don't poll the reader again after eof while waiting for the writer to flush

pull/894/head
Jacob Rothstein 4 years ago
parent 97a2fbed07
commit ae817ca1a2
No known key found for this signature in database
GPG Key ID: C38BA18C6CFE15A5

@ -7,6 +7,12 @@ use crate::io::{self, BufRead, BufReader, Read, Write};
use crate::task::{Context, Poll};
use crate::utils::Context as _;
// Note: There are two otherwise-identical implementations of this
// function because unstable has removed the `?Sized` bound for the
// reader and writer and accepts `R` and `W` instead of `&mut R` and
// `&mut W`. If making a change to either of the implementations,
// ensure that you copy it into the other.
/// Copies the entire contents of a reader into a writer.
///
/// This function will continuously read data from `reader` and then
@ -57,6 +63,7 @@ where
#[pin]
writer: W,
amt: u64,
reader_eof: bool
}
}
@ -69,13 +76,20 @@ where
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let mut this = self.project();
loop {
let buffer = futures_core::ready!(this.reader.as_mut().poll_fill_buf(cx))?;
if buffer.is_empty() {
if *this.reader_eof {
futures_core::ready!(this.writer.as_mut().poll_flush(cx))?;
return Poll::Ready(Ok(*this.amt));
}
let buffer = futures_core::ready!(this.reader.as_mut().poll_fill_buf(cx))?;
if buffer.is_empty() {
*this.reader_eof = true;
continue;
}
let i = futures_core::ready!(this.writer.as_mut().poll_write(cx, buffer))?;
if i == 0 {
return Poll::Ready(Err(io::ErrorKind::WriteZero.into()));
@ -89,6 +103,7 @@ where
let future = CopyFuture {
reader: BufReader::new(reader),
writer,
reader_eof: false,
amt: 0,
};
future.await.context(|| String::from("io::copy failed"))
@ -144,6 +159,7 @@ where
#[pin]
writer: W,
amt: u64,
reader_eof: bool
}
}
@ -156,13 +172,20 @@ where
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let mut this = self.project();
loop {
let buffer = futures_core::ready!(this.reader.as_mut().poll_fill_buf(cx))?;
if buffer.is_empty() {
if *this.reader_eof {
futures_core::ready!(this.writer.as_mut().poll_flush(cx))?;
return Poll::Ready(Ok(*this.amt));
}
let buffer = futures_core::ready!(this.reader.as_mut().poll_fill_buf(cx))?;
if buffer.is_empty() {
*this.reader_eof = true;
continue;
}
let i = futures_core::ready!(this.writer.as_mut().poll_write(cx, buffer))?;
if i == 0 {
return Poll::Ready(Err(io::ErrorKind::WriteZero.into()));
@ -176,6 +199,7 @@ where
let future = CopyFuture {
reader: BufReader::new(reader),
writer,
reader_eof: false,
amt: 0,
};
future.await.context(|| String::from("io::copy failed"))

@ -0,0 +1,72 @@
use std::{
io::Result,
pin::Pin,
task::{Context, Poll},
};
struct ReaderThatPanicsAfterEof {
read_count: usize,
has_sent_eof: bool,
max_read: usize,
}
impl async_std::io::Read for ReaderThatPanicsAfterEof {
fn poll_read(
mut self: Pin<&mut Self>,
_cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<Result<usize>> {
if self.has_sent_eof {
panic!("this should be unreachable because we should not poll after eof (Ready(Ok(0)))")
} else if self.read_count >= self.max_read {
self.has_sent_eof = true;
Poll::Ready(Ok(0))
} else {
self.read_count += 1;
Poll::Ready(Ok(buf.len()))
}
}
}
struct WriterThatTakesAWhileToFlush {
max_flush: usize,
flush_count: usize,
}
impl async_std::io::Write for WriterThatTakesAWhileToFlush {
fn poll_write(self: Pin<&mut Self>, _cx: &mut Context<'_>, buf: &[u8]) -> Poll<Result<usize>> {
Poll::Ready(Ok(buf.len()))
}
fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>> {
self.flush_count += 1;
if self.flush_count >= self.max_flush {
Poll::Ready(Ok(()))
} else {
cx.waker().wake_by_ref();
Poll::Pending
}
}
fn poll_close(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Result<()>> {
Poll::Ready(Ok(()))
}
}
#[test]
fn io_copy_does_not_poll_after_eof() {
async_std::task::block_on(async {
let mut reader = ReaderThatPanicsAfterEof {
has_sent_eof: false,
max_read: 10,
read_count: 0,
};
let mut writer = WriterThatTakesAWhileToFlush {
flush_count: 0,
max_flush: 10,
};
assert!(async_std::io::copy(&mut reader, &mut writer).await.is_ok());
})
}
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