websocket/conn.go

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// Copyright 2013 The Gorilla WebSocket Authors. All rights reserved.
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// 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"
"time"
)
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const (
maxFrameHeaderSize = 2 + 8 + 4 // Fixed header + length + mask
maxControlFramePayloadSize = 125
finalBit = 1 << 7
maskBit = 1 << 7
writeWait = time.Second
defaultReadBufferSize = 4096
defaultWriteBufferSize = 4096
continuationFrame = 0
noFrame = -1
)
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// 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
CloseTLSHandshake = 1015
)
// The message types are defined in RFC 6455, section 11.8.
const (
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// TextMessage denotes a text data message. The text message payload is
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// 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 ping control message. The optional message payload
// is UTF-8 encoded text.
PongMessage = 10
)
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// ErrCloseSent is returned when the application writes a message to the
// connection after sending a close message.
var ErrCloseSent = errors.New("websocket: close sent")
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// 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")
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// 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 close frame.
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 {
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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
}
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// 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
}
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var (
errWriteTimeout = &netError{msg: "websocket: write timeout", timeout: true, temporary: true}
errUnexpectedEOF = &CloseError{Code: CloseAbnormalClosure, Text: io.ErrUnexpectedEOF.Error()}
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errBadWriteOpCode = errors.New("websocket: bad write message type")
errWriteClosed = errors.New("websocket: write closed")
errInvalidControlFrame = errors.New("websocket: invalid control frame")
)
func hideTempErr(err error) error {
if e, ok := err.(net.Error); ok && e.Temporary() {
err = &netError{msg: e.Error(), timeout: e.Timeout()}
}
return err
}
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func isControl(frameType int) bool {
return frameType == CloseMessage || frameType == PingMessage || frameType == PongMessage
}
func isData(frameType int) bool {
return frameType == TextMessage || frameType == BinaryMessage
}
func maskBytes(key [4]byte, pos int, b []byte) int {
for i := range b {
b[i] ^= key[pos&3]
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pos++
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}
return pos & 3
}
func newMaskKey() [4]byte {
n := rand.Uint32()
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return [4]byte{byte(n), byte(n >> 8), byte(n >> 16), byte(n >> 24)}
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}
// Conn represents a WebSocket connection.
type Conn struct {
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conn net.Conn
isServer bool
subprotocol string
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// Write fields
mu chan bool // used as mutex to protect write to conn and closeSent
closeSent bool // true if close message was sent
// Message writer fields.
writeErr error
writeBuf []byte // frame is constructed in this buffer.
writePos int // end of data in writeBuf.
writeFrameType int // type of the current frame.
writeSeq int // incremented to invalidate message writers.
writeDeadline time.Time
isWriting bool // for best-effort concurrent write detection
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// Read fields
readErr error
br *bufio.Reader
readRemaining int64 // bytes remaining in current frame.
readFinal bool // true the current message has more frames.
readSeq int // incremented to invalidate message readers.
readLength int64 // Message size.
readLimit int64 // Maximum message size.
readMaskPos int
readMaskKey [4]byte
handlePong func(string) error
handlePing func(string) error
readErrCount int
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}
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func newConn(conn net.Conn, isServer bool, readBufferSize, writeBufferSize int) *Conn {
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mu := make(chan bool, 1)
mu <- true
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if readBufferSize == 0 {
readBufferSize = defaultReadBufferSize
}
if writeBufferSize == 0 {
writeBufferSize = defaultWriteBufferSize
}
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c := &Conn{
isServer: isServer,
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br: bufio.NewReaderSize(conn, readBufferSize),
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conn: conn,
mu: mu,
readFinal: true,
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writeBuf: make([]byte, writeBufferSize+maxFrameHeaderSize),
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writeFrameType: noFrame,
writePos: maxFrameHeaderSize,
}
c.SetPingHandler(nil)
c.SetPongHandler(nil)
return c
}
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// Subprotocol returns the negotiated protocol for the connection.
func (c *Conn) Subprotocol() string {
return c.subprotocol
}
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// Close closes the underlying network connection without sending or waiting for a close frame.
