zc.rs

use libc::{c_int, splice};
use std::os::unix::io::AsRawFd;
use std::io::Result;
use std::io::prelude::*;
const __NR_copy_file_range: ::libc::c_long = 326;

unsafe fn copy_file_range(fd_in: c_int, off_in: *mut ::libc::loff_t, fd_out: c_int, off_out: *mut ::libc::loff_t, len: usize, flags: u32) -> i64 {
    ::libc::syscall(__NR_copy_file_range, fd_in, off_in, fd_out, off_out, len, flags)
}
pub trait ZeroCopy<T> {
    unsafe fn copy_to_fd(&mut self, fd: &mut T, bytes: usize) -> Result<usize>;
}

impl <T, FD> ZeroCopy<FD> for T where T: AsRawFd + Read,
 FD: AsRawFd + Write {
    default unsafe fn copy_to_fd(&mut self, fd: &mut FD, bytes: usize) -> Result<usize> { 
        let res = splice(0, ::std::ptr::null_mut(), fd.as_raw_fd(), ::std::ptr::null_mut(), 12, 0);
        Ok(res as usize)    
    }
}

impl <FD> ZeroCopy<FD> for ::std::fs::File {
    unsafe fn copy_to_fd(&mut self, fd: &mut FD, bytes: usize) -> Result<usize> {
        ZeroCopy::copy_to_fd(self, fd, bytes);
    }
}
impl ZeroCopy<::std::fs::File> for ::std::fs::File {
    unsafe fn copy_to_fd(&mut self, fd: &mut ::std::fs::File, bytes: usize) -> Result<usize> {
        let bytes = copy_file_range(self.as_raw_fd(), ::std::ptr::null_mut(), fd.as_raw_fd(), ::std::ptr::null_mut(), bytes, 0);
        if bytes < 0 {
            Err(::std::io::Error::last_os_error())
        }
        else { Ok(bytes as usize) }

    }
}