normalize string_util (#708)

* refactoring string_util
* port string_util to iOS

11 files changed, 103 insertions, 93 deletions

diff --git a/Firestore/Example/Firestore.xcodeproj/project.pbxproj b/Firestore/Example/Firestore.xcodeproj/project.pbxproj
index 5db2b56..155b4f2 100644
--- a/Firestore/Example/Firestore.xcodeproj/project.pbxproj
+++ b/Firestore/Example/Firestore.xcodeproj/project.pbxproj
@@ -27,7 +27,6 @@
 		5436F32420008FAD006E51E3 /* string_printf_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = 5436F32320008FAD006E51E3 /* string_printf_test.cc */; };
 		54740A571FC914BA00713A1A /* secure_random_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = 54740A531FC913E500713A1A /* secure_random_test.cc */; };
 		54740A581FC914F000713A1A /* autoid_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = 54740A521FC913E500713A1A /* autoid_test.cc */; };
-		54764FAB1FAA0C320085E60A /* string_util_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = 54764FAA1FAA0C320085E60A /* string_util_test.cc */; };
 		54764FAF1FAA21B90085E60A /* FSTGoogleTestTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = 54764FAE1FAA21B90085E60A /* FSTGoogleTestTests.mm */; };
 		548DB927200D590300E00ABC /* assert_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = 548DB926200D590300E00ABC /* assert_test.cc */; };
 		548DB929200D59F600E00ABC /* comparison_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = 548DB928200D59F600E00ABC /* comparison_test.cc */; };
@@ -66,6 +65,7 @@
 		71719F9F1E33DC2100824A3D /* LaunchScreen.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 71719F9D1E33DC2100824A3D /* LaunchScreen.storyboard */; };
 		873B8AEB1B1F5CCA007FD442 /* Main.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 873B8AEA1B1F5CCA007FD442 /* Main.storyboard */; };
 		AB356EF7200EA5EB0089B766 /* field_value_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = AB356EF6200EA5EB0089B766 /* field_value_test.cc */; };
+		AB380CFE201A2F4500D97691 /* string_util_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = AB380CFC201A2EE200D97691 /* string_util_test.cc */; };
 		AB382F7C1FE02A1F007CA955 /* FIRDocumentReferenceTests.m in Sources */ = {isa = PBXBuildFile; fileRef = AB382F7B1FE02A1F007CA955 /* FIRDocumentReferenceTests.m */; };
 		AB382F7E1FE03059007CA955 /* FIRFieldPathTests.m in Sources */ = {isa = PBXBuildFile; fileRef = AB382F7D1FE03059007CA955 /* FIRFieldPathTests.m */; };
 		AB7BAB342012B519001E0872 /* geo_point_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = AB7BAB332012B519001E0872 /* geo_point_test.cc */; };
@@ -203,7 +203,6 @@
 		5436F32320008FAD006E51E3 /* string_printf_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = string_printf_test.cc; path = ../../core/test/firebase/firestore/util/string_printf_test.cc; sourceTree = "<group>"; };
 		54740A521FC913E500713A1A /* autoid_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = autoid_test.cc; path = ../../core/test/firebase/firestore/util/autoid_test.cc; sourceTree = "<group>"; };
 		54740A531FC913E500713A1A /* secure_random_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = secure_random_test.cc; path = ../../core/test/firebase/firestore/util/secure_random_test.cc; sourceTree = "<group>"; };
-		54764FAA1FAA0C320085E60A /* string_util_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = string_util_test.cc; path = ../../Port/string_util_test.cc; sourceTree = "<group>"; };
 		54764FAE1FAA21B90085E60A /* FSTGoogleTestTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; name = FSTGoogleTestTests.mm; path = GoogleTest/FSTGoogleTestTests.mm; sourceTree = "<group>"; };
 		548DB926200D590300E00ABC /* assert_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = assert_test.cc; path = ../../core/test/firebase/firestore/util/assert_test.cc; sourceTree = "<group>"; };
 		548DB928200D59F600E00ABC /* comparison_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = comparison_test.cc; path = ../../core/test/firebase/firestore/util/comparison_test.cc; sourceTree = "<group>"; };
@@ -250,6 +249,7 @@
 		9D52E67EE96AA7E5D6F69748 /* Pods-Firestore_IntegrationTests.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Firestore_IntegrationTests.debug.xcconfig"; path = "Pods/Target Support Files/Pods-Firestore_IntegrationTests/Pods-Firestore_IntegrationTests.debug.xcconfig"; sourceTree = "<group>"; };
 		9EF477AD4B2B643FD320867A /* Pods-Firestore_Example.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Firestore_Example.debug.xcconfig"; path = "Pods/Target Support Files/Pods-Firestore_Example/Pods-Firestore_Example.debug.xcconfig"; sourceTree = "<group>"; };
 		AB356EF6200EA5EB0089B766 /* field_value_test.cc */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = field_value_test.cc; sourceTree = "<group>"; };
