Crate failed_result
source ·Expand description
§failed-result
A small crate for converting various failed value to result with corresponding error type
§Motivation
Somtimes, in order to implement some features, we have to call native interface via FFI in Rust, and the conversion between native error with Rust error is commonly painful, so we need a more convenient way to do this.
In general, the error type is std::io::Error
, which correspond the common error type in each platform.
This crate introduces a trait LastError
, provides a method LastError::last_error
to get the last error by std::io::Error::last_os_error
, ant it is implemented by default for general types whose one of value represents a failed result, such as bool
(false), Option
(None), u32
(0, the FALSE
value of BOOL
type on Windows) and any Null-Pointer.
You can get the error as a Result
more easily, like this
use failed_result::*;
let res = OpenProcess(PROCESS_ALL_ACCESS, 0, 0).last_error();
assert_eq!(res.unwrap_err().kind(), ErrorKind::InvalidInput);
And the convenience becomes significant when the parent function returns a Result
fn get_process_path(pid: u32) -> anyhow::Result<String> {
unsafe {
let handle = OpenProcess(PROCESS_ALL_ACCESS, 0, pid).last_error()?;
let mut buf = [0u16; MAX_PATH];
GetModuleFileNameExW(handle, core::ptr::null_mut(), buf.as_mut_ptr(), buf.len() as u32).last_error()?;
CloseHandle(handle);
Ok(String::from_utf16(&buf)?)
}
}
In addition, there is also a trait [AsHResult
] on Windows platform, represents a result whose root type is HRESULT
, you can convert these types easily to a [windows::core::Result
] by using this trait.
I will implement more failed type includes other platform, depending on people’s needs, and any feedback is welcome.
§Example
use failed_result::*;
use std::io::ErrorKind;
use winapi::um::{processthreadsapi::*, winnt::PROCESS_ALL_ACCESS};
unsafe {
let res = OpenProcess(PROCESS_ALL_ACCESS, 0, 0).last_error();
assert_eq!(res.unwrap_err().kind(), ErrorKind::InvalidInput);
let res = OpenProcess(PROCESS_ALL_ACCESS, 0, std::process::id()).last_error();
assert!(res.is_ok());
}
Re-exports§
pub use self::linux::*;
Modules§
Traits§
- Trait to convert a failed value to Result with last os error