hash: more efficient memory allocation

Feed append the complete content at once.

BenchmarkAdler32KB       1000000              2534 ns/op         404.05 MB/s
BenchmarkCrc32KB          500000              4757 ns/op         215.26 MB/s
BenchmarkCrc64KB          500000              4769 ns/op         214.70 MB/s
BenchmarkFnv32KB         1000000              2417 ns/op         423.64 MB/s
BenchmarkFnv32aKB        1000000              2408 ns/op         425.23 MB/s
BenchmarkFnv64KB          500000              4262 ns/op         240.21 MB/s
BenchmarkFnv64aKB         500000              4234 ns/op         241.83 MB/s

R=iant, rsc, r, minux.ma
CC=golang-dev
https://golang.org/cl/5937053

src/pkg/hash/adler32/adler32.go

@@ -75,11 +75,7 @@ func (d *digest) Sum32() uint32 { return finish(d.a, d.b) }
 
 func (d *digest) Sum(in []byte) []byte {
 	s := d.Sum32()
-	in = append(in, byte(s>>24))
+	return append(in, byte(s>>24), byte(s>>16), byte(s>>8), byte(s))
-	in = append(in, byte(s>>16))
-	in = append(in, byte(s>>8))
-	in = append(in, byte(s))
-	return in
 }
 
 // Checksum returns the Adler-32 checksum of data.

src/pkg/hash/adler32/adler32_test.go

@@ -5,7 +5,6 @@
 package adler32
 
 import (
-	"bytes"
 	"io"
 	"testing"
 )
@@ -63,15 +62,19 @@ func TestGolden(t *testing.T) {
 	}
 }
 
-func BenchmarkGolden(b *testing.B) {
+func BenchmarkAdler32KB(b *testing.B) {
-	b.StopTimer()
+	b.SetBytes(1024)
-	c := New()
+	data := make([]byte, 1024)
-	var buf bytes.Buffer
+	for i := range data {
-	for _, g := range golden {
+		data[i] = byte(i)
-		buf.Write([]byte(g.in))
 	}
-	b.StartTimer()
+	h := New()
+	in := make([]byte, 0, h.Size())
+
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		c.Write(buf.Bytes())
+		h.Reset()
+		h.Write(data)
+		h.Sum(in)
 	}
 }

src/pkg/hash/crc32/crc32.go

@@ -123,11 +123,7 @@ func (d *digest) Sum32() uint32 { return d.crc }
 
 func (d *digest) Sum(in []byte) []byte {
 	s := d.Sum32()
-	in = append(in, byte(s>>24))
+	return append(in, byte(s>>24), byte(s>>16), byte(s>>8), byte(s))
-	in = append(in, byte(s>>16))
-	in = append(in, byte(s>>8))
-	in = append(in, byte(s))
-	return in
 }
 
 // Checksum returns the CRC-32 checksum of data

src/pkg/hash/crc32/crc32_test.go

@@ -82,16 +82,18 @@ func TestGolden(t *testing.T) {
 }
 
 func BenchmarkCrc32KB(b *testing.B) {
-	b.StopTimer()
+	b.SetBytes(1024)
-	data := make([]uint8, 1024)
+	data := make([]byte, 1024)
-	for i := 0; i < 1024; i++ {
+	for i := range data {
-		data[i] = uint8(i)
+		data[i] = byte(i)
 	}
-	c := NewIEEE()
+	h := NewIEEE()
-	b.StartTimer()
+	in := make([]byte, 0, h.Size())
-	b.SetBytes(int64(len(data)))
 
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		c.Write(data)
+		h.Reset()
+		h.Write(data)
+		h.Sum(in)
 	}
 }

src/pkg/hash/crc64/crc64.go

@@ -79,15 +79,7 @@ func (d *digest) Sum64() uint64 { return d.crc }
 
 func (d *digest) Sum(in []byte) []byte {
 	s := d.Sum64()
-	in = append(in, byte(s>>56))
+	return append(in, byte(s>>56), byte(s>>48), byte(s>>40), byte(s>>32), byte(s>>24), byte(s>>16), byte(s>>8), byte(s))
-	in = append(in, byte(s>>48))
-	in = append(in, byte(s>>40))
-	in = append(in, byte(s>>32))
-	in = append(in, byte(s>>24))
-	in = append(in, byte(s>>16))
-	in = append(in, byte(s>>8))
-	in = append(in, byte(s))
-	return in
 }
 