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) write(frameType int, deadline time.Time, bufs ...[]byte) error {
<-c.mu
defer func() { c.mu <- true }()
if c.closeSent {
return ErrCloseSent
} else if frameType == CloseMessage {
c.closeSent = true
}
c.conn.SetWriteDeadline(deadline)
for _, buf := range bufs {
if len(buf) > 0 {
n, err := c.conn.Write(buf)
if n != len(buf) {
// Close on partial write.
c.conn.Close()
}
if err != nil {
return err
}
}
}
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 := time.Hour * 1000
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 <- true }()
if c.closeSent {
return ErrCloseSent
} else if messageType == CloseMessage {
c.closeSent = true
}
c.conn.SetWriteDeadline(deadline)
n, err := c.conn.Write(buf)
if n != 0 && n != len(buf) {
c.conn.Close()
}
return hideTempErr(err)
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}
// 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.
func (c *Conn) NextWriter(messageType int) (io.WriteCloser, error) {
if c.writeErr != nil {
return nil, c.writeErr
}
if c.writeFrameType != noFrame {
if err := c.flushFrame(true, nil); err != nil {
return nil, err
}
}
if !isControl(messageType) && !isData(messageType) {
return nil, errBadWriteOpCode
}
c.writeFrameType = messageType
return messageWriter{c, c.writeSeq}, nil
}
func (c *Conn) flushFrame(final bool, extra []byte) error {
length := c.writePos - maxFrameHeaderSize + len(extra)
// Check for invalid control frames.
if isControl(c.writeFrameType) &&
(!final || length > maxControlFramePayloadSize) {
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c.writeSeq++
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c.writeFrameType = noFrame
c.writePos = maxFrameHeaderSize
return errInvalidControlFrame
}
b0 := byte(c.writeFrameType)
if final {
b0 |= finalBit
}
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:c.writePos])
if len(extra) > 0 {
c.writeErr = errors.New("websocket: internal error, extra used in client mode")
return c.writeErr
}
}
// 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
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c.writeErr = c.write(c.writeFrameType, c.writeDeadline, c.writeBuf[framePos:c.writePos], extra)
if !c.isWriting {
panic("concurrent write to websocket connection")
}
c.isWriting = false
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// Setup for next frame.
c.writePos = maxFrameHeaderSize
c.writeFrameType = continuationFrame
if final {
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c.writeSeq++
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c.writeFrameType = noFrame
}
return c.writeErr
}
type messageWriter struct {
c *Conn
seq int
}
func (w messageWriter) err() error {
c := w.c
if c.writeSeq != w.seq {
return errWriteClosed
}
if c.writeErr != nil {
return c.writeErr
}
return nil
}
func (w messageWriter) ncopy(max int) (int, error) {
n := len(w.c.writeBuf) - w.c.writePos
if n <= 0 {
if err := w.c.flushFrame(false, nil); err != nil {
return 0, err
}
n = len(w.c.writeBuf) - w.c.writePos
}
if n > max {
n = max
}
return n, nil
}
func (w messageWriter) write(final bool, p []byte) (int, error) {
if err := w.err(); err != nil {
return 0, err
}
if len(p) > 2*len(w.c.writeBuf) && w.c.isServer {
// Don't buffer large messages.
err := w.c.flushFrame(final, 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.c.writePos:], p[:n])
w.c.writePos += n
p = p[n:]
}
return nn, nil
}
func (w messageWriter) Write(p []byte) (int, error) {
return w.write(false, p)
}
func (w messageWriter) WriteString(p string) (int, error) {
if err := w.err(); err != nil {
return 0, 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.c.writePos:], p[:n])
w.c.writePos += n
p = p[n:]
}
return nn, nil
}
func (w messageWriter) ReadFrom(r io.Reader) (nn int64, err error) {
if err := w.err(); err != nil {
return 0, err
}
for {
if w.c.writePos == len(w.c.writeBuf) {
err = w.c.flushFrame(false, nil)
if err != nil {
break
}
}
var n int
n, err = r.Read(w.c.writeBuf[w.c.writePos:])
w.c.writePos += n
nn += int64(n)
if err != nil {
if err == io.EOF {
err = nil
}
break
}
}
return nn, err
}
func (w messageWriter) Close() error {
if err := w.err(); err != nil {
return err
}
return w.c.flushFrame(true, nil)
}
// 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 {
wr, err := c.NextWriter(messageType)
if err != nil {
return err
}
w := wr.(messageWriter)
if _, err := w.write(true, data); err != nil {
return err
}
if c.writeSeq == w.seq {
if err := c.flushFrame(true, nil); err != nil {
return err
}
}
return nil
}
// 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
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// not time out.
