std/sys/pal/unix/
fd.rs

1#![unstable(reason = "not public", issue = "none", feature = "fd")]
2
3#[cfg(test)]
4mod tests;
5
6#[cfg(not(any(
7    target_os = "linux",
8    target_os = "l4re",
9    target_os = "android",
10    target_os = "hurd",
11)))]
12use libc::off_t as off64_t;
13#[cfg(any(
14    target_os = "android",
15    target_os = "linux",
16    target_os = "l4re",
17    target_os = "hurd",
18))]
19use libc::off64_t;
20
21use crate::cmp;
22use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut, Read};
23use crate::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
24use crate::sys::cvt;
25use crate::sys_common::{AsInner, FromInner, IntoInner};
26
27#[derive(Debug)]
28pub struct FileDesc(OwnedFd);
29
30// The maximum read limit on most POSIX-like systems is `SSIZE_MAX`,
31// with the man page quoting that if the count of bytes to read is
32// greater than `SSIZE_MAX` the result is "unspecified".
33//
34// On Apple targets however, apparently the 64-bit libc is either buggy or
35// intentionally showing odd behavior by rejecting any read with a size
36// larger than or equal to INT_MAX. To handle both of these the read
37// size is capped on both platforms.
38const READ_LIMIT: usize = if cfg!(target_vendor = "apple") {
39    libc::c_int::MAX as usize - 1
40} else {
41    libc::ssize_t::MAX as usize
42};
43
44#[cfg(any(
45    target_os = "dragonfly",
46    target_os = "freebsd",
47    target_os = "netbsd",
48    target_os = "openbsd",
49    target_vendor = "apple",
50    target_os = "cygwin",
51))]
52const fn max_iov() -> usize {
53    libc::IOV_MAX as usize
54}
55
56#[cfg(any(
57    target_os = "android",
58    target_os = "emscripten",
59    target_os = "linux",
60    target_os = "nto",
61))]
62const fn max_iov() -> usize {
63    libc::UIO_MAXIOV as usize
64}
65
66#[cfg(not(any(
67    target_os = "android",
68    target_os = "dragonfly",
69    target_os = "emscripten",
70    target_os = "freebsd",
71    target_os = "linux",
72    target_os = "netbsd",
73    target_os = "nto",
74    target_os = "openbsd",
75    target_os = "horizon",
76    target_os = "vita",
77    target_vendor = "apple",
78    target_os = "cygwin",
79)))]
80const fn max_iov() -> usize {
81    16 // The minimum value required by POSIX.
82}
83
84impl FileDesc {
85    #[inline]
86    pub fn try_clone(&self) -> io::Result<Self> {
87        self.duplicate()
88    }
89
90    pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
91        let ret = cvt(unsafe {
92            libc::read(
93                self.as_raw_fd(),
94                buf.as_mut_ptr() as *mut libc::c_void,
95                cmp::min(buf.len(), READ_LIMIT),
96            )
97        })?;
98        Ok(ret as usize)
99    }
100
101    #[cfg(not(any(
102        target_os = "espidf",
103        target_os = "horizon",
104        target_os = "vita",
105        target_os = "nuttx"
106    )))]
107    pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
108        let ret = cvt(unsafe {
109            libc::readv(
110                self.as_raw_fd(),
111                bufs.as_mut_ptr() as *mut libc::iovec as *const libc::iovec,
112                cmp::min(bufs.len(), max_iov()) as libc::c_int,
113            )
114        })?;
115        Ok(ret as usize)
116    }
117
118    #[cfg(any(
119        target_os = "espidf",
120        target_os = "horizon",
121        target_os = "vita",
122        target_os = "nuttx"
123    ))]
124    pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
125        io::default_read_vectored(|b| self.read(b), bufs)
126    }
127
128    #[inline]
129    pub fn is_read_vectored(&self) -> bool {
130        cfg!(not(any(
131            target_os = "espidf",
132            target_os = "horizon",
133            target_os = "vita",
134            target_os = "nuttx"
135        )))
136    }
137
138    pub fn read_to_end(&self, buf: &mut Vec<u8>) -> io::Result<usize> {
139        let mut me = self;
140        (&mut me).read_to_end(buf)
141    }
142
143    #[cfg_attr(target_os = "vxworks", allow(unused_unsafe))]
