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| 1 | +use super::buf_writer::BufWriter; |
| 2 | +use futures_core::ready; |
| 3 | +use futures_core::task::{Context, Poll}; |
| 4 | +use futures_io::AsyncWrite; |
| 5 | +use futures_io::IoSlice; |
| 6 | +use pin_project_lite::pin_project; |
| 7 | +use std::io; |
| 8 | +use std::pin::Pin; |
| 9 | + |
| 10 | +pin_project! { |
| 11 | +/// Wrap a writer, like [`BufWriter`] does, but prioritizes buffering lines |
| 12 | +/// |
| 13 | +/// This was written based on `std::io::LineWriter` which goes into further details |
| 14 | +/// explaining the code. |
| 15 | +/// |
| 16 | +/// Buffering is actually done using `BufWriter`. This class will leverage `BufWriter` |
| 17 | +/// to write on-each-line. |
| 18 | +#[derive(Debug)] |
| 19 | +pub struct LineWriter<W: AsyncWrite> { |
| 20 | + #[pin] |
| 21 | + buf_writer: BufWriter<W>, |
| 22 | +} |
| 23 | +} |
| 24 | + |
| 25 | +impl<W: AsyncWrite> LineWriter<W> { |
| 26 | + /// Create a new `LineWriter` with default buffer capacity. The default is currently 1KB |
| 27 | + /// which was taken from `std::io::LineWriter` |
| 28 | + pub fn new(inner: W) -> LineWriter<W> { |
| 29 | + LineWriter::with_capacity(1024, inner) |
| 30 | + } |
| 31 | + |
| 32 | + /// Creates a new `LineWriter` with the specified buffer capacity. |
| 33 | + pub fn with_capacity(capacity: usize, inner: W) -> LineWriter<W> { |
| 34 | + LineWriter { buf_writer: BufWriter::with_capacity(capacity, inner) } |
| 35 | + } |
| 36 | + |
| 37 | + /// Flush `buf_writer` if last char is "new line" |
| 38 | + fn flush_if_completed_line(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> { |
| 39 | + let this = self.project(); |
| 40 | + match this.buf_writer.buffer().last().copied() { |
| 41 | + Some(b'\n') => this.buf_writer.flush_buf(cx), |
| 42 | + _ => Poll::Ready(Ok(())), |
| 43 | + } |
| 44 | + } |
| 45 | + |
| 46 | + /// Returns a reference to `buf_writer`'s internally buffered data. |
| 47 | + pub fn buffer(&self) -> &[u8] { |
| 48 | + self.buf_writer.buffer() |
| 49 | + } |
| 50 | + |
| 51 | + /// Acquires a reference to the underlying sink or stream that this combinator is |
| 52 | + /// pulling from. |
| 53 | + pub fn get_ref(&self) -> &W { |
| 54 | + self.buf_writer.get_ref() |
| 55 | + } |
| 56 | +} |
| 57 | + |
| 58 | +impl<W: AsyncWrite> AsyncWrite for LineWriter<W> { |
| 59 | + fn poll_write( |
| 60 | + mut self: Pin<&mut Self>, |
| 61 | + cx: &mut Context<'_>, |
| 62 | + buf: &[u8], |
| 63 | + ) -> Poll<io::Result<usize>> { |
| 64 | + let mut this = self.as_mut().project(); |
| 65 | + let newline_index = match memchr::memrchr(b'\n', buf) { |
| 66 | + None => { |
| 67 | + ready!(self.as_mut().flush_if_completed_line(cx)?); |
| 68 | + return self.project().buf_writer.poll_write(cx, buf); |
| 69 | + } |
| 70 | + Some(newline_index) => newline_index + 1, |
| 71 | + }; |
| 72 | + |
| 73 | + ready!(this.buf_writer.as_mut().poll_flush(cx)?); |
| 74 | + |
| 75 | + let lines = &buf[..newline_index]; |
| 76 | + |
