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
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
//! Generic WebSocket message stream.

pub mod frame;

mod message;

pub use self::{frame::CloseFrame, message::Message};

use self::{
    frame::{
        coding::{CloseCode, Control as OpCtl, Data as OpData, OpCode},
        Frame, FrameCodec,
    },
    message::{IncompleteMessage, IncompleteMessageType},
};
use crate::error::{Error, ProtocolError, Result};
use log::*;
use std::{
    io::{self, Read, Write},
    mem::replace,
};

/// 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 {
    /// Does nothing, instead use `max_write_buffer_size`.
    #[deprecated]
    pub max_send_queue: Option<usize>,
    /// The target minimum size of the write buffer to reach before writing the data
    /// to the underlying stream.
    /// The default value is 128 KiB.
    ///
    /// If set to `0` each message will be eagerly written to the underlying stream.
    /// It is often more optimal to allow them to buffer a little, hence the default value.
    ///
    /// Note: [`flush`](WebSocket::flush) will always fully write the buffer regardless.
    pub write_buffer_size: usize,
    /// The max size of the write buffer in bytes. Setting this can provide backpressure
    /// in the case the write buffer is filling up due to write errors.
    /// The default value is unlimited.
    ///
    /// Note: The write buffer only builds up past [`write_buffer_size`](Self::write_buffer_size)
    /// when writes to the underlying stream are failing. So the **write buffer can not
    /// fill up if you are not observing write errors even if not flushing**.
    ///
    /// Note: Should always be at least [`write_buffer_size + 1 message`](Self::write_buffer_size)
    /// and probably a little more depending on error handling strategy.
    pub max_write_buffer_size: usize,
    /// The maximum size of an incoming message. `None` means no size limit. The default value is 64 MiB
    /// 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 incoming message frame. `None` means no size limit. The limit is for
    /// frame payload NOT including the frame header. The default value is 16 MiB 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>,
    /// When set to `true`, the server will accept and handle unmasked frames
    /// from the client. According to the RFC 6455, the server must close the
    /// connection to the client in such cases, however it seems like there are
    /// some popular libraries that are sending unmasked frames, ignoring the RFC.
    /// By default this option is set to `false`, i.e. according to RFC 6455.
    pub accept_unmasked_frames: bool,
}

impl Default for WebSocketConfig {
    fn default() -> Self {
        #[allow(deprecated)]
        WebSocketConfig {
            max_send_queue: None,
            write_buffer_size: 128 * 1024,
            max_write_buffer_size: usize::MAX,
            max_message_size: Some(64 << 20),
            max_frame_size: Some(16 << 20),
            accept_unmasked_frames: false,
        }
    }
}

impl WebSocketConfig {
    /// Panic if values are invalid.
    pub(crate) fn assert_valid(&self) {
        assert!(
            self.max_write_buffer_size > self.write_buffer_size,
            "WebSocketConfig::max_write_buffer_size must be greater than write_buffer_size, \
            see WebSocketConfig docs`"
        );
    }
}

/// 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.
///
/// Use [`WebSocket::read`], [`WebSocket::send`] to received and send messages.
#[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.
    ///
    /// # Panics
    /// Panics if config is invalid e.g. `max_write_buffer_size <= write_buffer_size`.
    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.
    ///
    /// # Panics
    /// Panics if config is invalid e.g. `max_write_buffer_size <= write_buffer_size`.
    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.
    ///
    /// # Panics
    /// Panics if config is invalid e.g. `max_write_buffer_size <= write_buffer_size`.
    pub fn set_config(&mut self, set_func: impl FnOnce(&mut WebSocketConfig)) {
        self.context.set_config(set_func)
    }

    /// Read the configuration.
    pub fn get_config(&self) -> &WebSocketConfig {
        self.context.get_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.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 also queue responses to ping and close messages. These responses
    /// will be written and flushed on the next call to [`read`](Self::read),
    /// [`write`](Self::write) or [`flush`](Self::flush).
    ///
    /// # 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`](Self::read), [`write`](Self::write) or
    /// [`flush`](Self::flush) 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(&mut self) -> Result<Message> {
        self.context.read(&mut self.socket)
    }

    /// Writes and immediately flushes a message.
    /// Equivalent to calling [`write`](Self::write) then [`flush`](Self::flush).
    pub fn send(&mut self, message: Message) -> Result<()> {
        self.write(message)?;
        self.flush()
    }

