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Add hooks to support RFC 7692 (per-message compression extension)
Add newCompressionWriter and newDecompressionReader fields to Conn. When
not nil, these functions are used to create a compression/decompression
wrapper around an underlying message writer/reader.
Add code to set and check for RSV1 frame header bit.
Add functions compressNoContextTakeover and decompressNoContextTakeover
for creating no context takeover wrappers around an underlying message
writer/reader.
Work remaining:
- Add fields to Dialer and Upgrader for specifying compression options.
- Add compression negotiation to Dialer and Upgrader.
- Add function to enable/disable write compression:
// 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
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,85 @@ | ||
| // Copyright 2016 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 ( | ||
| "compress/flate" | ||
| "errors" | ||
| "io" | ||
| "strings" | ||
| ) | ||
|
|
||
| func decompressNoContextTakeover(r io.Reader) io.Reader { | ||
| const tail = | ||
| // Add four bytes as specified in RFC | ||
| "\x00\x00\xff\xff" + | ||
| // Add final block to squelch unexpected EOF error from flate reader. | ||
| "\x01\x00\x00\xff\xff" | ||
|
|
||
| return flate.NewReader(io.MultiReader(r, strings.NewReader(tail))) | ||
| } | ||
|
|
||
| func compressNoContextTakeover(w io.WriteCloser) (io.WriteCloser, error) { | ||
| tw := &truncWriter{w: w} | ||
| fw, err := flate.NewWriter(tw, 3) | ||
| return &flateWrapper{fw: fw, tw: tw}, err | ||
| } | ||
|
|
||
| // truncWriter is an io.Writer that writes all but the last four bytes of the | ||
| // stream to another io.Writer. | ||
| type truncWriter struct { | ||
| w io.WriteCloser | ||
| n int | ||
| p [4]byte | ||
| } | ||
|
|
||
| func (w *truncWriter) Write(p []byte) (int, error) { | ||
| n := 0 | ||
|
|
||
| // fill buffer first for simplicity. | ||
| if w.n < len(w.p) { | ||
| n = copy(w.p[w.n:], p) | ||
| p = p[n:] | ||
| w.n += n | ||
| if len(p) == 0 { | ||
| return n, nil | ||
| } | ||
| } | ||
|
|
||
| m := len(p) | ||
| if m > len(w.p) { | ||
| m = len(w.p) | ||
| } | ||
|
|
||
| if nn, err := w.w.Write(w.p[:m]); err != nil { | ||
| return n + nn, err | ||
| } | ||
|
|
||
| copy(w.p[:], w.p[m:]) | ||
| copy(w.p[len(w.p)-m:], p[len(p)-m:]) | ||
| nn, err := w.w.Write(p[:len(p)-m]) | ||
| return n + nn, err | ||
| } | ||
|
|
||
| type flateWrapper struct { | ||
| fw *flate.Writer | ||
| tw *truncWriter | ||
| } | ||
|
|
||
| func (w *flateWrapper) Write(p []byte) (int, error) { | ||
| return w.fw.Write(p) | ||
| } | ||
|
|
||
| func (w *flateWrapper) Close() error { | ||
| err1 := w.fw.Flush() | ||
| if w.tw.p != [4]byte{0, 0, 0xff, 0xff} { | ||
| return errors.New("websocket: internal error, unexpected bytes at end of flate stream") | ||
| } | ||
| err2 := w.tw.w.Close() | ||
| if err1 != nil { | ||
| return err1 | ||
| } | ||
| return err2 | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,31 @@ | ||
| package websocket | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "io" | ||
| "testing" | ||
| ) | ||
|
|
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| type nopCloser struct{ io.Writer } | ||
|
|
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| func (nopCloser) Close() error { return nil } | ||
|
|
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| func TestTruncWriter(t *testing.T) { | ||
| const data = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijlkmnopqrstuvwxyz987654321" | ||
| for n := 1; n <= 10; n++ { | ||
| var b bytes.Buffer | ||
| w := &truncWriter{w: nopCloser{&b}} | ||
| p := []byte(data) | ||
| for len(p) > 0 { | ||
| m := len(p) | ||
| if m > n { | ||
| m = n | ||
| } | ||
| w.Write(p[:m]) | ||
| p = p[m:] | ||
| } | ||
| if b.String() != data[:len(data)-len(w.p)] { | ||
| t.Errorf("%d: %q", n, b.String()) | ||
| } | ||
| } | ||
| } |
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