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use crate::io::util::read_line::read_line_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! {
/// Reads lines from an [`AsyncBufRead`].
///
/// A `Lines` can be turned into a `Stream` with [`LinesStream`].
///
/// This type is usually created using the [`lines`] method.
///
/// [`AsyncBufRead`]: crate::io::AsyncBufRead
/// [`lines`]: crate::io::AsyncBufReadExt::lines
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
#[cfg_attr(docsrs, doc(cfg(feature = "io-util")))]
pub struct Lines<R> {
#[pin]
reader: R,
buf: String,
bytes: Vec<u8>,
read: usize,
}
}
pub(crate) fn lines<R>(reader: R) -> Lines<R>
where
R: AsyncBufRead,
{
Lines {
reader,
buf: String::new(),
bytes: Vec::new(),
read: 0,
}
}
impl<R> Lines<R>
where
R: AsyncBufRead + Unpin,
{
/// Returns the next line in the stream.
///
/// # Cancel safety
///
/// This method is cancellation safe.
///
/// # Examples
///
/// ```
/// # use tokio::io::AsyncBufRead;
/// use tokio::io::AsyncBufReadExt;
///
/// # async fn dox(my_buf_read: impl AsyncBufRead + Unpin) -> std::io::Result<()> {
/// let mut lines = my_buf_read.lines();
///
/// while let Some(line) = lines.next_line().await? {
/// println!("length = {}", line.len())
/// }
/// # Ok(())
/// # }
/// ```
pub async fn next_line(&mut self) -> io::Result<Option<String>> {
use crate::future::poll_fn;
poll_fn(|cx| Pin::new(&mut *self).poll_next_line(cx)).await
}
/// Obtains a mutable reference to the underlying reader.
pub fn get_mut(&mut self) -> &mut R {
&mut self.reader
}
/// Obtains a reference to the underlying reader.
pub fn get_ref(&mut self) -> &R {
&self.reader
}
/// Unwraps this `Lines<R>`, returning the underlying reader.
///
/// Note that any leftover data in the internal buffer is lost.
/// Therefore, a following read from the underlying reader may lead to data loss.
pub fn into_inner(self) -> R {
self.reader
}
}
impl<R> Lines<R>
where
R: AsyncBufRead,
{
/// Polls for the next line in the stream.
///
/// This method returns:
///
/// * `Poll::Pending` if the next line is not yet available.
/// * `Poll::Ready(Ok(Some(line)))` if the next line is available.
/// * `Poll::Ready(Ok(None))` if there are no more lines in this stream.
/// * `Poll::Ready(Err(err))` if an IO error occurred while reading the next line.
///
/// 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_line`, only the `Waker` from the `Context` passed to the most
/// recent call is scheduled to receive a wakeup.
pub fn poll_next_line(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<io::Result<Option<String>>> {
let me = self.project();
let n = ready!(read_line_internal(me.reader, cx, me.buf, me.bytes, me.read))?;
debug_assert_eq!(*me.read, 0);
if n == 0 && me.buf.is_empty() {
return Poll::Ready(Ok(None));
}
if me.buf.ends_with('\n') {
me.buf.pop();
if me.buf.ends_with('\r') {
me.buf.pop();
}
}
Poll::Ready(Ok(Some(mem::take(me.buf))))
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn assert_unpin() {
crate::is_unpin::<Lines<()>>();
}
}