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//! Core I/O traits and combinators when working with Tokio. //! //! A description of the high-level I/O combinators can be [found online] in //! addition to a description of the [low level details]. //! //! [found online]: https://tokio.rs/docs/getting-started/core/ //! [low level details]: https://tokio.rs/docs/going-deeper-tokio/core-low-level/ #![deny(missing_docs, missing_debug_implementations, warnings)] #![doc(html_root_url = "https://docs.rs/tokio-io/0.1")] #[macro_use] extern crate log; #[macro_use] extern crate futures; extern crate bytes; use std::io as std_io; use std::io::Write; use futures::{Async, Future, Poll, Stream}; use bytes::{Buf, BufMut}; /// A convenience typedef around a `Future` whose error component is `io::Error` pub type IoFuture<T> = Box<Future<Item = T, Error = std_io::Error> + Send>; /// A convenience typedef around a `Stream` whose error component is `io::Error` pub type IoStream<T> = Box<Stream<Item = T, Error = std_io::Error> + Send>; /// A convenience macro for working with `io::Result<T>` from the `Read` and /// `Write` traits. /// /// This macro takes `io::Result<T>` as input, and returns `T` as the output. If /// the input type is of the `Err` variant, then `Poll::NotReady` is returned if /// it indicates `WouldBlock` or otherwise `Err` is returned. #[macro_export] macro_rules! try_nb { ($e:expr) => (match $e { Ok(t) => t, Err(ref e) if e.kind() == ::std::io::ErrorKind::WouldBlock => { return Ok(::futures::Async::NotReady) } Err(e) => return Err(e.into()), }) } pub mod io; pub mod codec; mod allow_std; mod codecs; mod copy; mod flush; mod framed; mod framed_read; mod framed_write; mod length_delimited; mod lines; mod read; mod read_exact; mod read_to_end; mod read_until; mod shutdown; mod split; mod window; mod write_all; use codec::{Decoder, Encoder, Framed}; use split::{ReadHalf, WriteHalf}; /// A trait for readable objects which operated in an asynchronous and /// futures-aware fashion. /// /// This trait inherits from `io::Read` and indicates as a marker that an I/O /// object is **nonblocking**, meaning that it will return an error instead of /// blocking when bytes are unavailable, but the stream hasn't reached EOF. /// Specifically this means that the `read` function for types that implement /// this trait can have a few return values: /// /// * `Ok(n)` means that `n` bytes of data was immediately read and placed into /// the output buffer, where `n` == 0 implies that EOF has been reached. /// * `Err(e) if e.kind() == ErrorKind::WouldBlock` means that no data was read /// into the buffer provided. The I/O object is not currently readable but may /// become readable in the future. Most importantly, **the current future's /// task is scheduled to get unparked when the object is readable**. This /// means that like `Future::poll` you'll receive a notification when the I/O /// object is readable again. /// * `Err(e)` for other errors are standard I/O errors coming from the /// underlying object. /// /// This trait importantly means that the `read` method only works in the /// context of a future's task. The object may panic if used outside of a task. pub trait AsyncRead: std_io::Read { /// Prepares an uninitialized buffer to be safe to pass to `read`. Returns /// `true` if the supplied buffer was zeroed out. /// /// While it would be highly unusual, implementations of [`io::Read`] are /// able to read data from the buffer passed as an argument. Because of /// this, the buffer passed to [`io::Read`] must be initialized memory. In /// situations where large numbers of buffers are used, constantly having to /// zero out buffers can be expensive. /// /// This function does any necessary work to prepare an uninitialized buffer /// to be safe to pass to `read`. If `read` guarantees to never attempt read /// data out of the supplied buffer, then `prepare_uninitialized_buffer` /// doesn't need to do any work. /// /// If this function returns `true`, then the memory has been zeroed out. /// This allows implementations of `AsyncRead` which are composed of /// multiple sub implementations to efficiently implement /// `prepare_uninitialized_buffer`. /// /// This function isn't actually `unsafe` to call but `unsafe` to implement. /// The implementor must ensure that either the whole `buf` has been zeroed /// or `read_buf()` overwrites the buffer without reading it and returns /// correct value. /// /// This function is called from [`read_buf`]. /// /// [`io::Read`]: https://doc.rust-lang.org/std/io/trait.Read.html /// [`read_buf`]: #method.read_buf unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool { for i in 0..buf.len() { buf[i] = 0; } true } /// Pull some bytes from this source into the specified `Buf`, returning /// how many bytes were read. /// /// The `buf` provided will have bytes read into it and the internal cursor /// will be advanced if any bytes were read. Note that this method typically /// will not reallocate the buffer provided. fn read_buf<B: BufMut>(&mut self, buf: &mut B) -> Poll<usize, std_io::Error> where Self: Sized, { if !buf.has_remaining_mut() { return Ok(Async::Ready(0)); } unsafe { let n = { let b = buf.bytes_mut(); self.prepare_uninitialized_buffer(b); try_nb!(self.read(b)) }; buf.advance_mut(n); Ok(Async::Ready(n)) } } /// Provides a `Stream` and `Sink` interface for reading and writing to this /// `Io` object, using `Decode` and `Encode` to read and write the raw data. /// /// Raw I/O objects work with byte sequences, but higher-level code usually /// wants to batch these into meaningful chunks, called "frames". This /// method layers framing on top of an I/O object, by using the `Codec` /// traits to handle encoding and decoding of messages frames. Note that /// the incoming and outgoing frame types may be distinct. /// /// This function returns a *single* object that is both `Stream` and /// `Sink`; grouping this into a single object is often useful for layering /// things like gzip or TLS, which require both read and write access to the /// underlying object. /// /// If you want to work more directly with the streams and sink, consider /// calling `split` on the `Framed` returned by this method, which will /// break them into separate objects, allowing them to interact more easily. fn framed<T: Encoder + Decoder>(self, codec: T) -> Framed<Self, T> where Self: AsyncWrite + Sized, { framed::framed(self, codec) } /// Helper method for splitting this read/write object into two halves. /// /// The two halves returned implement the `Read` and `Write` traits, /// respectively. fn split(self) -> (ReadHalf<Self>, WriteHalf<Self>) where Self: AsyncWrite + Sized, { split::split(self) } } impl<T: ?Sized + AsyncRead> AsyncRead for Box<T> { unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool { (**self).prepare_uninitialized_buffer(buf) } } impl<'a, T: ?Sized + AsyncRead> AsyncRead for &'a mut T { unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool { (**self).prepare_uninitialized_buffer(buf) } } impl<'a> AsyncRead for &'a [u8] { unsafe fn prepare_uninitialized_buffer(&self, _buf: &mut [u8]) -> bool { false } } /// A trait for writable objects which operated in an asynchronous and /// futures-aware fashion. /// /// This trait inherits from `io::Write` and indicates that an I/O object is /// **nonblocking**, meaning that it will return an error instead of blocking /// when bytes cannot currently be written, but hasn't closed. Specifically /// this means that the `write` function for types that implement this trait /// can have a few return values: /// /// * `Ok(n)` means that `n` bytes of data was immediately written . /// * `Err(e) if e.kind() == ErrorKind::WouldBlock` means that no data was /// written from the buffer provided. The I/O object is not currently /// writable but may become writable in the future. Most importantly, **the /// current future's task is scheduled to get unparked when the object is /// readable**. This means that like `Future::poll` you'll receive a /// notification when the I/O object is writable again. /// * `Err(e)` for other errors are standard I/O errors coming from the /// underlying object. /// /// This trait importantly means that the `write` method only works in the /// context of a future's task. The object may panic if used outside of a task. pub trait AsyncWrite: std_io::Write { /// Initiates or attempts to shut down this writer, returning success when /// the I/O connection has completely shut down. /// /// This method is intended to be used for asynchronous shutdown of I/O /// connections. For example this is suitable for implementing shutdown of a /// TLS connection or calling `TcpStream::shutdown` on a proxied connection. /// Protocols sometimes need to flush out final pieces of data or otherwise /// perform a graceful shutdown handshake, reading/writing more data as /// appropriate. This method is the hook for such protocols to implement the /// graceful