Function tcgetattr_fallback

src/backend/linux_raw/termios/syscalls.rs:57–98

(fd: BorrowedFd<'_>)

#[cfg(not(any(target_arch = "powerpc", target_arch = "powerpc64")))]
#[cold]
fn tcgetattr_fallback(fd: BorrowedFd<'_>) -> io::Result<Termios> {
    use core::ptr::{addr_of, addr_of_mut};

    let mut result = MaybeUninit::<Termios>::uninit();

    // SAFETY: This invokes the `TCGETS` ioctl which initializes the `Termios`
    // structure except for the `input_speed` and `output_speed` fields, which
    // we manually initialize before forming a reference to the full `Termios`.
    unsafe {
        // Do the old `TCGETS` call.
        ret(syscall!(__NR_ioctl, fd, c_uint(c::TCGETS), &mut result))?;

        // Read the `control_modes` field without forming a reference to the
        // `Termios` because it isn't fully initialized yet.
        let ptr = result.as_mut_ptr();
        let control_modes = addr_of!((*ptr).control_modes).read();

        // Infer the output speed and set `output_speed`.
        let encoded_out = control_modes.bits() & c::CBAUD;
        let output_speed = match speed::decode(encoded_out) {
            Some(output_speed) => output_speed,
            None => return Err(io::Errno::RANGE),
        };
        addr_of_mut!((*ptr).output_speed).write(output_speed);

        // Infer the input speed and set `input_speed`. `B0` is a special-case
        // that means the input speed is the same as the output speed.
        let encoded_in = (control_modes.bits() & c::CIBAUD) >> c::IBSHIFT;
        let input_speed = if encoded_in == c::B0 {
            output_speed
        } else {
            match speed::decode(encoded_in) {
                Some(input_speed) => input_speed,
                None => return Err(io::Errno::RANGE),
            }
        };
        addr_of_mut!((*ptr).input_speed).write(input_speed);

        // Now all the fields are set.
        Ok(result.assume_init())
    }
}

#[inline]
pub(crate) fn tcgetpgrp(fd: BorrowedFd<'_>) -> io::Result<Pid> {