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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201
// Copyright 2013 The Gorilla WebSocket Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package websocket

import (
	"bufio"
	"encoding/binary"
	"errors"
	"io"
	"io/ioutil"
	"math/rand"
	"net"
	"strconv"
	"sync"
	"time"
	"unicode/utf8"
)

const (
	// Frame header byte 0 bits from Section 5.2 of RFC 6455
	finalBit = 1 << 7
	rsv1Bit  = 1 << 6
	rsv2Bit  = 1 << 5
	rsv3Bit  = 1 << 4

	// Frame header byte 1 bits from Section 5.2 of RFC 6455
	maskBit = 1 << 7

	maxFrameHeaderSize         = 2 + 8 + 4 // Fixed header + length + mask
	maxControlFramePayloadSize = 125

	writeWait = time.Second

	defaultReadBufferSize  = 4096
	defaultWriteBufferSize = 4096

	continuationFrame = 0
	noFrame           = -1
)

// Close codes defined in RFC 6455, section 11.7.
const (
	CloseNormalClosure           = 1000
	CloseGoingAway               = 1001
	CloseProtocolError           = 1002
	CloseUnsupportedData         = 1003
	CloseNoStatusReceived        = 1005
	CloseAbnormalClosure         = 1006
	CloseInvalidFramePayloadData = 1007
	ClosePolicyViolation         = 1008
	CloseMessageTooBig           = 1009
	CloseMandatoryExtension      = 1010
	CloseInternalServerErr       = 1011
	CloseServiceRestart          = 1012
	CloseTryAgainLater           = 1013
	CloseTLSHandshake            = 1015
)

// The message types are defined in RFC 6455, section 11.8.
const (
	// TextMessage denotes a text data message. The text message payload is
	// interpreted as UTF-8 encoded text data.
	TextMessage = 1

	// BinaryMessage denotes a binary data message.
	BinaryMessage = 2

	// CloseMessage denotes a close control message. The optional message
	// payload contains a numeric code and text. Use the FormatCloseMessage
	// function to format a close message payload.
	CloseMessage = 8

	// PingMessage denotes a ping control message. The optional message payload
	// is UTF-8 encoded text.
	PingMessage = 9

	// PongMessage denotes a pong control message. The optional message payload
	// is UTF-8 encoded text.
	PongMessage = 10
)

// ErrCloseSent is returned when the application writes a message to the
// connection after sending a close message.
var ErrCloseSent = errors.New("websocket: close sent")

// ErrReadLimit is returned when reading a message that is larger than the
// read limit set for the connection.
var ErrReadLimit = errors.New("websocket: read limit exceeded")

// netError satisfies the net Error interface.
type netError struct {
	msg       string
	temporary bool
	timeout   bool
}

func (e *netError) Error() string   { return e.msg }
func (e *netError) Temporary() bool { return e.temporary }
func (e *netError) Timeout() bool   { return e.timeout }

// CloseError represents a close message.
type CloseError struct {
	// Code is defined in RFC 6455, section 11.7.
	Code int

	// Text is the optional text payload.
	Text string
}

func (e *CloseError) Error() string {
	s := []byte("websocket: close ")
	s = strconv.AppendInt(s, int64(e.Code), 10)
	switch e.Code {
	case CloseNormalClosure:
		s = append(s, " (normal)"...)
	case CloseGoingAway:
		s = append(s, " (going away)"...)
	case CloseProtocolError:
		s = append(s, " (protocol error)"...)
	case CloseUnsupportedData:
		s = append(s, " (unsupported data)"...)
	case CloseNoStatusReceived:
		s = append(s, " (no status)"...)
	case CloseAbnormalClosure:
		s = append(s, " (abnormal closure)"...)
	case CloseInvalidFramePayloadData:
		s = append(s, " (invalid payload data)"...)
	case ClosePolicyViolation:
		s = append(s, " (policy violation)"...)
	case CloseMessageTooBig:
		s = append(s, " (message too big)"...)
	case CloseMandatoryExtension:
		s = append(s, " (mandatory extension missing)"...)
	case CloseInternalServerErr:
		s = append(s, " (internal server error)"...)
	case CloseTLSHandshake:
		s = append(s, " (TLS handshake error)"...)
	}
	if e.Text != "" {
		s = append(s, ": "...)
		s = append(s, e.Text...)
	}
	return string(s)
}

