1//! Functions which operate on file descriptors which might be terminals.
2
3use crate::backend;
4#[cfg(any(
5    all(linux_raw, feature = "procfs"),
6    all(libc, not(any(target_os = "fuchsia", target_os = "wasi"))),
7))]
8use crate::io;
9use backend::fd::AsFd;
10#[cfg(any(
11    all(linux_raw, feature = "procfs"),
12    all(libc, not(any(target_os = "fuchsia", target_os = "wasi"))),
13))]
14use {
15    crate::ffi::CString, crate::path::SMALL_PATH_BUFFER_SIZE, alloc::vec::Vec,
16    backend::fd::BorrowedFd,
17};
18
19/// `isatty(fd)`—Tests whether a file descriptor refers to a terminal.
20///
21/// # References
22///  - [POSIX]
23///  - [Linux]
24///
25/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/isatty.html
26/// [Linux]: https://man7.org/linux/man-pages/man3/isatty.3.html
27#[inline]
28pub fn isatty<Fd: AsFd>(fd: Fd) -> bool {
29    backend::termios::syscalls::isatty(fd.as_fd())
30}
31
32/// `ttyname_r(fd)`
33///
34/// If `reuse` is non-empty, reuse its buffer to store the result if possible.
35///
36/// # References
37///  - [POSIX]
38///  - [Linux]
39///
40/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/ttyname.html
41/// [Linux]: https://man7.org/linux/man-pages/man3/ttyname.3.html
42#[cfg(not(any(target_os = "fuchsia", target_os = "wasi")))]
43#[cfg(feature = "procfs")]
44#[cfg_attr(doc_cfg, doc(cfg(feature = "procfs")))]
45#[inline]
46pub fn ttyname<Fd: AsFd, B: Into<Vec<u8>>>(dirfd: Fd, reuse: B) -> io::Result<CString> {
47    _ttyname(dirfd.as_fd(), reuse.into())
48}
49
50#[cfg(not(any(target_os = "fuchsia", target_os = "wasi")))]
51#[cfg(feature = "procfs")]
52fn _ttyname(dirfd: BorrowedFd<'_>, mut buffer: Vec<u8>) -> io::Result<CString> {
53    // This code would benefit from having a better way to read into
54    // uninitialized memory, but that requires `unsafe`.
55    buffer.clear();
56    buffer.reserve(SMALL_PATH_BUFFER_SIZE);
57    buffer.resize(buffer.capacity(), 0_u8);
58
59    loop {
60        match backend::termios::syscalls::ttyname(dirfd, &mut buffer) {
61            Err(io::Errno::RANGE) => {
62                buffer.reserve(1); // use `Vec` reallocation strategy to grow capacity exponentially
63                buffer.resize(buffer.capacity(), 0_u8);
64            }
65            Ok(len) => {
66                buffer.resize(len, 0_u8);
67                return Ok(CString::new(buffer).unwrap());
68            }
69            Err(errno) => return Err(errno),
70        }
71    }
72}
73