1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
//! Generic WebSocket message stream.

pub mod frame;

mod message;

pub use self::frame::CloseFrame;
pub use self::message::Message;

use log::*;
use std::collections::VecDeque;
use std::io::{ErrorKind as IoErrorKind, Read, Write};
use std::mem::replace;

use self::frame::coding::{CloseCode, Control as OpCtl, Data as OpData, OpCode};
use self::frame::{Frame, FrameCodec};
use self::message::{IncompleteMessage, IncompleteMessageType};
use crate::error::{Error, Result};
use crate::util::NonBlockingResult;

/// Indicates a Client or Server role of the websocket
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Role {
    /// This socket is a server
    Server,
    /// This socket is a client
    Client,
}

/// The configuration for WebSocket connection.
#[derive(Debug, Clone, Copy)]
pub struct WebSocketConfig {
    /// The size of the send queue. You can use it to turn on/off the backpressure features. `None`
    /// means here that the size of the queue is unlimited. The default value is the unlimited
    /// queue.
    pub max_send_queue: Option<usize>,
    /// The maximum size of a message. `None` means no size limit. The default value is 64 megabytes
    /// which should be reasonably big for all normal use-cases but small enough to prevent
    /// memory eating by a malicious user.
    pub max_message_size: Option<usize>,
    /// The maximum size of a single message frame. `None` means no size limit. The limit is for
    /// frame payload NOT including the frame header. The default value is 16 megabytes which should
    /// be reasonably big for all normal use-cases but small enough to prevent memory eating
    /// by a malicious user.
    pub max_frame_size: Option<usize>,
}

impl Default for WebSocketConfig {
    fn default() -> Self {
        WebSocketConfig {
            max_send_queue: None,
            max_message_size: Some(64 << 20),
            max_frame_size: Some(16 << 20),
        }
    }
}

/// WebSocket input-output stream.
///
/// This is THE structure you want to create to be able to speak the WebSocket protocol.
/// It may be created by calling `connect`, `accept` or `client` functions.
#[derive(Debug)]
pub struct WebSocket<Stream> {
    /// The underlying socket.
    socket: Stream,
    /// The context for managing a WebSocket.
    context: WebSocketContext,
}

impl<Stream> WebSocket<Stream> {
    /// Convert a raw socket into a WebSocket without performing a handshake.
    ///
    /// Call this function if you're using Tungstenite as a part of a web framework
    /// or together with an existing one. If you need an initial handshake, use
    /// `connect()` or `accept()` functions of the crate to construct a websocket.
    pub fn from_raw_socket(stream: Stream, role: Role, config: Option<WebSocketConfig>) -> Self {
        WebSocket {
            socket: stream,
            context: WebSocketContext::new(role, config),
        }
    }

    /// Convert a raw socket into a WebSocket without performing a handshake.
    ///
    /// Call this function if you're using Tungstenite as a part of a web framework
    /// or together with an existing one. If you need an initial handshake, use
    /// `connect()` or `accept()` functions of the crate to construct a websocket.
    pub fn from_partially_read(
        stream: Stream,
        part: Vec<u8>,
        role: Role,
        config: Option<WebSocketConfig>,
    ) -> Self {
        WebSocket {
            socket: stream,
            context: WebSocketContext::from_partially_read(part, role, config),
        }
    }

    /// Returns a shared reference to the inner stream.
    pub fn get_ref(&self) -> &Stream {
        &self.socket
    }
    /// Returns a mutable reference to the inner stream.
    pub fn get_mut(&mut self) -> &mut Stream {
        &mut self.socket
    }

    /// Change the configuration.
    pub fn set_config(&mut self, set_func: impl FnOnce(&mut WebSocketConfig)) {
        self.context.set_config(set_func)
    }

    /// Check if it is possible to read messages.
    ///
    /// Reading is impossible after receiving `Message::Close`. It is still possible after
    /// sending close frame since the peer still may send some data before confirming close.
    pub fn can_read(&self) -> bool {
        self.context.can_read()
    }

