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[draft] Store the path in io::Error without extra allocations. #86826

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[draft] Store the path in io::Error without extra allocations. #86826

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43 changes: 41 additions & 2 deletions library/std/src/io/error.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,9 @@
#![allow(unreachable_patterns)] // For empty OsWithPath on some platforms.

#[cfg(test)]
mod tests;

use crate::convert::From;
use crate::convert::{From, TryInto};
use crate::error;
use crate::fmt;
use crate::result;
Expand Down Expand Up @@ -68,9 +70,19 @@ impl fmt::Debug for Error {

enum Repr {
Os(i32),

// i16 to make sure the whole Repr remains two words in size.
// All known error codes fit in a i16.
// If for some reason it wouldn't fit, we just don't add the path and use
// Os(code) instead.
#[allow(dead_code)]
OsWithPath(i16, sys::fs::OsPathBuf),

Simple(ErrorKind),

// &str is a fat pointer, but &&str is a thin pointer.
SimpleMessage(ErrorKind, &'static &'static str),

Custom(Box<Custom>),
}

Expand Down Expand Up @@ -337,6 +349,16 @@ impl Error {
Error { repr: Repr::Os(code) }
}

#[allow(dead_code)]
pub(crate) fn with_path(self, path: sys::fs::OsPathBuf) -> Self {
if let Repr::Os(code) = self.repr {
if let Ok(code) = code.try_into() {
return Self { repr: Repr::OsWithPath(code, path) };
}
}
self
}

/// Returns the OS error that this error represents (if any).
///
/// If this [`Error`] was constructed via [`last_os_error`] or
Expand Down Expand Up @@ -371,6 +393,7 @@ impl Error {
pub fn raw_os_error(&self) -> Option<i32> {
match self.repr {
Repr::Os(i) => Some(i),
Repr::OsWithPath(i, _) => Some(i.into()),
Repr::Custom(..) => None,
Repr::Simple(..) => None,
Repr::SimpleMessage(..) => None,
Expand Down Expand Up @@ -409,6 +432,7 @@ impl Error {
pub fn get_ref(&self) -> Option<&(dyn error::Error + Send + Sync + 'static)> {
match self.repr {
Repr::Os(..) => None,
Repr::OsWithPath(..) => None,
Repr::Simple(..) => None,
Repr::SimpleMessage(..) => None,
Repr::Custom(ref c) => Some(&*c.error),
Expand Down Expand Up @@ -482,6 +506,7 @@ impl Error {
pub fn get_mut(&mut self) -> Option<&mut (dyn error::Error + Send + Sync + 'static)> {
match self.repr {
Repr::Os(..) => None,
Repr::OsWithPath(..) => None,
Repr::Simple(..) => None,
Repr::SimpleMessage(..) => None,
Repr::Custom(ref mut c) => Some(&mut *c.error),
Expand Down Expand Up @@ -520,6 +545,7 @@ impl Error {
pub fn into_inner(self) -> Option<Box<dyn error::Error + Send + Sync>> {
match self.repr {
Repr::Os(..) => None,
Repr::OsWithPath(..) => None,
Repr::Simple(..) => None,
Repr::SimpleMessage(..) => None,
Repr::Custom(c) => Some(c.error),
Expand Down Expand Up @@ -549,6 +575,7 @@ impl Error {
pub fn kind(&self) -> ErrorKind {
match self.repr {
Repr::Os(code) => sys::decode_error_kind(code),
Repr::OsWithPath(code, _) => sys::decode_error_kind(code.into()),
Repr::Custom(ref c) => c.kind,
Repr::Simple(kind) => kind,
Repr::SimpleMessage(kind, _) => kind,
Expand All @@ -565,6 +592,13 @@ impl fmt::Debug for Repr {
.field("kind", &sys::decode_error_kind(code))
.field("message", &sys::os::error_string(code))
.finish(),
Repr::OsWithPath(code, ref path) => fmt
.debug_struct("Os")
.field("code", &code)
.field("kind", &sys::decode_error_kind(code.into()))
.field("message", &sys::os::error_string(code.into()))
.field("path", path)
.finish(),
Repr::Custom(ref c) => fmt::Debug::fmt(&c, fmt),
Repr::Simple(kind) => fmt.debug_tuple("Kind").field(&kind).finish(),
Repr::SimpleMessage(kind, &message) => {
Expand All @@ -582,6 +616,9 @@ impl fmt::Display for Error {
let detail = sys::os::error_string(code);
write!(fmt, "{} (os error {})", detail, code)
}
Repr::OsWithPath(code, _) => {
fmt::Display::fmt(&Self::from_raw_os_error(code.into()), fmt)
}
Repr::Custom(ref c) => c.error.fmt(fmt),
Repr::Simple(kind) => write!(fmt, "{}", kind.as_str()),
Repr::SimpleMessage(_, &msg) => msg.fmt(fmt),
Expand All @@ -594,7 +631,7 @@ impl error::Error for Error {
#[allow(deprecated, deprecated_in_future)]
fn description(&self) -> &str {
match self.repr {
Repr::Os(..) | Repr::Simple(..) => self.kind().as_str(),
Repr::Os(..) | Repr::OsWithPath(..) | Repr::Simple(..) => self.kind().as_str(),
Repr::SimpleMessage(_, &msg) => msg,
Repr::Custom(ref c) => c.error.description(),
}
Expand All @@ -604,6 +641,7 @@ impl error::Error for Error {
fn cause(&self) -> Option<&dyn error::Error> {
match self.repr {
Repr::Os(..) => None,
Repr::OsWithPath(..) => None,
Repr::Simple(..) => None,
Repr::SimpleMessage(..) => None,
Repr::Custom(ref c) => c.error.cause(),
Expand All @@ -613,6 +651,7 @@ impl error::Error for Error {
fn source(&self) -> Option<&(dyn error::Error + 'static)> {
match self.repr {
Repr::Os(..) => None,
Repr::OsWithPath(..) => None,
Repr::Simple(..) => None,
Repr::SimpleMessage(..) => None,
Repr::Custom(ref c) => c.error.source(),
Expand Down
73 changes: 38 additions & 35 deletions library/std/src/sys/unix/fs.rs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,5 @@
mod ospathbuf;