+		AB380CFC201A2EE200D97691 /* string_util_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = string_util_test.cc; path = ../../core/test/firebase/firestore/util/string_util_test.cc; sourceTree = "<group>"; };
 		AB382F7B1FE02A1F007CA955 /* FIRDocumentReferenceTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = FIRDocumentReferenceTests.m; sourceTree = "<group>"; };
 		AB382F7D1FE03059007CA955 /* FIRFieldPathTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = FIRFieldPathTests.m; sourceTree = "<group>"; };
 		AB7BAB332012B519001E0872 /* geo_point_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = geo_point_test.cc; path = ../../core/test/firebase/firestore/geo_point_test.cc; sourceTree = "<group>"; };
@@ -408,6 +408,7 @@
 				54C2294E1FECABAE007D065B /* log_test.cc */,
 				54740A531FC913E500713A1A /* secure_random_test.cc */,
 				5436F32320008FAD006E51E3 /* string_printf_test.cc */,
+				AB380CFC201A2EE200D97691 /* string_util_test.cc */,
 			);
 			name = util;
 			sourceTree = "<group>";
@@ -427,7 +428,6 @@
 		54764FAD1FAA0C650085E60A /* Port */ = {
 			isa = PBXGroup;
 			children = (
-				54764FAA1FAA0C320085E60A /* string_util_test.cc */,
 			);
 			name = Port;
 			sourceTree = "<group>";
@@ -1221,6 +1221,7 @@
 				DE51B1E11F0D490D0013853F /* FSTMemoryRemoteDocumentCacheTests.m in Sources */,
 				DE51B1FF1F0D493A0013853F /* FSTAssertTests.m in Sources */,
 				DE51B1D31F0D48CD0013853F /* FSTViewSnapshotTest.m in Sources */,
+				AB380CFE201A2F4500D97691 /* string_util_test.cc in Sources */,
 				DE51B1F91F0D491F0013853F /* FSTWatchChangeTests.m in Sources */,
 				DE51B1F81F0D491F0013853F /* FSTWatchChange+Testing.m in Sources */,
 				DE51B1EB1F0D490D0013853F /* FSTWriteGroupTests.mm in Sources */,
@@ -1254,7 +1255,6 @@
 				DE51B1FB1F0D492C0013853F /* FSTMemorySpecTests.m in Sources */,
 				DE51B1DB1F0D490D0013853F /* FSTLevelDBQueryCacheTests.m in Sources */,
 				AB356EF7200EA5EB0089B766 /* field_value_test.cc in Sources */,
-				54764FAB1FAA0C320085E60A /* string_util_test.cc in Sources */,
 				54E9282C1F339CAD00C1953E /* XCTestCase+Await.m in Sources */,
 				AB99452E1FE30AC800DFC1E6 /* FIRFieldValueTests.m in Sources */,
 				AB7BAB342012B519001E0872 /* geo_point_test.cc in Sources */,
diff --git a/Firestore/Port/string_util.h b/Firestore/Port/string_util.h
deleted file mode 100644
index 6e85ba9..0000000
--- a/Firestore/Port/string_util.h
+++ /dev/null
@@ -1,66 +0,0 @@
-/*
- * 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.
- */
-
-// Useful string functions and so forth.  This is a grab-bag file.
-//
-// These functions work fine for UTF-8 strings as long as you can
-// consider them to be just byte strings.  For example, due to the
-// design of UTF-8 you do not need to worry about accidental matches,
-// as long as all your inputs are valid UTF-8 (use \uHHHH, not \xHH or \oOOO).
-
-#ifndef IPHONE_FIRESTORE_PORT_STRING_UTIL_H_
-#define IPHONE_FIRESTORE_PORT_STRING_UTIL_H_
-
-#include <string>
-
-namespace leveldb {
-class Slice;
-}
-
-namespace Firestore {
-
-// Returns the smallest lexicographically larger string of equal or smaller
-// length. Returns an empty string if there is no such successor (if the input
-// is empty or consists entirely of 0xff bytes).
-// Useful for calculating the smallest lexicographically larger string
-// that will not be prefixed by the input string.
-//
-// Examples:
-// "a" -> "b", "aaa" -> "aab", "aa\xff" -> "ab", "\xff" -> "", "" -> ""
-std::string PrefixSuccessor(leveldb::Slice prefix);
-
-// Returns the immediate lexicographically-following string. This is useful to
-// turn an inclusive range into something that can be used with Bigtable's
-// SetLimitRow():
-//
-//     // Inclusive range [min_element, max_element].
-//     string min_element = ...;
-//     string max_element = ...;
-//
-//     // Equivalent range [range_start, range_end).
-//     string range_start = min_element;
-//     string range_end = ImmediateSuccessor(max_element);
-//
-// WARNING: Returns the input string with a '\0' appended; if you call c_str()
-// on the result, it will compare equal to s.
-//
-// WARNING: Transforms "" -> "\0"; this doesn't account for Bigtable's special
-// treatment of "" as infinity.
-std::string ImmediateSuccessor(leveldb::Slice s);
-
-}  // namespace Firestore
-
-#endif  // IPHONE_FIRESTORE_PORT_STRING_UTIL_H_
diff --git a/Firestore/Source/Local/FSTLevelDBKey.mm b/Firestore/Source/Local/FSTLevelDBKey.mm
index c6f51b9..074d5c5 100644
--- a/Firestore/Source/Local/FSTLevelDBKey.mm
+++ b/Firestore/Source/Local/FSTLevelDBKey.mm
@@ -19,14 +19,12 @@
 #include <string>
 
