2 files changed, 187 insertions, 0 deletions
diff --git a/libgo/go/hash/crc32/crc32.go b/libgo/go/hash/crc32/crc32.go
new file mode 100644
index 000000000..2ab0c5491
--- /dev/null
+++ b/libgo/go/hash/crc32/crc32.go
@@ -0,0 +1,111 @@
+// 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.
+
+// This package implements the 32-bit cyclic redundancy check, or CRC-32, checksum.
+// See http://en.wikipedia.org/wiki/Cyclic_redundancy_check for information.
+package crc32
+
+import (
+	"hash"
+	"os"
+)
+
+// The size of a CRC-32 checksum in bytes.
+const Size = 4
+
+// Predefined polynomials.
+const (
+	// Far and away the most common CRC-32 polynomial.
+	// Used by ethernet (IEEE 802.3), v.42, fddi, gzip, zip, png, mpeg-2, ...
+	IEEE = 0xedb88320
+
+	// Castagnoli's polynomial, used in iSCSI.
+	// Has better error detection characteristics than IEEE.
+	// http://dx.doi.org/10.1109/26.231911
+	Castagnoli = 0x82f63b78
+
+	// Koopman's polynomial.
+	// Also has better error detection characteristics than IEEE.
+	// http://dx.doi.org/10.1109/DSN.2002.1028931
+	Koopman = 0xeb31d82e
+)
+
+// Table is a 256-word table representing the polynomial for efficient processing.
+type Table [256]uint32
+
+// MakeTable returns the Table constructed from the specified polynomial.
+func MakeTable(poly uint32) *Table {
+	t := new(Table)
+	for i := 0; i < 256; i++ {
+		crc := uint32(i)
+		for j := 0; j < 8; j++ {
+			if crc&1 == 1 {
+				crc = (crc >> 1) ^ poly
+			} else {
+				crc >>= 1
+			}
+		}
+		t[i] = crc
+	}
+	return t
+}
+
+// IEEETable is the table for the IEEE polynomial.
+var IEEETable = MakeTable(IEEE)
+
+// digest represents the partial evaluation of a checksum.
+type digest struct {
+	crc uint32
+	tab *Table
+}
+
+// New creates a new hash.Hash32 computing the CRC-32 checksum
+// using the polynomial represented by the Table.
+func New(tab *Table) hash.Hash32 { return &digest{0, tab} }
+
+// NewIEEE creates a new hash.Hash32 computing the CRC-32 checksum
+// using the IEEE polynomial.
+func NewIEEE() hash.Hash32 { return New(IEEETable) }
+
+func (d *digest) Size() int { return Size }
+
+func (d *digest) Reset() { d.crc = 0 }
+
+func update(crc uint32, tab *Table, p []byte) uint32 {
+	crc = ^crc
+	for _, v := range p {
+		crc = tab[byte(crc)^v] ^ (crc >> 8)
+	}
+	return ^crc
+}
+
+// Update returns the result of adding the bytes in p to the crc.
+func Update(crc uint32, tab *Table, p []byte) uint32 {
+	return update(crc, tab, p)
+}
+
+func (d *digest) Write(p []byte) (n int, err os.Error) {
+	d.crc = update(d.crc, d.tab, p)
+	return len(p), nil
+}
+
+func (d *digest) Sum32() uint32 { return d.crc }
+
+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 CRC-32 checksum of data
+// using the polynomial represented by the Table.
+func Checksum(data []byte, tab *Table) uint32 { return update(0, tab, data) }
+
+// ChecksumIEEE returns the CRC-32 checksum of data
+// using the IEEE polynomial.
+func ChecksumIEEE(data []byte) uint32 { return update(0, IEEETable, data) }
diff --git a/libgo/go/hash/crc32/crc32_test.go b/libgo/go/hash/crc32/crc32_test.go
new file mode 100644
index 000000000..cf5743c99
--- /dev/null
+++ b/libgo/go/hash/crc32/crc32_test.go
@@ -0,0 +1,76 @@
+// 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 crc32
+
+import (
+	"io"
+	"testing"
+)
+
+type test struct {
+	out uint32
+	in  string
+}
+
+var golden = []test{
+	{0x0, ""},
+	{0xe8b7be43, "a"},
+	{0x9e83486d, "ab"},
+	{0x352441c2, "abc"},
+	{0xed82cd11, "abcd"},
+	{0x8587d865, "abcde"},
+	{0x4b8e39ef, "abcdef"},
+	{0x312a6aa6, "abcdefg"},
+	{0xaeef2a50, "abcdefgh"},
+	{0x8da988af, "abcdefghi"},
+	{0x3981703a, "abcdefghij"},
+	{0x6b9cdfe7, "Discard medicine more than two years old."},
+	{0xc90ef73f, "He who has a shady past knows that nice guys finish last."},
+	{0xb902341f, "I wouldn't marry him with a ten foot pole."},
+	{0x42080e8, "Free! Free!/A trip/to Mars/for 900/empty jars/Burma Shave"},
+	{0x154c6d11, "The days of the digital watch are numbered.  -Tom Stoppard"},
+	{0x4c418325, "Nepal premier won't resign."},
+	{0x33955150, "For every action there is an equal and opposite government program."},
+	{0x26216a4b, "His money is twice tainted: 'taint yours and 'taint mine."},
+	{0x1abbe45e, "There is no reason for any individual to have a computer in their home. -Ken Olsen, 1977"},
+	{0xc89a94f7, "It's a tiny change to the code and not completely disgusting. - Bob Manchek"},
+	{0xab3abe14, "size:  a.out:  bad magic"},
+	{0xbab102b6, "The major problem is with sendmail.  -Mark Horton"},
+	{0x999149d7, "Give me a rock, paper and scissors and I will move the world.  CCFestoon"},
+	{0x6d52a33c, "If the enemy is within range, then so are you."},
+	{0x90631e8d, "It's well we cannot hear the screams/That we create in others' dreams."},
+	{0x78309130, "You remind me of a TV show, but that's all right: I watch it anyway."},
+	{0x7d0a377f, "C is as portable as Stonehedge!!"},
+	{0x8c79fd79, "Even if I could be Shakespeare, I think I should still choose to be Faraday. - A. Huxley"},
+	{0xa20b7167, "The fugacity of a constituent in a mixture of gases at a given temperature is proportional to its mole fraction.  Lewis-Randall Rule"},
+	{0x8e0bb443, "How can you write a big system without C++?  -Paul Glick"},
+}
+
+func TestGolden(t *testing.T) {
+	for i := 0; i < len(golden); i++ {
+		g := golden[i]
+		c := NewIEEE()
+		io.WriteString(c, g.in)
+		s := c.Sum32()
+		if s != g.out {
+			t.Errorf("crc32(%s) = 0x%x want 0x%x", g.in, s, g.out)
+			t.FailNow()
+		}
+	}
+}
+
+func BenchmarkCrc32KB(b *testing.B) {
+	b.StopTimer()
+	data := make([]uint8, 1024)
+	for i := 0; i < 1024; i++ {
+		data[i] = uint8(i)
+	}
+	c := NewIEEE()
+	b.StartTimer()
+
+	for i := 0; i < b.N; i++ {
+		c.Write(data)
+	}
+}