    /// Write a message to the provided stream, if possible.
    ///
    /// A subsequent call should be made to [`flush`](Self::flush) to flush writes.
    ///
    /// In the event of stream write failure the message frame will be stored
    /// in the write buffer and will try again on the next call to [`write`](Self::write)
    /// or [`flush`](Self::flush).
    ///
    /// If the write buffer would exceed the configured [`WebSocketConfig::max_write_buffer_size`]
    /// [`Err(WriteBufferFull(msg_frame))`](Error::WriteBufferFull) is returned.
    ///
    /// This call will generally not flush. However, if there are queued automatic messages
    /// they will be written and eagerly flushed.
    ///
    /// For example, upon receiving ping messages tungstenite queues pong replies automatically.
    /// The next call to [`read`](Self::read), [`write`](Self::write) or [`flush`](Self::flush)
    /// will write & flush the pong reply. 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`](Self::read) returns a ping, you should [`flush`](Self::flush) before passing
    /// a custom pong to [`write`](Self::write), otherwise the automatic queued response to the
    /// ping will not be sent as it will be replaced by your custom pong message.
    ///
    /// # Errors
    /// - If the WebSocket's write buffer is full, [`Error::WriteBufferFull`] will be returned
    ///   along with the equivalent passed message frame.
    /// - 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`](Self::read), [`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(&mut self, message: Message) -> Result<()> {
        self.context.write(&mut self.socket, message)
    }

    /// Flush writes.
    ///
    /// Ensures all messages previously passed to [`write`](Self::write) and automatic
    /// queued pong responses are written & flushed into the underlying stream.
    pub fn flush(&mut self) -> Result<()> {
        self.context.flush(&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::Close(..))`.
    ///
    /// After queuing the close frame you should continue calling [`read`](Self::read) or
    /// [`flush`](Self::flush) 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`](Self::read) or [`flush`](Self::flush) 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`](Self::read) or [`flush`](Self::flush).
    pub fn close(&mut self, code: Option<CloseFrame>) -> Result<()> {
        self.context.close(&mut self.socket, code)
    }

    /// Old name for [`read`](Self::read).
    #[deprecated(note = "Use `read`")]
    pub fn read_message(&mut self) -> Result<Message> {
        self.read()
    }

    /// Old name for [`send`](Self::send).
    #[deprecated(note = "Use `send`")]
    pub fn write_message(&mut self, message: Message) -> Result<()> {
        self.send(message)
    }

    /// Old name for [`flush`](Self::flush).
    #[deprecated(note = "Use `flush`")]
    pub fn write_pending(&mut self) -> Result<()> {
        self.flush()
    }
}

/// 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 in addition to regular messages E.g. "pong" or "close".
    additional_send: Option<Frame>,
    /// True indicates there is an additional message (like a pong)
    /// that failed to flush previously and we should try again.
    unflushed_additional: bool,
    /// The configuration for the websocket session.
    config: WebSocketConfig,
}

impl WebSocketContext {
    /// Create a WebSocket context that manages a post-handshake stream.
    ///
    /// # Panics
    /// Panics if config is invalid e.g. `max_write_buffer_size <= write_buffer_size`.
    pub fn new(role: Role, config: Option<WebSocketConfig>) -> Self {
        Self::_new(role, FrameCodec::new(), config.unwrap_or_default())
    }

    /// Create a WebSocket context that manages an post-handshake stream.
    ///
    /// # Panics
    /// Panics if config is invalid e.g. `max_write_buffer_size <= write_buffer_size`.
    pub fn from_partially_read(part: Vec<u8>, role: Role, config: Option<WebSocketConfig>) -> Self {
        Self::_new(role, FrameCodec::from_partially_read(part), config.unwrap_or_default())
    }

    fn _new(role: Role, mut frame: FrameCodec, config: WebSocketConfig) -> Self {
        config.assert_valid();
        frame.set_max_out_buffer_len(config.max_write_buffer_size);
        frame.set_out_buffer_write_len(config.write_buffer_size);
        Self {
            role,
            frame,
            state: WebSocketState::Active,
            incomplete: None,
            additional_send: None,
            unflushed_additional: false,
            config,
        }
    }

