async_std/io/buf_read/
lines.rs

1use std::mem;
2use std::pin::Pin;
3use std::str;
4
5use pin_project_lite::pin_project;
6
7use super::read_until_internal;
8use crate::io::{self, BufRead};
9use crate::stream::Stream;
10use crate::task::{Context, Poll};
11
12pin_project! {
13    /// A stream of lines in a byte stream.
14    ///
15    /// This stream is created by the [`lines`] method on types that implement [`BufRead`].
16    ///
17    /// This type is an async version of [`std::io::Lines`].
18    ///
19    /// [`lines`]: trait.BufRead.html#method.lines
20    /// [`BufRead`]: trait.BufRead.html
21    /// [`std::io::Lines`]: https://doc.rust-lang.org/std/io/struct.Lines.html
22    #[derive(Debug)]
23    pub struct Lines<R> {
24        #[pin]
25        pub(crate) reader: R,
26        pub(crate) buf: String,
27        pub(crate) bytes: Vec<u8>,
28        pub(crate) read: usize,
29    }
30}
31
32impl<R: BufRead> Stream for Lines<R> {
33    type Item = io::Result<String>;
34
35    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
36        let this = self.project();
37        let n = futures_core::ready!(read_line_internal(
38            this.reader,
39            cx,
40            this.buf,
41            this.bytes,
42            this.read
43        ))?;
44        if n == 0 && this.buf.is_empty() {
45            return Poll::Ready(None);
46        }
47        if this.buf.ends_with('\n') {
48            this.buf.pop();
49            if this.buf.ends_with('\r') {
50                this.buf.pop();
51            }
52        }
53        Poll::Ready(Some(Ok(mem::replace(this.buf, String::new()))))
54    }
55}
56
57pub fn read_line_internal<R: BufRead + ?Sized>(
58    reader: Pin<&mut R>,
59    cx: &mut Context<'_>,
60    buf: &mut String,
61    bytes: &mut Vec<u8>,
62    read: &mut usize,
63) -> Poll<io::Result<usize>> {
64    let ret = futures_core::ready!(read_until_internal(reader, cx, b'\n', bytes, read));
65    if str::from_utf8(&bytes).is_err() {
66        Poll::Ready(ret.and_then(|_| {
67            Err(io::Error::new(
68                io::ErrorKind::InvalidData,
69                "stream did not contain valid UTF-8",
70            ))
71        }))
72    } else {
73        debug_assert!(buf.is_empty());
74        debug_assert_eq!(*read, 0);
75        // Safety: `bytes` is a valid UTF-8 because `str::from_utf8` returned `Ok`.
76        mem::swap(unsafe { buf.as_mut_vec() }, bytes);
77        Poll::Ready(ret)
78    }
79}
async_std/io/buf_read/lines.rs

async_std/io/buf_read/
lines.rs
