diff options
Diffstat (limited to 'third_party/rust/tokio/src/io/mod.rs')
| -rw-r--r-- | third_party/rust/tokio/src/io/mod.rs | 276 |
1 files changed, 276 insertions, 0 deletions
diff --git a/third_party/rust/tokio/src/io/mod.rs b/third_party/rust/tokio/src/io/mod.rs new file mode 100644 index 0000000000..cfdda61f69 --- /dev/null +++ b/third_party/rust/tokio/src/io/mod.rs @@ -0,0 +1,276 @@ +#![cfg_attr(loom, allow(dead_code, unreachable_pub))] + +//! Traits, helpers, and type definitions for asynchronous I/O functionality. +//! +//! This module is the asynchronous version of `std::io`. Primarily, it +//! defines two traits, [`AsyncRead`] and [`AsyncWrite`], which are asynchronous +//! versions of the [`Read`] and [`Write`] traits in the standard library. +//! +//! # AsyncRead and AsyncWrite +//! +//! Like the standard library's [`Read`] and [`Write`] traits, [`AsyncRead`] and +//! [`AsyncWrite`] provide the most general interface for reading and writing +//! input and output. Unlike the standard library's traits, however, they are +//! _asynchronous_ — meaning that reading from or writing to a `tokio::io` +//! type will _yield_ to the Tokio scheduler when IO is not ready, rather than +//! blocking. This allows other tasks to run while waiting on IO. +//! +//! Another difference is that `AsyncRead` and `AsyncWrite` only contain +//! core methods needed to provide asynchronous reading and writing +//! functionality. Instead, utility methods are defined in the [`AsyncReadExt`] +//! and [`AsyncWriteExt`] extension traits. These traits are automatically +//! implemented for all values that implement `AsyncRead` and `AsyncWrite` +//! respectively. +//! +//! End users will rarely interact directly with `AsyncRead` and +//! `AsyncWrite`. Instead, they will use the async functions defined in the +//! extension traits. Library authors are expected to implement `AsyncRead` +//! and `AsyncWrite` in order to provide types that behave like byte streams. +//! +//! Even with these differences, Tokio's `AsyncRead` and `AsyncWrite` traits +//! can be used in almost exactly the same manner as the standard library's +//! `Read` and `Write`. Most types in the standard library that implement `Read` +//! and `Write` have asynchronous equivalents in `tokio` that implement +//! `AsyncRead` and `AsyncWrite`, such as [`File`] and [`TcpStream`]. +//! +//! For example, the standard library documentation introduces `Read` by +//! [demonstrating][std_example] reading some bytes from a [`std::fs::File`]. We +//! can do the same with [`tokio::fs::File`][`File`]: +//! +//! ```no_run +//! use tokio::io::{self, AsyncReadExt}; +//! use tokio::fs::File; +//! +//! #[tokio::main] +//! async fn main() -> io::Result<()> { +//! let mut f = File::open("foo.txt").await?; +//! let mut buffer = [0; 10]; +//! +//! // read up to 10 bytes +//! let n = f.read(&mut buffer).await?; +//! +//! println!("The bytes: {:?}", &buffer[..n]); +//! Ok(()) +//! } +//! ``` +//! +//! [`File`]: crate::fs::File +//! [`TcpStream`]: crate::net::TcpStream +//! [`std::fs::File`]: std::fs::File +//! [std_example]: std::io#read-and-write +//! +//! ## Buffered Readers and Writers +//! +//! Byte-based interfaces are unwieldy and can be inefficient, as we'd need to be +//! making near-constant calls to the operating system. To help with this, +//! `std::io` comes with [support for _buffered_ readers and writers][stdbuf], +//! and therefore, `tokio::io` does as well. +//! +//! Tokio provides an async version of the [`std::io::BufRead`] trait, +//! [`AsyncBufRead`]; and async [`BufReader`] and [`BufWriter`] structs, which +//! wrap readers and writers. These wrappers use a buffer, reducing the number +//! of calls and providing nicer methods for accessing exactly what you want. +//! +//! For example, [`BufReader`] works with the [`AsyncBufRead`] trait to add +//! extra methods to any async reader: +//! +//! ```no_run +//! use tokio::io::{self, BufReader, AsyncBufReadExt}; +//! use tokio::fs::File; +//! +//! #[tokio::main] +//! async fn main() -> io::Result<()> { +//! let f = File::open("foo.txt").await?; +//! let mut reader = BufReader::new(f); +//! let mut buffer = String::new(); +//! +//! // read a line into buffer +//! reader.read_line(&mut buffer).await?; +//! +//! println!