hash: new FNV-1a implementation

R=agl1, rsc
CC=golang-dev
https://golang.org/cl/4257042

src/pkg/Makefile

@@ -94,6 +94,7 @@ DIRS=\
 	hash/adler32\
 	hash/crc32\
 	hash/crc64\
+	hash/fnv\
 	html\
 	http\
 	http/cgi\

src/pkg/hash/fnv/Makefile

@@ -0,0 +1,11 @@
+# Copyright 2011 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+include ../../../Make.inc
+
+TARG=hash/fnv
+GOFILES=\
+	fnv.go\
+
+include ../../../Make.pkg

src/pkg/hash/fnv/fnv.go

@@ -0,0 +1,133 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// The fnv package implements FNV-1 and FNV-1a,
+// non-cryptographic hash functions created by
+// Glenn Fowler, Landon Curt Noll, and Phong Vo.
+// See http://isthe.com/chongo/tech/comp/fnv/.
+package fnv
+
+import (
+	"encoding/binary"
+	"hash"
+	"os"
+	"unsafe"
+)
+
+type (
+	sum32  uint32
+	sum32a uint32
+	sum64  uint64
+	sum64a uint64
+)
+
+const (
+	offset32 = 2166136261
+	offset64 = 14695981039346656037
+	prime32  = 16777619
+	prime64  = 1099511628211
+)
+
+// New32 returns a new 32-bit FNV-1 hash.Hash.
+func New32() hash.Hash32 {
+	var s sum32 = offset32
+	return &s
+}
+
+// New32a returns a new 32-bit FNV-1a hash.Hash.
+func New32a() hash.Hash32 {
+	var s sum32a = offset32
+	return &s
+}
+
+// New64 returns a new 64-bit FNV-1 hash.Hash.
+func New64() hash.Hash64 {
+	var s sum64 = offset64
+	return &s
+}
+
+// New64a returns a new 64-bit FNV-1a hash.Hash.
+func New64a() hash.Hash64 {
+	var s sum64a = offset64
+	return &s
+}
+
+func (s *sum32) Reset()  { *s = offset32 }
+func (s *sum32a) Reset() { *s = offset32 }
+func (s *sum64) Reset()  { *s = offset64 }
+func (s *sum64a) Reset() { *s = offset64 }
+
+func (s *sum32) Sum32() uint32  { return uint32(*s) }
+func (s *sum32a) Sum32() uint32 { return uint32(*s) }
+func (s *sum64) Sum64() uint64  { return uint64(*s) }
+func (s *sum64a) Sum64() uint64 { return uint64(*s) }
+
+func (s *sum32) Write(data []byte) (int, os.Error) {
+	hash := *s
+	for _, c := range data {
+		hash *= prime32
+		hash ^= sum32(c)
+	}
+	*s = hash
+	return len(data), nil
+}
+
+func (s *sum32a) Write(data []byte) (int, os.Error) {
+	hash := *s
+	for _, c := range data {
+		hash ^= sum32a(c)
+		hash *= prime32
+	}
+	*s = hash
+	return len(data), nil
+}
+
+func (s *sum64) Write(data []byte) (int, os.Error) {
+	hash := *s
+	for _, c := range data {
+		hash *= prime64
+		hash ^= sum64(c)
+	}
+	*s = hash
+	return len(data), nil
+}
+
+func (s *sum64a) Write(data []byte) (int, os.Error) {
+	hash := *s
+	for _, c := range data {
+		hash ^= sum64a(c)
+		hash *= prime64
+	}
+	*s = hash
+	return len(data), nil
+}
+
+func (s *sum32) Size() int  { return unsafe.Sizeof(*s) }
+func (s *sum32a) Size() int { return unsafe.Sizeof(*s) }
+func (s *sum64) Size() int  { return unsafe.Sizeof(*s) }
+func (s *sum64a) Size() int { return unsafe.Sizeof(*s) }
+
+func (s *sum32) Sum() []byte {
+	a := make([]byte, unsafe.Sizeof(*s))
+	binary.BigEndian.PutUint32(a, uint32(*s))
+	return a
+}
+
+func (s *sum32a) Sum() []byte {
+	a := make([]byte, unsafe.Sizeof(*s))
+	binary.BigEndian.PutUint32(a, uint32(*s))
+	return a
+}
+
+func (s *sum64) Sum() []byte {
+	a := make([]byte, unsafe.Sizeof(*s))
+	binary.BigEndian.PutUint64(a, uint64(*s))
+	return a
+}
+
+func (s *sum64a) Sum() []byte {
+	a := make([]byte, unsafe.Sizeof(*s))
+	binary.BigEndian.PutUint64(a, uint64(*s))
+	return a
+}

