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
//! List directory contents

use crate::errno::Errno;
use crate::fcntl::{self, OFlag};
use crate::sys;
use crate::{Error, NixPath, Result};
use cfg_if::cfg_if;
use std::ffi;
use std::os::unix::io::{AsRawFd, IntoRawFd, RawFd};
use std::ptr;

#[cfg(target_os = "linux")]
use libc::{dirent64 as dirent, readdir64_r as readdir_r};

#[cfg(not(target_os = "linux"))]
use libc::{dirent, readdir_r};

/// An open directory.
///
/// This is a lower-level interface than `std::fs::ReadDir`. Notable differences:
///    * can be opened from a file descriptor (as returned by `openat`, perhaps before knowing
///      if the path represents a file or directory).
///    * implements `AsRawFd`, so it can be passed to `fstat`, `openat`, etc.
///      The file descriptor continues to be owned by the `Dir`, so callers must not keep a `RawFd`
///      after the `Dir` is dropped.
///    * can be iterated through multiple times without closing and reopening the file
///      descriptor. Each iteration rewinds when finished.
///    * returns entries for `.` (current directory) and `..` (parent directory).
///    * returns entries' names as a `CStr` (no allocation or conversion beyond whatever libc
///      does).
#[derive(Debug, Eq, Hash, PartialEq)]
pub struct Dir(ptr::NonNull<libc::DIR>);

impl Dir {
    /// Opens the given path as with `fcntl::open`.
    pub fn open<P: ?Sized + NixPath>(
        path: &P,
        oflag: OFlag,
        mode: sys::stat::Mode,
    ) -> Result<Self> {
        let fd = fcntl::open(path, oflag, mode)?;
        Dir::from_fd(fd)
    }

    /// Opens the given path as with `fcntl::openat`.
    pub fn openat<P: ?Sized + NixPath>(
        dirfd: RawFd,
        path: &P,
        oflag: OFlag,
        mode: sys::stat::Mode,
    ) -> Result<Self> {
        let fd = fcntl::openat(dirfd, path, oflag, mode)?;
        Dir::from_fd(fd)
    }

    /// Converts from a descriptor-based object, closing the descriptor on success or failure.
    #[inline]
    pub fn from<F: IntoRawFd>(fd: F) -> Result<Self> {
        Dir::from_fd(fd.into_raw_fd())
    }

    /// Converts from a file descriptor, closing it on success or failure.
    #[doc(alias("fdopendir"))]
    pub fn from_fd(fd: RawFd) -> Result<Self> {
        let d = ptr::NonNull::new(unsafe { libc::fdopendir(fd) }).ok_or_else(
            || {
                let e = Error::last();
                unsafe { libc::close(fd) };
                e
            },
        )?;
        Ok(Dir(d))
    }

    /// Returns an iterator of `Result<Entry>` which rewinds when finished.
    pub fn iter(&mut self) -> Iter {
        Iter(self)
    }
}

// `Dir` is not `Sync`. With the current implementation, it could be, but according to
// https://www.gnu.org/software/libc/manual/html_node/Reading_002fClosing-Directory.html,
// future versions of POSIX are likely to obsolete `readdir_r` and specify that it's unsafe to
// call `readdir` simultaneously from multiple threads.
//
// `Dir` is safe to pass from one thread to another, as it's not reference-counted.
unsafe impl Send for Dir {}

impl AsRawFd for Dir {
    fn as_raw_fd(&self) -> RawFd {
        unsafe { libc::dirfd(self.0.as_ptr()) }
    }
}

impl Drop for Dir {
    fn drop(&mut self) {
        let e = Errno::result(unsafe { libc::closedir(self.0.as_ptr()) });
        if !std::thread::panicking() && e == Err(Errno::EBADF) {
            panic!("Closing an invalid file descriptor!");
        };
    }
}

fn next(dir: &mut Dir) -> Option<Result<Entry>> {
    unsafe {
        // Note: POSIX specifies that portable applications should dynamically allocate a
        // buffer with room for a `d_name` field of size `pathconf(..., _PC_NAME_MAX)` plus 1
        // for the NUL byte. It doesn't look like the std library does this; it just uses
        // fixed-sized buffers (and libc's dirent seems to be sized so this is appropriate).
        // Probably fine here too then.
        let mut ent = std::mem::MaybeUninit::<dirent>::uninit();
        let mut result = ptr::null_mut();
        if let Err(e) = Errno::result(readdir_r(
            dir.0.as_ptr(),
            ent.as_mut_ptr(),
            &mut result,
        )) {
            return Some(Err(e));
        }
        if result.is_null() {
            return None;
        }
        assert_eq!(result, ent.as_mut_ptr());
        Some(Ok(Entry(ent.assume_init())))
    }
}