 #include "Firestore/Port/ordered_code.h"
-#include "Firestore/Port/string_util.h"
 #import "Firestore/Source/Model/FSTDocumentKey.h"
 #import "Firestore/Source/Model/FSTPath.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
 using Firestore::OrderedCode;
-using Firestore::PrefixSuccessor;
 using Firestore::StringView;
 using leveldb::Slice;
 
diff --git a/Firestore/Source/Local/FSTLevelDBMutationQueue.mm b/Firestore/Source/Local/FSTLevelDBMutationQueue.mm
index 56a22a1..74463ee 100644
--- a/Firestore/Source/Local/FSTLevelDBMutationQueue.mm
+++ b/Firestore/Source/Local/FSTLevelDBMutationQueue.mm
@@ -35,7 +35,7 @@
 #import "Firestore/Source/Util/FSTAssert.h"
 
 #include "Firestore/Port/ordered_code.h"
-#include "Firestore/Port/string_util.h"
+#include "Firestore/core/src/firebase/firestore/util/string_util.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -164,7 +164,7 @@ static ReadOptions StandardReadOptions() {
   while (moreUserIDs) {
     // Compute the first key after the last mutation for nextUserID.
     auto userEnd = [FSTLevelDBMutationKey keyPrefixWithUserID:nextUserID];
-    userEnd = Firestore::PrefixSuccessor(userEnd);
+    userEnd = firebase::firestore::util::PrefixSuccessor(userEnd);
 