use crate::os::unix::prelude::*;

use crate::ffi::{CStr, CString, OsStr, OsString};
Expand Down Expand Up @@ -50,6 +52,8 @@ use libc::{

pub use crate::sys_common::fs::{remove_dir_all, try_exists};

pub use ospathbuf::OsPathBuf;

pub struct File(FileDesc);

// FIXME: This should be available on Linux with all `target_env`.
Expand Down Expand Up @@ -729,8 +733,8 @@ impl OpenOptions {

impl File {
pub fn open(path: &Path, opts: &OpenOptions) -> io::Result<File> {
let path = cstr(path)?;
File::open_c(&path, opts)
let path = OsPathBuf::new(path)?;
File::open_c(&path, opts).map_err(|e| e.with_path(path))
}

pub fn open_c(path: &CStr, opts: &OpenOptions) -> io::Result<File> {
Expand Down Expand Up @@ -898,8 +902,8 @@ impl DirBuilder {
}

pub fn mkdir(&self, p: &Path) -> io::Result<()> {
let p = cstr(p)?;
cvt(unsafe { libc::mkdir(p.as_ptr(), self.mode) })?;
let p = OsPathBuf::new(p)?;
cvt(unsafe { libc::mkdir(p.as_ptr(), self.mode) }).map_err(|e| e.with_path(p))?;
Ok(())
}

Expand All @@ -908,10 +912,6 @@ impl DirBuilder {
}
}

fn cstr(path: &Path) -> io::Result<CString> {
Ok(CString::new(path.as_os_str().as_bytes())?)
}

impl FromInner<c_int> for File {
fn from_inner(fd: c_int) -> File {
File(FileDesc::new(fd))
Expand Down Expand Up @@ -998,11 +998,11 @@ impl fmt::Debug for File {

pub fn readdir(p: &Path) -> io::Result<ReadDir> {
let root = p.to_path_buf();
let p = cstr(p)?;
let p = OsPathBuf::new(p)?;
unsafe {
let ptr = libc::opendir(p.as_ptr());
if ptr.is_null() {
Err(Error::last_os_error())
Err(Error::last_os_error().with_path(p))
} else {
let inner = InnerReadDir { dirp: Dir(ptr), root };
Ok(ReadDir {
Expand All @@ -1020,39 +1020,42 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
}

pub fn unlink(p: &Path) -> io::Result<()> {
let p = cstr(p)?;
cvt(unsafe { libc::unlink(p.as_ptr()) })?;
let p = OsPathBuf::new(p)?;
cvt(unsafe { libc::unlink(p.as_ptr()) }).map_err(|e| e.with_path(p))?;
Ok(())
}

pub fn rename(old: &Path, new: &Path) -> io::Result<()> {
let old = cstr(old)?;
let new = cstr(new)?;
let old = OsPathBuf::new(old)?;
let new = OsPathBuf::new(new)?;
cvt(unsafe { libc::rename(old.as_ptr(), new.as_ptr()) })?;
Ok(())
}

pub fn set_perm(p: &Path, perm: FilePermissions) -> io::Result<()> {
let p = cstr(p)?;
cvt_r(|| unsafe { libc::chmod(p.as_ptr(), perm.mode) })?;
let p = OsPathBuf::new(p)?;
cvt_r(|| unsafe { libc::chmod(p.as_ptr(), perm.mode) }).map_err(|e| e.with_path(p))?;
Ok(())
}

