().is_reparse_point() {
let mut b = Align8([0; c::MAXIMUM_REPARSE_DATA_BUFFER_SIZE]); let mut b =
Align8([MaybeUninit::<u8>::uninit(); c::MAXIMUM_REPARSE_DATA_BUFFER_SIZE]);
if let Ok((_, buf)) = self.reparse_point(&mut b) { if let Ok((_, buf)) = self.reparse_point(&mut b) {
attr.reparse_tag = (*buf).ReparseTag; attr.reparse_tag = (*buf).ReparseTag;
} }
@ -463,7 +465,7 @@ impl File {
// avoid narrowing provenance to the actual `REPARSE_DATA_BUFFER`. // avoid narrowing provenance to the actual `REPARSE_DATA_BUFFER`.
fn reparse_point( fn reparse_point(
&self, &self,
space: &mut Align8<[u8]>, space: &mut Align8<[MaybeUninit<u8>]>,
) -> io::Result<(c::DWORD, *const c::REPARSE_DATA_BUFFER)> { ) -> io::Result<(c::DWORD, *const c::REPARSE_DATA_BUFFER)> {
unsafe { unsafe {
let mut bytes = 0; let mut bytes = 0;
@ -488,7 +490,7 @@ impl File {
} }
fn readlink(&self) -> io::Result<PathBuf> { fn readlink(&self) -> io::Result<PathBuf> {
let mut space = Align8([0u8; c::MAXIMUM_REPARSE_DATA_BUFFER_SIZE]); let mut space = Align8([MaybeUninit::<u8>::uninit(); c::MAXIMUM_REPARSE_DATA_BUFFER_SIZE]);
let (_bytes, buf) = self.reparse_point(&mut space)?; let (_bytes, buf) = self.reparse_point(&mut space)?;
unsafe { unsafe {
let (path_buffer, subst_off, subst_len, relative) = match (*buf).ReparseTag { let (path_buffer, subst_off, subst_len, relative) = match (*buf).ReparseTag {
@ -658,12 +660,16 @@ impl File {
/// A buffer for holding directory entries. /// A buffer for holding directory entries.
struct DirBuff { struct DirBuff {
buffer: Box<Align8<[u8; Self::BUFFER_SIZE]>>, buffer: Box<Align8<[MaybeUninit<u8>; Self::BUFFER_SIZE]>>,
} }
impl DirBuff { impl DirBuff {
const BUFFER_SIZE: usize = 1024; const BUFFER_SIZE: usize = 1024;
fn new() -> Self { fn new() -> Self {
Self { buffer: Box::new(Align8([0u8; Self::BUFFER_SIZE])) } Self {
// Safety: `Align8<[MaybeUninit<u8>; N]>` does not need
// initialization.
buffer: unsafe { Box::new_uninit().assume_init() },
}
} }
fn capacity(&self) -> usize { fn capacity(&self) -> usize {
self.buffer.0.len() self.buffer.0.len()
@ -676,8 +682,8 @@ impl DirBuff {
DirBuffIter::new(self) DirBuffIter::new(self)
} }
} }
impl AsRef<[u8]> for DirBuff { impl AsRef<[MaybeUninit<u8>]> for DirBuff {
fn as_ref(&self) -> &[u8] { fn as_ref(&self) -> &[MaybeUninit<u8>] {
&self.buffer.0 &self.buffer.0
} }
} }
@ -686,7 +692,7 @@ impl AsRef<[u8]> for DirBuff {
/// ///
/// Currently only returns file names (UTF-16 encoded). /// Currently only returns file names (UTF-16 encoded).
struct DirBuffIter<'a> { struct DirBuffIter<'a> {
buffer: Option<&'a [u8]>, buffer: Option<&'a [MaybeUninit<u8>]>,
cursor: usize, cursor: usize,
} }
impl<'a> DirBuffIter<'a> { impl<'a> DirBuffIter<'a> {
@ -701,9 +707,13 @@ impl<'a> Iterator for DirBuffIter<'a> {
let buffer = &self.buffer?[self.cursor..]; let buffer = &self.buffer?[self.cursor..];
// Get the name and next entry from the buffer. // Get the name and next entry from the buffer.
// SAFETY: The buffer contains a `FILE_ID_BOTH_DIR_INFO` struct but the // SAFETY:
// last field (the file name) is unsized. So an offset has to be // - The buffer contains a `FILE_ID_BOTH_DIR_INFO` struct but the last
// used to get the file name slice. // field (the file name) is unsized. So an offset has to be used to
// get the file name slice.
// - The OS has guaranteed initialization of the fields of
// `FILE_ID_BOTH_DIR_INFO` and the trailing filename (for at least
// `FileNameLength` bytes)
let (name, is_directory, next_entry) = unsafe { let (name, is_directory, next_entry) = unsafe {
let info = buffer.as_ptr().cast::<c::FILE_ID_BOTH_DIR_INFO>(); let info = buffer.as_ptr().cast::<c::FILE_ID_BOTH_DIR_INFO>();
// Guaranteed to be aligned in documentation for // Guaranteed to be aligned in documentation for
@ -1349,7 +1359,7 @@ fn symlink_junction_inner(original: &Path, junction: &Path) -> io::Result<()> {
let h = f.as_inner().as_raw_handle(); let h = f.as_inner().as_raw_handle();
unsafe { unsafe {
let mut data = Align8([0u8; c::MAXIMUM_REPARSE_DATA_BUFFER_SIZE]); let mut data = Align8([MaybeUninit::<u8>::uninit(); c::MAXIMUM_REPARSE_DATA_BUFFER_SIZE]);
let data_ptr = data.0.as_mut_ptr(); let data_ptr = data.0.as_mut_ptr();
let db = data_ptr.cast::<c::REPARSE_MOUNTPOINT_DATA_BUFFER>(); let db = data_ptr.cast::<c::REPARSE_MOUNTPOINT_DATA_BUFFER>();
let buf = ptr::addr_of_mut!((*db).ReparseTarget).cast::<c::WCHAR>(); let buf = ptr::addr_of_mut!((*db).ReparseTarget).cast::<c::WCHAR>();