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https://github.com/golang/go
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encoding/binary: add a non-reflect fast path for Read
before/after: binary.BenchmarkRead 200000 10860 ns/op binary.BenchmarkRead 500000 2846 ns/op R=rsc CC=golang-dev https://golang.org/cl/4547062
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@ -125,6 +125,54 @@ func (bigEndian) GoString() string { return "binary.BigEndian" }
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// Bytes read from r are decoded using the specified byte order
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// and written to successive fields of the data.
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func Read(r io.Reader, order ByteOrder, data interface{}) os.Error {
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// Fast path for basic types
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var n int
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switch data.(type) {
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case *int8:
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n = 1
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case *uint8:
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n = 1
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case *int16:
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n = 2
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case *uint16:
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n = 2
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case *int32:
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n = 4
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case *uint32:
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n = 4
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case *int64:
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n = 8
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case *uint64:
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n = 8
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}
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if n != 0 {
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var buf [8]byte
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bs := buf[:n]
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if _, err := io.ReadFull(r, bs); err != nil {
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return err
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}
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switch v := data.(type) {
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case *int8:
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*v = int8(buf[0])
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case *uint8:
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*v = buf[0]
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case *int16:
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*v = int16(order.Uint16(bs))
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case *uint16:
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*v = order.Uint16(bs)
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case *int32:
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*v = int32(order.Uint32(bs))
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case *uint32:
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*v = order.Uint32(bs)
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case *int64:
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*v = int64(order.Uint64(bs))
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case *uint64:
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*v = order.Uint64(bs)
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}
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return nil
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}
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// Fallback to reflect-based.
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var v reflect.Value
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switch d := reflect.ValueOf(data); d.Kind() {
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case reflect.Ptr:
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@ -5,6 +5,7 @@
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package binary
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import (
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"io"
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"os"
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"bytes"
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"math"
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@ -160,3 +161,43 @@ func TestWriteT(t *testing.T) {
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}
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}
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}
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type byteSliceReader struct {
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remain []byte
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}
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func (br *byteSliceReader) Read(p []byte) (int, os.Error) {
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n := copy(p, br.remain)
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br.remain = br.remain[n:]
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return n, nil
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}
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func BenchmarkRead(b *testing.B) {
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var ls Struct
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bsr := &byteSliceReader{}
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var r io.Reader = bsr
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for i := 0; i < b.N; i++ {
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bsr.remain = big
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Read(r, BigEndian, &ls.Int8)
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Read(r, BigEndian, &ls.Int16)
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Read(r, BigEndian, &ls.Int32)
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Read(r, BigEndian, &ls.Int64)
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Read(r, BigEndian, &ls.Uint8)
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Read(r, BigEndian, &ls.Uint16)
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Read(r, BigEndian, &ls.Uint32)
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Read(r, BigEndian, &ls.Uint64)
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}
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want := s
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want.Float32 = 0
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want.Float64 = 0
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want.Complex64 = 0
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want.Complex128 = 0
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for i := range want.Array {
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want.Array[i] = 0
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}
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if !reflect.DeepEqual(ls, want) {
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panic("no match")
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}
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}
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