integer encode/decode

R=rsc
DELTA=185  (175 added, 10 deleted, 0 changed)
OCL=30863
CL=30871

4 files changed, 178 insertions, 10 deletions

diff --git a/src/pkg/gob/codec_test.go b/src/pkg/gob/codec_test.go
new file mode 100644
index 000000000..8142aac69
--- /dev/null
+++ b/src/pkg/gob/codec_test.go
@@ -0,0 +1,98 @@
+// 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 gob
+
+import (
+	"bytes";
+	"gob";
+	"io";
+	"os";
+	"testing";
+)
+
+// Guarantee encoding format by comparing some encodings to hand-written values
+type EncodeT struct {
+	x	uint64;
+	b	[]byte;
+}
+var encodeT = []EncodeT {
+	EncodeT{ 0x00,	[]byte{0x80} },
+	EncodeT{ 0x0f,	[]byte{0x8f} },
+	EncodeT{ 0xff,	[]byte{0x7f, 0x81} },
+	EncodeT{ 0xffff,	[]byte{0x7f, 0x7f, 0x83} },
+	EncodeT{ 0xffffff,	[]byte{0x7f, 0x7f, 0x7f, 0x87} },
+	EncodeT{ 0xffffffff,	[]byte{0x7f, 0x7f, 0x7f, 0x7f, 0x8f} },
+	EncodeT{ 0xffffffffff,	[]byte{0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x9f} },
+	EncodeT{ 0xffffffffffff,	[]byte{0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0xbf} },
+	EncodeT{ 0xffffffffffffff,	[]byte{0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0xff} },
+	EncodeT{ 0xffffffffffffffff,	[]byte{0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x81} },
+	EncodeT{ 0x1111,	[]byte{0x11, 0xa2} },
+	EncodeT{ 0x1111111111111111,	[]byte{0x11, 0x22, 0x44, 0x08, 0x11, 0x22, 0x44, 0x08, 0x91} },
+	EncodeT{ 0x8888888888888888,	[]byte{0x08, 0x11, 0x22, 0x44, 0x08, 0x11, 0x22, 0x44, 0x08, 0x81} },
+	EncodeT{ 1<<63,	[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x81} },
+}
+
+// Test basic encode/decode routines for unsigned integers
+func TestUintCodec(t *testing.T) {
+	var b = new(io.ByteBuffer);
+	for i, tt := range encodeT {
+		b.Reset();
+		err := EncodeUint(b, tt.x);
+		if err != nil {
+			t.Error("EncodeUint:", tt.x, err)
+		}
+		if !bytes.Equal(tt.b, b.Data()) {
+			t.Errorf("EncodeUint: expected % x got % x", tt.b, b.Data())
+		}
+	}
+	for u := uint64(0); ; u = (u+1) * 7 {
+		b.Reset();
+		err := EncodeUint(b, u);
+		if err != nil {
+			t.Error("EncodeUint:", u, err)
+		}
+		v, err := DecodeUint(b);
+		if err != nil {
+			t.Error("DecodeUint:", u, err)
+		}
+		if u != v {
+			t.Errorf("Encode/Decode: sent %#x received %#x\n", u, v)
+		}
+		if u & (1<<63) != 0 {
+			break
+		}
+	}
+}
+
+func verifyInt(i int64, t *testing.T) {
+	var b = new(io.ByteBuffer);
+	err := EncodeInt(b, i);
+	if err != nil {
+		t.Error("EncodeInt:", i, err)
+	}
+	j, err := DecodeInt(b);
+	if err != nil {
+		t.Error("DecodeInt:", i, err)
+	}
+	if i != j {
+		t.Errorf("Encode/Decode: sent %#x received %#x\n", uint64(i), uint64(j))
+	}
+}
+
+// Test basic encode/decode routines for signed integers
+func TestIntCodec(t *testing.T) {
+	var b = new(io.ByteBuffer);
+	for u := uint64(0); ; u = (u+1) * 7 {
+		// Do positive and negative values
+		i := int64(u);
+		verifyInt(i, t);
+		verifyInt(-i, t);
+		verifyInt(^i, t);
+		if u & (1<<63) != 0 {
+			break
+		}
+	}
+	verifyInt(-1<<63, t);	// a tricky case
+}
diff --git a/src/pkg/gob/decode.go b/src/pkg/gob/decode.go
new file mode 100644
index 000000000..5104627cd
--- /dev/null
+++ b/src/pkg/gob/decode.go
@@ -0,0 +1,40 @@
+// 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 gob
+
+import (
+	"io";
+	"os";
+)
+
+// DecodeUint reads an encoded unsigned integer from r.
+func DecodeUint(r io.Reader) (x uint64, err os.Error) {
+	var buf [1]byte;
+	for shift := uint(0);; shift += 7 {
+		n, err := r.Read(&buf);
+		if n != 1 {
+			return 0, err
+		}
+		b := uint64(buf[0]);
+		x |= b << shift;
+		if b&0x80 != 0 {
+			x &^= 0x80 << shift;
+			break
+		}
+	}
+	return x, nil;
+}
+
+// DecodeInt reads an encoded signed integer from r.
+func DecodeInt(r io.Reader) (i int64, err os.Error) {
+	x, err := DecodeUint(r);
+	if err != nil {
+		return
+	}
+	if x & 1 != 0 {
+		return ^int64(x>>1), nil
+	}
+	return int64(x >> 1), nil
+}
diff --git a/src/pkg/gob/encode.go b/src/pkg/gob/encode.go
new file mode 100644
index 000000000..ecddee23e
--- /dev/null
+++ b/src/pkg/gob/encode.go
@@ -0,0 +1,40 @@
+// 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 gob
+
+import (
+	"io";
+	"os";
+)
+
+// Integers encode as a variant of Google's protocol buffer varint (varvarint?).
+// The variant is that the continuation bytes have a zero top bit instead of a one.
+// That way there's only one bit to clear and the value is a little easier to see if
+// you're the unfortunate sort of person who must read the hex to debug.
+
+// EncodeUint writes an encoded unsigned integer to w.
+func EncodeUint(w io.Writer, x uint64) os.Error {
+	var buf [16]byte;
+	var n int;
+	for n = 0; x > 127; n++ {
+		buf[n] = uint8(x & 0x7F);
+		x >>= 7;
+	}
+	buf[n] = 0x80 | uint8(x);
+	nn, err := w.Write(buf[0:n+1]);
+	return err;
+}
+
+// EncodeInt writes an encoded signed integer to w.
+// The low bit of the encoding says whether to bit complement the (other bits of the) uint to recover the int.
+func EncodeInt(w io.Writer, i int64) os.Error {
+	var x uint64;
+	if i < 0 {
+		x = uint64(^i << 1) | 1
+	} else {
+		x = uint64(i << 1)
+	}
+	return EncodeUint(w, uint64(x))
+}
diff --git a/src/pkg/gob/type_test.go b/src/pkg/gob/type_test.go
index a2efee9ba..f07bdf36a 100644
--- a/src/pkg/gob/type_test.go
+++ b/src/pkg/gob/type_test.go
@@ -5,21 +5,11 @@
 package gob
 
 import (
-"fmt";
 	"gob";
 	"os";
 	"testing";
 )
 
-func checkType(ti Type, expected string, t *testing.T) {
-	if ti.String() != expected {
-		t.Errorf("checkType: expected %q got %s", expected, ti.String())
-	}
-	if ti.id() == 0 {
-		t.Errorf("id for %q is zero", expected)
-	}
-}
-
 type typeT struct {
 	typ	Type;
 	str	string;