    /// Check if it is possible to write messages.
    ///
    /// Writing gets impossible immediately after sending or receiving `Message::Close`.
    pub fn can_write(&self) -> bool {
        self.context.can_write()
    }
}

impl<Stream: Read + Write> WebSocket<Stream> {
    /// Read a message from stream, if possible.
    ///
    /// This will queue responses to ping and close messages to be sent. It will call
    /// `write_pending` before trying to read in order to make sure that those responses
    /// make progress even if you never call `write_pending`. That does mean that they
    /// get sent out earliest on the next call to `read_message`, `write_message` or `write_pending`.
    ///
    /// ## Closing the connection
    /// When the remote endpoint decides to close the connection this will return
    /// the close message with an optional close frame.
    ///
    /// You should continue calling `read_message`, `write_message` or `write_pending` to drive
    /// the reply to the close frame until [Error::ConnectionClosed] is returned. Once that happens
    /// it is safe to drop the underlying connection.
    pub fn read_message(&mut self) -> Result<Message> {
        self.context.read_message(&mut self.socket)
    }

    /// Send a message to stream, if possible.
    ///
    /// WebSocket will buffer a configurable number of messages at a time, except to reply to Ping
    /// requests. A Pong reply will jump the queue because the
    /// [websocket RFC](https://tools.ietf.org/html/rfc6455#section-5.5.2) specifies it should be sent
    /// as soon as is practical.
    ///
    /// Note that upon receiving a ping message, tungstenite cues a pong reply automatically.
    /// When you call either `read_message`, `write_message` or `write_pending` next it will try to send
    /// that pong out if the underlying connection can take more data. This means you should not
    /// respond to ping frames manually.
    ///
    /// You can however send pong frames manually in order to indicate a unidirectional heartbeat
    /// as described in [RFC 6455](https://tools.ietf.org/html/rfc6455#section-5.5.3). Note that
    /// if `read_message` returns a ping, you should call `write_pending` until it doesn't return
    /// WouldBlock before passing a pong to `write_message`, otherwise the response to the
    /// ping will not be sent, but rather replaced by your custom pong message.
    ///
    /// ## Errors
    /// - If the WebSocket's send queue is full, `SendQueueFull` will be returned
    /// along with the passed message. Otherwise, the message is queued and Ok(()) is returned.
    /// - If the connection is closed and should be dropped, this will return [Error::ConnectionClosed].
    /// - If you try again after [Error::ConnectionClosed] was returned either from here or from `read_message`,
    ///   [Error::AlreadyClosed] will be returned. This indicates a program error on your part.
    /// - [Error::Io] is returned if the underlying connection returns an error
    ///   (consider these fatal except for WouldBlock).
    /// - [Error::Capacity] if your message size is bigger than the configured max message size.
    pub fn write_message(&mut self, message: Message) -> Result<()> {
        self.context.write_message(&mut self.socket, message)
    }

    /// Flush the pending send queue.
    pub fn write_pending(&mut self) -> Result<()> {
        self.context.write_pending(&mut self.socket)
    }

    /// Close the connection.
    ///
    /// This function guarantees that the close frame will be queued.
    /// There is no need to call it again. Calling this function is
    /// the same as calling `write_message(Message::Close(..))`.
    ///
    /// After queing the close frame you should continue calling `read_message` or
    /// `write_pending` to drive the close handshake to completion.
    ///
    /// The websocket RFC defines that the underlying connection should be closed
    /// by the server. Tungstenite takes care of this asymmetry for you.
    ///
    /// When the close handshake is finished (we have both sent and received
    /// a close message), `read_message` or `write_pending` will return
    /// [Error::ConnectionClosed] if this endpoint is the server.
    ///
    /// If this endpoint is a client, [Error::ConnectionClosed] will only be
    /// returned after the server has closed the underlying connection.
    ///
    /// It is thus safe to drop the underlying connection as soon as [Error::ConnectionClosed]
    /// is returned from `read_message` or `write_pending`.
    pub fn close(&mut self, code: Option<CloseFrame>) -> Result<()> {
        self.context.close(&mut self.socket, code)
    }
}