     // Seek to that key with the intent of finding the boundary between nextUserID's mutations
     // and the one after that (if any).
diff --git a/Firestore/Source/Local/FSTLevelDBQueryCache.mm b/Firestore/Source/Local/FSTLevelDBQueryCache.mm
index 8388b96..5feb9f1 100644
--- a/Firestore/Source/Local/FSTLevelDBQueryCache.mm
+++ b/Firestore/Source/Local/FSTLevelDBQueryCache.mm
@@ -30,7 +30,6 @@
 #import "Firestore/Source/Util/FSTAssert.h"
 
 #include "Firestore/Port/ordered_code.h"
-#include "Firestore/Port/string_util.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
diff --git a/Firestore/Source/Local/FSTLevelDBRemoteDocumentCache.mm b/Firestore/Source/Local/FSTLevelDBRemoteDocumentCache.mm
index 02f9f3e..039712c 100644
--- a/Firestore/Source/Local/FSTLevelDBRemoteDocumentCache.mm
+++ b/Firestore/Source/Local/FSTLevelDBRemoteDocumentCache.mm
@@ -33,7 +33,6 @@
 #import "Firestore/Source/Util/FSTAssert.h"
 
 #include "Firestore/Port/ordered_code.h"
-#include "Firestore/Port/string_util.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
diff --git a/Firestore/core/src/firebase/firestore/util/CMakeLists.txt b/Firestore/core/src/firebase/firestore/util/CMakeLists.txt
index 09db164..51621a0 100644
--- a/Firestore/core/src/firebase/firestore/util/CMakeLists.txt
+++ b/Firestore/core/src/firebase/firestore/util/CMakeLists.txt
@@ -113,6 +113,8 @@ cc_library(
     firebase_assert.h
     log.h
     secure_random.h
+    string_util.cc
+    string_util.h
   DEPENDS
     ${UTIL_DEPENDS}
     firebase_firestore_util_base
diff --git a/Firestore/Port/string_util.cc b/Firestore/core/src/firebase/firestore/util/string_util.cc
index 2587860..b7f1ed9 100644
--- a/Firestore/Port/string_util.cc
+++ b/Firestore/core/src/firebase/firestore/util/string_util.cc
@@ -14,19 +14,19 @@
  * limitations under the License.
  */
 
-#include "Firestore/Port/string_util.h"
+#include "Firestore/core/src/firebase/firestore/util/string_util.h"
 
-#include <leveldb/db.h>
+namespace firebase {
+namespace firestore {
+namespace util {
 
-namespace Firestore {
-
-std::string PrefixSuccessor(leveldb::Slice prefix) {
+std::string PrefixSuccessor(absl::string_view prefix) {
   // We can increment the last character in the string and be done
   // unless that character is 255 (0xff), in which case we have to erase the
   // last character and increment the previous character, unless that
   // is 255, etc. If the string is empty or consists entirely of
   // 255's, we just return the empty string.
-  std::string limit(prefix.data(), prefix.size());
+  std::string limit(prefix);
   while (!limit.empty()) {
     size_t index = limit.length() - 1;
     if (limit[index] == '\xff') {  // char literal avoids signed/unsigned.
@@ -39,7 +39,7 @@ std::string PrefixSuccessor(leveldb::Slice prefix) {
   return limit;
 }
 
-std::string ImmediateSuccessor(leveldb::Slice s) {
+std::string ImmediateSuccessor(absl::string_view s) {
   // Return the input string, with an additional NUL byte appended.
   std::string out;
   out.reserve(s.size() + 1);
@@ -48,4 +48,6 @@ std::string ImmediateSuccessor(leveldb::Slice s) {
   return out;
 }
 
