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use futures_core::ready;
use futures_core::task::{Context, Poll};
#[cfg(feature = "read-initializer")]
use futures_io::Initializer;
use futures_io::{AsyncRead, AsyncBufRead};
use pin_project_lite::pin_project;
use std::{cmp, io};
use std::pin::Pin;
pin_project! {
#[derive(Debug)]
#[must_use = "readers do nothing unless you `.await` or poll them"]
pub struct Take<R> {
#[pin]
inner: R,
limit_: u64,
}
}
impl<R: AsyncRead> Take<R> {
pub(super) fn new(inner: R, limit: u64) -> Self {
Self { inner, limit_: limit }
}
pub fn limit(&self) -> u64 {
self.limit_
}
pub fn set_limit(&mut self, limit: u64) {
self.limit_ = limit
}
delegate_access_inner!(inner, R, ());
}
impl<R: AsyncRead> AsyncRead for Take<R> {
fn poll_read(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<Result<usize, io::Error>> {
let this = self.project();
if *this.limit_ == 0 {
return Poll::Ready(Ok(0));
}
let max = cmp::min(buf.len() as u64, *this.limit_) as usize;
let n = ready!(this.inner.poll_read(cx, &mut buf[..max]))?;
*this.limit_ -= n as u64;
Poll::Ready(Ok(n))
}
#[cfg(feature = "read-initializer")]
unsafe fn initializer(&self) -> Initializer {
self.inner.initializer()
}
}
impl<R: AsyncBufRead> AsyncBufRead for Take<R> {
fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<&[u8]>> {
let this = self.project();
if *this.limit_ == 0 {
return Poll::Ready(Ok(&[]));
}
let buf = ready!(this.inner.poll_fill_buf(cx)?);
let cap = cmp::min(buf.len() as u64, *this.limit_) as usize;
Poll::Ready(Ok(&buf[..cap]))
}
fn consume(self: Pin<&mut Self>, amt: usize) {
let this = self.project();
let amt = cmp::min(amt as u64, *this.limit_) as usize;
*this.limit_ -= amt as u64;
this.inner.consume(amt);
}
}