144    pub fn read_at(&self, buf: &mut [u8], offset: u64) -> io::Result<usize> {
145        #[cfg(not(any(
146            all(target_os = "linux", not(target_env = "musl")),
147            target_os = "android",
148            target_os = "hurd"
149        )))]
150        use libc::pread as pread64;
151        #[cfg(any(
152            all(target_os = "linux", not(target_env = "musl")),
153            target_os = "android",
154            target_os = "hurd"
155        ))]
156        use libc::pread64;
157
158        unsafe {
159            cvt(pread64(
160                self.as_raw_fd(),
161                buf.as_mut_ptr() as *mut libc::c_void,
162                cmp::min(buf.len(), READ_LIMIT),
163                offset as off64_t,
164            ))
165            .map(|n| n as usize)
166        }
167    }
168
169    pub fn read_buf(&self, mut cursor: BorrowedCursor<'_>) -> io::Result<()> {
170        let ret = cvt(unsafe {
171            libc::read(
172                self.as_raw_fd(),
173                cursor.as_mut().as_mut_ptr() as *mut libc::c_void,
174                cmp::min(cursor.capacity(), READ_LIMIT),
175            )
176        })?;
177
178        // Safety: `ret` bytes were written to the initialized portion of the buffer
179        unsafe {
180            cursor.advance_unchecked(ret as usize);
181        }
182        Ok(())
183    }
184
185    #[cfg(any(
186        target_os = "aix",
187        target_os = "dragonfly", // DragonFly 1.5
188        target_os = "emscripten",
189        target_os = "freebsd",
190        target_os = "fuchsia",
191        target_os = "hurd",
192        target_os = "illumos",
193        target_os = "linux",
194        target_os = "netbsd",
195        target_os = "openbsd", // OpenBSD 2.7
196    ))]
197    pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
198        let ret = cvt(unsafe {
199            libc::preadv(
200                self.as_raw_fd(),
201                bufs.as_mut_ptr() as *mut libc::iovec as *const libc::iovec,
202                cmp::min(bufs.len(), max_iov()) as libc::c_int,
203                offset as _,
204            )
205        })?;
206        Ok(ret as usize)
207    }
208
209    #[cfg(not(any(
210        target_os = "aix",
211        target_os = "android",
212        target_os = "dragonfly",
213        target_os = "emscripten",
214        target_os = "freebsd",
215        target_os = "fuchsia",
216        target_os = "hurd",
217        target_os = "illumos",
218        target_os = "linux",
219        target_os = "netbsd",
220        target_os = "openbsd",
221        target_vendor = "apple",
222    )))]
223    pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
224        io::default_read_vectored(|b| self.read_at(b, offset), bufs)
225    }
226
227    // We support some old Android versions that do not have `preadv` in libc,
228    // so we use weak linkage and fallback to a direct syscall if not available.
229    //
230    // On 32-bit targets, we don't want to deal with weird ABI issues around
231    // passing 64-bits parameters to syscalls, so we fallback to the default
232    // implementation if `preadv` is not available.
233    #[cfg(all(target_os = "android", target_pointer_width = "64"))]
234    pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
235        super::weak::syscall! {
236            fn preadv(
237                fd: libc::c_int,
238                iovec: *const libc::iovec,
239                n_iovec: libc::c_int,
240                offset: off64_t
241            ) -> isize
242        }
243
244        let ret = cvt(unsafe {
245            preadv(
246                self.as_raw_fd(),
247                bufs.as_mut_ptr() as *mut libc::iovec as *const libc::iovec,
248                cmp::min(bufs.len(), max_iov()) as libc::c_int,
249                offset as _,
250            )
251        })?;
252        Ok(ret as usize)
253    }
254
255    #[cfg(all(target_os = "android", target_pointer_width = "32"))]
256    // FIXME(#115199): Rust currently omits weak function definitions
257    // and its metadata from LLVM IR.