    /// Change the configuration.
    ///
    /// # Panics
    /// Panics if config is invalid e.g. `max_write_buffer_size <= write_buffer_size`.
    pub fn set_config(&mut self, set_func: impl FnOnce(&mut WebSocketConfig)) {
        set_func(&mut self.config);
        self.config.assert_valid();
        self.frame.set_max_out_buffer_len(self.config.max_write_buffer_size);
        self.frame.set_out_buffer_write_len(self.config.write_buffer_size);
    }

    /// Read the configuration.
    pub fn get_config(&self) -> &WebSocketConfig {
        &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<Stream>(&mut self, stream: &mut Stream) -> Result<Message>
    where
        Stream: Read + Write,
    {
        // Do not read from already closed connections.
        self.state.check_not_terminated()?;

        loop {
            if self.additional_send.is_some() || self.unflushed_additional {
                // Since we may get ping or close, we need to reply to the messages even during read.
                match self.flush(stream) {
                    Ok(_) => {}
                    Err(Error::Io(err)) if err.kind() == io::ErrorKind::WouldBlock => {
                        // If blocked continue reading, but try again later
                        self.unflushed_additional = true;
                    }
                    Err(err) => return Err(err),
                }
            } else if self.role == Role::Server && !self.state.can_read() {
                self.state = WebSocketState::Terminated;
                return Err(Error::ConnectionClosed);
            }

            // 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);
            }
        }
    }

    /// Write a message to the provided stream.
    ///
    /// A subsequent call should be made to [`flush`](Self::flush) to flush writes.
    ///
    /// In the event of stream write failure the message frame will be stored
    /// in the write buffer and will try again on the next call to [`write`](Self::write)
    /// or [`flush`](Self::flush).
    ///
    /// If the write buffer would exceed the configured [`WebSocketConfig::max_write_buffer_size`]
    /// [`Err(WriteBufferFull(msg_frame))`](Error::WriteBufferFull) is returned.
    pub fn write<Stream>(&mut self, stream: &mut Stream, message: Message) -> Result<()>
    where
        Stream: Read + Write,
    {
        // When terminated, return AlreadyClosed.
        self.state.check_not_terminated()?;

        // Do not write after sending a close frame.
        if !self.state.is_active() {
            return Err(Error::Protocol(ProtocolError::SendAfterClosing));
        }

        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.set_additional(Frame::pong(data));
                // Note: user pongs can be user flushed so no need to flush here
                return self._write(stream, None).map(|_| ());
            }
            Message::Close(code) => return self.close(stream, code),
            Message::Frame(f) => f,
        };

        let should_flush = self._write(stream, Some(frame))?;
        if should_flush {
            self.flush(stream)?;
        }
        Ok(())
    }

    /// Flush writes.
    ///
    /// Ensures all messages previously passed to [`write`](Self::write) and automatically
    /// queued pong responses are written & flushed into the `stream`.
    #[inline]
    pub fn flush<Stream>(&mut self, stream: &mut Stream) -> Result<()>
    where
        Stream: Read + Write,
    {
        self._write(stream, None)?;
        self.frame.write_out_buffer(stream)?;
        stream.flush()?;
        self.unflushed_additional = false;
        Ok(())
    }

    /// Writes any data in the out_buffer, `additional_send` and given `data`.
    ///
    /// Does **not** flush.
    ///
    /// Returns true if the write contents indicate we should flush immediately.
    fn _write<Stream>(&mut self, stream: &mut Stream, data: Option<Frame>) -> Result<bool>
    where
        Stream: Read + Write,
    {
        if let Some(data) = data {
            self.buffer_frame(stream, data)?;
        }

        // 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)
        let should_flush = if let Some(msg) = self.additional_send.take() {
            trace!("Sending pong/close");
            match self.buffer_frame(stream, msg) {
                Err(Error::WriteBufferFull(Message::Frame(msg))) => {
                    // if an system message would exceed the buffer put it back in
                    // `additional_send` for retry. Otherwise returning this error
                    // may not make sense to the user, e.g. calling `flush`.
                    self.set_additional(msg);
                    false
                }
                Err(err) => return Err(err),
                Ok(_) => true,
            }
        } else {
            self.unflushed_additional
        };

        // 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.frame.write_out_buffer(stream)?;
            self.state = WebSocketState::Terminated;
            Err(Error::ConnectionClosed)
        } else {
            Ok(should_flush)
        }
    }

