normalize string_util (#708)

* refactoring string_util
* port string_util to iOS

2 files changed, 43 insertions, 0 deletions

diff --git a/Firestore/core/test/firebase/firestore/util/CMakeLists.txt b/Firestore/core/test/firebase/firestore/util/CMakeLists.txt
index 5e7612c..13a2e46 100644
--- a/Firestore/core/test/firebase/firestore/util/CMakeLists.txt
+++ b/Firestore/core/test/firebase/firestore/util/CMakeLists.txt
@@ -38,6 +38,7 @@ cc_test(
     autoid_test.cc
     comparison_test.cc
     string_printf_test.cc
+    string_util_test.cc
   DEPENDS
     firebase_firestore_util
 )
diff --git a/Firestore/core/test/firebase/firestore/util/string_util_test.cc b/Firestore/core/test/firebase/firestore/util/string_util_test.cc
new file mode 100644
index 0000000..f94596f
--- /dev/null
+++ b/Firestore/core/test/firebase/firestore/util/string_util_test.cc
@@ -0,0 +1,42 @@
+/*
+ * Copyright 2017 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "Firestore/core/src/firebase/firestore/util/string_util.h"
+
+#include <gtest/gtest.h>
+
+namespace firebase {
+namespace firestore {
+namespace util {
+
+TEST(StringUtil, PrefixSuccessor) {
+  EXPECT_EQ(PrefixSuccessor("a"), "b");
+  EXPECT_EQ(PrefixSuccessor("aaAA"), "aaAB");
+  EXPECT_EQ(PrefixSuccessor("aaa\xff"), "aab");
+  EXPECT_EQ(PrefixSuccessor(std::string("\x00", 1)), "\x01");
+  EXPECT_EQ(PrefixSuccessor("az\xe0"), "az\xe1");
+  EXPECT_EQ(PrefixSuccessor("\xff\xff\xff"), "");
+  EXPECT_EQ(PrefixSuccessor(""), "");
+}
+
+TEST(StringUtil, ImmediateSuccessor) {
+  EXPECT_EQ(ImmediateSuccessor("hello"), std::string("hello\0", 6));
+  EXPECT_EQ(ImmediateSuccessor(""), std::string("\0", 1));
+}
+
+}  // namespace util
+}  // namespace firestore
+}  // namespace firebase