lib.rs

use std::fs::File;
use std::io;
use std::mem;

pub fn close(file: &mut File) -> io::Result<()> {
    imp::close(mem::replace(file, imp::invalid_file()))
}

#[cfg(unix)]
mod imp {
    extern crate libc;

    use std::fs::File;
    use std::os::unix::prelude::*;
    use std::io;

    pub fn close(file: File) -> io::Result<()> {
        let fd = file.into_raw_fd();
        let rc = unsafe {
            libc::close(fd)
        };
        if rc == -1 {
            Ok(())
        } else {
            Err(io::Error::last_os_error())
        }
    }

    pub fn invalid_file() -> File {
        unsafe { File::from_raw_fd(-1) }
    }
}

#[cfg(windows)]
mod imp {
    extern crate winapi;
    extern crate kernel32;

    use std::fs::File;
    use std::os::windows::prelude::*;
    use std::io;

    pub fn close(file: File) -> io::Result<()> {
        let handle = file.into_raw_handle();
        let rc = unsafe {
            kernel32::CloseHandle(handle)
        };
        if rc != 0 {
            Ok(())
        } else {
            Err(io::Error::last_os_error())
        }
    }

    pub fn invalid_file() -> File {
        unsafe { File::from_raw_handle(winapi::INVALID_HANDLE_VALUE) }
    }
}