// IsCloseError returns boolean indicating whether the error is a *CloseError
// with one of the specified codes.
func IsCloseError(err error, codes ...int) bool {
	if e, ok := err.(*CloseError); ok {
		for _, code := range codes {
			if e.Code == code {
				return true
			}
		}
	}
	return false
}

// IsUnexpectedCloseError returns boolean indicating whether the error is a
// *CloseError with a code not in the list of expected codes.
func IsUnexpectedCloseError(err error, expectedCodes ...int) bool {
	if e, ok := err.(*CloseError); ok {
		for _, code := range expectedCodes {
			if e.Code == code {
				return false
			}
		}
		return true
	}
	return false
}

var (
	errWriteTimeout        = &netError{msg: "websocket: write timeout", timeout: true, temporary: true}
	errUnexpectedEOF       = &CloseError{Code: CloseAbnormalClosure, Text: io.ErrUnexpectedEOF.Error()}
	errBadWriteOpCode      = errors.New("websocket: bad write message type")
	errWriteClosed         = errors.New("websocket: write closed")
	errInvalidControlFrame = errors.New("websocket: invalid control frame")
)

func newMaskKey() [4]byte {
	n := rand.Uint32()
	return [4]byte{byte(n), byte(n >> 8), byte(n >> 16), byte(n >> 24)}
}

func hideTempErr(err error) error {
	if e, ok := err.(net.Error); ok && e.Temporary() {
		err = &netError{msg: e.Error(), timeout: e.Timeout()}
	}
	return err
}

func isControl(frameType int) bool {
	return frameType == CloseMessage || frameType == PingMessage || frameType == PongMessage
}

func isData(frameType int) bool {
	return frameType == TextMessage || frameType == BinaryMessage
}

var validReceivedCloseCodes = map[int]bool{
	// see http://www.iana.org/assignments/websocket/websocket.xhtml#close-code-number

	CloseNormalClosure:           true,
	CloseGoingAway:               true,
	CloseProtocolError:           true,
	CloseUnsupportedData:         true,
	CloseNoStatusReceived:        false,
	CloseAbnormalClosure:         false,
	CloseInvalidFramePayloadData: true,
	ClosePolicyViolation:         true,
	CloseMessageTooBig:           true,
	CloseMandatoryExtension:      true,
	CloseInternalServerErr:       true,
	CloseServiceRestart:          true,
	CloseTryAgainLater:           true,
	CloseTLSHandshake:            false,
}

func isValidReceivedCloseCode(code int) bool {
	return validReceivedCloseCodes[code] || (code >= 3000 && code <= 4999)
}

// BufferPool represents a pool of buffers. The *sync.Pool type satisfies this
// interface.  The type of the value stored in a pool is not specified.
type BufferPool interface {
	// Get gets a value from the pool or returns nil if the pool is empty.
	Get() interface{}
	// Put adds a value to the pool.
	Put(interface{})
}

// writePoolData is the type added to the write buffer pool. This wrapper is
// used to prevent applications from peeking at and depending on the values
// added to the pool.
type writePoolData struct{ buf []byte }

// The Conn type represents a WebSocket connection.
type Conn struct {
	conn        net.Conn
	isServer    bool
	subprotocol string

	// Write fields
	mu            chan struct{} // used as mutex to protect write to conn
	writeBuf      []byte        // frame is constructed in this buffer.
	writePool     BufferPool
	writeBufSize  int
	writeDeadline time.Time
	writer        io.WriteCloser // the current writer returned to the application
	isWriting     bool           // for best-effort concurrent write detection

	writeErrMu sync.Mutex
	writeErr   error

	enableWriteCompression bool
	compressionLevel       int
	newCompressionWriter   func(io.WriteCloser, int) io.WriteCloser

	// Read fields
	reader  io.ReadCloser // the current reader returned to the application
	readErr error
	br      *bufio.Reader
	// bytes remaining in current frame.
	// set setReadRemaining to safely update this value and prevent overflow
	readRemaining int64
	readFinal     bool  // true the current message has more frames.
	readLength    int64 // Message size.
	readLimit     int64 // Maximum message size.
	readMaskPos   int
	readMaskKey   [4]byte
	handlePong    func(string) error
	handlePing    func(string) error
	handleClose   func(int, string) error
	readErrCount  int
	messageReader *messageReader // the current low-level reader

	readDecompress         bool // whether last read frame had RSV1 set
	newDecompressionReader func(io.Reader) io.ReadCloser
}

