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-rw-r--r--libgo/go/hash/adler32/adler32.go88
-rw-r--r--libgo/go/hash/adler32/adler32_test.go63
2 files changed, 151 insertions, 0 deletions
diff --git a/libgo/go/hash/adler32/adler32.go b/libgo/go/hash/adler32/adler32.go
new file mode 100644
index 000000000..cd0c2599a
--- /dev/null
+++ b/libgo/go/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.
+
+// This package 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 i := 0; i < len(p); i++ {
+ a += uint32(p[i])
+ 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/libgo/go/hash/adler32/adler32_test.go b/libgo/go/hash/adler32/adler32_test.go
new file mode 100644
index 000000000..ffa5569bc
--- /dev/null
+++ b/libgo/go/hash/adler32/adler32_test.go
@@ -0,0 +1,63 @@
+// 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 (
+ "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()
+ }
+ }
+}