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use std::{fmt, io}; use AsyncRead; use framed::Fuse; use futures::{Async, Poll, Stream, Sink, StartSend}; use bytes::BytesMut; /// Decoding of frames via buffers. /// /// This trait is used when constructing an instance of `Framed` or /// `FramedRead`. An implementation of `Decoder` takes a byte stream that has /// already been buffered in `src` and decodes the data into a stream of /// `Self::Item` frames. /// /// Implementations are able to track state on `self`, which enables /// implementing stateful streaming parsers. In many cases, though, this type /// will simply be a unit struct (e.g. `struct HttpDecoder`). pub trait Decoder { /// The type of decoded frames. type Item; /// The type of unrecoverable frame decoding errors. /// /// If an individual message is ill-formed but can be ignored without /// interfering with the processing of future messages, it may be more /// useful to report the failure as an `Item`. /// /// `From<io::Error>` is required in the interest of making `Error` suitable /// for returning directly from a `FramedRead`, and to enable the default /// implementation of `decode_eof` to yield an `io::Error` when the decoder /// fails to consume all available data. /// /// Note that implementors of this trait can simply indicate `type Error = /// io::Error` to use I/O errors as this type. type Error: From<io::Error>; /// Attempts to decode a frame from the provided buffer of bytes. /// /// This method is called by `FramedRead` whenever bytes are ready to be /// parsed. The provided buffer of bytes is what's been read so far, and /// this instance of `Decode` can determine whether an entire frame is in /// the buffer and is ready to be returned. /// /// If an entire frame is available, then this instance will remove those /// bytes from the buffer provided and return them as a decoded /// frame. Note that removing bytes from the provided buffer doesn't always /// necessarily copy the bytes, so this should be an efficient operation in /// most circumstances. /// /// If the bytes look valid, but a frame isn't fully available yet, then /// `Ok(None)` is returned. This indicates to the `Framed` instance that /// it needs to read some more bytes before calling this method again. /// /// Note that the bytes provided may be empty. If a previous call to /// `decode` consumed all the bytes in the buffer then `decode` will be /// called again until it returns `None`, indicating that more bytes need to /// be read. /// /// Finally, if the bytes in the buffer are malformed then an error is /// returned indicating why. This informs `Framed` that the stream is now /// corrupt and should be terminated. fn decode(&mut self, src: &mut BytesMut) -> Result<Option<Self::Item>, Self::Error>; /// A default method available to be called when there are no more bytes /// available to be read from the underlying I/O. /// /// This method defaults to calling `decode` and returns an error if /// `Ok(None)` is returned while there is unconsumed data in `buf`. /// Typically this doesn't need to be implemented unless the framing /// protocol differs near the end of the stream. /// /// Note that the `buf` argument may be empty. If a previous call to /// `decode_eof` consumed all the bytes in the buffer, `decode_eof` will be /// called again until it returns `None`, indicating that there are no more /// frames to yield. This behavior enables returning finalization frames /// that may not be based on inbound data. fn decode_eof(&mut self, buf: &mut BytesMut) -> Result<Option<Self::Item>, Self::Error> { match try!