1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
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
    /// [`LinesStream`]: https://docs.rs/tokio-stream/0.1/tokio_stream/wrappers/struct.LinesStream.html
    /// [`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<()>>();
    }
}