1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315
use crate::fd::{AsFd, BorrowedFd, OwnedFd};
use crate::ffi::{CStr, CString};
use crate::fs::{
fcntl_getfl, fstat, fstatfs, fstatvfs, openat, FileType, Mode, OFlags, Stat, StatFs, StatVfs,
};
use crate::io;
#[cfg(feature = "process")]
use crate::process::fchdir;
use crate::utils::as_ptr;
use alloc::borrow::ToOwned;
use alloc::vec::Vec;
use core::fmt;
use core::mem::size_of;
use linux_raw_sys::general::{linux_dirent64, SEEK_SET};
/// `DIR*`
pub struct Dir {
/// The `OwnedFd` that we read directory entries from.
fd: OwnedFd,
/// Have we seen any errors in this iteration?
any_errors: bool,
/// Should we rewind the stream on the next iteration?
rewind: bool,
/// The buffer for `linux_dirent64` entries.
buf: Vec<u8>,
/// Where we are in the buffer.
pos: usize,
}
impl Dir {
/// Take ownership of `fd` and construct a `Dir` that reads entries from
/// the given directory file descriptor.
#[inline]
pub fn new<Fd: Into<OwnedFd>>(fd: Fd) -> io::Result<Self> {
Self::_new(fd.into())
}
#[inline]
fn _new(fd: OwnedFd) -> io::Result<Self> {
Ok(Self {
fd,
any_errors: false,
rewind: false,
buf: Vec::new(),
pos: 0,
})
}
/// Borrow `fd` and construct a `Dir` that reads entries from the given
/// directory file descriptor.
#[inline]
pub fn read_from<Fd: AsFd>(fd: Fd) -> io::Result<Self> {
Self::_read_from(fd.as_fd())
}
#[inline]
fn _read_from(fd: BorrowedFd<'_>) -> io::Result<Self> {
let flags = fcntl_getfl(fd)?;
let fd_for_dir = openat(fd, cstr!("."), flags | OFlags::CLOEXEC, Mode::empty())?;
Ok(Self {
fd: fd_for_dir,
any_errors: false,
rewind: false,
buf: Vec::new(),
pos: 0,
})
}
/// `rewinddir(self)`
#[inline]
pub fn rewind(&mut self) {
self.any_errors = false;
self.rewind = true;
self.pos = self.buf.len();
}
/// `readdir(self)`, where `None` means the end of the directory.
pub fn read(&mut self) -> Option<io::Result<DirEntry>> {
// If we've seen errors, don't continue to try to read anything further.
if self.any_errors {
return None;
}
// If a rewind was requested, seek to the beginning.
if self.rewind {
self.rewind = false;
match io::retry_on_intr(|| {
crate::backend::fs::syscalls::_seek(self.fd.as_fd(), 0, SEEK_SET)
}) {
Ok(_) => (),
Err(err) => {
self.any_errors = true;
return Some(Err(err));
}
}
}
// Compute linux_dirent64 field offsets.
let z = linux_dirent64 {
d_ino: 0_u64,
d_off: 0_i64,
d_type: 0_u8,
d_reclen: 0_u16,
d_name: Default::default(),
};
let base = as_ptr(&z) as usize;
let offsetof_d_reclen = (as_ptr(&z.d_reclen) as usize) - base;
let offsetof_d_name = (as_ptr(&z.d_name) as usize) - base;
let offsetof_d_ino = (as_ptr(&z.d_ino) as usize) - base;
let offsetof_d_type = (as_ptr(&z.d_type) as usize) - base;
// Test if we need more entries, and if so, read more.
if self.buf.len() - self.pos < size_of::<linux_dirent64>() {
match self.read_more()? {
Ok(()) => (),
Err(err) => return Some(Err(err)),
}
}
// We successfully read an entry. Extract the fields.
let pos = self.pos;
// Do an unaligned u16 load.
let d_reclen = u16::from_ne_bytes([
self.buf[pos + offsetof_d_reclen],
self.buf[pos + offsetof_d_reclen + 1],
]);
assert!(self.buf.len() - pos >= d_reclen as usize);
self.pos += d_reclen as usize;
// Read the NUL-terminated name from the `d_name` field. Without
// `unsafe`, we need to scan for the NUL twice: once to obtain a size
// for the slice, and then once within `CStr::from_bytes_with_nul`.
let name_start = pos + offsetof_d_name;
let name_len = self.buf[name_start..]