pub fn rmdir(p: &Path) -> io::Result<()> {
let p = cstr(p)?;
cvt(unsafe { libc::rmdir(p.as_ptr()) })?;
let p = OsPathBuf::new(p)?;
cvt(unsafe { libc::rmdir(p.as_ptr()) }).map_err(|e| e.with_path(p))?;
Ok(())
}

pub fn readlink(p: &Path) -> io::Result<PathBuf> {
let c_path = cstr(p)?;
let p = c_path.as_ptr();
let p = OsPathBuf::new(p)?;

let mut buf = Vec::with_capacity(256);

loop {
let buf_read =
cvt(unsafe { libc::readlink(p, buf.as_mut_ptr() as *mut _, buf.capacity()) })? as usize;
let buf_read = match cvt(unsafe {
libc::readlink(p.as_ptr(), buf.as_mut_ptr() as *mut _, buf.capacity())
}) {
Ok(r) => r as usize,
Err(e) => return Err(e.with_path(p)),
};

unsafe {
buf.set_len(buf_read);
Expand All @@ -1072,15 +1075,15 @@ pub fn readlink(p: &Path) -> io::Result<PathBuf> {
}

pub fn symlink(original: &Path, link: &Path) -> io::Result<()> {
let original = cstr(original)?;
let link = cstr(link)?;
let original = OsPathBuf::new(original)?;
let link = OsPathBuf::new(link)?;
cvt(unsafe { libc::symlink(original.as_ptr(), link.as_ptr()) })?;
Ok(())
}

pub fn link(original: &Path, link: &Path) -> io::Result<()> {
let original = cstr(original)?;
let link = cstr(link)?;
let original = OsPathBuf::new(original)?;
let link = OsPathBuf::new(link)?;
cfg_if::cfg_if! {
if #[cfg(any(target_os = "vxworks", target_os = "redox", target_os = "android"))] {
// VxWorks, Redox, and old versions of Android lack `linkat`, so use
Expand All @@ -1099,7 +1102,7 @@ pub fn link(original: &Path, link: &Path) -> io::Result<()> {
}

pub fn stat(p: &Path) -> io::Result<FileAttr> {
let p = cstr(p)?;
let p = OsPathBuf::new(p)?;

cfg_has_statx! {
if let Some(ret) = unsafe { try_statx(
Expand All @@ -1108,17 +1111,17 @@ pub fn stat(p: &Path) -> io::Result<FileAttr> {
libc::AT_STATX_SYNC_AS_STAT,
libc::STATX_ALL,
) } {
return ret;
return ret.map_err(|e| e.with_path(p));
}
}

let mut stat: stat64 = unsafe { mem::zeroed() };
cvt(unsafe { stat64(p.as_ptr(), &mut stat) })?;
cvt(unsafe { stat64(p.as_ptr(), &mut stat) }).map_err(|e| e.with_path(p))?;
Ok(FileAttr::from_stat64(stat))
}

pub fn lstat(p: &Path) -> io::Result<FileAttr> {
let p = cstr(p)?;
let p = OsPathBuf::new(p)?;

cfg_has_statx! {
if let Some(ret) = unsafe { try_statx(
Expand All @@ -1127,12 +1130,12 @@ pub fn lstat(p: &Path) -> io::Result<FileAttr> {
libc::AT_SYMLINK_NOFOLLOW | libc::AT_STATX_SYNC_AS_STAT,
libc::STATX_ALL,
) } {
return ret;
return ret.map_err(|e| e.with_path(p));
}
}

let mut stat: stat64 = unsafe { mem::zeroed() };
cvt(unsafe { lstat64(p.as_ptr(), &mut stat) })?;
cvt(unsafe { lstat64(p.as_ptr(), &mut stat) }).map_err(|e| e.with_path(p))?;
Ok(FileAttr::from_stat64(stat))
}

Expand Down Expand Up @@ -1284,7 +1287,7 @@ pub fn copy(from: &Path, to: &Path) -> io::Result<u64> {
// Opportunistically attempt to create a copy-on-write clone of `from`
// using `fclonefileat`.
if HAS_FCLONEFILEAT.load(Ordering::Relaxed) {
let to = cstr(to)?;
let to = OsPathBuf::new(to)?;
let clonefile_result =
cvt(unsafe { fclonefileat(reader.as_raw_fd(), libc::AT_FDCWD, to.as_ptr(), 0) });
match clonefile_result {
Expand Down Expand Up @@ -1331,7 +1334,7 @@ pub fn copy(from: &Path, to: &Path) -> io::Result<u64> {

#[cfg(not(any(target_os = "fuchsia", target_os = "vxworks")))]
pub fn chroot(dir: &Path) -> io::Result<()> {
let dir = cstr(dir)?;
cvt(unsafe { libc::chroot(dir.as_ptr()) })?;
let dir = OsPathBuf::new(dir)?;
cvt(unsafe { libc::chroot(dir.as_ptr()) }).map_err(|e| e.with_path(dir))?;
Ok(())
}
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