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func (c *Conn) SetWriteDeadline(t time.Time) error {
c.writeDeadline = t
return nil
}
// Read methods
// readFull is like io.ReadFull except that io.EOF is never returned.
func (c *Conn) readFull(p []byte) (err error) {
var n int
for n < len(p) && err == nil {
var nn int
nn, err = c.br.Read(p[n:])
n += nn
}
if n == len(p) {
err = nil
} else if err == io.EOF {
err = errUnexpectedEOF
}
return
}
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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.
var b [8]byte
if err := c.readFull(b[:2]); err != nil {
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return noFrame, err
}
final := b[0]&finalBit != 0
frameType := int(b[0] & 0xf)
reserved := int((b[0] >> 4) & 0x7)
mask := b[1]&maskBit != 0
c.readRemaining = int64(b[1] & 0x7f)
if reserved != 0 {
return noFrame, c.handleProtocolError("unexpected reserved bits " + strconv.Itoa(reserved))
}
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.
switch c.readRemaining {
case 126:
if err := c.readFull(b[:2]); err != nil {
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return noFrame, err
}
c.readRemaining = int64(binary.BigEndian.Uint16(b[:2]))
case 127:
if err := c.readFull(b[:8]); err != nil {
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return noFrame, err
}
c.readRemaining = int64(binary.BigEndian.Uint64(b[:8]))
}
// 4. Handle frame masking.
if mask != c.isServer {
return noFrame, c.handleProtocolError("incorrect mask flag")
}
if mask {
c.readMaskPos = 0
if err := c.readFull(c.readMaskKey[:]); err != nil {
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return noFrame, err
}
}
// 5. For text and binary messages, enforce read limit and return.
if frameType == continuationFrame || frameType == TextMessage || frameType == BinaryMessage {
c.readLength += c.readRemaining
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 = make([]byte, c.readRemaining)
c.readRemaining = 0
if err := c.readFull(payload); err != nil {
return noFrame, err
}
if c.isServer {
maskBytes(c.readMaskKey, 0, payload)
}
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}
// 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:
echoMessage := []byte{}
closeCode := CloseNoStatusReceived
closeText := ""
if len(payload) >= 2 {
echoMessage = payload[:2]
closeCode = int(binary.BigEndian.Uint16(payload))
closeText = string(payload[2:])
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}
c.WriteControl(CloseMessage, echoMessage, time.Now().Add(writeWait))
return noFrame, &CloseError{Code: closeCode, Text: closeText}
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}
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.
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func (c *Conn) NextReader() (messageType int, r io.Reader, err error) {
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c.readSeq++
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c.readLength = 0
for c.readErr == nil {
frameType, err := c.advanceFrame()
if err != nil {
c.readErr = hideTempErr(err)
break
}
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if frameType == TextMessage || frameType == BinaryMessage {
return frameType, messageReader{c, c.readSeq}, 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")
}
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return noFrame, nil, c.readErr
}
type messageReader struct {
c *Conn
seq int
}
func (r messageReader) Read(b []byte) (int, error) {
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if r.seq != r.c.readSeq {
return 0, io.EOF
}
for r.c.readErr == nil {
if r.c.readRemaining > 0 {
if int64(len(b)) > r.c.readRemaining {
b = b[:r.c.readRemaining]
}
n, err := r.c.br.Read(b)
r.c.readErr = hideTempErr(err)
if r.c.isServer {
r.c.readMaskPos = maskBytes(r.c.readMaskKey, r.c.readMaskPos, b[:n])
}
r.c.readRemaining -= int64(n)
if r.c.readRemaining > 0 && r.c.readErr == io.EOF {
r.c.readErr = errUnexpectedEOF
}
return n, r.c.readErr
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}
if r.c.readFinal {
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r.c.readSeq++
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return 0, io.EOF
}
frameType, err := r.c.advanceFrame()
switch {
case err != nil:
r.c.readErr = hideTempErr(err)
case frameType == TextMessage || frameType == BinaryMessage:
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r.c.readErr = errors.New("websocket: internal error, unexpected text or binary in Reader")
}
}
err := r.c.readErr
if err == io.EOF && r.seq == r.c.readSeq {
err = errUnexpectedEOF
}
return 0, err
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}
// 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.
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func (c *Conn) SetReadDeadline(t time.Time) error {
return c.conn.SetReadDeadline(t)
}
// SetReadLimit sets the maximum size for a message read from the peer. If a
// message exceeds the limit, the connection sends a close frame to the peer
// and returns ErrReadLimit to the application.
func (c *Conn) SetReadLimit(limit int64) {
c.readLimit = limit
}
// SetPingHandler sets the handler for ping messages received from the peer.
// The appData argument to h is the PING frame application data. The default
// ping handler sends a pong to the peer.
func (c *Conn) SetPingHandler(h func(appData string) error) {
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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
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}
}
c.handlePing = h
}
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// SetPongHandler sets the handler for pong messages received from the peer.
// The appData argument to h is the PONG frame application data. The default
// pong handler does nothing.
func (c *Conn) SetPongHandler(h func(appData string) error) {
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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
}
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// FormatCloseMessage formats closeCode and text as a WebSocket close message.
func FormatCloseMessage(closeCode int, text string) []byte {
buf := make([]byte, 2+len(text))
binary.BigEndian.PutUint16(buf, uint16(closeCode))
copy(buf[2:], text)
return buf
}