 // Checksum returns the CRC-64 checksum of data

src/pkg/hash/crc64/crc64_test.go

@@ -64,15 +64,18 @@ func TestGolden(t *testing.T) {
 }
 
 func BenchmarkCrc64KB(b *testing.B) {
-	b.StopTimer()
+	b.SetBytes(1024)
-	data := make([]uint8, 1024)
+	data := make([]byte, 1024)
-	for i := 0; i < 1024; i++ {
+	for i := range data {
-		data[i] = uint8(i)
+		data[i] = byte(i)
 	}
-	c := New(tab)
+	h := New(tab)
-	b.StartTimer()
+	in := make([]byte, 0, h.Size())
 
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		c.Write(data)
+		h.Reset()
+		h.Write(data)
+		h.Sum(in)
 	}
 }

src/pkg/hash/fnv/fnv.go

@@ -111,44 +111,20 @@ func (s *sum64a) BlockSize() int { return 1 }
 
 func (s *sum32) Sum(in []byte) []byte {
 	v := uint32(*s)
-	in = append(in, byte(v>>24))
+	return append(in, byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
-	in = append(in, byte(v>>16))
-	in = append(in, byte(v>>8))
-	in = append(in, byte(v))
-	return in
 }
 
 func (s *sum32a) Sum(in []byte) []byte {
 	v := uint32(*s)
-	in = append(in, byte(v>>24))
+	return append(in, byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
-	in = append(in, byte(v>>16))
-	in = append(in, byte(v>>8))
-	in = append(in, byte(v))
-	return in
 }
 
 func (s *sum64) Sum(in []byte) []byte {
 	v := uint64(*s)
-	in = append(in, byte(v>>56))
+	return append(in, byte(v>>56), byte(v>>48), byte(v>>40), byte(v>>32), byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
-	in = append(in, byte(v>>48))
-	in = append(in, byte(v>>40))
-	in = append(in, byte(v>>32))
-	in = append(in, byte(v>>24))
-	in = append(in, byte(v>>16))
-	in = append(in, byte(v>>8))
-	in = append(in, byte(v))
-	return in
 }
 
 func (s *sum64a) Sum(in []byte) []byte {
 	v := uint64(*s)
-	in = append(in, byte(v>>56))
+	return append(in, byte(v>>56), byte(v>>48), byte(v>>40), byte(v>>32), byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
-	in = append(in, byte(v>>48))
-	in = append(in, byte(v>>40))
-	in = append(in, byte(v>>32))
-	in = append(in, byte(v>>24))
-	in = append(in, byte(v>>16))
-	in = append(in, byte(v>>8))
-	in = append(in, byte(v))
-	return in
 }

src/pkg/hash/fnv/fnv_test.go

@@ -11,8 +11,6 @@ import (
 	"testing"
 )
 
-const testDataSize = 40
-
 type golden struct {
 	sum  []byte
 	text string
@@ -134,34 +132,34 @@ func testIntegrity(t *testing.T, h hash.Hash) {
 	}
 }
 
-func Benchmark32(b *testing.B) {
+func BenchmarkFnv32KB(b *testing.B) {
-	benchmark(b, New32())
+	benchmarkKB(b, New32())
 }
 
-func Benchmark32a(b *testing.B) {
+func BenchmarkFnv32aKB(b *testing.B) {
-	benchmark(b, New32a())
+	benchmarkKB(b, New32a())
 }
 
-func Benchmark64(b *testing.B) {
+func BenchmarkFnv64KB(b *testing.B) {
-	benchmark(b, New64())
+	benchmarkKB(b, New64())
 }
 
-func Benchmark64a(b *testing.B) {
+func BenchmarkFnv64aKB(b *testing.B) {
-	benchmark(b, New64a())
+	benchmarkKB(b, New64a())
 }
 
-func benchmark(b *testing.B, h hash.Hash) {
+func benchmarkKB(b *testing.B, h hash.Hash) {
-	b.ResetTimer()
+	b.SetBytes(1024)
-	b.SetBytes(testDataSize)
+	data := make([]byte, 1024)
-	data := make([]byte, testDataSize)
 	for i := range data {
-		data[i] = byte(i + 'a')
+		data[i] = byte(i)
 	}
+	in := make([]byte, 0, h.Size())
 
-	b.StartTimer()
+	b.ResetTimer()
-	for todo := b.N; todo != 0; todo-- {
+	for i := 0; i < b.N; i++ {
 		h.Reset()
 		h.Write(data)
-		h.Sum(nil)
+		h.Sum(in)
 	}
 }