Port comparison to C++ (#678)

This reimplements our comparison functions as C++ Comparators and then provides compatibility shims for interoperating with existing Objective-C usage.

A few specialized comparators aren't suitable for porting but only have a single usage (e.g. CompareBytes for comparing NSData * instances). In these cases I've moved them into the caller.

* Use int32_t for typeof(ID) in FSTDocumentReference

* Migrate callers of FSTComparison.h to Objective-C++

* Port comparison to C++

* Migrate usages of FSTComparison.h to C++ equivalents

* Remove FSTComparison

Firestore/Example/Firestore.xcodeproj/project.pbxproj

@@ -30,6 +30,7 @@
 		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 */; };
 		5491BC721FB44593008B3588 /* FSTIntegrationTestCase.mm in Sources */ = {isa = PBXBuildFile; fileRef = 5491BC711FB44593008B3588 /* FSTIntegrationTestCase.mm */; };
 		5491BC731FB44593008B3588 /* FSTIntegrationTestCase.mm in Sources */ = {isa = PBXBuildFile; fileRef = 5491BC711FB44593008B3588 /* FSTIntegrationTestCase.mm */; };
 		54C2294F1FECABAE007D065B /* log_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = 54C2294E1FECABAE007D065B /* log_test.cc */; };
@@ -148,7 +149,6 @@
 		DE51B1FD1F0D492C0013853F /* FSTSpecTests.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1991F0D48AC0013853F /* FSTSpecTests.m */; };
 		DE51B1FE1F0D492C0013853F /* FSTSyncEngineTestDriver.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B19B1F0D48AC0013853F /* FSTSyncEngineTestDriver.m */; };
 		DE51B1FF1F0D493A0013853F /* FSTAssertTests.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1861F0D48AC0013853F /* FSTAssertTests.m */; };
-		DE51B2001F0D493A0013853F /* FSTComparisonTests.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1871F0D48AC0013853F /* FSTComparisonTests.m */; };
 		DE51B2011F0D493E0013853F /* FSTHelpers.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1891F0D48AC0013853F /* FSTHelpers.m */; };
 		F104BBD69BC3F0796E3A77C1 /* Pods_Firestore_Tests.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 69F6A10DBD6187489481CD76 /* Pods_Firestore_Tests.framework */; };
 /* End PBXBuildFile section */
@@ -204,6 +204,7 @@
 		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>"; };
 		5491BC711FB44593008B3588 /* FSTIntegrationTestCase.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = FSTIntegrationTestCase.mm; sourceTree = "<group>"; };
 		54C2294E1FECABAE007D065B /* log_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = log_test.cc; path = ../../core/test/firebase/firestore/util/log_test.cc; sourceTree = "<group>"; };
 		54DA129C1F315EE100DD57A1 /* collection_spec_test.json */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.json; path = collection_spec_test.json; sourceTree = "<group>"; };
@@ -308,7 +309,6 @@
 		DE51B1821F0D48AC0013853F /* FSTPathTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTPathTests.m; sourceTree = "<group>"; };
 		DE51B1841F0D48AC0013853F /* FIRGeoPointTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FIRGeoPointTests.m; sourceTree = "<group>"; };
 		DE51B1861F0D48AC0013853F /* FSTAssertTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTAssertTests.m; sourceTree = "<group>"; };
-		DE51B1871F0D48AC0013853F /* FSTComparisonTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTComparisonTests.m; sourceTree = "<group>"; };
 		DE51B1881F0D48AC0013853F /* FSTHelpers.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = FSTHelpers.h; sourceTree = "<group>"; };
 		DE51B1891F0D48AC0013853F /* FSTHelpers.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTHelpers.m; sourceTree = "<group>"; };
 		DE51B1941F0D48AC0013853F /* FSTLevelDBSpecTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTLevelDBSpecTests.m; sourceTree = "<group>"; };
@@ -400,6 +400,7 @@
 			children = (
 				548DB926200D590300E00ABC /* assert_test.cc */,
 				54740A521FC913E500713A1A /* autoid_test.cc */,
+				548DB928200D59F600E00ABC /* comparison_test.cc */,
 				54C2294E1FECABAE007D065B /* log_test.cc */,
 				54740A531FC913E500713A1A /* secure_random_test.cc */,
 				5436F32320008FAD006E51E3 /* string_printf_test.cc */,
@@ -646,7 +647,6 @@
 				54E9281E1F33950B00C1953E /* FSTIntegrationTestCase.h */,
 				5491BC711FB44593008B3588 /* FSTIntegrationTestCase.mm */,
 				DE51B1861F0D48AC0013853F /* FSTAssertTests.m */,
-				DE51B1871F0D48AC0013853F /* FSTComparisonTests.m */,
 				DE51B1881F0D48AC0013853F /* FSTHelpers.h */,
 				DE51B1891F0D48AC0013853F /* FSTHelpers.m */,
 				54E9282A1F339CAD00C1953E /* XCTestCase+Await.h */,
@@ -1210,7 +1210,6 @@
 				DE2EF0881F3D0B6E003D0CDC /* FSTTreeSortedDictionaryTests.m in Sources */,
 				DE51B1FD1F0D492C0013853F /* FSTSpecTests.m in Sources */,
 				ABAEEF4F1FD5F8B100C966CB /* FIRQueryTests.m in Sources */,
-				DE51B2001F0D493A0013853F /* FSTComparisonTests.m in Sources */,
 				ABF341051FE860CA00C48322 /* FSTAPIHelpers.m in Sources */,
 				DE51B1CC1F0D48C00013853F /* FIRGeoPointTests.m in Sources */,
 				DE51B1E11F0D490D0013853F /* FSTMemoryRemoteDocumentCacheTests.m in Sources */,
@@ -1276,6 +1275,7 @@
 				DE51B1E41F0D490D0013853F /* FSTQueryCacheTests.m in Sources */,
 				DE51B1CD1F0D48CD0013853F /* FSTDatabaseInfoTests.m in Sources */,
 				AB382F7E1FE03059007CA955 /* FIRFieldPathTests.m in Sources */,
+				548DB929200D59F600E00ABC /* comparison_test.cc in Sources */,
 				DE51B1F21F0D49140013853F /* FSTPathTests.m in Sources */,
 				AB99452C1FE3018D00DFC1E6 /* FIRQuerySnapshotTests.m in Sources */,
 				54740A571FC914BA00713A1A /* secure_random_test.cc in Sources */,

