1 //! Owned and borrowed Unix-like file descriptors.
3 #![unstable(feature = "io_safety", issue = "87074")]
4 #![deny(unsafe_op_in_unsafe_fn)]
6 use super::raw::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
9 use crate::marker::PhantomData;
10 use crate::mem::forget;
11 #[cfg(not(target_os = "wasi"))]
13 use crate::sys_common::{AsInner, FromInner, IntoInner};
15 /// A borrowed file descriptor.
17 /// This has a lifetime parameter to tie it to the lifetime of something that
18 /// owns the file descriptor.
20 /// This uses `repr(transparent)` and has the representation of a host file
21 /// descriptor, so it can be used in FFI in places where a file descriptor is
22 /// passed as an argument, it is not captured or consumed, and it never has the
24 #[derive(Copy, Clone)]
26 #[rustc_layout_scalar_valid_range_start(0)]
27 // libstd/os/raw/mod.rs assures me that every libstd-supported platform has a
28 // 32-bit c_int. Below is -2, in two's complement, but that only works out
29 // because c_int is 32 bits.
30 #[rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FE)]
31 #[unstable(feature = "io_safety", issue = "87074")]
32 pub struct BorrowedFd<'fd> {
34 _phantom: PhantomData<&'fd OwnedFd>,
37 /// An owned file descriptor.
39 /// This closes the file descriptor on drop.
41 /// This uses `repr(transparent)` and has the representation of a host file
42 /// descriptor, so it can be used in FFI in places where a file descriptor is
43 /// passed as a consumed argument or returned as an owned value, and it never
44 /// has the value `-1`.
46 #[rustc_layout_scalar_valid_range_start(0)]
47 // libstd/os/raw/mod.rs assures me that every libstd-supported platform has a
48 // 32-bit c_int. Below is -2, in two's complement, but that only works out
49 // because c_int is 32 bits.
50 #[rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FE)]
51 #[unstable(feature = "io_safety", issue = "87074")]
57 /// Return a `BorrowedFd` holding the given raw file descriptor.
61 /// The resource pointed to by `fd` must remain open for the duration of
62 /// the returned `BorrowedFd`, and it must not have the value `-1`.
64 #[unstable(feature = "io_safety", issue = "87074")]
65 pub unsafe fn borrow_raw_fd(fd: RawFd) -> Self {
66 assert_ne!(fd, u32::MAX as RawFd);
67 // SAFETY: we just asserted that the value is in the valid range and isn't `-1` (the only value bigger than `0xFF_FF_FF_FE` unsigned)
68 unsafe { Self { fd, _phantom: PhantomData } }
73 /// Creates a new `OwnedFd` instance that shares the same underlying file handle
74 /// as the existing `OwnedFd` instance.
75 #[cfg(not(target_os = "wasi"))]
76 pub fn try_clone(&self) -> crate::io::Result<Self> {
77 // We want to atomically duplicate this file descriptor and set the
78 // CLOEXEC flag, and currently that's done via F_DUPFD_CLOEXEC. This
79 // is a POSIX flag that was added to Linux in 2.6.24.
80 #[cfg(not(target_os = "espidf"))]
81 let cmd = libc::F_DUPFD_CLOEXEC;
83 // For ESP-IDF, F_DUPFD is used instead, because the CLOEXEC semantics
84 // will never be supported, as this is a bare metal framework with
85 // no capabilities for multi-process execution. While F_DUPFD is also
86 // not supported yet, it might be (currently it returns ENOSYS).
87 #[cfg(target_os = "espidf")]
88 let cmd = libc::F_DUPFD;
90 let fd = cvt(unsafe { libc::fcntl(self.as_raw_fd(), cmd, 0) })?;
91 Ok(unsafe { Self::from_raw_fd(fd) })
94 #[cfg(target_os = "wasi")]
95 pub fn try_clone(&self) -> crate::io::Result<Self> {
96 Err(crate::io::Error::new_const(
97 crate::io::ErrorKind::Unsupported,
98 &"operation not supported on WASI yet",
103 #[unstable(feature = "io_safety", issue = "87074")]
104 impl AsRawFd for BorrowedFd<'_> {
106 fn as_raw_fd(&self) -> RawFd {
111 #[unstable(feature = "io_safety", issue = "87074")]
112 impl AsRawFd for OwnedFd {
114 fn as_raw_fd(&self) -> RawFd {
119 #[unstable(feature = "io_safety", issue = "87074")]
120 impl IntoRawFd for OwnedFd {
122 fn into_raw_fd(self) -> RawFd {
129 #[unstable(feature = "io_safety", issue = "87074")]
130 impl FromRawFd for OwnedFd {
131 /// Constructs a new instance of `Self` from the given raw file descriptor.
135 /// The resource pointed to by `fd` must be open and suitable for assuming
136 /// ownership. The resource must not require any cleanup other than `close`.
138 unsafe fn from_raw_fd(fd: RawFd) -> Self {
139 assert_ne!(fd, u32::MAX as RawFd);
140 // SAFETY: we just asserted that the value is in the valid range and isn't `-1` (the only value bigger than `0xFF_FF_FF_FE` unsigned)
141 unsafe { Self { fd } }
145 #[unstable(feature = "io_safety", issue = "87074")]
146 impl Drop for OwnedFd {
150 // Note that errors are ignored when closing a file descriptor. The
151 // reason for this is that if an error occurs we don't actually know if
152 // the file descriptor was closed or not, and if we retried (for
153 // something like EINTR), we might close another valid file descriptor
154 // opened after we closed ours.
