blob: d871b76f2af51fb49c0a26b8b9251959fa6f7d7e [file] [log] [blame]
use crate::stream::Fuse;
use futures_core::stream::Stream;
use futures_core::task::{LocalWaker, Poll};
use pin_utils::{unsafe_pinned, unsafe_unpinned};
use std::marker::Unpin;
use std::mem;
use std::pin::Pin;
use std::prelude::v1::*;
/// 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<St: Stream> {
stream: Fuse<St>,
items: Vec<St::Item>,
}
impl<St: Unpin + Stream> Unpin for Chunks<St> {}
impl<St: Stream> Chunks<St> where St: Stream {
unsafe_unpinned!(items: Vec<St::Item>);
unsafe_pinned!(stream: Fuse<St>);
pub(super) fn new(stream: St, capacity: usize) -> Chunks<St> {
assert!(capacity > 0);
Chunks {
stream: super::Fuse::new(stream),
items: Vec::with_capacity(capacity),
}
}
fn take(mut self: Pin<&mut Self>) -> Vec<St::Item> {
let cap = self.items.capacity();
mem::replace(self.as_mut().items(), Vec::with_capacity(cap))
}
/// Acquires a reference to the underlying stream that this combinator is
/// pulling from.
pub fn get_ref(&self) -> &St {
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 St {
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) -> St {
self.stream.into_inner()
}
}
impl<St: Stream> Stream for Chunks<St> {
type Item = Vec<St::Item>;
fn poll_next(
mut self: Pin<&mut Self>,
lw: &LocalWaker,
) -> Poll<Option<Self::Item>> {
let cap = self.items.capacity();
loop {
match ready!(self.as_mut().stream().poll_next(lw)) {
// 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.
Some(item) => {
self.as_mut().items().push(item);
if self.items.len() >= cap {
return Poll::Ready(Some(self.as_mut().take()))
}
}
// Since the underlying stream ran out of values, return what we
// have buffered, if we have anything.
None => {
let last = if self.items.is_empty() {
None
} else {
let full_buf = mem::replace(self.as_mut().items(), Vec::new());
Some(full_buf)
};
return Poll::Ready(last);
}
}
}
}
}
/* TODO
// Forwarding impl of Sink from the underlying stream
impl<S> Sink for Chunks<S>
where S: Sink + Stream
{
type SinkItem = S::SinkItem;
type SinkError = S::SinkError;
delegate_sink!(stream);
}
*/