Fix fast string comparison bug.

service/datastore/properties.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 datastore
 
 import (
         "bytes"
         "encoding/base64"
         "errors"
@@ skipping 915 matching lines @@
         // not be performed.
         fastCmp(o byteSequence) (int, bool)
 }
 
 func cmpByteSequence(a, b byteSequence) int {
         if v, ok := a.fastCmp(b); ok {
                 return v
         }
 
         // Byte-by-byte "slow" comparison.
-        ld := a.len() - b.len()
-        if ld < 0 {
-                ld = -ld
+        ln := a.len()
+        if bln := b.len(); bln < ln {
+                ln = bln
         }
-        for i := 0; i < ld; i++ {
+
+        for i := 0; i < ln; i++ {
                 av, bv := a.get(i), b.get(i)
                 switch {
                 case av < bv:
                         return -1
                 case av > bv:
                         return 1
                 }
         }
 
-        return ld
+        return a.len() - b.len()
 }
 
 // bytesByteSequence is a byteSequence implementation for a byte slice.
 type bytesByteSequence []byte
 
 func (s bytesByteSequence) len() int           { return len(s) }
 func (s bytesByteSequence) get(i int) byte     { return s[i] }
 func (s bytesByteSequence) value() interface{} { return []byte(s) }
 func (s bytesByteSequence) string() string     { return string(s) }
 func (s bytesByteSequence) bytes() []byte      { return []byte(s) }
@@ skipping 14 matching lines @@
 func (s stringByteSequence) bytes() []byte      { return []byte(s) }
 func (s stringByteSequence) fastCmp(o byteSequence) (int, bool) {
         if t, ok := o.(stringByteSequence); ok {
                 // This pattern is used for string comparison in strings.Compare.
                 if string(s) == string(t) {
                         return 0, true
                 }
                 if string(s) < string(t) {
                         return -1, true
                 }
-                return 0, true
+                return 1, true
         }
         return 0, false
 }