258    #[no_sanitize(cfi)]
259    pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
260        super::weak::weak!(fn preadv64(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);
261
262        match preadv64.get() {
263            Some(preadv) => {
264                let ret = cvt(unsafe {
265                    preadv(
266                        self.as_raw_fd(),
267                        bufs.as_mut_ptr() as *mut libc::iovec as *const libc::iovec,
268                        cmp::min(bufs.len(), max_iov()) as libc::c_int,
269                        offset as _,
270                    )
271                })?;
272                Ok(ret as usize)
273            }
274            None => io::default_read_vectored(|b| self.read_at(b, offset), bufs),
275        }
276    }
277
278    // We support old MacOS, iOS, watchOS, tvOS and visionOS. `preadv` was added in the following
279    // Apple OS versions:
280    // ios 14.0
281    // tvos 14.0
282    // macos 11.0
283    // watchos 7.0
284    //
285    // These versions may be newer than the minimum supported versions of OS's we support so we must
286    // use "weak" linking.
287    #[cfg(target_vendor = "apple")]
288    pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
289        super::weak::weak!(fn preadv(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);
290
291        match preadv.get() {
292            Some(preadv) => {
293                let ret = cvt(unsafe {
294                    preadv(
295                        self.as_raw_fd(),
296                        bufs.as_mut_ptr() as *mut libc::iovec as *const libc::iovec,
297                        cmp::min(bufs.len(), max_iov()) as libc::c_int,
298                        offset as _,
299                    )
300                })?;
301                Ok(ret as usize)
302            }
303            None => io::default_read_vectored(|b| self.read_at(b, offset), bufs),
304        }
305    }
306
307    pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
308        let ret = cvt(unsafe {
309            libc::write(
310                self.as_raw_fd(),
311                buf.as_ptr() as *const libc::c_void,
312                cmp::min(buf.len(), READ_LIMIT),
313            )
314        })?;
315        Ok(ret as usize)
316    }
317
318    #[cfg(not(any(
319        target_os = "espidf",
320        target_os = "horizon",
321        target_os = "vita",
322        target_os = "nuttx"
323    )))]
324    pub fn write_vectored(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
325        let ret = cvt(unsafe {
326            libc::writev(
327                self.as_raw_fd(),
328                bufs.as_ptr() as *const libc::iovec,
329                cmp::min(bufs.len(), max_iov()) as libc::c_int,
330            )
331        })?;
332        Ok(ret as usize)
333    }
334
335    #[cfg(any(
336        target_os = "espidf",
337        target_os = "horizon",
338        target_os = "vita",
339        target_os = "nuttx"
340    ))]
341    pub fn write_vectored(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
342        io::default_write_vectored(|b| self.write(b), bufs)
343    }
344
345    #[inline]
346    pub fn is_write_vectored(&self) -> bool {
347        cfg!(not(any(
348            target_os = "espidf",
349            target_os = "horizon",
350            target_os = "vita",
351            target_os = "nuttx"
352        )))
353    }
354
355    #[cfg_attr(target_os = "vxworks", allow(unused_unsafe))]
356    pub fn write_at(&self, buf: &[u8], offset: u64) -> io::Result<usize> {
357        #[cfg(not(any(
358            all(target_os = "linux", not(target_env = "musl")),
359            target_os = "android",
360            target_os = "hurd"
361        )))]
362        use libc::pwrite as pwrite64;
363        #[cfg(any(
364            all(target_os = "linux", not(target_env = "musl")),
365            target_os = "android",
366            target_os = "hurd"
367        ))]
368        use libc::pwrite64;
369
370        unsafe {
371            cvt(pwrite64(
372                self.as_raw_fd(),
373                buf.as_ptr() as *const libc::c_void,
374                cmp::min(buf.len(), READ_LIMIT),
375                offset as off64_t,
376            ))
377            .map(|n| n as usize)
378        }
379    }
380
381    #[cfg(any(
382        target_os = "aix",
383        target_os = "dragonfly", // DragonFly 1.5
384        target_os = "emscripten",
385        target_os = "freebsd",
386        target_os = "fuchsia",
387        target_os = "hurd",
388        target_os = "illumos",
389        target_os = "linux",
390        target_os = "netbsd",
391        target_os = "openbsd", // OpenBSD 2.7
392    ))]
393    pub fn write_vectored_at(&self, bufs: &[IoSlice<'_>], offset: u64) -> io::Result<usize> {
394        let ret = cvt(unsafe {
395            libc::pwritev(
396                self.as_raw_fd(),
397                bufs.as_ptr() as *const libc::iovec,
398                cmp::min(bufs.len(), max_iov()) as libc::c_int,
399                offset as _,
400            )
401        })?;
402        Ok(ret as usize)
403    }
404
405    #[cfg(not(any(
406        target_os = "aix",
407        target_os = "android",
408        target_os = "dragonfly",
409        target_os = "emscripten",
410        target_os = "freebsd",
411        target_os = "fuchsia",
412        target_os = "hurd",
413        target_os = "illumos",
414        target_os = "linux",
415        target_os = "netbsd",
416        target_os = "openbsd",
417        target_vendor = "apple",
418    )))]
419    pub fn write_vectored_at(&self, bufs: &[IoSlice<'_>], offset: u64) -> io::Result<usize> {
420        io::default_write_vectored(|b| self.write_at(b, offset), bufs)
421    }
422
423    // We support some old Android versions that do not have `pwritev` in libc,
424    // so we use weak linkage and fallback to a direct syscall if not available.