func newConn(conn net.Conn, isServer bool, readBufferSize, writeBufferSize int, writeBufferPool BufferPool, br *bufio.Reader, writeBuf []byte) *Conn {

	if br == nil {
		if readBufferSize == 0 {
			readBufferSize = defaultReadBufferSize
		} else if readBufferSize < maxControlFramePayloadSize {
			// must be large enough for control frame
			readBufferSize = maxControlFramePayloadSize
		}
		br = bufio.NewReaderSize(conn, readBufferSize)
	}

	if writeBufferSize <= 0 {
		writeBufferSize = defaultWriteBufferSize
	}
	writeBufferSize += maxFrameHeaderSize

	if writeBuf == nil && writeBufferPool == nil {
		writeBuf = make([]byte, writeBufferSize)
	}

	mu := make(chan struct{}, 1)
	mu <- struct{}{}
	c := &Conn{
		isServer:               isServer,
		br:                     br,
		conn:                   conn,
		mu:                     mu,
		readFinal:              true,
		writeBuf:               writeBuf,
		writePool:              writeBufferPool,
		writeBufSize:           writeBufferSize,
		enableWriteCompression: true,
		compressionLevel:       defaultCompressionLevel,
	}
	c.SetCloseHandler(nil)
	c.SetPingHandler(nil)
	c.SetPongHandler(nil)
	return c
}

// setReadRemaining tracks the number of bytes remaining on the connection. If n
// overflows, an ErrReadLimit is returned.
func (c *Conn) setReadRemaining(n int64) error {
	if n < 0 {
		return ErrReadLimit
	}

	c.readRemaining = n
	return nil
}

// Subprotocol returns the negotiated protocol for the connection.
func (c *Conn) Subprotocol() string {
	return c.subprotocol
}

// Close closes the underlying network connection without sending or waiting
// for a close message.
func (c *Conn) Close() error {
	return c.conn.Close()
}

// LocalAddr returns the local network address.
func (c *Conn) LocalAddr() net.Addr {
	return c.conn.LocalAddr()
}

// RemoteAddr returns the remote network address.
func (c *Conn) RemoteAddr() net.Addr {
	return c.conn.RemoteAddr()
}

// Write methods

func (c *Conn) writeFatal(err error) error {
	err = hideTempErr(err)
	c.writeErrMu.Lock()
	if c.writeErr == nil {
		c.writeErr = err
	}
	c.writeErrMu.Unlock()
	return err
}

func (c *Conn) read(n int) ([]byte, error) {
	p, err := c.br.Peek(n)
	if err == io.EOF {
		err = errUnexpectedEOF
	}
	c.br.Discard(len(p))
	return p, err
}

func (c *Conn) write(frameType int, deadline time.Time, buf0, buf1 []byte) error {
	<-c.mu
	defer func() { c.mu <- struct{}{} }()

	c.writeErrMu.Lock()
	err := c.writeErr
	c.writeErrMu.Unlock()
	if err != nil {
		return err
	}

	c.conn.SetWriteDeadline(deadline)
	if len(buf1) == 0 {
		_, err = c.conn.Write(buf0)
	} else {
		err = c.writeBufs(buf0, buf1)
	}
	if err != nil {
		return c.writeFatal(err)
	}
	if frameType == CloseMessage {
		c.writeFatal(ErrCloseSent)
	}
	return nil
}

// WriteControl writes a control message with the given deadline. The allowed
// message types are CloseMessage, PingMessage and PongMessage.
func (c *Conn) WriteControl(messageType int, data []byte, deadline time.Time) error {
	if !isControl(messageType) {
		return errBadWriteOpCode
	}
	if len(data) > maxControlFramePayloadSize {
		return errInvalidControlFrame
	}

	b0 := byte(messageType) | finalBit
	b1 := byte(len(data))
	if !c.isServer {
		b1 |= maskBit
	}

	buf := make([]byte, 0, maxFrameHeaderSize+maxControlFramePayloadSize)
	buf = append(buf, b0, b1)

	if c.isServer {
		buf = append(buf, data...)
	} else {
		key := newMaskKey()
		buf = append(buf, key[:]...)
		buf = append(buf, data...)
		maskBytes(key, 0, buf[6:])
	}

	d := 1000 * time.Hour
	if !deadline.IsZero() {
		d = deadline.Sub(time.Now())
		if d < 0 {
			return errWriteTimeout
		}
	}

	timer := time.NewTimer(d)
	select {
	case <-c.mu:
		timer.Stop()
	case <-timer.C:
		return errWriteTimeout
	}
	defer func() { c.mu <- struct{}{} }()

	c.writeErrMu.Lock()
	err := c.writeErr
	c.writeErrMu.Unlock()
	if err != nil {
		return err
	}

	c.conn.SetWriteDeadline(deadline)
	_, err = c.conn.Write(buf)
	if err != nil {
		return c.writeFatal(err)
	}
	if messageType == CloseMessage {
		c.writeFatal(ErrCloseSent)
	}
	return err
}

