blob: d5f5c34d67ac2f1d6075c62accafd941d0851d70 [file] [log] [blame]
use std::io::{self, Read, Write};
use futures::{Future, Poll};
/// A future which will copy all data from a reader into a writer.
/// Created by the [`copy`] function, this future will resolve to the number of
/// bytes copied or an error if one happens.
/// [`copy`]: fn.copy.html
#[must_use = "futures do nothing unless polled"]
pub struct Copy<R, W> {
reader: R,
read_done: bool,
writer: W,
pos: usize,
cap: usize,
amt: u64,
buf: Box<[u8]>,
/// Creates a future which represents copying all the bytes from one object to
/// another.
/// The returned future will copy all the bytes read from `reader` into the
/// `writer` specified. This future will only complete once the `reader` has hit
/// EOF and all bytes have been written to and flushed from the `writer`
/// provided.
/// On success the number of bytes is returned and the `reader` and `writer` are
/// consumed. On error the error is returned and the I/O objects are consumed as
/// well.
pub fn copy<R, W>(reader: R, writer: W) -> Copy<R, W>
where R: Read,
W: Write,
Copy {
reader: reader,
read_done: false,
writer: writer,
amt: 0,
pos: 0,
cap: 0,
buf: Box::new([0; 2048]),
impl<R, W> Future for Copy<R, W>
where R: Read,
W: Write,
type Item = u64;
type Error = io::Error;
fn poll(&mut self) -> Poll<u64, io::Error> {
loop {
// If our buffer is empty, then we need to read some data to
// continue.
if self.pos == self.cap && !self.read_done {
let n = try_nb!( self.buf));
if n == 0 {
self.read_done = true;
} else {
self.pos = 0;
self.cap = n;
// If our buffer has some data, let's write it out!
while self.pos < self.cap {
let i = try_nb!(self.writer.write(&self.buf[self.pos..self.cap]));
self.pos += i;
self.amt += i as u64;
// If we've written all the data and we've seen EOF, flush out the
// data and finish the transfer.
// done with the entire transfer.
if self.pos == self.cap && self.read_done {
return Ok(self.amt.into())