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292 lines
8.6 KiB
292 lines
8.6 KiB
use std::collections::VecDeque;
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use std::error;
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use std::io;
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use std::iter;
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use std::mem;
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use byteorder::{ByteOrder, LittleEndian, ReadBytesExt};
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use mio;
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use mio::TryRead;
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use super::constants::*;
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use super::packet::{MutPacket, Packet, ReadFromPacket, WriteToPacket};
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/*========*
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* PARSER *
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*========*/
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/// This enum defines the possible states of a packet parser state machine.
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#[derive(Debug, Clone, Copy)]
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enum State {
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/// The parser is waiting to read enough bytes to determine the
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/// length of the following packet.
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ReadingLength,
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/// The parser is waiting to read enough bytes to form the entire
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/// packet.
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ReadingPacket,
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}
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#[derive(Debug)]
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struct Parser {
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state: State,
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num_bytes_left: usize,
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buffer: Vec<u8>,
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}
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impl Parser {
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pub fn new() -> Self {
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Parser {
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state: State::ReadingLength,
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num_bytes_left: U32_SIZE,
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buffer: vec![0; U32_SIZE],
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}
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}
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/// Attemps to read a packet in a non-blocking fashion.
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/// If enough bytes can be read from the given byte stream to form a
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/// complete packet `p`, returns `Ok(Some(p))`.
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/// If not enough bytes are available, returns `Ok(None)`.
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/// If an I/O error `e` arises when trying to read the underlying stream,
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/// returns `Err(e)`.
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/// Note: as long as this function returns `Ok(Some(p))`, the caller is
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/// responsible for calling it once more to ensure that all packets are
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/// read as soon as possible.
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pub fn try_read<U>(&mut self, stream: &mut U) -> io::Result<Option<Packet>>
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where U: io::Read
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{
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// Try to read as many bytes as we currently need from the underlying
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// byte stream.
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let offset = self.buffer.len() - self.num_bytes_left;
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match try!(stream.try_read(&mut self.buffer[offset..])) {
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None => (),
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Some(num_bytes_read) => {
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self.num_bytes_left -= num_bytes_read;
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},
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}
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// If we haven't read enough bytes, return.
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if self.num_bytes_left > 0 {
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return Ok(None);
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}
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// Otherwise, the behavior depends on what state we were in.
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match self.state {
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State::ReadingLength => {
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// If we have finished reading the length prefix, then
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// deserialize it, switch states and try to read the packet
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// bytes.
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let message_len =
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LittleEndian::read_u32(&mut self.buffer) as usize;
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if message_len > MAX_MESSAGE_SIZE {
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unimplemented!();
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};
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self.state = State::ReadingPacket;
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self.num_bytes_left = message_len;
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self.buffer.extend(iter::repeat(0).take(message_len));
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self.try_read(stream)
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},
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State::ReadingPacket => {
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// If we have finished reading the packet, swap the full buffer
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// out and return the packet made from the full buffer.
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self.state = State::ReadingLength;
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self.num_bytes_left = U32_SIZE;
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let new_buffer = vec![0;U32_SIZE];
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let old_buffer = mem::replace(&mut self.buffer, new_buffer);
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Ok(Some(Packet::from_bytes(old_buffer)))
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}
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}
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}
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}
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/*========*
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* OUTBUF *
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*========*/
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/// A struct used for writing bytes to a TryWrite sink.
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#[derive(Debug)]
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struct OutBuf {
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cursor: usize,
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bytes: Vec<u8>
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}
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impl From<Vec<u8>> for OutBuf {
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fn from(bytes: Vec<u8>) -> Self {
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OutBuf {
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cursor: 0,
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bytes: bytes
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}
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}
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}
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impl OutBuf {
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#[inline]
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fn remaining(&self) -> usize {
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self.bytes.len() - self.cursor
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}
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#[inline]
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fn has_remaining(&self) -> bool {
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self.remaining() > 0
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}
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fn try_write_to<T>(&mut self, mut writer: T) -> io::Result<Option<usize>>
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where T: mio::TryWrite
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{
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let result = writer.try_write(&self.bytes[self.cursor..]);
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if let Ok(Some(bytes_written)) = result {
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self.cursor += bytes_written;
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}
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result
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}
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}
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/*========*
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* STREAM *
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*========*/
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/// This trait is implemented by packet sinks to which a stream can forward
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/// the packets it reads.
