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use std::io as std_io; use bytes::Buf; use futures::{Async, Poll}; use AsyncRead; /// Writes bytes asynchronously. /// /// The trait inherits from `std::io::Write` and indicates that an I/O object is /// **nonblocking**. All non-blocking I/O objects must return an error when /// bytes cannot be written instead of blocking the current thread. /// /// Specifically, this means that the `write` function will return one of the /// following: /// /// * `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. /// /// Note that this trait also represents that the `Write::flush` method works /// very similarly to the `write` method, notably that `Ok(())` means that the /// writer has successfully been flushed, a "would block" error means that the /// current task is ready to receive a notification when flushing can make more /// progress, and otherwise normal errors can happen as well. pub trait AsyncWrite: std_io::Write { /// Attempt to write bytes from `buf` into the object. /// /// On success, returns `Ok(Async::Ready(num_bytes_written))`. /// /// If the object is not ready for writing, the method returns /// `Ok(Async::Pending)` and arranges for the current task (via /// `cx.waker()`) to receive a notification when the object becomes /// readable or is closed. fn poll_write(&mut self, buf: &[u8]) -> Poll<usize, std_io::Error> { match self.write(buf) { Ok(t) => Ok(Async::Ready(t)), Err(ref e) if e.kind() == std_io::ErrorKind::WouldBlock => { return Ok(Async::NotReady) } Err(e) => return Err(e.into()), } } /// Attempt to flush the object, ensuring that any buffered data reach /// their destination. /// /// On success, returns `Ok(Async::Ready(()))`. /// /// If flushing cannot immediately complete, this method returns /// `Ok(Async::Pending)` and arranges for the current task (via /// `cx.waker()`) to receive a notification when the object can make /// progress towards flushing. fn poll_flush(&mut self) -> Poll<(), std_io::Error> { match self.flush() { Ok(t) => Ok(Async::Ready(t)), Err(ref e) if e.kind() == std_io::ErrorKind::WouldBlock => { return Ok(Async::NotReady) } Err(e) => return Err(e.into()), } } /// 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_ready!(self.poll_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_ready!(self.poll_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()) } }