/// A context for managing WebSocket stream.
#[derive(Debug)]
pub struct WebSocketContext {
    /// Server or client?
    role: Role,
    /// encoder/decoder of frame.
    frame: FrameCodec,
    /// The state of processing, either "active" or "closing".
    state: WebSocketState,
    /// Receive: an incomplete message being processed.
    incomplete: Option<IncompleteMessage>,
    /// Send: a data send queue.
    send_queue: VecDeque<Frame>,
    /// Send: an OOB pong message.
    pong: Option<Frame>,
    /// The configuration for the websocket session.
    config: WebSocketConfig,
}

impl WebSocketContext {
    /// Create a WebSocket context that manages a post-handshake stream.
    pub fn new(role: Role, config: Option<WebSocketConfig>) -> Self {
        WebSocketContext {
            role,
            frame: FrameCodec::new(),
            state: WebSocketState::Active,
            incomplete: None,
            send_queue: VecDeque::new(),
            pong: None,
            config: config.unwrap_or_else(WebSocketConfig::default),
        }
    }

    /// Create a WebSocket context that manages an post-handshake stream.
    pub fn from_partially_read(part: Vec<u8>, role: Role, config: Option<WebSocketConfig>) -> Self {
        WebSocketContext {
            frame: FrameCodec::from_partially_read(part),
            ..WebSocketContext::new(role, config)
        }
    }

    /// Change the configuration.
    pub fn set_config(&mut self, set_func: impl FnOnce(&mut WebSocketConfig)) {
        set_func(&mut self.config)
    }

    /// Check if it is possible to read messages.
    ///
    /// Reading is impossible after receiving `Message::Close`. It is still possible after
    /// sending close frame since the peer still may send some data before confirming close.
    pub fn can_read(&self) -> bool {
        self.state.can_read()
    }

    /// Check if it is possible to write messages.
    ///
    /// Writing gets impossible immediately after sending or receiving `Message::Close`.
    pub fn can_write(&self) -> bool {
        self.state.is_active()
    }

    /// Read a message from the provided stream, if possible.
    ///
    /// This function sends pong and close responses automatically.
    /// However, it never blocks on write.
    pub fn read_message<Stream>(&mut self, stream: &mut Stream) -> Result<Message>
    where
        Stream: Read + Write,
    {
        // Do not read from already closed connections.
        self.state.check_active()?;

        loop {
            // Since we may get ping or close, we need to reply to the messages even during read.
            // Thus we call write_pending() but ignore its blocking.
            self.write_pending(stream).no_block()?;
            // If we get here, either write blocks or we have nothing to write.
            // Thus if read blocks, just let it return WouldBlock.
            if let Some(message) = self.read_message_frame(stream)? {
                trace!("Received message {}", message);
                return Ok(message);
            }
        }
    }

    /// Send a message to the provided stream, if possible.
    ///
    /// WebSocket will buffer a configurable number of messages at a time, except to reply to Ping
    /// and Close requests. If the WebSocket's send queue is full, `SendQueueFull` will be returned
    /// along with the passed message. Otherwise, the message is queued and Ok(()) is returned.
    ///
    /// Note that only the last pong frame is stored to be sent, and only the
    /// most recent pong frame is sent if multiple pong frames are queued.
    pub fn write_message<Stream>(&mut self, stream: &mut Stream, message: Message) -> Result<()>
    where
        Stream: Read + Write,
    {
        // When terminated, return AlreadyClosed.
        self.state.check_active()?;

        // Do not write after sending a close frame.
        if !self.state.is_active() {
            return Err(Error::Protocol(
                "Sending after closing is not allowed".into(),
            ));
        }

        if let Some(max_send_queue) = self.config.max_send_queue {
            if self.send_queue.len() >= max_send_queue {
                // Try to make some room for the new message.
                // Do not return here if write would block, ignore WouldBlock silently
                // since we must queue the message anyway.
                self.write_pending(stream).no_block()?;
            }

            if self.send_queue.len() >= max_send_queue {
                return Err(Error::SendQueueFull(message));
            }
        }

        let frame = match message {
            Message::Text(data) => Frame::message(data.into(), OpCode::Data(OpData::Text), true),
            Message::Binary(data) => Frame::message(data, OpCode::Data(OpData::Binary), true),
            Message::Ping(data) => Frame::ping(data),
            Message::Pong(data) => {
                self.pong = Some(Frame::pong(data));
                return self.write_pending(stream);
            }
            Message::Close(code) => return self.close(stream, code),
        };

        self.send_queue.push_back(frame);
        self.write_pending(stream)
    }

    /// Flush the pending send queue.
    pub fn write_pending<Stream>(&mut self, stream: &mut Stream) -> Result<()>
    where
        Stream: Read + Write,
    {
        // First, make sure we have no pending frame sending.
        self.frame.write_pending(stream)?;

