149 lines
3.1 KiB
Go
149 lines
3.1 KiB
Go
// Copyright 2017 The Gorilla WebSocket Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package websocket
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import (
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"compress/flate"
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"errors"
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"io"
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"strings"
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"sync"
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)
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const (
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minCompressionLevel = -2 // flate.HuffmanOnly not defined in Go < 1.6
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maxCompressionLevel = flate.BestCompression
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defaultCompressionLevel = 1
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)
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var (
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flateWriterPools [maxCompressionLevel - minCompressionLevel + 1]sync.Pool
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flateReaderPool = sync.Pool{New: func() interface{} {
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return flate.NewReader(nil)
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}}
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)
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func decompressNoContextTakeover(r io.Reader) io.ReadCloser {
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const tail =
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// Add four bytes as specified in RFC
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"\x00\x00\xff\xff" +
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// Add final block to squelch unexpected EOF error from flate reader.
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"\x01\x00\x00\xff\xff"
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fr, _ := flateReaderPool.Get().(io.ReadCloser)
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fr.(flate.Resetter).Reset(io.MultiReader(r, strings.NewReader(tail)), nil)
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return &flateReadWrapper{fr}
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}
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func isValidCompressionLevel(level int) bool {
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return minCompressionLevel <= level && level <= maxCompressionLevel
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}
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func compressNoContextTakeover(w io.WriteCloser, level int) io.WriteCloser {
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p := &flateWriterPools[level-minCompressionLevel]
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tw := &truncWriter{w: w}
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fw, _ := p.Get().(*flate.Writer)
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if fw == nil {
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fw, _ = flate.NewWriter(tw, level)
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} else {
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fw.Reset(tw)
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}
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return &flateWriteWrapper{fw: fw, tw: tw, p: p}
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}
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// truncWriter is an io.Writer that writes all but the last four bytes of the
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// stream to another io.Writer.
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type truncWriter struct {
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w io.WriteCloser
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n int
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p [4]byte
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}
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func (w *truncWriter) Write(p []byte) (int, error) {
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n := 0
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// fill buffer first for simplicity.
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if w.n < len(w.p) {
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n = copy(w.p[w.n:], p)
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p = p[n:]
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w.n += n
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if len(p) == 0 {
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return n, nil
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}
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}
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m := len(p)
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if m > len(w.p) {
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m = len(w.p)
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}
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if nn, err := w.w.Write(w.p[:m]); err != nil {
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return n + nn, err
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}
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copy(w.p[:], w.p[m:])
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copy(w.p[len(w.p)-m:], p[len(p)-m:])
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nn, err := w.w.Write(p[:len(p)-m])
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return n + nn, err
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}
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type flateWriteWrapper struct {
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fw *flate.Writer
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tw *truncWriter
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p *sync.Pool
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}
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func (w *flateWriteWrapper) Write(p []byte) (int, error) {
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if w.fw == nil {
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return 0, errWriteClosed
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}
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return w.fw.Write(p)
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}
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func (w *flateWriteWrapper) Close() error {
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if w.fw == nil {
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return errWriteClosed
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}
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err1 := w.fw.Flush()
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w.p.Put(w.fw)
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w.fw = nil
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if w.tw.p != [4]byte{0, 0, 0xff, 0xff} {
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return errors.New("websocket: internal error, unexpected bytes at end of flate stream")
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}
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err2 := w.tw.w.Close()
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if err1 != nil {
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return err1
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}
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return err2
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}
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type flateReadWrapper struct {
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fr io.ReadCloser
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}
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func (r *flateReadWrapper) Read(p []byte) (int, error) {
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if r.fr == nil {
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return 0, io.ErrClosedPipe
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}
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n, err := r.fr.Read(p)
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if err == io.EOF {
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// Preemptively place the reader back in the pool. This helps with
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// scenarios where the application does not call NextReader() soon after
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// this final read.
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r.Close()
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}
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return n, err
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}
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func (r *flateReadWrapper) Close() error {
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if r.fr == nil {
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return io.ErrClosedPipe
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}
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err := r.fr.Close()
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flateReaderPool.Put(r.fr)
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r.fr = nil
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return err
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}
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