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https://github.com/soheilhy/cmux.git
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Replace buffer with bufferedReader
bufferedReader is an optimized implementation of io.Reader that behaves like ``` io.MultiReader(bytes.NewReader(buffer.Bytes()), io.TeeReader(source, buffer)) ``` without allocating. This has a measurable effect on benchmarks: ``` name old time/op new time/op delta CMuxConn-4 1.09µs ± 4% 0.99µs ±19% -9.32% (p=0.000 n=17+19) name old alloc/op new alloc/op delta CMuxConn-4 240B ± 0% 260B ± 0% +8.33% (p=0.000 n=20+20) name old allocs/op new allocs/op delta CMuxConn-4 9.00 ± 0% 5.00 ± 0% -44.44% (p=0.000 n=20+20) ``` Note that appropriate test coverage is provided by `TestRead`.
This commit is contained in:
Tamir Duberstein
Soheil Hassas Yeganeh
parent
d710784914
commit
59b6f01712
81
buffer.go
81
buffer.go
@ -1,57 +1,42 @@
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package cmux
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import "io"
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import (
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"bytes"
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"io"
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)
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var _ io.ReadWriter = (*buffer)(nil)
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type buffer struct {
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read int
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data []byte
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// bufferedReader is an optimized implementation of io.Reader that behaves like
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// ```
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// io.MultiReader(bytes.NewReader(buffer.Bytes()), io.TeeReader(source, buffer))
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// ```
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// without allocating.
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type bufferedReader struct {
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source io.Reader
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buffer bytes.Buffer
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bufferRead int
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bufferSize int
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sniffing bool
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}
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// From the io.Reader documentation:
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//
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// When Read encounters an error or end-of-file condition after
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// successfully reading n > 0 bytes, it returns the number of
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// bytes read. It may return the (non-nil) error from the same call
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// or return the error (and n == 0) from a subsequent call.
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// An instance of this general case is that a Reader returning
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// a non-zero number of bytes at the end of the input stream may
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// return either err == EOF or err == nil. The next Read should
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// return 0, EOF.
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//
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// This function implements the latter behaviour, returning the
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// (non-nil) error from the same call.
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func (b *buffer) Read(p []byte) (int, error) {
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var err error
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n := copy(p, b.data[b.read:])
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b.read += n
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if b.read == len(b.data) {
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err = io.EOF
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func (s *bufferedReader) Read(p []byte) (int, error) {
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// Functionality of bytes.Reader.
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bn := copy(p, s.buffer.Bytes()[s.bufferRead:s.bufferSize])
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s.bufferRead += bn
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p = p[bn:]
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// Funtionality of io.TeeReader.
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sn, sErr := s.source.Read(p)
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if sn > 0 && s.sniffing {
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if wn, wErr := s.buffer.Write(p[:sn]); wErr != nil {
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return bn + wn, wErr
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}
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return n, err
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}
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return bn + sn, sErr
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}
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func (b *buffer) Len() int {
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return len(b.data) - b.read
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}
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func (b *buffer) resetRead() {
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b.read = 0
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}
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// From the io.Writer documentation:
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//
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// Write writes len(p) bytes from p to the underlying data stream.
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// It returns the number of bytes written from p (0 <= n <= len(p))
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// and any error encountered that caused the write to stop early.
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// Write must return a non-nil error if it returns n < len(p).
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// Write must not modify the slice data, even temporarily.
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//
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// Implementations must not retain p.
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//
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// In a previous incarnation, this implementation retained the incoming slice.
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func (b *buffer) Write(p []byte) (int, error) {
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b.data = append(b.data, p...)
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return len(p), nil
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func (s *bufferedReader) reset(snif bool) {
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s.sniffing = snif
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s.bufferRead = 0
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s.bufferSize = s.buffer.Len()
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}
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113
buffer_test.go
113
buffer_test.go
@ -1,113 +0,0 @@
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package cmux
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import (
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"bytes"
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"io"
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"testing"
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)
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func TestWriteNoModify(t *testing.T) {
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var b buffer
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const origWriteByte = 0
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const postWriteByte = 1
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writeBytes := []byte{origWriteByte}
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if _, err := b.Write(writeBytes); err != nil {
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t.Fatal(err)
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}
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writeBytes[0] = postWriteByte
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readBytes := make([]byte, 1)
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if _, err := b.Read(readBytes); err != io.EOF {
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t.Fatal(err)
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}
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if readBytes[0] != origWriteByte {
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t.Fatalf("expected to read %x, but read %x; buffer retained passed-in slice", origWriteByte, postWriteByte)
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}
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}
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const writeString = "deadbeef"
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func TestBuffer(t *testing.T) {
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writeBytes := []byte(writeString)
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const numWrites = 10
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var b buffer
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for i := 0; i < numWrites; i++ {
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n, err := b.Write(writeBytes)
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if err != nil && err != io.EOF {
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t.Fatal(err)
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}
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if n != len(writeBytes) {
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t.Fatalf("cannot write all the bytes: want=%d got=%d", len(writeBytes), n)
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}
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}
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for j := 0; j < 2; j++ {
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readBytes := make([]byte, len(writeBytes))
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for i := 0; i < numWrites; i++ {
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n, err := b.Read(readBytes)
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if i == numWrites-1 {
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// The last read should report EOF.