// beginMessage prepares a connection and message writer for a new message.
func (c *Conn) beginMessage(mw *messageWriter, messageType int) error {
	// Close previous writer if not already closed by the application. It's
	// probably better to return an error in this situation, but we cannot
	// change this without breaking existing applications.
	if c.writer != nil {
		c.writer.Close()
		c.writer = nil
	}

	if !isControl(messageType) && !isData(messageType) {
		return errBadWriteOpCode
	}

	c.writeErrMu.Lock()
	err := c.writeErr
	c.writeErrMu.Unlock()
	if err != nil {
		return err
	}

	mw.c = c
	mw.frameType = messageType
	mw.pos = maxFrameHeaderSize

	if c.writeBuf == nil {
		wpd, ok := c.writePool.Get().(writePoolData)
		if ok {
			c.writeBuf = wpd.buf
		} else {
			c.writeBuf = make([]byte, c.writeBufSize)
		}
	}
	return nil
}

// NextWriter returns a writer for the next message to send. The writer's Close
// method flushes the complete message to the network.
//
// There can be at most one open writer on a connection. NextWriter closes the
// previous writer if the application has not already done so.
//
// All message types (TextMessage, BinaryMessage, CloseMessage, PingMessage and
// PongMessage) are supported.
func (c *Conn) NextWriter(messageType int) (io.WriteCloser, error) {
	var mw messageWriter
	if err := c.beginMessage(&mw, messageType); err != nil {
		return nil, err
	}
	c.writer = &mw
	if c.newCompressionWriter != nil && c.enableWriteCompression && isData(messageType) {
		w := c.newCompressionWriter(c.writer, c.compressionLevel)
		mw.compress = true
		c.writer = w
	}
	return c.writer, nil
}

type messageWriter struct {
	c         *Conn
	compress  bool // whether next call to flushFrame should set RSV1
	pos       int  // end of data in writeBuf.
	frameType int  // type of the current frame.
	err       error
}

func (w *messageWriter) endMessage(err error) error {
	if w.err != nil {
		return err
	}
	c := w.c
	w.err = err
	c.writer = nil
	if c.writePool != nil {
		c.writePool.Put(writePoolData{buf: c.writeBuf})
		c.writeBuf = nil
	}
	return err
}

// flushFrame writes buffered data and extra as a frame to the network. The
// final argument indicates that this is the last frame in the message.
func (w *messageWriter) flushFrame(final bool, extra []byte) error {
	c := w.c
	length := w.pos - maxFrameHeaderSize + len(extra)

	// Check for invalid control frames.
	if isControl(w.frameType) &&
		(!final || length > maxControlFramePayloadSize) {
		return w.endMessage(errInvalidControlFrame)
	}

	b0 := byte(w.frameType)
	if final {
		b0 |= finalBit
	}
	if w.compress {
		b0 |= rsv1Bit
	}
	w.compress = false

	b1 := byte(0)
	if !c.isServer {
		b1 |= maskBit
	}

	// Assume that the frame starts at beginning of c.writeBuf.
	framePos := 0
	if c.isServer {
		// Adjust up if mask not included in the header.
		framePos = 4
	}

	switch {
	case length >= 65536:
		c.writeBuf[framePos] = b0
		c.writeBuf[framePos+1] = b1 | 127
		binary.BigEndian.PutUint64(c.writeBuf[framePos+2:], uint64(length))
	case length > 125:
		framePos += 6
		c.writeBuf[framePos] = b0
		c.writeBuf[framePos+1] = b1 | 126
		binary.BigEndian.PutUint16(c.writeBuf[framePos+2:], uint16(length))
	default:
		framePos += 8
		c.writeBuf[framePos] = b0
		c.writeBuf[framePos+1] = b1 | byte(length)
	}

	if !c.isServer {
		key := newMaskKey()
		copy(c.writeBuf[maxFrameHeaderSize-4:], key[:])
		maskBytes(key, 0, c.writeBuf[maxFrameHeaderSize:w.pos])
		if len(extra) > 0 {
			return w.endMessage(c.writeFatal(errors.New("websocket: internal error, extra used in client mode")))
		}
	}