shutdown logic. /// /// This `shutdown` method is required by implementors of the /// `AsyncWrite` trait. Wrappers typically just want to proxy this call /// through to the wrapped type, and base types will typically implement /// shutdown logic here or just return `Ok(().into())`. Note that if you're /// wrapping an underlying `AsyncWrite` a call to `shutdown` implies that /// transitively the entire stream has been shut down. After your wrapper's /// shutdown logic has been executed you should shut down the underlying /// stream. /// /// Invocation of a `shutdown` implies an invocation of `flush`. Once this /// method returns `Ready` it implies that a flush successfully happened /// before the shutdown happened. That is, callers don't need to call /// `flush` before calling `shutdown`. They can rely that by calling /// `shutdown` any pending buffered data will be written out. /// /// # Return value /// /// This function returns a `Poll<(), io::Error>` classified as such: /// /// * `Ok(Async::Ready(()))` - indicates that the connection was /// successfully shut down and is now safe to deallocate/drop/close /// resources associated with it. This method means that the current task /// will no longer receive any notifications due to this method and the /// I/O object itself is likely no longer usable. /// /// * `Ok(Async::NotReady)` - indicates that shutdown is initiated but could /// not complete just yet. This may mean that more I/O needs to happen to /// continue this shutdown operation. The current task is scheduled to /// receive a notification when it's otherwise ready to continue the /// shutdown operation. When woken up this method should be called again. /// /// * `Err(e)` - indicates a fatal error has happened with shutdown, /// indicating that the shutdown operation did not complete successfully. /// This typically means that the I/O object is no longer usable. /// /// # Errors /// /// This function can return normal I/O errors through `Err`, described /// above. Additionally this method may also render the underlying /// `Write::write` method no longer usable (e.g. will return errors in the /// future). It's recommended that once `shutdown` is called the /// `write` method is no longer called. /// /// # Panics /// /// This function will panic if not called within the context of a future's /// task. fn shutdown(&mut self) -> Poll<(), std_io::Error>; /// Write a `Buf` into this value, returning how many bytes were written. /// /// Note that this method will advance the `buf` provided automatically by /// the number of bytes written. fn write_buf<B: Buf>(&mut self, buf: &mut B) -> Poll<usize, std_io::Error> where Self: Sized, { if !buf.has_remaining() { return Ok(Async::Ready(0)); } let n = try_nb!(self.write(buf.bytes())); buf.advance(n); Ok(Async::Ready(n)) } } impl<T: ?Sized + AsyncWrite> AsyncWrite for Box<T> { fn shutdown(&mut self) -> Poll<(), std_io::Error> { (**self).shutdown() } } impl<'a, T: ?Sized + AsyncWrite> AsyncWrite for &'a mut T { fn shutdown(&mut self) -> Poll<(), std_io::Error> { (**self).shutdown() } } impl AsyncRead for std_io::Repeat { unsafe fn prepare_uninitialized_buffer(&self, _: &mut [u8]) -> bool { false } } impl AsyncWrite for std_io::Sink { fn shutdown(&mut self) -> Poll<(), std_io::Error> { Ok(().into()) } } // TODO: Implement `prepare_uninitialized_buffer` for `io::Take`. // This is blocked on rust-lang/rust#27269 impl<T: AsyncRead> AsyncRead for std_io::Take<T> { } // TODO: Implement `prepare_uninitialized_buffer` when upstream exposes inner // parts impl<T, U> AsyncRead for std_io::Chain<T, U> where T: AsyncRead, U: AsyncRead, { } impl<T: AsyncWrite> AsyncWrite for std_io::BufWriter<T> { fn shutdown(&mut self) -> Poll<(), std_io::Error> { try_nb!(self.flush()); self.get_mut().shutdown() } } impl<T: AsyncRead> AsyncRead for std_io::BufReader<T> { unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool { self.get_ref().prepare_uninitialized_buffer(buf) } } impl<T: AsRef<[u8]>> AsyncRead for std_io::Cursor<T> { } impl<'a> AsyncWrite for std_io::Cursor<&'a mut [u8]> { fn shutdown(&mut self) -> Poll<(), std_io::Error> { Ok(().into()) } } impl AsyncWrite for std_io::Cursor<Vec<u8>> { fn shutdown(&mut self) -> Poll<(), std_io::Error> { Ok(().into()) } } impl AsyncWrite for std_io::Cursor<Box<[u8]>> { fn shutdown(&mut self) -> Poll<(), std_io::Error> { Ok(().into()) } } fn _assert_objects() { fn _assert<T>() {} _assert::<Box<AsyncRead>>(); _assert::<Box<AsyncWrite>>(); }