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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! {
/// Stream for the [`lines`](crate::io::AsyncBufReadExt::lines) method.
#[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.
///
/// # 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
}
}
impl<R> Lines<R>
where
R: AsyncBufRead,
{
#[doc(hidden)]
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))?;
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::replace(me.buf, String::new()))))
}
}
#[cfg(feature = "stream")]
impl<R: AsyncBufRead> crate::stream::Stream for Lines<R> {
type Item = io::Result<String>;
fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
Poll::Ready(match ready!(self.poll_next_line(cx)) {
Ok(Some(line)) => Some(Ok(line)),
Ok(None) => None,
Err(err) => Some(Err(err)),
})
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn assert_unpin() {
crate::is_unpin::<Lines<()>>();
}
}
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