mirror of
https://github.com/denoland/deno
synced 2024-09-13 13:21:50 +00:00
65 lines
1.8 KiB
Rust
65 lines
1.8 KiB
Rust
// Copyright (c) 2019 Tokio Contributors. All rights reserved. MIT license.
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// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
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// Forked from: https://github.com/tokio-rs/tokio/blob/9b3f8564af4bb1aee07fab3c401eb412ca5eeac5/tokio-io/src/io/read.rs
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use crate::resources::DenoAsyncRead;
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use deno::ErrBox;
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use futures::{Future, Poll};
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use std::mem;
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/// This is almost the same implementation as in tokio, the only difference is
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/// that error type is `ErrBox` instead of `std::io::Error`.
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#[derive(Debug)]
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enum State<R, T> {
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Pending { rd: R, buf: T },
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Empty,
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}
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/// Tries to read some bytes directly into the given `buf` in asynchronous
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/// manner, returning a future type.
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///
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/// The returned future will resolve to both the I/O stream and the buffer
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/// as well as the number of bytes read once the read operation is completed.
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pub fn read<R, T>(rd: R, buf: T) -> Read<R, T>
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where
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R: DenoAsyncRead,
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T: AsMut<[u8]>,
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{
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Read {
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state: State::Pending { rd, buf },
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}
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}
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/// A future which can be used to easily read available number of bytes to fill
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/// a buffer.
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///
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/// Created by the [`read`] function.
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#[derive(Debug)]
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pub struct Read<R, T> {
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state: State<R, T>,
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}
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impl<R, T> Future for Read<R, T>
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where
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R: DenoAsyncRead,
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T: AsMut<[u8]>,
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{
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type Item = (R, T, usize);
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type Error = ErrBox;
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fn poll(&mut self) -> Poll<(R, T, usize), ErrBox> {
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let nread = match self.state {
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State::Pending {
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ref mut rd,
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ref mut buf,
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} => try_ready!(rd.poll_read(&mut buf.as_mut()[..])),
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State::Empty => panic!("poll a Read after it's done"),
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};
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match mem::replace(&mut self.state, State::Empty) {
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State::Pending { rd, buf } => Ok((rd, buf, nread).into()),
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State::Empty => panic!("invalid internal state"),
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}
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}
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}
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