use crate::io::util::read_until::read_until_internal;
use crate::io::AsyncBufRead;
use pin_project_lite::pin_project;
use std::io;
use std::mem;
use std::pin::Pin;
use std::task::{Context, Poll};
pin_project! {
/// Splitter for the [`split`](crate::io::AsyncBufReadExt::split) method.
///
/// A `Split` can be turned into a `Stream` with [`SplitStream`].
///
/// [`SplitStream`]:
https://docs.rs/tokio-stream/0.1/tokio_stream/wrappers/struct.SplitStream.html
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
#[cfg_attr(docsrs, doc(cfg(feature = "io-util")))]
pub struct Split<R> {
#[pin]
reader: R,
buf: Vec<u8>,
delim: u8,
read: usize,
}
}
pub(crate) fn split<R>(reader: R, delim: u8) -> Split<R>
where
R: AsyncBufRead,
{
Split {
reader,
buf: Vec::new(),
delim,
read: 0,
}
}
impl<R> Split<R>
where
R: AsyncBufRead + Unpin,
{
/// Returns the next segment in the stream.
///
/// # Examples
///
/// ```
/// # use tokio::io::AsyncBufRead;
/// use tokio::io::AsyncBufReadExt;
///
/// # async fn dox(my_buf_read: impl AsyncBufRead + Unpin) -> std::io::Result<()> {
/// let mut segments = my_buf_read.split(b'f');
///
/// while let Some(segment) = segments.next_segment().await? {
/// println!("length = {}", segment.len())
/// }
/// # Ok(())
/// # }
/// ```
pub async fn next_segment(&mut self) -> io::Result<Option<Vec<u8>>> {
use crate::future::poll_fn;
poll_fn(|cx| Pin::new(&mut *self).poll_next_segment(cx)).await
}
}
impl<R> Split<R>
where
R: AsyncBufRead,
{
/// Polls for the next segment in the stream.
///
/// This method returns:
///
/// * `Poll::Pending` if the next segment is not yet available.
/// * `Poll::Ready(Ok(Some(segment)))` if the next segment is available.
/// * `Poll::Ready(Ok(None))` if there are no more segments in this stream.
/// * `Poll::Ready(Err(err))` if an IO error occurred while reading the
/// next segment.
///
/// When the method returns `Poll::Pending`, the `Waker` in the provided
/// `Context` is scheduled to receive a wakeup when more bytes become
/// available on the underlying IO resource.
///
/// Note that on multiple calls to `poll_next_segment`, only the `Waker`
/// from the `Context` passed to the most recent call is scheduled to
/// receive a wakeup.
pub fn poll_next_segment(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<io::Result<Option<Vec<u8>>>> {
let me = self.project();
let n = ready!(read_until_internal(
me.reader, cx, *me.delim, me.buf, me.read,
))?;
// read_until_internal resets me.read to zero once it finds the delimiter
debug_assert_eq!(*me.read, 0);
if n == 0 && me.buf.is_empty() {
return Poll::Ready(Ok(None));
}
if me.buf.last() == Some(me.delim) {
me.buf.pop();
}
Poll::Ready(Ok(Some(mem::take(me.buf))))
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn assert_unpin() {
crate::is_unpin::<Split<()>>();
}
}