        // Upon receipt of a Ping frame, an endpoint MUST send a Pong frame in
        // response, unless it already received a Close frame. It SHOULD
        // respond with Pong frame as soon as is practical. (RFC 6455)
        if let Some(pong) = self.pong.take() {
            trace!("Sending pong reply");
            self.send_one_frame(stream, pong)?;
        }
        // If we have any unsent frames, send them.
        trace!("Frames still in queue: {}", self.send_queue.len());
        while let Some(data) = self.send_queue.pop_front() {
            self.send_one_frame(stream, data)?;
        }

        // If we get to this point, the send queue is empty and the underlying socket is still
        // willing to take more data.

        // If we're closing and there is nothing to send anymore, we should close the connection.
        if self.role == Role::Server && !self.state.can_read() {
            // The underlying TCP connection, in most normal cases, SHOULD be closed
            // first by the server, so that it holds the TIME_WAIT state and not the
            // client (as this would prevent it from re-opening the connection for 2
            // maximum segment lifetimes (2MSL), while there is no corresponding
            // server impact as a TIME_WAIT connection is immediately reopened upon
            // a new SYN with a higher seq number). (RFC 6455)
            self.state = WebSocketState::Terminated;
            Err(Error::ConnectionClosed)
        } else {
            Ok(())
        }
    }

    /// Close the connection.
    ///
    /// This function guarantees that the close frame will be queued.
    /// There is no need to call it again. Calling this function is
    /// the same as calling `write(Message::Close(..))`.
    pub fn close<Stream>(&mut self, stream: &mut Stream, code: Option<CloseFrame>) -> Result<()>
    where
        Stream: Read + Write,
    {
        if let WebSocketState::Active = self.state {
            self.state = WebSocketState::ClosedByUs;
            let frame = Frame::close(code);
            self.send_queue.push_back(frame);
        } else {
            // Already closed, nothing to do.
        }
        self.write_pending(stream)
    }
}

impl WebSocketContext {
    /// Try to decode one message frame. May return None.
    fn read_message_frame<Stream>(&mut self, stream: &mut Stream) -> Result<Option<Message>>
    where
        Stream: Read + Write,
    {
        if let Some(mut frame) = self
            .frame
            .read_frame(stream, self.config.max_frame_size)
            .check_connection_reset(self.state)?
        {
            if !self.state.can_read() {
                return Err(Error::Protocol(
                    "Remote sent frame after having sent a Close Frame".into(),
                ));
            }
            // MUST be 0 unless an extension is negotiated that defines meanings
            // for non-zero values.  If a nonzero value is received and none of
            // the negotiated extensions defines the meaning of such a nonzero
            // value, the receiving endpoint MUST _Fail the WebSocket
            // Connection_.
            {
                let hdr = frame.header();
                if hdr.rsv1 || hdr.rsv2 || hdr.rsv3 {
                    return Err(Error::Protocol("Reserved bits are non-zero".into()));
                }
            }

            match self.role {
                Role::Server => {
                    if frame.is_masked() {
                        // A server MUST remove masking for data frames received from a client
                        // as described in Section 5.3. (RFC 6455)
                        frame.apply_mask()
                    } else {
                        // The server MUST close the connection upon receiving a
                        // frame that is not masked. (RFC 6455)
                        return Err(Error::Protocol(
                            "Received an unmasked frame from client".into(),
                        ));
                    }
                }
                Role::Client => {
                    if frame.is_masked() {
                        // A client MUST close a connection if it detects a masked frame. (RFC 6455)
                        return Err(Error::Protocol(
                            "Received a masked frame from server".into(),
                        ));
                    }
                }
            }

            match frame.header().opcode {
                OpCode::Control(ctl) => {
                    match ctl {
                        // All control frames MUST have a payload length of 125 bytes or less
                        // and MUST NOT be fragmented. (RFC 6455)
                        _ if !frame.header().is_final => {
                            Err(Error::Protocol("Fragmented control frame".into()))
                        }
                        _ if frame.payload().len() > 125 => {
                            Err(Error::Protocol("Control frame too big".into()))
                        }
                        OpCtl::Close => Ok(self.do_close(frame.into_close()?).map(Message::Close)),
                        OpCtl::Reserved(i) => Err(Error::Protocol(
                            format!("Unknown control frame type {}", i).into(),
                        )),
                        OpCtl::Ping => {
                            let data = frame.into_data();
                            // No ping processing after we sent a close frame.
                            if self.state.is_active() {
                                self.pong = Some(Frame::pong(data.clone()));
                            }
                            Ok(Some(Message::Ping(data)))
                        }
                        OpCtl::Pong => Ok(Some(Message::Pong(frame.into_data()))),
                    }
                }