("{}", buffer); +//! Ok(()) +//! } +//! ``` +//! +//! [`BufWriter`] doesn't add any new ways of writing; it just buffers every call +//! to [`write`](crate::io::AsyncWriteExt::write). However, you **must** flush +//! [`BufWriter`] to ensure that any buffered data is written. +//! +//! ```no_run +//! use tokio::io::{self, BufWriter, AsyncWriteExt}; +//! use tokio::fs::File; +//! +//! #[tokio::main] +//! async fn main() -> io::Result<()> { +//! let f = File::create("foo.txt").await?; +//! { +//! let mut writer = BufWriter::new(f); +//! +//! // Write a byte to the buffer. +//! writer.write(&[42u8]).await?; +//! +//! // Flush the buffer before it goes out of scope. +//! writer.flush().await?; +//! +//! } // Unless flushed or shut down, the contents of the buffer is discarded on drop. +//! +//! Ok(()) +//! } +//! ``` +//! +//! [stdbuf]: std::io#bufreader-and-bufwriter +//! [`std::io::BufRead`]: std::io::BufRead +//! [`AsyncBufRead`]: crate::io::AsyncBufRead +//! [`BufReader`]: crate::io::BufReader +//! [`BufWriter`]: crate::io::BufWriter +//! +//! ## Implementing AsyncRead and AsyncWrite +//! +//! Because they are traits, we can implement [`AsyncRead`] and [`AsyncWrite`] for +//! our own types, as well. Note that these traits must only be implemented for +//! non-blocking I/O types that integrate with the futures type system. In +//! other words, these types must never block the thread, and instead the +//! current task is notified when the I/O resource is ready. +//! +//! ## Conversion to and from Sink/Stream +//! +//! It is often convenient to encapsulate the reading and writing of +//! bytes and instead work with a [`Sink`] or [`Stream`] of some data +//! type that is encoded as bytes and/or decoded from bytes. Tokio +//! provides some utility traits in the [tokio-util] crate that +//! abstract the asynchronous buffering that is required and allows +//! you to write [`Encoder`] and [`Decoder`] functions working with a +//! buffer of bytes, and then use that ["codec"] to transform anything +//! that implements [`AsyncRead`] and [`AsyncWrite`] into a `Sink`/`Stream` of +//! your structured data. +//! +//! [tokio-util]: https://docs.rs/tokio-util/0.6/tokio_util/codec/index.html +//! +//! # Standard input and output +//! +//! Tokio provides asynchronous APIs to standard [input], [output], and [error]. +//! These APIs are very similar to the ones provided by `std`, but they also +//! implement [`AsyncRead`] and [`AsyncWrite`]. +//! +//! Note that the standard input / output APIs **must** be used from the +//! context of the Tokio runtime, as they require Tokio-specific features to +//! function. Calling these functions outside of a Tokio runtime will panic. +//! +//! [input]: fn@stdin +//! [output]: fn@stdout +//! [error]: fn@stderr +//! +//! # `std` re-exports +//! +//! Additionally, [`Error`], [`ErrorKind`], [`Result`], and [`SeekFrom`] are +//! re-exported from `std::io` for ease of use. +//! +//! [`AsyncRead`]: trait@AsyncRead +//! [`AsyncWrite`]: trait@AsyncWrite +//! [`AsyncReadExt`]: trait@AsyncReadExt +//! [`AsyncWriteExt`]: trait@AsyncWriteExt +//! ["codec"]: https://docs.rs/tokio-util/0.6/tokio_util/codec/index.html +//! [`Encoder`]: https://docs.rs/tokio-util/0.6/tokio_util/codec/trait.Encoder.html +//! [`Decoder`]: https://docs.rs/tokio-util/0.6/tokio_util/codec/trait.Decoder.html +//! [`Error`]: struct@Error +//! [`ErrorKind`]: enum@ErrorKind +//! [`Result`]: type@Result +//! [`Read`]: std::io::Read +//! [`SeekFrom`]: enum@SeekFrom +//! [`Sink`]: https://docs.rs/futures/0.3/futures/sink/trait.Sink.html +//! [`Stream`]: https://docs.rs/futures/0.3/futures/stream/trait.Stream.html +//! [`Write`]: std::io::Write +cfg_io_blocking! { + pub(crate) mod blocking; +} + +mod async_buf_read; +pub use self::async_buf_read::AsyncBufRead; + +mod async_read; +pub use self::async_read::AsyncRead; + +mod async_seek; +pub use self::async_seek::AsyncSeek; + +mod async_write; +pub use self::async_write::AsyncWrite; + +mod read_buf; +pub use self::read_buf::ReadBuf; + +// Re-export some types from `std::io` so that users don't have to deal +// with conflicts when `use`ing `tokio::io` and `std::io`. +#[doc(no_inline)] +pub use std::io::{Error, ErrorKind, Result, SeekFrom}; + +cfg_io_driver_impl! { + pub(crate) mod driver; + + cfg_net! { + pub use driver::{Interest, Ready}; + } + + mod poll_evented; + + #[cfg(not(loom))] + pub(crate) use poll_evented::PollEvented; +} + +cfg_aio! { + /// BSD-specific I/O types. + pub mod bsd { + mod poll_aio; + + pub use poll_aio::{Aio, AioEvent, AioSource}; + } +} + +cfg_net_unix! { + mod async_fd; + + pub mod unix { + //! Asynchronous IO structures specific to Unix-like operating systems. + pub use super::async_fd::{AsyncFd, AsyncFdReadyGuard, AsyncFdReadyMutGuard, TryIoError}; + } +} + +cfg_io_std! { + mod stdio_common; + + mod stderr; + pub use stderr::{stderr, Stderr}; + + mod stdin; + pub use stdin::{stdin, Stdin}; + + mod stdout; + pub use stdout::{stdout, Stdout}; +} + +cfg_io_util! { + mod split; + pub use split::{split, ReadHalf, WriteHalf}; + + pub(crate) mod seek; + pub(crate) mod util; + pub use util::{ + copy, copy_bidirectional, copy_buf, duplex, empty, repeat, sink, AsyncBufReadExt, AsyncReadExt, AsyncSeekExt, AsyncWriteExt, + BufReader, BufStream, BufWriter, DuplexStream, Empty, Lines, Repeat, Sink, Split, Take, + }; +} + +cfg_not_io_util! { + cfg_process! { + pub(crate) mod util; + } +} + +cfg_io_blocking! { + /// Types in this module can be mocked out in tests. + mod sys { + // TODO: don't rename + pub(crate) use crate::blocking::spawn_blocking as run; + pub(crate) use crate::blocking::JoinHandle as Blocking; + } +} |