blob: 3a361eb6f270425696d080cb15a46ccd79c65475 [file] [log] [blame]
use std::mem;
use std::prelude::v1::*;
use {Async, Poll};
use stream::{Stream, Fuse};
/// An adaptor that chunks up elements in a vector.
///
/// This adaptor will buffer up a list of items in the stream and pass on the
/// vector used for buffering when a specified capacity has been reached. This
/// is created by the `Stream::chunks` method.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct Chunks<S>
where S: Stream
{
items: Vec<S::Item>,
err: Option<S::Error>,
stream: Fuse<S>
}
pub fn new<S>(s: S, capacity: usize) -> Chunks<S>
where S: Stream
{
assert!(capacity > 0);
Chunks {
items: Vec::with_capacity(capacity),
err: None,
stream: super::fuse::new(s),
}
}
// Forwarding impl of Sink from the underlying stream
impl<S> ::sink::Sink for Chunks<S>
where S: ::sink::Sink + Stream
{
type SinkItem = S::SinkItem;
type SinkError = S::SinkError;
fn start_send(&mut self, item: S::SinkItem) -> ::StartSend<S::SinkItem, S::SinkError> {
self.stream.start_send(item)
}
fn poll_complete(&mut self) -> Poll<(), S::SinkError> {
self.stream.poll_complete()
}
fn close(&mut self) -> Poll<(), S::SinkError> {
self.stream.close()
}
}
impl<S> Chunks<S> where S: Stream {
fn take(&mut self) -> Vec<S::Item> {
let cap = self.items.capacity();
mem::replace(&mut self.items, Vec::with_capacity(cap))
}
/// Acquires a reference to the underlying stream that this combinator is
/// pulling from.
pub fn get_ref(&self) -> &S {
self.stream.get_ref()
}
/// Acquires a mutable reference to the underlying stream that this
/// combinator is pulling from.
///
/// Note that care must be taken to avoid tampering with the state of the
/// stream which may otherwise confuse this combinator.
pub fn get_mut(&mut self) -> &mut S {
self.stream.get_mut()
}
/// Consumes this combinator, returning the underlying stream.
///
/// Note that this may discard intermediate state of this combinator, so
/// care should be taken to avoid losing resources when this is called.
pub fn into_inner(self) -> S {
self.stream.into_inner()
}
}
impl<S> Stream for Chunks<S>
where S: Stream
{
type Item = Vec<<S as Stream>::Item>;
type Error = <S as Stream>::Error;
fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
if let Some(err) = self.err.take() {
return Err(err)
}
let cap = self.items.capacity();
loop {
match self.stream.poll() {
Ok(Async::NotReady) => return Ok(Async::NotReady),
// Push the item into the buffer and check whether it is full.
// If so, replace our buffer with a new and empty one and return
// the full one.
Ok(Async::Ready(Some(item))) => {
self.items.push(item);
if self.items.len() >= cap {
return Ok(Some(self.take()).into())
}
}
// Since the underlying stream ran out of values, return what we
// have buffered, if we have anything.
Ok(Async::Ready(None)) => {
return if self.items.len() > 0 {
let full_buf = mem::replace(&mut self.items, Vec::new());
Ok(Some(full_buf).into())
} else {
Ok(Async::Ready(None))
}
}
// If we've got buffered items be sure to return them first,
// we'll defer our error for later.
Err(e) => {
if self.items.len() == 0 {
return Err(e)
} else {
self.err = Some(e);
return Ok(Some(self.take()).into())
}
}
}
}
}
}