	// Write the buffers to the connection with best-effort detection of
	// concurrent writes. See the concurrency section in the package
	// documentation for more info.

	if c.isWriting {
		panic("concurrent write to websocket connection")
	}
	c.isWriting = true

	err := c.write(w.frameType, c.writeDeadline, c.writeBuf[framePos:w.pos], extra)

	if !c.isWriting {
		panic("concurrent write to websocket connection")
	}
	c.isWriting = false

	if err != nil {
		return w.endMessage(err)
	}

	if final {
		w.endMessage(errWriteClosed)
		return nil
	}

	// Setup for next frame.
	w.pos = maxFrameHeaderSize
	w.frameType = continuationFrame
	return nil
}

func (w *messageWriter) ncopy(max int) (int, error) {
	n := len(w.c.writeBuf) - w.pos
	if n <= 0 {
		if err := w.flushFrame(false, nil); err != nil {
			return 0, err
		}
		n = len(w.c.writeBuf) - w.pos
	}
	if n > max {
		n = max
	}
	return n, nil
}

func (w *messageWriter) Write(p []byte) (int, error) {
	if w.err != nil {
		return 0, w.err
	}

	if len(p) > 2*len(w.c.writeBuf) && w.c.isServer {
		// Don't buffer large messages.
		err := w.flushFrame(false, p)
		if err != nil {
			return 0, err
		}
		return len(p), nil
	}

	nn := len(p)
	for len(p) > 0 {
		n, err := w.ncopy(len(p))
		if err != nil {
			return 0, err
		}
		copy(w.c.writeBuf[w.pos:], p[:n])
		w.pos += n
		p = p[n:]
	}
	return nn, nil
}

func (w *messageWriter) WriteString(p string) (int, error) {
	if w.err != nil {
		return 0, w.err
	}

	nn := len(p)
	for len(p) > 0 {
		n, err := w.ncopy(len(p))
		if err != nil {
			return 0, err
		}
		copy(w.c.writeBuf[w.pos:], p[:n])
		w.pos += n
		p = p[n:]
	}
	return nn, nil
}

func (w *messageWriter) ReadFrom(r io.Reader) (nn int64, err error) {
	if w.err != nil {
		return 0, w.err
	}
	for {
		if w.pos == len(w.c.writeBuf) {
			err = w.flushFrame(false, nil)
			if err != nil {
				break
			}
		}
		var n int
		n, err = r.Read(w.c.writeBuf[w.pos:])
		w.pos += n
		nn += int64(n)
		if err != nil {
			if err == io.EOF {
				err = nil
			}
			break
		}
	}
	return nn, err
}

func (w *messageWriter) Close() error {
	if w.err != nil {
		return w.err
	}
	return w.flushFrame(true, nil)
}

// WritePreparedMessage writes prepared message into connection.
func (c *Conn) WritePreparedMessage(pm *PreparedMessage) error {
	frameType, frameData, err := pm.frame(prepareKey{
		isServer:         c.isServer,
		compress:         c.newCompressionWriter != nil && c.enableWriteCompression && isData(pm.messageType),
		compressionLevel: c.compressionLevel,
	})
	if err != nil {
		return err
	}
	if c.isWriting {
		panic("concurrent write to websocket connection")
	}
	c.isWriting = true
	err = c.write(frameType, c.writeDeadline, frameData, nil)
	if !c.isWriting {
		panic("concurrent write to websocket connection")
	}
	c.isWriting = false
	return err
}

// WriteMessage is a helper method for getting a writer using NextWriter,
// writing the message and closing the writer.
func (c *Conn) WriteMessage(messageType int, data []byte) error {

	if c.isServer && (c.newCompressionWriter == nil || !c.enableWriteCompression) {
		// Fast path with no allocations and single frame.

		var mw messageWriter
		if err := c.beginMessage(&mw, messageType); err != nil {
			return err
		}
		n := copy(c.writeBuf[mw.pos:], data)
		mw.pos += n
		data = data[n:]
		return mw.flushFrame(true, data)
	}

	w, err := c.NextWriter(messageType)
	if err != nil {
		return err
	}
	if _, err = w.Write(data); err != nil {
		return err
	}
	return w.Close()
}

