integer encode/decode

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

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))
+}