155 let _ = libc::close(self.fd);
160 #[unstable(feature = "io_safety", issue = "87074")]
161 impl fmt::Debug for BorrowedFd<'_> {
162 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
163 f.debug_struct("BorrowedFd").field("fd", &self.fd).finish()
167 #[unstable(feature = "io_safety", issue = "87074")]
168 impl fmt::Debug for OwnedFd {
169 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
170 f.debug_struct("OwnedFd").field("fd", &self.fd).finish()
174 /// A trait to borrow the file descriptor from an underlying object.
176 /// This is only available on unix platforms and must be imported in order to
177 /// call the method. Windows platforms have a corresponding `AsHandle` and
178 /// `AsSocket` set of traits.
179 #[unstable(feature = "io_safety", issue = "87074")]
181 /// Borrows the file descriptor.
186 /// # #![feature(io_safety)]
187 /// use std::fs::File;
189 /// # #[cfg(target_os = "wasi")]
190 /// # use std::os::wasi::io::{AsFd, BorrowedFd};
192 /// # use std::os::unix::io::{AsFd, BorrowedFd};
194 /// let mut f = File::open("foo.txt")?;
195 /// # #[cfg(any(unix, target_os = "wasi"))]
196 /// let borrowed_fd: BorrowedFd<'_> = f.as_fd();
197 /// # Ok::<(), io::Error>(())
199 #[unstable(feature = "io_safety", issue = "87074")]
200 fn as_fd(&self) -> BorrowedFd<'_>;
203 #[unstable(feature = "io_safety", issue = "87074")]
204 impl AsFd for BorrowedFd<'_> {
206 fn as_fd(&self) -> BorrowedFd<'_> {
211 #[unstable(feature = "io_safety", issue = "87074")]
212 impl AsFd for OwnedFd {
214 fn as_fd(&self) -> BorrowedFd<'_> {
215 // Safety: `OwnedFd` and `BorrowedFd` have the same validity
216 // invariants, and the `BorrowdFd` is bounded by the lifetime
218 unsafe { BorrowedFd::borrow_raw_fd(self.as_raw_fd()) }
222 #[unstable(feature = "io_safety", issue = "87074")]
223 impl AsFd for fs::File {
225 fn as_fd(&self) -> BorrowedFd<'_> {
226 self.as_inner().as_fd()
230 #[unstable(feature = "io_safety", issue = "87074")]
231 impl From<fs::File> for OwnedFd {
233 fn from(file: fs::File) -> OwnedFd {
234 file.into_inner().into_inner().into_inner()
238 #[unstable(feature = "io_safety", issue = "87074")]
239 impl From<OwnedFd> for fs::File {
241 fn from(owned_fd: OwnedFd) -> Self {
242 Self::from_inner(FromInner::from_inner(FromInner::from_inner(owned_fd)))
246 #[unstable(feature = "io_safety", issue = "87074")]
247 impl AsFd for crate::net::TcpStream {
249 fn as_fd(&self) -> BorrowedFd<'_> {
250 self.as_inner().socket().as_fd()
254 #[unstable(feature = "io_safety", issue = "87074")]
255 impl From<crate::net::TcpStream> for OwnedFd {
257 fn from(tcp_stream: crate::net::TcpStream) -> OwnedFd {
258 tcp_stream.into_inner().into_socket().into_inner().into_inner().into()
262 #[unstable(feature = "io_safety", issue = "87074")]
263 impl From<OwnedFd> for crate::net::TcpStream {
265 fn from(owned_fd: OwnedFd) -> Self {
266 Self::from_inner(FromInner::from_inner(FromInner::from_inner(FromInner::from_inner(
272 #[unstable(feature = "io_safety", issue = "87074")]
273 impl AsFd for crate::net::TcpListener {
275 fn as_fd(&self) -> BorrowedFd<'_> {
276 self.as_inner().socket().as_fd()
280 #[unstable(feature = "io_safety", issue = "87074")]
281 impl From<crate::net::TcpListener> for OwnedFd {
283 fn from(tcp_listener: crate::net::TcpListener) -> OwnedFd {
284 tcp_listener.into_inner().into_socket().into_inner().into_inner().into()
288 #[unstable(feature = "io_safety", issue = "87074")]
289 impl From<OwnedFd> for crate::net::TcpListener {
291 fn from(owned_fd: OwnedFd) -> Self {
292 Self::from_inner(FromInner::from_inner(FromInner::from_inner(FromInner::from_inner(
298 #[unstable(feature = "io_safety", issue = "87074")]
299 impl AsFd for crate::net::UdpSocket {
301 fn as_fd(&self) -> BorrowedFd<'_> {
302 self.as_inner().socket().as_fd()
306 #[unstable(feature = "io_safety", issue = "87074")]
307 impl From<crate::net::UdpSocket> for OwnedFd {
309 fn from(udp_socket: crate::net::UdpSocket) -> OwnedFd {
310 udp_socket.into_inner().into_socket().into_inner().into_inner().into()
314 #[unstable(feature = "io_safety", issue = "87074")]
315 impl From<OwnedFd> for crate::net::UdpSocket {
317 fn from(owned_fd: OwnedFd) -> Self {
318 Self::from_inner(FromInner::from_inner(FromInner::from_inner(FromInner::from_inner(