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//! TODO: Dox
use super::{BufStream, SizeHint};
use bytes::{BytesMut, Bytes, Buf, BufMut};
use flate2::{Compress, Compression, FlushCompress, Status};
use futures::Poll;
use futures::Async::*;
use std::cmp;
use std::io;
/// Compress a buf stream using zlib deflate.
#[derive(Debug)]
pub struct CompressStream<T> {
// The inner BufStream
inner: T,
// `true` when the inner buffer returned `None`
inner_eof: bool,
// `true` when the deflated stream is complete
eof: bool,
// Buffers input
src_buf: BytesMut,
// Buffers output
dst_buf: BytesMut,
// Compression
compress: Compress,
}
/// Errors returned by `CompressStream`.
#[derive(Debug)]
pub struct Error<T> {
/// `None` represents a deflate error
inner: Option<T>,
}
const MIN_BUF: usize = 1024;
impl<T> CompressStream<T>
where T: BufStream,
{
/// Create a new `CompressStream` which returns the compressed data from
/// `inner`.
///
/// `level` specifies the compression level.
pub fn new(inner: T, level: Compression) -> CompressStream<T> {
CompressStream {
inner,
inner_eof: false,
eof: false,
src_buf: BytesMut::new(),
dst_buf: BytesMut::new(),
compress: Compress::new(level, false),
}
}
}
impl<T> BufStream for CompressStream<T>
where T: BufStream,
{
type Item = io::Cursor<Bytes>;
type Error = Error<T::Error>;
fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
loop {
if self.eof {
return Ok(Ready(None));
}
// First, if needed, try filling the buffer
if !self.inner_eof {
let res = self.inner.poll()
.map_err(|e| {
Error { inner: Some(e) }
});
match try_ready!(res) {
Some(buf) => {
self.src_buf.reserve(buf.remaining());
self.src_buf.put(buf);
}
None => {
self.inner_eof = true;
}
}
}
let before_out = self.compress.total_out();
let before_in = self.compress.total_in();
let flush = if self.inner_eof {
FlushCompress::Finish
} else {
FlushCompress::None
};
// Ensure the destination buffer has capacity
let amt = cmp::max(self.src_buf.len() / 2, MIN_BUF);
self.dst_buf.reserve(amt);
let ret = unsafe {
self.compress.compress(
&self.src_buf,
self.dst_buf.bytes_mut(),
flush)
};
let written = (self.compress.total_out() - before_out) as usize;
let consumed = (self.compress.total_in() - before_in) as usize;
unsafe { self.dst_buf.advance_mut(written); }
self.src_buf.split_to(consumed);
match ret {
// If we haven't ready any data and we haven't hit EOF yet,
// then we need to keep asking for more data because if we
// return that 0 bytes of data have been read then it will
// be interpreted as EOF.
Ok(Status::Ok) | Ok(Status::BufError) if written == 0 && !self.inner_eof => {
continue
}
Ok(Status::Ok) | Ok(Status::BufError) => {
break;
}
Ok(Status::StreamEnd) => {
self.eof = true;
break;
}
Err(..) => {
return Err(Error { inner: None });
}
}
}
let buf = io::Cursor::new(self.dst_buf.take().freeze());
return Ok(Ready(Some(buf)));
}
fn size_hint(&self) -> SizeHint {
// TODO: How should this work?
self.inner.size_hint()
}
}