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// 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 ping 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 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 {
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)
}
// The Conn type represents a WebSocket connection.
type Conn struct {
conn net.Conn
isServer bool
subprotocol string
// Write fields
mu chan bool // used as mutex to protect write to conn
writeBuf []byte // frame is constructed in this buffer.
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
readRemaining int64 // bytes remaining in current frame.
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) *Conn {
mu := make(chan bool, 1)
mu <- true
if readBufferSize == 0 {
readBufferSize = defaultReadBufferSize
}
if readBufferSize < maxControlFramePayloadSize {
readBufferSize = maxControlFramePayloadSize
}
if writeBufferSize == 0 {
writeBufferSize = defaultWriteBufferSize
}
c := &Conn{
isServer: isServer,
br: bufio.NewReaderSize(conn, readBufferSize),
conn: conn,
mu: mu,
readFinal: true,
writeBuf: make([]byte, writeBufferSize+maxFrameHeaderSize),
enableWriteCompression: true,
compressionLevel: defaultCompressionLevel,
}
c.SetCloseHandler(nil)
c.SetPingHandler(nil)
c.SetPongHandler(nil)
return c
}
// 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 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) 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) write(frameType int, deadline time.Time, bufs ...[]byte) error {
<-c.mu
defer func() { c.mu <- true }()
c.writeErrMu.Lock()
err := c.writeErr
c.writeErrMu.Unlock()
if err != nil {
return err
}
c.conn.SetWriteDeadline(deadline)
for _, buf := range bufs {
if len(buf) > 0 {
_, err := c.conn.Write(buf)
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 := 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 }()
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
}
func (c *Conn) prepWrite(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()
return err
}
// 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 err := c.prepWrite(messageType); err != nil {
return nil, err
}
mw := &messageWriter{
c: c,
frameType: messageType,
pos: maxFrameHeaderSize,
}
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) fatal(err error) error {
if w.err != nil {
w.err = err
w.c.writer = 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.fatal(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 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.fatal(err)
}
if final {
c.writer = nil
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
}
if err := w.flushFrame(true, nil); err != nil {
return err
}
w.err = errWriteClosed
return 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 {
if c.isServer && (c.newCompressionWriter == nil || !c.enableWriteCompression) {
// Fast path with no allocations and single frame.
if err := c.prepWrite(messageType); err != nil {
return err
}
mw := messageWriter{c: c, frameType: messageType, pos: maxFrameHeaderSize}
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.readRemaining = 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.
switch c.readRemaining {
case 126:
p, err := c.read(2)
if err != nil {
return noFrame, err
}
c.readRemaining = int64(binary.BigEndian.Uint16(p))
case 127:
p, err := c.read(8)
if err != nil {
return noFrame, err
}
c.readRemaining = int64(binary.BigEndian.Uint64(p))
}
// 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
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.readRemaining = 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])
}
c.readRemaining -= int64(n)
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 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
}
// 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 frame
// back to the peer.
//
// The application must read the connection to process close messages as
// described in the section on Control Frames above.
//
// The connection read methods return a CloseError when a close frame 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 frame 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 := []byte{}
if code != CloseNoStatusReceived {
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 frame application data. The default
// ping handler sends a pong to the peer.
//
// The application must read the connection to process ping messages as
// described in the section on Control Frames 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 frame application data. The default
// pong handler does nothing.
//
// The application must read the connection to process ping messages as
// described in the section on Control Frames 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.
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
}