-}  // namespace Firestore
+}  // namespace util
+}  // namespace firestore
+}  // namespace firebase
diff --git a/Firestore/core/src/firebase/firestore/util/string_util.h b/Firestore/core/src/firebase/firestore/util/string_util.h
new file mode 100644
index 0000000..3de177d
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/util/string_util.h
@@ -0,0 +1,72 @@
+/*
+ * 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.
+ */
+
+// Useful string functions and so forth.  This is a grab-bag file.
+//
+// These functions work fine for UTF-8 strings as long as you can
+// consider them to be just byte strings.  For example, due to the
+// design of UTF-8 you do not need to worry about accidental matches,
+// as long as all your inputs are valid UTF-8 (use \uHHHH, not \xHH or \oOOO).
+
+#ifndef FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_UTIL_STRING_UTIL_H_
+#define FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_UTIL_STRING_UTIL_H_
+
+#include <string>
+
+#include "absl/strings/string_view.h"
+
+namespace firebase {
+namespace firestore {
+namespace util {
+
+/*
+ * Returns the smallest lexicographically larger string of equal or smaller
+ * length. Returns an empty string if there is no such successor (if the input
+ * is empty or consists entirely of 0xff bytes).
+ * Useful for calculating the smallest lexicographically larger string
+ * that will not be prefixed by the input string.
+ *
+ * Examples:
+ * "a" -> "b", "aaa" -> "aab", "aa\xff" -> "ab", "\xff" -> "", "" -> ""
+ */
+std::string PrefixSuccessor(absl::string_view prefix);
+
+/*
+ * Returns the immediate lexicographically-following string. This is useful to
+ * turn an inclusive range into something that can be used with Bigtable's
+ * SetLimitRow():
+ *
+ *     // Inclusive range [min_element, max_element].
+ *     string min_element = ...;
+ *     string max_element = ...;
+ *
+ *     // Equivalent range [range_start, range_end).
+ *     string range_start = min_element;
+ *     string range_end = ImmediateSuccessor(max_element);
+ *
+ * WARNING: Returns the input string with a '\0' appended; if you call c_str()
+ * on the result, it will compare equal to s.
+ *
+ * WARNING: Transforms "" -> "\0"; this doesn't account for Bigtable's special
+ * treatment of "" as infinity.
+ */
+std::string ImmediateSuccessor(absl::string_view s);
+
+}  // namespace util
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_UTIL_STRING_UTIL_H_
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/Port/string_util_test.cc b/Firestore/core/test/firebase/firestore/util/string_util_test.cc
index 331f96e..f94596f 100644
--- a/Firestore/Port/string_util_test.cc
+++ b/Firestore/core/test/firebase/firestore/util/string_util_test.cc
@@ -14,16 +14,15 @@
  * limitations under the License.
  */
 
-#include "Firestore/Port/string_util.h"
+#include "Firestore/core/src/firebase/firestore/util/string_util.h"
 
 #include <gtest/gtest.h>
-#include <leveldb/db.h>
 
-using Firestore::PrefixSuccessor;
-using Firestore::ImmediateSuccessor;
-using leveldb::Slice;
+namespace firebase {
+namespace firestore {
+namespace util {
 
-TEST(Util, PrefixSuccessor) {
+TEST(StringUtil, PrefixSuccessor) {
   EXPECT_EQ(PrefixSuccessor("a"), "b");
   EXPECT_EQ(PrefixSuccessor("aaAA"), "aaAB");
   EXPECT_EQ(PrefixSuccessor("aaa\xff"), "aab");
@@ -33,7 +32,11 @@ TEST(Util, PrefixSuccessor) {
   EXPECT_EQ(PrefixSuccessor(""), "");
 }
 
-TEST(Util, ImmediateSuccessor) {
-  EXPECT_EQ(ImmediateSuccessor("hello"), Slice("hello\0", 6));
-  EXPECT_EQ(ImmediateSuccessor(""), Slice("\0", 1));
+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