| use crate::io::AsyncBufRead; |
| |
| use pin_project_lite::pin_project; |
| use std::future::Future; |
| use std::io; |
| use std::marker::PhantomPinned; |
| use std::pin::Pin; |
| use std::task::{Context, Poll}; |
| |
| pin_project! { |
| /// Future for the [`fill_buf`](crate::io::AsyncBufReadExt::fill_buf) method. |
| #[derive(Debug)] |
| #[must_use = "futures do nothing unless you `.await` or poll them"] |
| pub struct FillBuf<'a, R: ?Sized> { |
| reader: Option<&'a mut R>, |
| #[pin] |
| _pin: PhantomPinned, |
| } |
| } |
| |
| pub(crate) fn fill_buf<R>(reader: &mut R) -> FillBuf<'_, R> |
| where |
| R: AsyncBufRead + ?Sized + Unpin, |
| { |
| FillBuf { |
| reader: Some(reader), |
| _pin: PhantomPinned, |
| } |
| } |
| |
| impl<'a, R: AsyncBufRead + ?Sized + Unpin> Future for FillBuf<'a, R> { |
| type Output = io::Result<&'a [u8]>; |
| |
| fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { |
| let me = self.project(); |
| |
| // Due to a limitation in the borrow-checker, we cannot return the value |
| // directly on Ready. Once Rust starts using the polonius borrow checker, |
| // this can be simplified. |
| let reader = me.reader.take().expect("Polled after completion."); |
| match Pin::new(&mut *reader).poll_fill_buf(cx) { |
| Poll::Ready(_) => match Pin::new(reader).poll_fill_buf(cx) { |
| Poll::Ready(slice) => Poll::Ready(slice), |
| Poll::Pending => panic!("poll_fill_buf returned Pending while having data"), |
| }, |
| Poll::Pending => { |
| *me.reader = Some(reader); |
| Poll::Pending |
| } |
| } |
| } |
| } |