integer encode/decode

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

diff --git a/src/pkg/gob/codec_test.go b/src/pkg/gob/codec_test.go
new file mode 100644 (file)
index 0000000..8142aac
--- /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 (file)
index 0000000..5104627
--- /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 (file)
index 0000000..ecddee2
--- /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 a2efee9bac0e17d857896ea18e168d66efb9d21d..f07bdf36a6d882ed67fbbc83a9c03516757d5850 100644 (file)
--- 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;