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176: Add BufRead::fill_buf r=stjepang a=tirr-c Tracking issue: #131. Docs from `std`. **Note** that there is a use of `unsafe` in `fill_buf.rs` that transmutes the lifetime of output buffer. Co-authored-by: Wonwoo Choi <[email protected]>
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Original file line number | Diff line number | Diff line change |
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use std::pin::Pin; | ||
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use futures_io::AsyncBufRead; | ||
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use crate::future::Future; | ||
use crate::io; | ||
use crate::task::{Context, Poll}; | ||
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#[doc(hidden)] | ||
#[allow(missing_debug_implementations)] | ||
pub struct FillBufFuture<'a, R: ?Sized> { | ||
reader: &'a mut R, | ||
} | ||
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impl<'a, R: ?Sized> FillBufFuture<'a, R> { | ||
pub(crate) fn new(reader: &'a mut R) -> Self { | ||
Self { reader } | ||
} | ||
} | ||
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impl<'a, R: AsyncBufRead + Unpin + ?Sized> Future for FillBufFuture<'a, R> { | ||
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]>> { | ||
let Self { reader } = &mut *self; | ||
let result = Pin::new(reader).poll_fill_buf(cx); | ||
// This is safe because: | ||
// 1. The buffer is valid for the lifetime of the reader. | ||
// 2. Output is unrelated to the wrapper (Self). | ||
result.map_ok(|buf| unsafe { std::mem::transmute::<&'_ [u8], &'a [u8]>(buf) }) | ||
} | ||
} |
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