Function select

src/backend/linux_raw/event/syscalls.rs:107–224

(
    nfds: i32,
    readfds: Option<&mut [FdSetElement]>,
    writefds: Option<&mut [FdSetElement]>,
    exceptfds: Option<&mut [FdSetElement]>,
    timeout: Option<&crate::timespec::Timespec>,
)

}

pub(crate) unsafe fn select(
    nfds: i32,
    readfds: Option<&mut [FdSetElement]>,
    writefds: Option<&mut [FdSetElement]>,
    exceptfds: Option<&mut [FdSetElement]>,
    timeout: Option<&crate::timespec::Timespec>,
) -> io::Result<i32> {
    let len = crate::event::fd_set_num_elements_for_bitvector(nfds);

    let readfds = match readfds {
        Some(readfds) => {
            assert!(readfds.len() >= len);
            readfds.as_mut_ptr()
        }
        None => null_mut(),
    };
    let writefds = match writefds {
        Some(writefds) => {
            assert!(writefds.len() >= len);
            writefds.as_mut_ptr()
        }
        None => null_mut(),
    };
    let exceptfds = match exceptfds {
        Some(exceptfds) => {
            assert!(exceptfds.len() >= len);
            exceptfds.as_mut_ptr()
        }
        None => null_mut(),
    };

    #[cfg(target_pointer_width = "32")]
    {
        // If we don't have Linux 5.1, and the timeout fits in a
        // `__kernel_old_timespec`, use plain `pselect6`.
        //
        // We do this unconditionally, rather than trying `pselect6_time64` and
        // falling back on `Errno::NOSYS`, because seccomp configurations will
        // sometimes abort the process on syscalls they don't recognize.
        #[cfg(not(feature = "linux_5_1"))]
        {
            use linux_raw_sys::general::__kernel_old_timespec;

            // If we don't have a timeout, or if we can convert the timeout to
            // a `__kernel_old_timespec`, the use `__NR_pselect6`.
            fn convert(timeout: &Timespec) -> Option<__kernel_old_timespec> {
                Some(__kernel_old_timespec {
                    tv_sec: timeout.tv_sec.try_into().ok()?,
                    tv_nsec: timeout.tv_nsec.try_into().ok()?,
                })
            }
            let old_timeout = if let Some(timeout) = timeout {
                match convert(timeout) {
                    // Could not convert timeout.
                    None => None,
                    // Could convert timeout. Ok!
                    Some(old_timeout) => Some(Some(old_timeout)),
                }