Function try_decode_raw_fd

src/backend/linux_raw/io/errno.rs:179–199

(
    raw: RetReg<Num>,
)

/// success.
#[inline]
pub(in crate::backend) unsafe fn try_decode_raw_fd<Num: RetNumber>(
    raw: RetReg<Num>,
) -> io::Result<RawFd> {
    // Instead of using `check_result` here, we just check for negative, since
    // this function is only used for system calls which return file
    // descriptors, and this produces smaller code.
    if raw.is_negative() {
        debug_assert!(raw.is_in_range(-4095..0));

        // Tell the optimizer that we know the value is in the error range.
        // This helps it avoid unnecessary integer conversions.
        #[cfg(core_intrinsics)]
        {
            core::intrinsics::assume(raw.is_in_range(-4095..0));
        }

        return Err(Errno(raw.decode_error_code()));
    }

    Ok(raw.decode_raw_fd())
}

/// Check for an error from the result of a syscall which encodes no value on
/// success. On success, return the unconsumed `raw` value.