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if err != io.EOF {
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t.Fatal(err)
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}
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} else if err != nil {
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t.Fatal(err)
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}
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if n != len(readBytes) {
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t.Fatalf("cannot read all the bytes: want=%d got=%d", len(readBytes), n)
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}
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if !bytes.Equal(writeBytes, readBytes) {
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t.Errorf("different bytes read: want=%d got=%d", writeBytes, readBytes)
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}
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}
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n, err := b.Read(readBytes)
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if err != io.EOF {
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t.Errorf("expected EOF")
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}
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if n != 0 {
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t.Errorf("expected buffer to be empty, but got %d bytes", n)
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}
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b.resetRead()
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}
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}
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func TestBufferOffset(t *testing.T) {
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writeBytes := []byte(writeString)
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var b buffer
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n, err := b.Write(writeBytes)
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if err != nil {
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t.Fatal(err)
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}
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if n != len(writeBytes) {
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t.Fatalf("cannot write all the bytes: want=%d got=%d", len(writeBytes), n)
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}
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const readSize = 2
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numReads := len(writeBytes) / readSize
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for i := 0; i < numReads; i++ {
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readBytes := make([]byte, readSize)
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n, err := b.Read(readBytes)
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if i == numReads-1 {
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// The last read should report EOF.
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if err != io.EOF {
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t.Fatal(err)
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}
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} else if err != nil {
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t.Fatal(err)
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}
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if n != readSize {
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t.Fatalf("cannot read the bytes: want=%d got=%d", readSize, n)
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}
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if got := writeBytes[i*readSize : i*readSize+readSize]; !bytes.Equal(got, readBytes) {
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t.Fatalf("different bytes read: want=%s got=%s", readBytes, got)
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}
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}
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}
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26
cmux.go
26
cmux.go
@ -125,9 +125,9 @@ func (m *cMux) serve(c net.Conn, donec <-chan struct{}, wg *sync.WaitGroup) {
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muc := newMuxConn(c)
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for _, sl := range m.sls {
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for _, s := range sl.ss {
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matched := s(muc.sniffer())
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muc.reset()
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matched := s(muc.startSniffing())
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if matched {
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muc.doneSniffing()
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select {
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case sl.l.connc <- muc:
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case <-donec:
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@ -177,12 +177,13 @@ func (l muxListener) Accept() (net.Conn, error) {
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// MuxConn wraps a net.Conn and provides transparent sniffing of connection data.
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type MuxConn struct {
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net.Conn
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buf buffer
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buf bufferedReader
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}
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func newMuxConn(c net.Conn) *MuxConn {
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return &MuxConn{
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Conn: c,
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buf: bufferedReader{source: c},
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}
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}
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@ -196,22 +197,15 @@ func newMuxConn(c net.Conn) *MuxConn {
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// a non-zero number of bytes at the end of the input stream may
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// return either err == EOF or err == nil. The next Read should
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// return 0, EOF.
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//
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// This function implements the latter behaviour, returning the
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// (non-nil) error from the same call.
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func (m *MuxConn) Read(p []byte) (int, error) {
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n1, err := m.buf.Read(p)
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if err != io.EOF {
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return n1, err
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}
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n2, err := m.Conn.Read(p[n1:])
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return n1 + n2, err
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return m.buf.Read(p)
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}
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func (m *MuxConn) sniffer() io.Reader {
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return io.MultiReader(&m.buf, io.TeeReader(m.Conn, &m.buf))
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func (m *MuxConn) startSniffing() io.Reader {
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m.buf.reset(true)
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return &m.buf
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}
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func (m *MuxConn) reset() {
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m.buf.resetRead()
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func (m *MuxConn) doneSniffing() {
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m.buf.reset(false)
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}
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