| 77 | + let flushed = { ready!(this.buf_writer.as_mut().inner_poll_write(cx, lines))? }; |
| 78 | + |
| 79 | + if flushed == 0 { |
| 80 | + return Poll::Ready(Ok(0)); |
| 81 | + } |
| 82 | + |
| 83 | + let tail = if flushed >= newline_index { |
| 84 | + &buf[flushed..] |
| 85 | + } else if newline_index - flushed <= this.buf_writer.capacity() { |
| 86 | + &buf[flushed..newline_index] |
| 87 | + } else { |
| 88 | + let scan_area = &buf[flushed..]; |
| 89 | + let scan_area = &scan_area[..this.buf_writer.capacity()]; |
| 90 | + match memchr::memrchr(b'\n', scan_area) { |
| 91 | + Some(newline_index) => &scan_area[..newline_index + 1], |
| 92 | + None => scan_area, |
| 93 | + } |
| 94 | + }; |
| 95 | + |
| 96 | + let buffered = this.buf_writer.as_mut().write_to_buf(tail); |
| 97 | + Poll::Ready(Ok(flushed + buffered)) |
| 98 | + } |
| 99 | + |
| 100 | + fn poll_write_vectored( |
| 101 | + mut self: Pin<&mut Self>, |
| 102 | + cx: &mut Context<'_>, |
| 103 | + bufs: &[IoSlice<'_>], |
| 104 | + ) -> Poll<io::Result<usize>> { |
| 105 | + let mut this = self.as_mut().project(); |
| 106 | + // `is_write_vectored()` is handled in original code, but not in this crate |
| 107 | + // see https://github.com/rust-lang/rust/issues/70436 |
| 108 | + |
| 109 | + let last_newline_buf_idx = bufs |
| 110 | + .iter() |
| 111 | + .enumerate() |
| 112 | + .rev() |
| 113 | + .find_map(|(i, buf)| memchr::memchr(b'\n', buf).map(|_| i)); |
| 114 | + let last_newline_buf_idx = match last_newline_buf_idx { |
| 115 | + None => { |
| 116 | + ready!(self.as_mut().flush_if_completed_line(cx)?); |
| 117 | + return self.project().buf_writer.poll_write_vectored(cx, bufs); |
| 118 | + } |
| 119 | + Some(i) => i, |
| 120 | + }; |
| 121 | + |
| 122 | + ready!(this.buf_writer.as_mut().poll_flush(cx)?); |
| 123 | + |
| 124 | + let (lines, tail) = bufs.split_at(last_newline_buf_idx + 1); |
| 125 | + |
| 126 | + let flushed = { ready!(this.buf_writer.as_mut().inner_poll_write_vectored(cx, lines))? }; |
| 127 | + if flushed == 0 { |
| 128 | + return Poll::Ready(Ok(0)); |
| 129 | + } |
| 130 | + |
| 131 | + let lines_len = lines.iter().map(|buf| buf.len()).sum(); |
| 132 | + if flushed < lines_len { |
| 133 | + return Poll::Ready(Ok(flushed)); |
| 134 | + } |
| 135 | + |
| 136 | + let buffered: usize = tail |
| 137 | + .iter() |
| 138 | + .filter(|buf| !buf.is_empty()) |
| 139 | + .map(|buf| this.buf_writer.as_mut().write_to_buf(buf)) |
| 140 | + .take_while(|&n| n > 0) |
| 141 | + .sum(); |
| 142 | + |
| 143 | + Poll::Ready(Ok(flushed + buffered)) |
| 144 | + } |
| 145 | + |
| 146 | + /// Forward to `buf_writer` 's `BufWriter::poll_flush()` |
| 147 | + fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> { |
| 148 | + self.as_mut().project().buf_writer.poll_flush(cx) |
| 149 | + } |
| 150 | + |
| 151 | + /// Forward to `buf_writer` 's `BufWriter::poll_close()` |
| 152 | + fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> { |
| 153 | + self.as_mut().project().buf_writer.poll_close(cx) |
| 154 | + } |
| 155 | +} |
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