Change default and add API for compression level

Change the default compression level to 1. This level is faster and uses
less memory.

Add Conn.SetCompressionLevel API to allow applications to tune
compression on a per message basis.
This commit is contained in:
Gary Burd 2017-01-19 11:00:23 -08:00
parent bb547c6c5c
commit b0dc45572b
4 changed files with 59 additions and 15 deletions

View File

@ -12,11 +12,14 @@ import (
"sync"
)
const (
minCompressionLevel = flate.HuffmanOnly
maxCompressionLevel = flate.BestCompression
defaultCompressionLevel = 1
)
var (
flateWriterPool = sync.Pool{New: func() interface{} {
fw, _ := flate.NewWriter(nil, 3)
return fw
}}
flateWriterPools [maxCompressionLevel - minCompressionLevel]sync.Pool
flateReaderPool = sync.Pool{New: func() interface{} {
return flate.NewReader(nil)
}}
@ -34,11 +37,20 @@ func decompressNoContextTakeover(r io.Reader) io.ReadCloser {
return &flateReadWrapper{fr}
}
func compressNoContextTakeover(w io.WriteCloser) io.WriteCloser {
func isValidCompressionLevel(level int) bool {
return minCompressionLevel <= level && level <= maxCompressionLevel
}
func compressNoContextTakeover(w io.WriteCloser, level int) io.WriteCloser {
p := &flateWriterPools[level-minCompressionLevel]
tw := &truncWriter{w: w}
fw, _ := flateWriterPool.Get().(*flate.Writer)
fw, _ := p.Get().(*flate.Writer)
if fw == nil {
fw, _ = flate.NewWriter(tw, level)
} else {
fw.Reset(tw)
return &flateWriteWrapper{fw: fw, tw: tw}
}
return &flateWriteWrapper{fw: fw, tw: tw, p: p}
}
// truncWriter is an io.Writer that writes all but the last four bytes of the
@ -80,6 +92,7 @@ func (w *truncWriter) Write(p []byte) (int, error) {
type flateWriteWrapper struct {
fw *flate.Writer
tw *truncWriter
p *sync.Pool
}
func (w *flateWriteWrapper) Write(p []byte) (int, error) {
@ -94,7 +107,7 @@ func (w *flateWriteWrapper) Close() error {
return errWriteClosed
}
err1 := w.fw.Flush()
flateWriterPool.Put(w.fw)
w.p.Put(w.fw)
w.fw = nil
if w.tw.p != [4]byte{0, 0, 0xff, 0xff} {
return errors.New("websocket: internal error, unexpected bytes at end of flate stream")

View File

@ -64,3 +64,17 @@ func BenchmarkWriteWithCompression(b *testing.B) {
}
b.ReportAllocs()
}
func TestValidCompressionLevel(t *testing.T) {
c := newConn(fakeNetConn{}, false, 1024, 1024)
for _, level := range []int{minCompressionLevel - 1, maxCompressionLevel + 1} {
if err := c.SetCompressionLevel(level); err == nil {
t.Errorf("no error for level %d", level)
}
}
for _, level := range []int{minCompressionLevel, maxCompressionLevel} {
if err := c.SetCompressionLevel(level); err != nil {
t.Errorf("error for level %d", level)
}
}
}

20
conn.go
View File

@ -241,7 +241,8 @@ type Conn struct {
writeErr error
enableWriteCompression bool
newCompressionWriter func(io.WriteCloser) io.WriteCloser
compressionLevel int
newCompressionWriter func(io.WriteCloser, int) io.WriteCloser
// Read fields
reader io.ReadCloser // the current reader returned to the application
@ -285,6 +286,7 @@ func newConn(conn net.Conn, isServer bool, readBufferSize, writeBufferSize int)
readFinal: true,
writeBuf: make([]byte, writeBufferSize+maxFrameHeaderSize),
enableWriteCompression: true,
compressionLevel: defaultCompressionLevel,
}
c.SetCloseHandler(nil)
c.SetPingHandler(nil)
@ -450,7 +452,7 @@ func (c *Conn) NextWriter(messageType int) (io.WriteCloser, error) {
}
c.writer = mw
if c.newCompressionWriter != nil && c.enableWriteCompression && isData(messageType) {
w := c.newCompressionWriter(c.writer)
w := c.newCompressionWriter(c.writer, c.compressionLevel)
mw.compress = true
c.writer = w
}
@ -1061,6 +1063,20 @@ 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. Valid levels range from -2 to 9. Level -1 uses the default
// compression level. Level -2 uses Huffman compression only, Level 0 does not
// attempt any compression. Levels 1 through 9 range from best speed to best
// compression.
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))

7
doc.go
View File

@ -118,9 +118,10 @@
//
// Applications are responsible for ensuring that no more than one goroutine
// calls the write methods (NextWriter, SetWriteDeadline, WriteMessage,
// WriteJSON) concurrently and that no more than one goroutine calls the read
// methods (NextReader, SetReadDeadline, ReadMessage, ReadJSON, SetPongHandler,
// SetPingHandler) concurrently.
// WriteJSON, EnableWriteCompression, SetCompressionLevel) concurrently and
// that no more than one goroutine calls the read methods (NextReader,
// SetReadDeadline, ReadMessage, ReadJSON, SetPongHandler, SetPingHandler)
// concurrently.
//
// The Close and WriteControl methods can be called concurrently with all other
// methods.