/// Return type of [`Dir::iter`].
#[derive(Debug, Eq, Hash, PartialEq)]
pub struct Iter<'d>(&'d mut Dir);

impl<'d> Iterator for Iter<'d> {
    type Item = Result<Entry>;

    fn next(&mut self) -> Option<Self::Item> {
        next(self.0)
    }
}

impl<'d> Drop for Iter<'d> {
    fn drop(&mut self) {
        unsafe { libc::rewinddir((self.0).0.as_ptr()) }
    }
}

/// The return type of [Dir::into_iter]
#[derive(Debug, Eq, Hash, PartialEq)]
pub struct OwningIter(Dir);

impl Iterator for OwningIter {
    type Item = Result<Entry>;

    fn next(&mut self) -> Option<Self::Item> {
        next(&mut self.0)
    }
}

/// The file descriptor continues to be owned by the `OwningIter`,
/// so callers must not keep a `RawFd` after the `OwningIter` is dropped.
impl AsRawFd for OwningIter {
    fn as_raw_fd(&self) -> RawFd {
        self.0.as_raw_fd()
    }
}

impl IntoIterator for Dir {
    type Item = Result<Entry>;
    type IntoIter = OwningIter;

    /// Creates a owning iterator, that is, one that takes ownership of the
    /// `Dir`. The `Dir` cannot be used after calling this.  This can be useful
    /// when you have a function that both creates a `Dir` instance and returns
    /// an `Iterator`.
    ///
    /// Example:
    ///
    /// ```
    /// use nix::{dir::Dir, fcntl::OFlag, sys::stat::Mode};
    /// use std::{iter::Iterator, string::String};
    ///
    /// fn ls_upper(dirname: &str) -> impl Iterator<Item=String> {
    ///     let d = Dir::open(dirname, OFlag::O_DIRECTORY, Mode::S_IXUSR).unwrap();
    ///     d.into_iter().map(|x| x.unwrap().file_name().as_ref().to_string_lossy().to_ascii_uppercase())
    /// }
    /// ```
    fn into_iter(self) -> Self::IntoIter {
        OwningIter(self)
    }
}

/// A directory entry, similar to `std::fs::DirEntry`.
///
/// Note that unlike the std version, this may represent the `.` or `..` entries.
#[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
#[repr(transparent)]
pub struct Entry(dirent);

/// Type of file referenced by a directory entry
#[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
pub enum Type {
    /// FIFO (Named pipe)
    Fifo,
    /// Character device
    CharacterDevice,
    /// Directory
    Directory,
    /// Block device
    BlockDevice,
    /// Regular file
    File,
    /// Symbolic link
    Symlink,
    /// Unix-domain socket
    Socket,
}

impl Entry {
    /// Returns the inode number (`d_ino`) of the underlying `dirent`.
    #[allow(clippy::useless_conversion)] // Not useless on all OSes
    // The cast is not unnecessary on all platforms.
    #[allow(clippy::unnecessary_cast)]
    pub fn ino(&self) -> u64 {
        cfg_if! {
            if #[cfg(any(target_os = "android",
                         target_os = "emscripten",
                         target_os = "fuchsia",
                         target_os = "haiku",
                         target_os = "illumos",
                         target_os = "ios",
                         target_os = "l4re",
                         target_os = "linux",
                         target_os = "macos",
                         target_os = "solaris"))] {
                self.0.d_ino as u64
            } else {
                u64::from(self.0.d_fileno)
            }
        }
    }

    /// Returns the bare file name of this directory entry without any other leading path component.
    pub fn file_name(&self) -> &ffi::CStr {
        unsafe { ::std::ffi::CStr::from_ptr(self.0.d_name.as_ptr()) }
    }

    /// Returns the type of this directory entry, if known.
    ///
    /// See platform `readdir(3)` or `dirent(5)` manpage for when the file type is known;
    /// notably, some Linux filesystems don't implement this. The caller should use `stat` or
    /// `fstat` if this returns `None`.
    pub fn file_type(&self) -> Option<Type> {
        #[cfg(not(any(
            target_os = "illumos",
            target_os = "solaris",
            target_os = "haiku"
        )))]
        match self.0.d_type {
            libc::DT_FIFO => Some(Type::Fifo),
            libc::DT_CHR => Some(Type::CharacterDevice),
            libc::DT_DIR => Some(Type::Directory),
            libc::DT_BLK => Some(Type::BlockDevice),
            libc::DT_REG => Some(Type::File),
            libc::DT_LNK => Some(Type::Symlink),
            libc::DT_SOCK => Some(Type::Socket),
            /* libc::DT_UNKNOWN | */ _ => None,
        }

        // illumos, Solaris, and Haiku systems do not have the d_type member at all:
        #[cfg(any(
            target_os = "illumos",
            target_os = "solaris",
            target_os = "haiku"
        ))]
        None
    }
}