.iter()
.position(|x| *x == b'\0')
.unwrap();
let name = CStr::from_bytes_with_nul(&self.buf[name_start..][..=name_len]).unwrap();
let name = name.to_owned();
assert!(name.as_bytes().len() <= self.buf.len() - name_start);
// Do an unaligned u64 load.
let d_ino = u64::from_ne_bytes([
self.buf[pos + offsetof_d_ino],
self.buf[pos + offsetof_d_ino + 1],
self.buf[pos + offsetof_d_ino + 2],
self.buf[pos + offsetof_d_ino + 3],
self.buf[pos + offsetof_d_ino + 4],
self.buf[pos + offsetof_d_ino + 5],
self.buf[pos + offsetof_d_ino + 6],
self.buf[pos + offsetof_d_ino + 7],
]);
let d_type = self.buf[pos + offsetof_d_type];
// Check that our types correspond to the `linux_dirent64` types.
let _ = linux_dirent64 {
d_ino,
d_off: 0,
d_type,
d_reclen,
d_name: Default::default(),
};
Some(Ok(DirEntry {
d_ino,
d_type,
name,
}))
}
#[must_use]
fn read_more(&mut self) -> Option<io::Result<()>> {
// The first few times we're called, we allocate a relatively small
// buffer, because many directories are small. If we're called more,
// use progressively larger allocations, up to a fixed maximum.
//
// The specific sizes and policy here have not been tuned in detail yet
// and may need to be adjusted. In doing so, we should be careful to
// avoid unbounded buffer growth. This buffer only exists to share the
// cost of a `getdents` call over many entries, so if it gets too big,
// cache and heap usage will outweigh the benefit. And ultimately,
// directories can contain more entries than we can allocate contiguous
// memory for, so we'll always need to cap the size at some point.
if self.buf.len() < 1024 * size_of::<linux_dirent64>() {
self.buf.reserve(32 * size_of::<linux_dirent64>());
}
self.buf.resize(self.buf.capacity(), 0);
let nread = match io::retry_on_intr(|| {
crate::backend::fs::syscalls::getdents(self.fd.as_fd(), &mut self.buf)
}) {
Ok(nread) => nread,
Err(io::Errno::NOENT) => {
self.any_errors = true;
return None;
}
Err(err) => {
self.any_errors = true;
return Some(Err(err));
}
};
self.buf.resize(nread, 0);
self.pos = 0;
if nread == 0 {
None
} else {
Some(Ok(()))
}
}
/// `fstat(self)`
#[inline]
pub fn stat(&self) -> io::Result<Stat> {
fstat(&self.fd)
}
/// `fstatfs(self)`
#[inline]
pub fn statfs(&self) -> io::Result<StatFs> {
fstatfs(&self.fd)
}
/// `fstatvfs(self)`
#[inline]
pub fn statvfs(&self) -> io::Result<StatVfs> {
fstatvfs(&self.fd)
}
/// `fchdir(self)`
#[cfg(feature = "process")]
#[cfg_attr(docsrs, doc(cfg(feature = "process")))]
#[inline]
pub fn chdir(&self) -> io::Result<()> {
fchdir(&self.fd)
}
}
impl Iterator for Dir {
type Item = io::Result<DirEntry>;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
Self::read(self)
}
}
impl fmt::Debug for Dir {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Dir").field("fd", &self.fd).finish()
}
}
/// `struct dirent`
#[derive(Debug)]
pub struct DirEntry {
d_ino: u64,
d_type: u8,
name: CString,
}
impl DirEntry {
/// Returns the file name of this directory entry.
#[inline]
pub fn file_name(&self) -> &CStr {
&self.name
}
/// Returns the type of this directory entry.
#[inline]
pub fn file_type(&self) -> FileType {
FileType::from_dirent_d_type(self.d_type)
}
/// Return the inode number of this directory entry.
#[inline]
pub fn ino(&self) -> u64 {
self.d_ino
}
}
#[test]
fn dir_iterator_handles_io_errors() {
// create a dir, keep the FD, then delete the dir
let tmp = tempfile::tempdir().unwrap();
let fd = crate::fs::openat(
crate::fs::CWD,
tmp.path(),
crate::fs::OFlags::RDONLY | crate::fs::OFlags::CLOEXEC,
crate::fs::Mode::empty(),
)
.unwrap();
let file_fd = crate::fs::openat(
&fd,
tmp.path().join("test.txt"),
crate::fs::OFlags::WRONLY | crate::fs::OFlags::CREATE,
crate::fs::Mode::RWXU,
)
.unwrap();
let mut dir = Dir::read_from(&fd).unwrap();
// Reach inside the `Dir` and replace its directory with a file, which
// will cause the subsequent `getdents64` to fail.
crate::io::dup2(&file_fd, &mut dir.fd).unwrap();
assert!(matches!(dir.next(), Some(Err(_))));
assert!(dir.next().is_none());
}