src/pkg/hash/fnv/fnv_test.go

@@ -0,0 +1,167 @@
+// Copyright 2011 The Go 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 fnv
+
+import (
+	"bytes"
+	"encoding/binary"
+	"hash"
+	"testing"
+)
+
+const testDataSize = 40
+
+type golden struct {
+	sum  []byte
+	text string
+}
+
+var golden32 = []golden{
+	{[]byte{0x81, 0x1c, 0x9d, 0xc5}, ""},
+	{[]byte{0x05, 0x0c, 0x5d, 0x7e}, "a"},
+	{[]byte{0x70, 0x77, 0x2d, 0x38}, "ab"},
+	{[]byte{0x43, 0x9c, 0x2f, 0x4b}, "abc"},
+}
+
+var golden32a = []golden{
+	{[]byte{0x81, 0x1c, 0x9d, 0xc5}, ""},
+	{[]byte{0xe4, 0x0c, 0x29, 0x2c}, "a"},
+	{[]byte{0x4d, 0x25, 0x05, 0xca}, "ab"},
+	{[]byte{0x1a, 0x47, 0xe9, 0x0b}, "abc"},
+}
+
+var golden64 = []golden{
+	{[]byte{0xcb, 0xf2, 0x9c, 0xe4, 0x84, 0x22, 0x23, 0x25}, ""},
+	{[]byte{0xaf, 0x63, 0xbd, 0x4c, 0x86, 0x01, 0xb7, 0xbe}, "a"},
+	{[]byte{0x08, 0x32, 0x67, 0x07, 0xb4, 0xeb, 0x37, 0xb8}, "ab"},
+	{[]byte{0xd8, 0xdc, 0xca, 0x18, 0x6b, 0xaf, 0xad, 0xcb}, "abc"},
+}
+
+var golden64a = []golden{
+	{[]byte{0xcb, 0xf2, 0x9c, 0xe4, 0x84, 0x22, 0x23, 0x25}, ""},
+	{[]byte{0xaf, 0x63, 0xdc, 0x4c, 0x86, 0x01, 0xec, 0x8c}, "a"},
+	{[]byte{0x08, 0x9c, 0x44, 0x07, 0xb5, 0x45, 0x98, 0x6a}, "ab"},
+	{[]byte{0xe7, 0x1f, 0xa2, 0x19, 0x05, 0x41, 0x57, 0x4b}, "abc"},
+}
+
+func TestGolden32(t *testing.T) {
+	testGolden(t, New32(), golden32)
+}
+
+func TestGolden32a(t *testing.T) {
+	testGolden(t, New32a(), golden32a)
+}
+
+func TestGolden64(t *testing.T) {
+	testGolden(t, New64(), golden64)
+}
+
+func TestGolden64a(t *testing.T) {
+	testGolden(t, New64a(), golden64a)
+}
+
+func testGolden(t *testing.T, hash hash.Hash, gold []golden) {
+	for _, g := range gold {
+		hash.Reset()
+		done, error := hash.Write([]byte(g.text))
+		if error != nil {
+			t.Fatalf("write error: %s", error)
+		}
+		if done != len(g.text) {
+			t.Fatalf("wrote only %d out of %d bytes", done, len(g.text))
+		}
+		if actual := hash.Sum(); !bytes.Equal(g.sum, actual) {
+			t.Errorf("hash(%q) = 0x%x want 0x%x", g.text, actual, g.sum)
+		}
+	}
+}
+
+func TestIntegrity32(t *testing.T) {
+	testIntegrity(t, New32())
+}
+
+func TestIntegrity32a(t *testing.T) {
+	testIntegrity(t, New32a())
+}
+
+func TestIntegrity64(t *testing.T) {
+	testIntegrity(t, New64())
+}
+
+func TestIntegrity64a(t *testing.T) {
+	testIntegrity(t, New64a())
+}
+
+func testIntegrity(t *testing.T, h hash.Hash) {
+	data := []byte{'1', '2', 3, 4, 5}
+	h.Write(data)
+	sum := h.Sum()
+
+	if size := h.Size(); size != len(sum) {
+		t.Fatalf("Size()=%d but len(Sum())=%d", size, len(sum))
+	}
+
+	if a := h.Sum(); !bytes.Equal(sum, a) {
+		t.Fatalf("first Sum()=0x%x, second Sum()=0x%x", sum, a)
+	}
+
+	h.Reset()
+	h.Write(data)
+	if a := h.Sum(); !bytes.Equal(sum, a) {
+		t.Fatalf("Sum()=0x%x, but after Reset() Sum()=0x%x", sum, a)
+	}
+
+	h.Reset()
+	h.Write(data[:2])
+	h.Write(data[2:])
+	if a := h.Sum(); !bytes.Equal(sum, a) {
+		t.Fatalf("Sum()=0x%x, but with partial writes, Sum()=0x%x", sum, a)
+	}
+
+	switch h.Size() {
+	case 4:
+		sum32 := h.(hash.Hash32).Sum32()
+		if sum32 != binary.BigEndian.Uint32(sum) {
+			t.Fatalf("Sum()=0x%x, but Sum32()=0x%x", sum, sum32)
+		}
+	case 8:
+		sum64 := h.(hash.Hash64).Sum64()
+		if sum64 != binary.BigEndian.Uint64(sum) {
+			t.Fatalf("Sum()=0x%x, but Sum64()=0x%x", sum, sum64)
+		}
+	}
+}
+
+func Benchmark32(b *testing.B) {
+	benchmark(b, New32())
+}
+
+func Benchmark32a(b *testing.B) {
+	benchmark(b, New32a())
+}
+
+func Benchmark64(b *testing.B) {
+	benchmark(b, New64())
+}
+
+func Benchmark64a(b *testing.B) {
+	benchmark(b, New64a())
+}
+
+func benchmark(b *testing.B, h hash.Hash) {
+	b.ResetTimer()
+	b.SetBytes(testDataSize)
+	data := make([]byte, testDataSize)
+	for i, _ := range data {
+		data[i] = byte(i + 'a')
+	}
+
+	b.StartTimer()
+	for todo := b.N; todo != 0; todo-- {
+		h.Reset()
+		h.Write(data)
+		h.Sum()
+	}
+}