// SetWriteDeadline sets the write deadline on the underlying network
// connection. After a write has timed out, the websocket state is corrupt and
// all future writes will return an error. A zero value for t means writes will
// not time out.
func (c *Conn) SetWriteDeadline(t time.Time) error {
	c.writeDeadline = t
	return nil
}

// Read methods

func (c *Conn) advanceFrame() (int, error) {
	// 1. Skip remainder of previous frame.

	if c.readRemaining > 0 {
		if _, err := io.CopyN(ioutil.Discard, c.br, c.readRemaining); err != nil {
			return noFrame, err
		}
	}

	// 2. Read and parse first two bytes of frame header.

	p, err := c.read(2)
	if err != nil {
		return noFrame, err
	}

	final := p[0]&finalBit != 0
	frameType := int(p[0] & 0xf)
	mask := p[1]&maskBit != 0
	c.setReadRemaining(int64(p[1] & 0x7f))

	c.readDecompress = false
	if c.newDecompressionReader != nil && (p[0]&rsv1Bit) != 0 {
		c.readDecompress = true
		p[0] &^= rsv1Bit
	}

	if rsv := p[0] & (rsv1Bit | rsv2Bit | rsv3Bit); rsv != 0 {
		return noFrame, c.handleProtocolError("unexpected reserved bits 0x" + strconv.FormatInt(int64(rsv), 16))
	}

	switch frameType {
	case CloseMessage, PingMessage, PongMessage:
		if c.readRemaining > maxControlFramePayloadSize {
			return noFrame, c.handleProtocolError("control frame length > 125")
		}
		if !final {
			return noFrame, c.handleProtocolError("control frame not final")
		}
	case TextMessage, BinaryMessage:
		if !c.readFinal {
			return noFrame, c.handleProtocolError("message start before final message frame")
		}
		c.readFinal = final
	case continuationFrame:
		if c.readFinal {
			return noFrame, c.handleProtocolError("continuation after final message frame")
		}
		c.readFinal = final
	default:
		return noFrame, c.handleProtocolError("unknown opcode " + strconv.Itoa(frameType))
	}

	// 3. Read and parse frame length as per
	// https://tools.ietf.org/html/rfc6455#section-5.2
	//
	// The length of the "Payload data", in bytes: if 0-125, that is the payload
	// length.
	// - If 126, the following 2 bytes interpreted as a 16-bit unsigned
	// integer are the payload length.
	// - If 127, the following 8 bytes interpreted as
	// a 64-bit unsigned integer (the most significant bit MUST be 0) are the
	// payload length. Multibyte length quantities are expressed in network byte
	// order.

	switch c.readRemaining {
	case 126:
		p, err := c.read(2)
		if err != nil {
			return noFrame, err
		}

		if err := c.setReadRemaining(int64(binary.BigEndian.Uint16(p))); err != nil {
			return noFrame, err
		}
	case 127:
		p, err := c.read(8)
		if err != nil {
			return noFrame, err
		}

		if err := c.setReadRemaining(int64(binary.BigEndian.Uint64(p))); err != nil {
			return noFrame, err
		}
	}

	// 4. Handle frame masking.

	if mask != c.isServer {
		return noFrame, c.handleProtocolError("incorrect mask flag")
	}

	if mask {
		c.readMaskPos = 0
		p, err := c.read(len(c.readMaskKey))
		if err != nil {
			return noFrame, err
		}
		copy(c.readMaskKey[:], p)
	}

	// 5. For text and binary messages, enforce read limit and return.

	if frameType == continuationFrame || frameType == TextMessage || frameType == BinaryMessage {

		c.readLength += c.readRemaining
		// Don't allow readLength to overflow in the presence of a large readRemaining
		// counter.
		if c.readLength < 0 {
			return noFrame, ErrReadLimit
		}

		if c.readLimit > 0 && c.readLength > c.readLimit {
			c.WriteControl(CloseMessage, FormatCloseMessage(CloseMessageTooBig, ""), time.Now().Add(writeWait))
			return noFrame, ErrReadLimit
		}

		return frameType, nil
	}

	// 6. Read control frame payload.

	var payload []byte
	if c.readRemaining > 0 {
		payload, err = c.read(int(c.readRemaining))
		c.setReadRemaining(0)
		if err != nil {
			return noFrame, err
		}
		if c.isServer {
			maskBytes(c.readMaskKey, 0, payload)
		}
	}

