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Add BufRead::fill_buf (#176)
* Add BufRead::fill_buf * Make FillBufFuture constructor pub(crate) * Give more information about the transmutation source type
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32
src/io/buf_read/fill_buf.rs
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32
src/io/buf_read/fill_buf.rs
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@ -0,0 +1,32 @@
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use std::pin::Pin;
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use futures_io::AsyncBufRead;
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use crate::future::Future;
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use crate::io;
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use crate::task::{Context, Poll};
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#[doc(hidden)]
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#[allow(missing_debug_implementations)]
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pub struct FillBufFuture<'a, R: ?Sized> {
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reader: &'a mut R,
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}
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impl<'a, R: ?Sized> FillBufFuture<'a, R> {
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pub(crate) fn new(reader: &'a mut R) -> Self {
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Self { reader }
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}
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}
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impl<'a, R: AsyncBufRead + Unpin + ?Sized> Future for FillBufFuture<'a, R> {
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type Output = io::Result<&'a [u8]>;
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fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<&'a [u8]>> {
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let Self { reader } = &mut *self;
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let result = Pin::new(reader).poll_fill_buf(cx);
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// This is safe because:
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// 1. The buffer is valid for the lifetime of the reader.
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// 2. Output is unrelated to the wrapper (Self).
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result.map_ok(|buf| unsafe { std::mem::transmute::<&'_ [u8], &'a [u8]>(buf) })
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}
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}
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@ -1,7 +1,9 @@
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mod fill_buf;
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mod lines;
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mod read_line;
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mod read_until;
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use fill_buf::FillBufFuture;
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pub use lines::Lines;
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use read_line::ReadLineFuture;
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use read_until::ReadUntilFuture;
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@ -41,6 +43,26 @@ cfg_if! {
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/// [`futures::io::AsyncBufRead`]:
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/// https://docs.rs/futures-preview/0.3.0-alpha.17/futures/io/trait.AsyncBufRead.html
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pub trait BufRead {
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/// Returns the contents of the internal buffer, filling it with more data from the inner
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/// reader if it is empty.
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///
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/// This function is a lower-level call. It needs to be paired with the [`consume`] method to
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/// function properly. When calling this method, none of the contents will be "read" in the
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/// sense that later calling `read` may return the same contents. As such, [`consume`] must be
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/// called with the number of bytes that are consumed from this buffer to ensure that the bytes
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/// are never returned twice.
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///
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/// [`consume`]: #tymethod.consume
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///
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/// An empty buffer returned indicates that the stream has reached EOF.
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// TODO: write a proper doctest with `consume`
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fn fill_buf<'a>(&'a mut self) -> ret!('a, FillBufFuture, io::Result<&'a [u8]>)
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where
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Self: Unpin,
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{
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FillBufFuture::new(self)
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}
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/// Reads all bytes into `buf` until the delimiter `byte` or EOF is reached.
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///
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/// This function will read bytes from the underlying stream until the delimiter or EOF is
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