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pub trait SendPacket {
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type Value: ReadFromPacket;
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type Error: error::Error;
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fn send_packet(&mut self, Self::Value) -> Result<(), Self::Error>;
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}
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/// This enum defines the possible actions the stream wants to take after
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/// processing an event.
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#[derive(Debug, Clone, Copy)]
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pub enum Intent {
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/// The stream is done, the event loop handler can drop it.
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Done,
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/// The stream wants to wait for the next event matching the given
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/// `EventSet`.
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Continue(mio::EventSet),
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}
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/// This struct wraps around an mio byte stream and handles packet reads and
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/// writes.
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#[derive(Debug)]
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pub struct Stream<T, U>
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where T: io::Read + io::Write + mio::Evented,
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U: SendPacket
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{
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parser: Parser,
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queue: VecDeque<OutBuf>,
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sender: U,
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stream: T,
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}
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impl<T, U> Stream<T, U>
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where T: io::Read + io::Write + mio::Evented,
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U: SendPacket
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{
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/// Returns a new struct wrapping the provided byte stream, which will
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/// forward packets to the provided sink.
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pub fn new(stream: T, sender: U) -> Self {
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Stream {
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parser: Parser::new(),
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queue: VecDeque::new(),
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sender: sender,
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stream: stream,
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}
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}
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/// Returns a reference to the underlying byte stream, to allow it to be
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/// registered with an event loop.
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pub fn evented(&self) -> &T {
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&self.stream
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}
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fn on_readable(&mut self) -> Result<(), String> {
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loop {
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let mut packet = match self.parser.try_read(&mut self.stream) {
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Ok(Some(packet)) => packet,
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Ok(None) => {
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break
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},
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Err(e) => {
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return Err(format!("Error reading stream: {}", e))
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}
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};
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let value = match packet.read_value() {
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Ok(value) => value,
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Err(e) => {
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return Err(format!("Error parsing packet: {}", e))
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}
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};
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if let Err(e) = self.sender.send_packet(value) {
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return Err(format!("Error sending parsed packet: {}", e))
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}
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}
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Ok(())
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}
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fn on_writable(&mut self) -> io::Result<()> {
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loop {
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let mut outbuf = match self.queue.pop_front() {
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Some(outbuf) => outbuf,
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None => break
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};
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let option = try!(outbuf.try_write_to(&mut self.stream));
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match option {
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Some(_) => {
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if outbuf.has_remaining() {
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self.queue.push_front(outbuf)
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}
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// Continue looping
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},
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None => {
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self.queue.push_front(outbuf);
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break
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}
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}
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}
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Ok(())
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}
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/// The stream is ready to read, write, or both.
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pub fn on_ready(&mut self, event_set: mio::EventSet) -> Intent {
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if event_set.is_readable() {
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let result = self.on_readable();
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if let Err(e) = result {
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error!("Stream input error: {}", e);
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return Intent::Done
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}
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}
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if event_set.is_writable() {
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let result = self.on_writable();
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if let Err(e) = result {
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error!("Stream output error: {}", e);
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return Intent::Done
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}
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}
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// We're always interested in reading more.
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// If there is still stuff to write in the queue, we're interested in
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// the socket becoming writable too.
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let event_set = if self.queue.len() > 0 {
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mio::EventSet::readable() | mio::EventSet::writable()
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} else {
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mio::EventSet::readable()
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};
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Intent::Continue(event_set)
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}
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/// The stream has been notified.
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pub fn on_notify<V>(&mut self, payload: &V) -> Intent
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where V: WriteToPacket
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{
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let mut packet = MutPacket::new();
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let result = packet.write_value(payload);
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if let Err(e) = result {
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error!("Error writing payload to packet: {}", e);
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return Intent::Done
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}
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self.queue.push_back(OutBuf::from(packet.into_bytes()));
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Intent::Continue(mio::EventSet::readable() | mio::EventSet::writable())
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}
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}
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