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extern crate libc;

use std::os::unix::ffi::OsStrExt;
use std::path::Path;
use std::{io, ffi};

unsafe fn renameat2(
	olddirfd: libc::c_int, oldpath: *const libc::c_char, 
	newdirfd: libc::c_int, newpath: *const libc::c_char, flags: libc::c_int
) -> libc::c_int {
	libc::syscall(libc::SYS_renameat2, olddirfd, oldpath, newdirfd, newpath, flags) as libc::c_int
}

pub fn swap<A, B>(a: A, b: B) -> io::Result<()> where A: AsRef<Path>, B: AsRef<Path> {
	let a_path = ffi::CString::new(a.as_ref().as_os_str().as_bytes())?;
	let b_path = ffi::CString::new(b.as_ref().as_os_str().as_bytes())?;

	unsafe {
		match renameat2(libc::AT_FDCWD, a_path.as_ptr(), libc::AT_FDCWD, b_path.as_ptr(), libc::RENAME_EXCHANGE) {
			0 => Ok(()),
			_ => Err(io::Error::new(io::ErrorKind::Other, format!("renameat2 failed with code: {}", *libc::__errno_location()))),
		}
	}
}