48 lines
1.5 KiB
Rust
48 lines
1.5 KiB
Rust
use futures_core::future::Future;
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use futures_core::task::{Context, Poll};
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use futures_io::AsyncBufRead;
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use std::io;
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use std::pin::Pin;
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use std::slice;
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/// Future for the [`fill_buf`](super::AsyncBufReadExt::fill_buf) method.
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#[derive(Debug)]
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#[must_use = "futures do nothing unless you `.await` or poll them"]
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pub struct FillBuf<'a, R: ?Sized> {
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reader: Option<&'a mut R>,
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}
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impl<R: ?Sized> Unpin for FillBuf<'_, R> {}
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impl<'a, R: AsyncBufRead + ?Sized + Unpin> FillBuf<'a, R> {
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pub(super) fn new(reader: &'a mut R) -> Self {
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Self { reader: Some(reader) }
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}
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}
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impl<'a, R> Future for FillBuf<'a, R>
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where
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R: AsyncBufRead + ?Sized + Unpin,
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{
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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<Self::Output> {
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let this = &mut *self;
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let reader = this.reader.take().expect("Polled FillBuf after completion");
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match Pin::new(&mut *reader).poll_fill_buf(cx) {
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Poll::Ready(Ok(slice)) => {
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// With polonius it is possible to remove this lifetime transmutation and just have
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// the correct lifetime of the reference inferred based on which branch is taken
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let slice: &'a [u8] = unsafe { slice::from_raw_parts(slice.as_ptr(), slice.len()) };
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Poll::Ready(Ok(slice))
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}
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Poll::Ready(Err(err)) => Poll::Ready(Err(err)),
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Poll::Pending => {
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this.reader = Some(reader);
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Poll::Pending
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}
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}
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}
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}
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