                OpCode::Data(data) => {
                    let fin = frame.header().is_final;
                    match data {
                        OpData::Continue => {
                            if let Some(ref mut msg) = self.incomplete {
                                msg.extend(frame.into_data(), self.config.max_message_size)?;
                            } else {
                                return Err(Error::Protocol(
                                    "Continue frame but nothing to continue".into(),
                                ));
                            }
                            if fin {
                                Ok(Some(self.incomplete.take().unwrap().complete()?))
                            } else {
                                Ok(None)
                            }
                        }
                        c if self.incomplete.is_some() => Err(Error::Protocol(
                            format!("Received {} while waiting for more fragments", c).into(),
                        )),
                        OpData::Text | OpData::Binary => {
                            let msg = {
                                let message_type = match data {
                                    OpData::Text => IncompleteMessageType::Text,
                                    OpData::Binary => IncompleteMessageType::Binary,
                                    _ => panic!("Bug: message is not text nor binary"),
                                };
                                let mut m = IncompleteMessage::new(message_type);
                                m.extend(frame.into_data(), self.config.max_message_size)?;
                                m
                            };
                            if fin {
                                Ok(Some(msg.complete()?))
                            } else {
                                self.incomplete = Some(msg);
                                Ok(None)
                            }
                        }
                        OpData::Reserved(i) => Err(Error::Protocol(
                            format!("Unknown data frame type {}", i).into(),
                        )),
                    }
                }
            } // match opcode
        } else {
            // Connection closed by peer
            match replace(&mut self.state, WebSocketState::Terminated) {
                WebSocketState::ClosedByPeer | WebSocketState::CloseAcknowledged => {
                    Err(Error::ConnectionClosed)
                }
                _ => Err(Error::Protocol(
                    "Connection reset without closing handshake".into(),
                )),
            }
        }
    }

    /// Received a close frame. Tells if we need to return a close frame to the user.
    #[allow(clippy::option_option)]
    fn do_close<'t>(&mut self, close: Option<CloseFrame<'t>>) -> Option<Option<CloseFrame<'t>>> {
        debug!("Received close frame: {:?}", close);
        match self.state {
            WebSocketState::Active => {
                let close_code = close.as_ref().map(|f| f.code);
                self.state = WebSocketState::ClosedByPeer;
                let reply = if let Some(code) = close_code {
                    if code.is_allowed() {
                        Frame::close(Some(CloseFrame {
                            code: CloseCode::Normal,
                            reason: "".into(),
                        }))
                    } else {
                        Frame::close(Some(CloseFrame {
                            code: CloseCode::Protocol,
                            reason: "Protocol violation".into(),
                        }))
                    }
                } else {
                    Frame::close(None)
                };
                debug!("Replying to close with {:?}", reply);
                self.send_queue.push_back(reply);

                Some(close)
            }
            WebSocketState::ClosedByPeer | WebSocketState::CloseAcknowledged => {
                // It is already closed, just ignore.
                None
            }
            WebSocketState::ClosedByUs => {
                // We received a reply.
                self.state = WebSocketState::CloseAcknowledged;
                Some(close)
            }
            WebSocketState::Terminated => unreachable!(),
        }
    }

    /// Send a single pending frame.
    fn send_one_frame<Stream>(&mut self, stream: &mut Stream, mut frame: Frame) -> Result<()>
    where
        Stream: Read + Write,
    {
        match self.role {
            Role::Server => {}
            Role::Client => {
                // 5.  If the data is being sent by the client, the frame(s) MUST be
                // masked as defined in Section 5.3. (RFC 6455)
                frame.set_random_mask();
            }
        }

        trace!("Sending frame: {:?}", frame);
        self.frame
            .write_frame(stream, frame)
            .check_connection_reset(self.state)
    }
}

