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use crate::libc::EOVERFLOW;
use core::ffi::c_int;
use core::marker::PhantomData;
pub const MAX_ERRNO: c_int = 4096;
pub const ERRNO_START: usize = usize::MAX - MAX_ERRNO as usize;
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
#[repr(transparent)]
pub struct Result<T>([usize; 2], PhantomData<T>);
impl<T> From<Result<T>> for [usize; 2] {
#[inline]
fn from(res: Result<T>) -> Self {
res.0
}
}
impl<T> From<[usize; 2]> for Result<T> {
#[inline]
fn from(ret: [usize; 2]) -> Self {
Self(ret, PhantomData)
}
}
impl From<Result<()>> for crate::Result<()> {
#[inline]
fn from(res: Result<()>) -> Self {
match res.0 {
[errno @ ERRNO_START..=usize::MAX, _] => Err(-(errno as c_int)),
_ => Ok(()),
}
}
}
impl From<Result<c_int>> for crate::Result<c_int> {
#[inline]
fn from(res: Result<c_int>) -> Self {
match res.0 {
[errno @ ERRNO_START..=usize::MAX, _] => Err(-(errno as c_int)),
[ret, _] if ret <= c_int::MAX as usize => Ok(ret as c_int),
_ => Err(EOVERFLOW),
}
}
}
impl From<Result<usize>> for crate::Result<usize> {
#[inline]
fn from(res: Result<usize>) -> Self {
match res.0 {
[errno @ ERRNO_START..=usize::MAX, _] => Err(-(errno as c_int)),
[ret, _] => Ok(ret),
}
}
}
impl From<Result<isize>> for crate::Result<usize> {
#[inline]
fn from(res: Result<isize>) -> Self {
Result::<usize>(res.0, PhantomData).into()
}
}
#[cfg(test)]
mod tests {
use super::*;
use libc::{self, EPERM, F_GETFD};
#[test]
fn result() {
const ERRNO: c_int = EPERM;
let expected: Result<isize> = [-ERRNO as usize, 0].into();
assert_eq!(
Result::from([unsafe { libc::fcntl(-1, F_GETFD) } as usize, 0]),
expected
);
let res: crate::Result<_> = expected.into();
assert_eq!(res, Err(ERRNO));
}
}