Refactor serialization helpers from impl/memory -> service/datastore/serialize

service/datastore/serialize/binary_tools.go

+// Copyright 2015 The Chromium 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 serialize
+
+import (
+        "bytes"
+)
+
+// Join is a convenience invocation of bytes.Join(itms, nil)
+func Join(itms ...[]byte) []byte {
+        return bytes.Join(itms, nil)
+}
+
+// Invert simply inverts all the bytes in bs.
+func Invert(bs []byte) []byte {
+        if len(bs) == 0 {
+                return nil
+        }
+        ret := make([]byte, len(bs))
+        for i, b := range bs {
+                ret[i] = 0xFF ^ b
+        }
+        return ret
+}
+
+// Increment attempts to increment a copy of bstr as if adding 1 to an integer.
+//
+// If it overflows, the returned []byte will be all 0's, and the overflow bool
+// will be true.
+func Increment(bstr []byte) ([]byte, bool) {
+        ret := Join(bstr)
+        for i := len(ret) - 1; i >= 0; i-- {
+                if ret[i] == 0xFF {
+                        ret[i] = 0
+                } else {
+                        ret[i]++
+                        return ret, false
+                }
+        }
+        return ret, true
+}