/// The current connection state.
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
enum WebSocketState {
    /// The connection is active.
    Active,
    /// We initiated a close handshake.
    ClosedByUs,
    /// The peer initiated a close handshake.
    ClosedByPeer,
    /// The peer replied to our close handshake.
    CloseAcknowledged,
    /// The connection does not exist anymore.
    Terminated,
}

impl WebSocketState {
    /// Tell if we're allowed to process normal messages.
    fn is_active(self) -> bool {
        match self {
            WebSocketState::Active => true,
            _ => false,
        }
    }

    /// Tell if we should process incoming data. Note that if we send a close frame
    /// but the remote hasn't confirmed, they might have sent data before they receive our
    /// close frame, so we should still pass those to client code, hence ClosedByUs is valid.
    fn can_read(self) -> bool {
        match self {
            WebSocketState::Active | WebSocketState::ClosedByUs => true,
            _ => false,
        }
    }

    /// Check if the state is active, return error if not.
    fn check_active(self) -> Result<()> {
        match self {
            WebSocketState::Terminated => Err(Error::AlreadyClosed),
            _ => Ok(()),
        }
    }
}

/// Translate "Connection reset by peer" into `ConnectionClosed` if appropriate.
trait CheckConnectionReset {
    fn check_connection_reset(self, state: WebSocketState) -> Self;
}

impl<T> CheckConnectionReset for Result<T> {
    fn check_connection_reset(self, state: WebSocketState) -> Self {
        match self {
            Err(Error::Io(io_error)) => Err({
                if !state.can_read() && io_error.kind() == IoErrorKind::ConnectionReset {
                    Error::ConnectionClosed
                } else {
                    Error::Io(io_error)
                }
            }),
            x => x,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::{Message, Role, WebSocket, WebSocketConfig};

    use std::io;
    use std::io::Cursor;

    struct WriteMoc<Stream>(Stream);

    impl<Stream> io::Write for WriteMoc<Stream> {
        fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
            Ok(buf.len())
        }
        fn flush(&mut self) -> io::Result<()> {
            Ok(())
        }
    }

    impl<Stream: io::Read> io::Read for WriteMoc<Stream> {
        fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
            self.0.read(buf)
        }
    }

    #[test]
    fn receive_messages() {
        let incoming = Cursor::new(vec![
            0x89, 0x02, 0x01, 0x02, 0x8a, 0x01, 0x03, 0x01, 0x07, 0x48, 0x65, 0x6c, 0x6c, 0x6f,
            0x2c, 0x20, 0x80, 0x06, 0x57, 0x6f, 0x72, 0x6c, 0x64, 0x21, 0x82, 0x03, 0x01, 0x02,
            0x03,
        ]);
        let mut socket = WebSocket::from_raw_socket(WriteMoc(incoming), Role::Client, None);
        assert_eq!(socket.read_message().unwrap(), Message::Ping(vec![1, 2]));
        assert_eq!(socket.read_message().unwrap(), Message::Pong(vec![3]));
        assert_eq!(
            socket.read_message().unwrap(),
            Message::Text("Hello, World!".into())
        );
        assert_eq!(
            socket.read_message().unwrap(),
            Message::Binary(vec![0x01, 0x02, 0x03])
        );
    }

    #[test]
    fn size_limiting_text_fragmented() {
        let incoming = Cursor::new(vec![
            0x01, 0x07, 0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x2c, 0x20, 0x80, 0x06, 0x57, 0x6f, 0x72,
            0x6c, 0x64, 0x21,
        ]);
        let limit = WebSocketConfig {
            max_message_size: Some(10),
            ..WebSocketConfig::default()
        };
        let mut socket = WebSocket::from_raw_socket(WriteMoc(incoming), Role::Client, Some(limit));
        assert_eq!(
            socket.read_message().unwrap_err().to_string(),
            "Space limit exceeded: Message too big: 7 + 6 > 10"
        );
    }

    #[test]
    fn size_limiting_binary() {
        let incoming = Cursor::new(vec![0x82, 0x03, 0x01, 0x02, 0x03]);
        let limit = WebSocketConfig {
            max_message_size: Some(2),
            ..WebSocketConfig::default()
        };
        let mut socket = WebSocket::from_raw_socket(WriteMoc(incoming), Role::Client, Some(limit));
        assert_eq!(
            socket.read_message().unwrap_err().to_string(),
            "Space limit exceeded: Message too big: 0 + 3 > 2"
        );
    }
}