425    //
426    // On 32-bit targets, we don't want to deal with weird ABI issues around
427    // passing 64-bits parameters to syscalls, so we fallback to the default
428    // implementation if `pwritev` is not available.
429    #[cfg(all(target_os = "android", target_pointer_width = "64"))]
430    pub fn write_vectored_at(&self, bufs: &[IoSlice<'_>], offset: u64) -> io::Result<usize> {
431        super::weak::syscall! {
432            fn pwritev(
433                fd: libc::c_int,
434                iovec: *const libc::iovec,
435                n_iovec: libc::c_int,
436                offset: off64_t
437            ) -> isize
438        }
439
440        let ret = cvt(unsafe {
441            pwritev(
442                self.as_raw_fd(),
443                bufs.as_ptr() as *const libc::iovec,
444                cmp::min(bufs.len(), max_iov()) as libc::c_int,
445                offset as _,
446            )
447        })?;
448        Ok(ret as usize)
449    }
450
451    #[cfg(all(target_os = "android", target_pointer_width = "32"))]
452    pub fn write_vectored_at(&self, bufs: &[IoSlice<'_>], offset: u64) -> io::Result<usize> {
453        super::weak::weak!(fn pwritev64(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);
454
455        match pwritev64.get() {
456            Some(pwritev) => {
457                let ret = cvt(unsafe {
458                    pwritev(
459                        self.as_raw_fd(),
460                        bufs.as_ptr() as *const libc::iovec,
461                        cmp::min(bufs.len(), max_iov()) as libc::c_int,
462                        offset as _,
463                    )
464                })?;
465                Ok(ret as usize)
466            }
467            None => io::default_write_vectored(|b| self.write_at(b, offset), bufs),
468        }
469    }
470
471    // We support old MacOS, iOS, watchOS, tvOS and visionOS. `pwritev` was added in the following
472    // Apple OS versions:
473    // ios 14.0
474    // tvos 14.0
475    // macos 11.0
476    // watchos 7.0
477    //
478    // These versions may be newer than the minimum supported versions of OS's we support so we must
479    // use "weak" linking.