(self.decode(buf)) { Some(frame) => Ok(Some(frame)), None => { if buf.is_empty() { Ok(None) } else { Err(io::Error::new(io::ErrorKind::Other, "bytes remaining on stream").into()) } } } } } /// A `Stream` of messages decoded from an `AsyncRead`. pub struct FramedRead<T, D> { inner: FramedRead2<Fuse<T, D>>, } pub struct FramedRead2<T> { inner: T, eof: bool, is_readable: bool, buffer: BytesMut, } const INITIAL_CAPACITY: usize = 8 * 1024; // ===== impl FramedRead ===== impl<T, D> FramedRead<T, D> where T: AsyncRead, D: Decoder, { /// Creates a new `FramedRead` with the given `decoder`. pub fn new(inner: T, decoder: D) -> FramedRead<T, D> { FramedRead { inner: framed_read2(Fuse(inner, decoder)), } } } impl<T, D> FramedRead<T, D> { /// Returns a reference to the underlying I/O stream wrapped by /// `FramedRead`. /// /// Note that care should be taken to not tamper with the underlying stream /// of data coming in as it may corrupt the stream of frames otherwise /// being worked with. pub fn get_ref(&self) -> &T { &self.inner.inner.0 } /// Returns a mutable reference to the underlying I/O stream wrapped by /// `FramedRead`. /// /// Note that care should be taken to not tamper with the underlying stream /// of data coming in as it may corrupt the stream of frames otherwise /// being worked with. pub fn get_mut(&mut self) -> &mut T { &mut self.inner.inner.0 } /// Consumes the `FramedRead`, returning its underlying I/O stream. /// /// Note that care should be taken to not tamper with the underlying stream /// of data coming in as it may corrupt the stream of frames otherwise /// being worked with. pub fn into_inner(self) -> T { self.inner.inner.0 } /// Returns a reference to the underlying decoder. pub fn decoder(&self) -> &D { &self.inner.inner.1 } /// Returns a mutable reference to the underlying decoder. pub fn decoder_mut(&mut self) -> &mut D { &mut self.inner.inner.1 } } impl<T, D> Stream for FramedRead<T, D> where T: AsyncRead, D: Decoder, { type Item = D::Item; type Error = D::Error; fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> { self.inner.poll() } } impl<T, D> Sink for FramedRead<T, D> where T: Sink, { type SinkItem = T::SinkItem; type SinkError = T::SinkError; fn start_send(&mut self, item: Self::SinkItem) -> StartSend<Self::SinkItem, Self::SinkError> { self.inner.inner.0.start_send(item) } fn poll_complete(&mut self) -> Poll<(), Self::SinkError> { self.inner.inner.0.poll_complete() } fn close(&mut self) -> Poll<(), Self::SinkError> { self.inner.inner.0.close() } } impl<T, D> fmt::Debug for FramedRead<T, D> where T: fmt::Debug, D: fmt::Debug, { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { f.debug_struct("FramedRead") .field("inner", &self.inner.inner.0) .field("decoder", &self.inner.inner.1) .field("eof", &self.inner.eof) .field("is_readable", &self.inner.is_readable) .field("buffer", &self.inner.buffer) .finish() } } // ===== impl FramedRead2 ===== pub fn framed_read2<T>(inner: T) -> FramedRead2<T> { FramedRead2 { inner: inner, eof: false, is_readable: false, buffer: BytesMut::with_capacity(INITIAL_CAPACITY), } } pub fn framed_read2_with_buffer<T>(inner: T, mut buf: BytesMut) -> FramedRead2<T> { if buf.capacity() < INITIAL_CAPACITY { let bytes_to_reserve = INITIAL_CAPACITY - buf.capacity(); buf.reserve(bytes_to_reserve); } FramedRead2 { inner: inner, eof: false, is_readable: buf.len() > 0, buffer: buf, } } impl<T> FramedRead2<T> { pub fn get_ref(&self) -> &T { &self.inner } pub fn into_inner(self) -> T { self.inner } pub fn into_parts(self) -> (T, BytesMut) { (self.inner, self.buffer) } pub fn get_mut(&mut self) -> &mut T { &mut self.inner } } impl<T> Stream for FramedRead2<T> where T: AsyncRead + Decoder, { type Item = T::Item; type Error = T::Error; fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> { loop { // Repeatedly call `decode` or `decode_eof` as long as it is // "readable". Readable is defined as not having returned `None`. If // the upstream has returned EOF, and the decoder is no longer // readable, it can be assumed that the decoder will never become // readable again, at which point the stream is terminated. if self.is_readable { if self.eof { let frame = try!(self.inner.decode_eof(&mut self.buffer)); return Ok(Async::Ready(frame)); } trace!("attempting to decode a frame"); if let Some(frame) = try!(self.inner.decode(&mut self.buffer)) { trace!("frame decoded from buffer"); return Ok(Async::Ready(Some(frame))); } self.is_readable = false; } assert!(!self.eof); // Otherwise, try to read more data and try again. Make sure we've // got room for at least one byte to read to ensure that we don't // get a spurious 0 that looks like EOF self.buffer.reserve(1); if 0 == try_ready!(self.inner.read_buf(&mut self.buffer)) { self.eof = true; } self.is_readable = true; } } }