Imported Upstream version 60upstream/60

3 files changed, 176 insertions, 0 deletions

diff --git a/src/pkg/hash/adler32/Makefile b/src/pkg/hash/adler32/Makefile
new file mode 100644
index 000000000..38ce537ba
--- /dev/null
+++ b/src/pkg/hash/adler32/Makefile
@@ -0,0 +1,11 @@
+# Copyright 2009 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/adler32
+GOFILES=\
+	adler32.go\
+
+include ../../../Make.pkg
diff --git a/src/pkg/hash/adler32/adler32.go b/src/pkg/hash/adler32/adler32.go
new file mode 100644
index 000000000..84943d9ae
--- /dev/null
+++ b/src/pkg/hash/adler32/adler32.go
@@ -0,0 +1,88 @@
+// Copyright 2009 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 adler32 implements the Adler-32 checksum.
+// Defined in RFC 1950:
+//	Adler-32 is composed of two sums accumulated per byte: s1 is
+//	the sum of all bytes, s2 is the sum of all s1 values. Both sums
+//	are done modulo 65521. s1 is initialized to 1, s2 to zero.  The
+//	Adler-32 checksum is stored as s2*65536 + s1 in most-
+//	significant-byte first (network) order.
+package adler32
+
+import (
+	"hash"
+	"os"
+)
+
+const (
+	mod = 65521
+)
+
+// The size of an Adler-32 checksum in bytes.
+const Size = 4
+
+// digest represents the partial evaluation of a checksum.
+type digest struct {
+	// invariant: (a < mod && b < mod) || a <= b
+	// invariant: a + b + 255 <= 0xffffffff
+	a, b uint32
+}
+
+func (d *digest) Reset() { d.a, d.b = 1, 0 }
+
+// New returns a new hash.Hash32 computing the Adler-32 checksum.
+func New() hash.Hash32 {
+	d := new(digest)
+	d.Reset()
+	return d
+}
+
+func (d *digest) Size() int { return Size }
+
+// Add p to the running checksum a, b.
+func update(a, b uint32, p []byte) (aa, bb uint32) {
+	for _, pi := range p {
+		a += uint32(pi)
+		b += a
+		// invariant: a <= b
+		if b > (0xffffffff-255)/2 {
+			a %= mod
+			b %= mod
+			// invariant: a < mod && b < mod
+		} else {
+			// invariant: a + b + 255 <= 2 * b + 255 <= 0xffffffff
+		}
+	}
+	return a, b
+}
+
+// Return the 32-bit checksum corresponding to a, b.
+func finish(a, b uint32) uint32 {
+	if b >= mod {
+		a %= mod
+		b %= mod
+	}
+	return b<<16 | a
+}
+
+func (d *digest) Write(p []byte) (nn int, err os.Error) {
+	d.a, d.b = update(d.a, d.b, p)
+	return len(p), nil
+}
+
+func (d *digest) Sum32() uint32 { return finish(d.a, d.b) }
+
+func (d *digest) Sum() []byte {
+	p := make([]byte, 4)
+	s := d.Sum32()
+	p[0] = byte(s >> 24)
+	p[1] = byte(s >> 16)
+	p[2] = byte(s >> 8)
+	p[3] = byte(s)
+	return p
+}
+
+// Checksum returns the Adler-32 checksum of data.
+func Checksum(data []byte) uint32 { return finish(update(1, 0, data)) }
diff --git a/src/pkg/hash/adler32/adler32_test.go b/src/pkg/hash/adler32/adler32_test.go
new file mode 100644
index 000000000..01f931c68
--- /dev/null
+++ b/src/pkg/hash/adler32/adler32_test.go
@@ -0,0 +1,77 @@
+// Copyright 2009 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 adler32
+
+import (
+	"bytes"
+	"io"
+	"testing"
+)
+
+type _Adler32Test struct {
+	out uint32
+	in  string
+}
+
+var golden = []_Adler32Test{
+	{0x1, ""},
+	{0x620062, "a"},
+	{0x12600c4, "ab"},
+	{0x24d0127, "abc"},
+	{0x3d8018b, "abcd"},
+	{0x5c801f0, "abcde"},
+	{0x81e0256, "abcdef"},
+	{0xadb02bd, "abcdefg"},
+	{0xe000325, "abcdefgh"},
+	{0x118e038e, "abcdefghi"},
+	{0x158603f8, "abcdefghij"},
+	{0x3f090f02, "Discard medicine more than two years old."},
+	{0x46d81477, "He who has a shady past knows that nice guys finish last."},
+	{0x40ee0ee1, "I wouldn't marry him with a ten foot pole."},
+	{0x16661315, "Free! Free!/A trip/to Mars/for 900/empty jars/Burma Shave"},
+	{0x5b2e1480, "The days of the digital watch are numbered.  -Tom Stoppard"},
+	{0x8c3c09ea, "Nepal premier won't resign."},
+	{0x45ac18fd, "For every action there is an equal and opposite government program."},
+	{0x53c61462, "His money is twice tainted: 'taint yours and 'taint mine."},
+	{0x7e511e63, "There is no reason for any individual to have a computer in their home. -Ken Olsen, 1977"},
+	{0xe4801a6a, "It's a tiny change to the code and not completely disgusting. - Bob Manchek"},
+	{0x61b507df, "size:  a.out:  bad magic"},
+	{0xb8631171, "The major problem is with sendmail.  -Mark Horton"},
+	{0x8b5e1904, "Give me a rock, paper and scissors and I will move the world.  CCFestoon"},
+	{0x7cc6102b, "If the enemy is within range, then so are you."},
+	{0x700318e7, "It's well we cannot hear the screams/That we create in others' dreams."},
+	{0x1e601747, "You remind me of a TV show, but that's all right: I watch it anyway."},
+	{0xb55b0b09, "C is as portable as Stonehedge!!"},
+	{0x39111dd0, "Even if I could be Shakespeare, I think I should still choose to be Faraday. - A. Huxley"},
+	{0x91dd304f, "The fugacity of a constituent in a mixture of gases at a given temperature is proportional to its mole fraction.  Lewis-Randall Rule"},
+	{0x2e5d1316, "How can you write a big system without C++?  -Paul Glick"},
+	{0xd0201df6, "'Invariant assertions' is the most elegant programming technique!  -Tom Szymanski"},
+}
+
+func TestGolden(t *testing.T) {
+	for i := 0; i < len(golden); i++ {
+		g := golden[i]
+		c := New()
+		io.WriteString(c, g.in)
+		s := c.Sum32()
+		if s != g.out {
+			t.Errorf("adler32(%s) = 0x%x want 0x%x", g.in, s, g.out)
+			t.FailNow()
+		}
+	}
+}
+
+func BenchmarkGolden(b *testing.B) {
+	b.StopTimer()
+	c := New()
+	var buf bytes.Buffer
+	for _, g := range golden {
+		buf.Write([]byte(g.in))
+	}
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		c.Write(buf.Bytes())
+	}
+}