480    #[cfg(target_vendor = "apple")]
481    pub fn write_vectored_at(&self, bufs: &[IoSlice<'_>], offset: u64) -> io::Result<usize> {
482        super::weak::weak!(fn pwritev(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);
483
484        match pwritev.get() {
485            Some(pwritev) => {
486                let ret = cvt(unsafe {
487                    pwritev(
488                        self.as_raw_fd(),
489                        bufs.as_ptr() as *const libc::iovec,
490                        cmp::min(bufs.len(), max_iov()) as libc::c_int,
491                        offset as _,
492                    )
493                })?;
494                Ok(ret as usize)
495            }
496            None => io::default_write_vectored(|b| self.write_at(b, offset), bufs),
497        }
498    }
499
500    #[cfg(not(any(
501        target_env = "newlib",
502        target_os = "solaris",
503        target_os = "illumos",
504        target_os = "emscripten",
505        target_os = "fuchsia",
506        target_os = "l4re",
507        target_os = "linux",
508        target_os = "cygwin",
509        target_os = "haiku",
510        target_os = "redox",
511        target_os = "vxworks",
512        target_os = "nto",
513    )))]
514    pub fn set_cloexec(&self) -> io::Result<()> {
515        unsafe {
516            cvt(libc::ioctl(self.as_raw_fd(), libc::FIOCLEX))?;
517            Ok(())
518        }
519    }
520    #[cfg(any(
521        all(
522            target_env = "newlib",
523            not(any(target_os = "espidf", target_os = "horizon", target_os = "vita"))
524        ),
525        target_os = "solaris",
526        target_os = "illumos",
527        target_os = "emscripten",
528        target_os = "fuchsia",
529        target_os = "l4re",
530        target_os = "linux",
531        target_os = "cygwin",
532        target_os = "haiku",
533        target_os = "redox",
534        target_os = "vxworks",
535        target_os = "nto",
536    ))]
537    pub fn set_cloexec(&self) -> io::Result<()> {
538        unsafe {
539            let previous = cvt(libc::fcntl(self.as_raw_fd(), libc::F_GETFD))?;
540            let new = previous | libc::FD_CLOEXEC;
541            if new != previous {
542                cvt(libc::fcntl(self.as_raw_fd(), libc::F_SETFD, new))?;
543            }
544            Ok(())
545        }
546    }
547    #[cfg(any(target_os = "espidf", target_os = "horizon", target_os = "vita"))]
548    pub fn set_cloexec(&self) -> io::Result<()> {
549        // FD_CLOEXEC is not supported in ESP-IDF, Horizon OS and Vita but there's no need to,
550        // because none of them supports spawning processes.
551        Ok(())
552    }
553
554    #[cfg(target_os = "linux")]
555    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
556        unsafe {
557            let v = nonblocking as libc::c_int;
558            cvt(libc::ioctl(self.as_raw_fd(), libc::FIONBIO, &v))?;
559            Ok(())
560        }
561    }
562
563    #[cfg(not(target_os = "linux"))]
564    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
565        unsafe {
566            let previous = cvt(libc::fcntl(self.as_raw_fd(), libc::F_GETFL))?;
567            let new = if nonblocking {
568                previous | libc::O_NONBLOCK
569            } else {
570                previous & !libc::O_NONBLOCK
571            };
572            if new != previous {
573                cvt(libc::fcntl(self.as_raw_fd(), libc::F_SETFL, new))?;
574            }
575            Ok(())
576        }
577    }
578
579    #[inline]
580    pub fn duplicate(&self) -> io::Result<FileDesc> {
581        Ok(Self(self.0.try_clone()?))
582    }
583}
584
585impl<'a> Read for &'a FileDesc {
586    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
587        (**self).read(buf)
588    }
589
590    fn read_buf(&mut self, cursor: BorrowedCursor<'_>) -> io::Result<()> {
591        (**self).read_buf(cursor)
592    }
593
594    fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
595        (**self).read_vectored(bufs)
596    }
597
598    #[inline]
599    fn is_read_vectored(&self) -> bool {
600        (**self).is_read_vectored()
601    }
602}
603
604impl AsInner<OwnedFd> for FileDesc {
605    #[inline]
606    fn as_inner(&self) -> &OwnedFd {
607        &self.0
608    }
609}
610
611impl IntoInner<OwnedFd> for FileDesc {
612    fn into_inner(self) -> OwnedFd {
613        self.0
614    }
615}
616
617impl FromInner<OwnedFd> for FileDesc {
618    fn from_inner(owned_fd: OwnedFd) -> Self {
619        Self(owned_fd)
620    }
621}
622
623impl AsFd for FileDesc {
624    fn as_fd(&self) -> BorrowedFd<'_> {
625        self.0.as_fd()
626    }
627}
628
629impl AsRawFd for FileDesc {
630    #[inline]
631    fn as_raw_fd(&self) -> RawFd {
632        self.0.as_raw_fd()
633    }
634}
635
636impl IntoRawFd for FileDesc {
637    fn into_raw_fd(self) -> RawFd {
638        self.0.into_raw_fd()
639    }
640}
641
642impl FromRawFd for FileDesc {
643    unsafe fn from_raw_fd(raw_fd: RawFd) -> Self {
644        Self(FromRawFd::from_raw_fd(raw_fd))
645    }
646}