    /// 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 `send(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._write(stream, Some(frame))?;
        }
        self.flush(stream)
    }

    /// 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(ProtocolError::ReceivedAfterClosing));
            }
            // 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(ProtocolError::NonZeroReservedBits));
                }
            }

            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 if !self.config.accept_unmasked_frames {
                        // The server MUST close the connection upon receiving a
                        // frame that is not masked. (RFC 6455)
                        // The only exception here is if the user explicitly accepts given
                        // stream by setting WebSocketConfig.accept_unmasked_frames to true
                        return Err(Error::Protocol(ProtocolError::UnmaskedFrameFromClient));
                    }
                }
                Role::Client => {
                    if frame.is_masked() {
                        // A client MUST close a connection if it detects a masked frame. (RFC 6455)
                        return Err(Error::Protocol(ProtocolError::MaskedFrameFromServer));
                    }
                }
            }

            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(ProtocolError::FragmentedControlFrame))
                        }
                        _ if frame.payload().len() > 125 => {
                            Err(Error::Protocol(ProtocolError::ControlFrameTooBig))
                        }
                        OpCtl::Close => Ok(self.do_close(frame.into_close()?).map(Message::Close)),
                        OpCtl::Reserved(i) => {
                            Err(Error::Protocol(ProtocolError::UnknownControlFrameType(i)))
                        }
                        OpCtl::Ping => {
                            let data = frame.into_data();
                            // No ping processing after we sent a close frame.
                            if self.state.is_active() {
                                self.set_additional(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(
                                    ProtocolError::UnexpectedContinueFrame,
                                ));
                            }
                            if fin {
                                Ok(Some(self.incomplete.take().unwrap().complete()?))
                            } else {
                                Ok(None)
                            }
                        }
                        c if self.incomplete.is_some() => {
                            Err(Error::Protocol(ProtocolError::ExpectedFragment(c)))
                        }
                        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(ProtocolError::UnknownDataFrameType(i)))
                        }
                    }
                }
            } // match opcode
        } else {
            // Connection closed by peer
            match replace(&mut self.state, WebSocketState::Terminated) {
                WebSocketState::ClosedByPeer | WebSocketState::CloseAcknowledged => {
                    Err(Error::ConnectionClosed)
                }
                _ => Err(Error::Protocol(ProtocolError::ResetWithoutClosingHandshake)),
            }
        }
    }

    /// 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 => {
                self.state = WebSocketState::ClosedByPeer;

                let close = close.map(|frame| {
                    if !frame.code.is_allowed() {
                        CloseFrame {
                            code: CloseCode::Protocol,
                            reason: "Protocol violation".into(),
                        }
                    } else {
                        frame
                    }
                });

                let reply = Frame::close(close.clone());
                debug!("Replying to close with {:?}", reply);
                self.set_additional(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!(),
        }
    }

    /// Write a single frame into the write-buffer.
    fn buffer_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.buffer_frame(stream, frame).check_connection_reset(self.state)
    }

    /// Replace `additional_send` if it is currently a `Pong` message.
    fn set_additional(&mut self, add: Frame) {
        let empty_or_pong = self
            .additional_send
            .as_ref()
            .map_or(true, |f| f.header().opcode == OpCode::Control(OpCtl::Pong));
        if empty_or_pong {
            self.additional_send.replace(add);
        }
    }
}

/// 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 {
        matches!(self, WebSocketState::Active)
    }

    /// 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 {
        matches!(self, WebSocketState::Active | WebSocketState::ClosedByUs)
    }

    /// Check if the state is active, return error if not.
    fn check_not_terminated(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() == io::ErrorKind::ConnectionReset {
                    Error::ConnectionClosed
                } else {
                    Error::Io(io_error)
                }
            }),
            x => x,
        }
    }
}

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

    use std::{io, 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().unwrap(), Message::Ping(vec![1, 2]));
        assert_eq!(socket.read().unwrap(), Message::Pong(vec![3]));
        assert_eq!(socket.read().unwrap(), Message::Text("Hello, World!".into()));
        assert_eq!(socket.read().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!(matches!(
            socket.read(),
            Err(Error::Capacity(CapacityError::MessageTooLong { size: 13, max_size: 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!(matches!(
            socket.read(),
            Err(Error::Capacity(CapacityError::MessageTooLong { size: 3, max_size: 2 }))
        ));
    }
}