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122 lines
3.2 KiB
122 lines
3.2 KiB
//! Handling C `errno` error values in Rust
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use super::*;
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use std::{
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fmt, error,
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};
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use libc::c_char;
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use libc::__errno_location;
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use once_cell::sync::OnceCell;
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use std::num::NonZeroI32;
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/// Size of errno string message buffer
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const MESSAGE_BUF_SIZE: usize = 512;
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/// A raw errno error code.
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pub type RawError = i32;
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/// Get the raw errno error value.
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#[inline] pub fn raw() -> RawError
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{
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unsafe {
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*__errno_location()
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}
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}
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/// Convert raw error code into its message
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fn get_message(raw: RawError) -> String
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{
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use libc::strerror_r;
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use std::ffi::CStr;
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let mut buffer = [0u8; MESSAGE_BUF_SIZE+1];
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let cstr = unsafe {
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strerror_r(raw, buffer.as_mut_ptr() as *mut c_char, MESSAGE_BUF_SIZE);
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debug_if!(if {
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buffer[MESSAGE_BUF_SIZE] = 0;
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});
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CStr::from_ptr(buffer.as_mut_ptr() as *const c_char)
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};
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cstr.to_string_lossy().into_owned()
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}
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/// A raw C error
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#[derive(Debug)]
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pub struct Errno
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{
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errno: NonZeroI32,
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message: OnceCell<String>,
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}
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impl Errno
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{
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/// Get the raw errno value of this error.
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pub const fn raw(&self) -> i32
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{
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self.errno.get()
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}
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/// Get the errno message for this error
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pub fn message(&self) -> &str
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{
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&self.message.get_or_init(|| get_message(self.errno.into()))
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}
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/// Create a new error wrapper for this errno value without checking if it was success.
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///
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/// # Safety
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/// The caller **must** verify that `raw` is not 0 (success) or memory corruption may be possible.
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pub const unsafe fn new_unchecked(raw: RawError) -> Self
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{
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Self{errno: NonZeroI32::new_unchecked(raw), message: OnceCell::new()}
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}
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/// Create a new error wrapper for this errno value if it was not success.
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pub const fn new(raw: RawError) -> Result<(), Self>
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{
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if raw == 0 {
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Ok(())
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} else {
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Err(unsafe {Self::new_unchecked(raw)})
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}
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}
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/// Create a new error wrapper for the last errno value set on this thread if it was not success.
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pub fn last() -> Result<(), Self>
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{
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Self::new(raw())
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}
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/// Create a new `Result` that returns the last errno value set if it was an error, or calls this function and returns the value returned from it if it was success.
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pub fn or_last_with<F, T>(fun: F) -> Result<T, Self>
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where F: FnOnce() -> T
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{
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Self::last().map(move |_| fun())
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}
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/// Create a new `Result` that returns the last errno value set if it was an error, or returns the provided value if it was success.
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#[inline] pub fn or_last<T>(val: T) -> Result<T, Self>
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{
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Self::or_last_with(move || val)
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}
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/// Create a new `Result` that returns the this errno value if it was an error, or calls this function and returns the value returned from it if it was success.
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pub fn or_new_with<F, T>(raw: RawError, fun: F) -> Result<T, Self>
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where F: FnOnce() -> T
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{
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Self::new(raw).map(move |_| fun())
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}
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/// Create a new `Result` that returns this errno value if it was an error, or returns the provided value if it was success.
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#[inline] pub fn or_new<T>(raw: RawError, val: T) -> Result<T, Self>
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{
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Self::or_new_with(raw, move || val)
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}
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}
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impl error::Error for Errno{}
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impl fmt::Display for Errno
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{
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
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{
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write!(f, "{}", self.message())
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}
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}
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