	// 7. Process control frame payload.

	switch frameType {
	case PongMessage:
		if err := c.handlePong(string(payload)); err != nil {
			return noFrame, err
		}
	case PingMessage:
		if err := c.handlePing(string(payload)); err != nil {
			return noFrame, err
		}
	case CloseMessage:
		closeCode := CloseNoStatusReceived
		closeText := ""
		if len(payload) >= 2 {
			closeCode = int(binary.BigEndian.Uint16(payload))
			if !isValidReceivedCloseCode(closeCode) {
				return noFrame, c.handleProtocolError("invalid close code")
			}
			closeText = string(payload[2:])
			if !utf8.ValidString(closeText) {
				return noFrame, c.handleProtocolError("invalid utf8 payload in close frame")
			}
		}
		if err := c.handleClose(closeCode, closeText); err != nil {
			return noFrame, err
		}
		return noFrame, &CloseError{Code: closeCode, Text: closeText}
	}

	return frameType, nil
}

func (c *Conn) handleProtocolError(message string) error {
	c.WriteControl(CloseMessage, FormatCloseMessage(CloseProtocolError, message), time.Now().Add(writeWait))
	return errors.New("websocket: " + message)
}

// NextReader returns the next data message received from the peer. The
// returned messageType is either TextMessage or BinaryMessage.
//
// There can be at most one open reader on a connection. NextReader discards
// the previous message if the application has not already consumed it.
//
// Applications must break out of the application's read loop when this method
// returns a non-nil error value. Errors returned from this method are
// permanent. Once this method returns a non-nil error, all subsequent calls to
// this method return the same error.
func (c *Conn) NextReader() (messageType int, r io.Reader, err error) {
	// Close previous reader, only relevant for decompression.
	if c.reader != nil {
		c.reader.Close()
		c.reader = nil
	}

	c.messageReader = nil
	c.readLength = 0

	for c.readErr == nil {
		frameType, err := c.advanceFrame()
		if err != nil {
			c.readErr = hideTempErr(err)
			break
		}

		if frameType == TextMessage || frameType == BinaryMessage {
			c.messageReader = &messageReader{c}
			c.reader = c.messageReader
			if c.readDecompress {
				c.reader = c.newDecompressionReader(c.reader)
			}
			return frameType, c.reader, nil
		}
	}

	// Applications that do handle the error returned from this method spin in
	// tight loop on connection failure. To help application developers detect
	// this error, panic on repeated reads to the failed connection.
	c.readErrCount++
	if c.readErrCount >= 1000 {
		panic("repeated read on failed websocket connection")
	}

	return noFrame, nil, c.readErr
}

type messageReader struct{ c *Conn }

func (r *messageReader) Read(b []byte) (int, error) {
	c := r.c
	if c.messageReader != r {
		return 0, io.EOF
	}

	for c.readErr == nil {

		if c.readRemaining > 0 {
			if int64(len(b)) > c.readRemaining {
				b = b[:c.readRemaining]
			}
			n, err := c.br.Read(b)
			c.readErr = hideTempErr(err)
			if c.isServer {
				c.readMaskPos = maskBytes(c.readMaskKey, c.readMaskPos, b[:n])
			}
			rem := c.readRemaining
			rem -= int64(n)
			c.setReadRemaining(rem)
			if c.readRemaining > 0 && c.readErr == io.EOF {
				c.readErr = errUnexpectedEOF
			}
			return n, c.readErr
		}

		if c.readFinal {
			c.messageReader = nil
			return 0, io.EOF
		}

		frameType, err := c.advanceFrame()
		switch {
		case err != nil:
			c.readErr = hideTempErr(err)
		case frameType == TextMessage || frameType == BinaryMessage:
			c.readErr = errors.New("websocket: internal error, unexpected text or binary in Reader")
		}
	}

	err := c.readErr
	if err == io.EOF && c.messageReader == r {
		err = errUnexpectedEOF
	}
	return 0, err
}

func (r *messageReader) Close() error {
	return nil
}

// ReadMessage is a helper method for getting a reader using NextReader and
// reading from that reader to a buffer.
func (c *Conn) ReadMessage() (messageType int, p []byte, err error) {
	var r io.Reader
	messageType, r, err = c.NextReader()
	if err != nil {
		return messageType, nil, err
	}
	p, err = ioutil.ReadAll(r)
	return messageType, p, err
}

// SetReadDeadline sets the read deadline on the underlying network connection.
// After a read has timed out, the websocket connection state is corrupt and
// all future reads will return an error. A zero value for t means reads will
// not time out.
func (c *Conn) SetReadDeadline(t time.Time) error {
	return c.conn.SetReadDeadline(t)
}

// SetReadLimit sets the maximum size in bytes for a message read from the peer. If a
// message exceeds the limit, the connection sends a close message to the peer
// and returns ErrReadLimit to the application.
func (c *Conn) SetReadLimit(limit int64) {
	c.readLimit = limit
}

// CloseHandler returns the current close handler
func (c *Conn) CloseHandler() func(code int, text string) error {
	return c.handleClose
}

// SetCloseHandler sets the handler for close messages received from the peer.
// The code argument to h is the received close code or CloseNoStatusReceived
// if the close message is empty. The default close handler sends a close
// message back to the peer.
//
// The handler function is called from the NextReader, ReadMessage and message
// reader Read methods. The application must read the connection to process
// close messages as described in the section on Control Messages above.
//
// The connection read methods return a CloseError when a close message is
// received. Most applications should handle close messages as part of their
// normal error handling. Applications should only set a close handler when the
// application must perform some action before sending a close message back to
// the peer.
func (c *Conn) SetCloseHandler(h func(code int, text string) error) {
	if h == nil {
		h = func(code int, text string) error {
			message := FormatCloseMessage(code, "")
			c.WriteControl(CloseMessage, message, time.Now().Add(writeWait))
			return nil
		}
	}
	c.handleClose = h
}

// PingHandler returns the current ping handler
func (c *Conn) PingHandler() func(appData string) error {
	return c.handlePing
}

// SetPingHandler sets the handler for ping messages received from the peer.
// The appData argument to h is the PING message application data. The default
// ping handler sends a pong to the peer.
//
// The handler function is called from the NextReader, ReadMessage and message
// reader Read methods. The application must read the connection to process
// ping messages as described in the section on Control Messages above.
func (c *Conn) SetPingHandler(h func(appData string) error) {
	if h == nil {
		h = func(message string) error {
			err := c.WriteControl(PongMessage, []byte(message), time.Now().Add(writeWait))
			if err == ErrCloseSent {
				return nil
			} else if e, ok := err.(net.Error); ok && e.Temporary() {
				return nil
			}
			return err
		}
	}
	c.handlePing = h
}

// PongHandler returns the current pong handler
func (c *Conn) PongHandler() func(appData string) error {
	return c.handlePong
}

// SetPongHandler sets the handler for pong messages received from the peer.
// The appData argument to h is the PONG message application data. The default
// pong handler does nothing.
//
// The handler function is called from the NextReader, ReadMessage and message
// reader Read methods. The application must read the connection to process
// pong messages as described in the section on Control Messages above.
func (c *Conn) SetPongHandler(h func(appData string) error) {
	if h == nil {
		h = func(string) error { return nil }
	}
	c.handlePong = h
}

// UnderlyingConn returns the internal net.Conn. This can be used to further
// modifications to connection specific flags.
func (c *Conn) UnderlyingConn() net.Conn {
	return c.conn
}

// EnableWriteCompression enables and disables write compression of
// subsequent text and binary messages. This function is a noop if
// compression was not negotiated with the peer.
func (c *Conn) EnableWriteCompression(enable bool) {
	c.enableWriteCompression = enable
}

// SetCompressionLevel sets the flate compression level for subsequent text and
// binary messages. This function is a noop if compression was not negotiated
// with the peer. See the compress/flate package for a description of
// compression levels.
func (c *Conn) SetCompressionLevel(level int) error {
	if !isValidCompressionLevel(level) {
		return errors.New("websocket: invalid compression level")
	}
	c.compressionLevel = level
	return nil
}

// FormatCloseMessage formats closeCode and text as a WebSocket close message.
// An empty message is returned for code CloseNoStatusReceived.
func FormatCloseMessage(closeCode int, text string) []byte {
	if closeCode == CloseNoStatusReceived {
		// Return empty message because it's illegal to send
		// CloseNoStatusReceived. Return non-nil value in case application
		// checks for nil.
		return []byte{}
	}
	buf := make([]byte, 2+len(text))
	binary.BigEndian.PutUint16(buf, uint16(closeCode))
	copy(buf[2:], text)
	return buf
}