Firestore/Source/API/FIRGeoPoint.m → Firestore/Source/API/FIRGeoPoint.mm

@@ -16,9 +16,14 @@
 
 #import "Firestore/Source/API/FIRGeoPoint+Internal.h"
 
-#import "Firestore/Source/Util/FSTComparison.h"
+#import "Firestore/core/src/firebase/firestore/util/comparison.h"
+
 #import "Firestore/Source/Util/FSTUsageValidation.h"
 
+using firebase::firestore::util::DoubleBitwiseEquals;
+using firebase::firestore::util::DoubleBitwiseHash;
+using firebase::firestore::util::WrapCompare;
+
 NS_ASSUME_NONNULL_BEGIN
 
 @implementation FIRGeoPoint
@@ -45,11 +50,11 @@ - (instancetype)initWithLatitude:(double)latitude longitude:(double)longitude {
 }
 
 - (NSComparisonResult)compare:(FIRGeoPoint *)other {
-  NSComparisonResult result = FSTCompareDoubles(self.latitude, other.latitude);
+  NSComparisonResult result = WrapCompare<double>(self.latitude, other.latitude);
   if (result != NSOrderedSame) {
     return result;
   } else {
-    return FSTCompareDoubles(self.longitude, other.longitude);
+    return WrapCompare<double>(self.longitude, other.longitude);
   }
 }
 
@@ -67,12 +72,12 @@ - (BOOL)isEqual:(id)other {
     return NO;
   }
   FIRGeoPoint *otherGeoPoint = (FIRGeoPoint *)other;
-  return FSTDoubleBitwiseEquals(self.latitude, otherGeoPoint.latitude) &&
-         FSTDoubleBitwiseEquals(self.longitude, otherGeoPoint.longitude);
+  return DoubleBitwiseEquals(self.latitude, otherGeoPoint.latitude) &&
+         DoubleBitwiseEquals(self.longitude, otherGeoPoint.longitude);
 }
 
 - (NSUInteger)hash {
-  return 31 * FSTDoubleBitwiseHash(self.latitude) + FSTDoubleBitwiseHash(self.longitude);
+  return 31 * DoubleBitwiseHash(self.latitude) + DoubleBitwiseHash(self.longitude);
 }
 
 /** Implements NSCopying without actually copying because geopoints are immutable. */

Firestore/Source/Core/FSTTimestamp.m → Firestore/Source/Core/FSTTimestamp.mm

@@ -16,8 +16,11 @@
 
 #import "Firestore/Source/Core/FSTTimestamp.h"
 
+#include "Firestore/core/src/firebase/firestore/util/comparison.h"
+
 #import "Firestore/Source/Util/FSTAssert.h"
-#import "Firestore/Source/Util/FSTComparison.h"
+
+using firebase::firestore::util::WrapCompare;
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -110,11 +113,11 @@ - (NSString *)ISO8601String {
 }
 
 - (NSComparisonResult)compare:(FSTTimestamp *)other {
-  NSComparisonResult result = FSTCompareInt64s(self.seconds, other.seconds);
+  NSComparisonResult result = WrapCompare<int64_t>(self.seconds, other.seconds);
   if (result != NSOrderedSame) {
     return result;
   }
-  return FSTCompareInt32s(self.nanos, other.nanos);
+  return WrapCompare<int32_t>(self.nanos, other.nanos);
 }
 
 @end

Firestore/Source/Local/FSTDocumentReference.h

@@ -32,7 +32,7 @@ NS_ASSUME_NONNULL_BEGIN
 @interface FSTDocumentReference : NSObject <NSCopying>
 
 /** Initializes the document reference with the given key and ID. */
-- (instancetype)initWithKey:(FSTDocumentKey *)key ID:(int)ID NS_DESIGNATED_INITIALIZER;
+- (instancetype)initWithKey:(FSTDocumentKey *)key ID:(int32_t)ID NS_DESIGNATED_INITIALIZER;
 
 - (instancetype)init NS_UNAVAILABLE;
 
@@ -43,7 +43,7 @@ NS_ASSUME_NONNULL_BEGIN
  * The targetID of a referring target or the batchID of a referring mutation batch. (Which this
  * is depends upon which FSTReferenceSet this reference is a part of.)
  */
-@property(nonatomic, assign, readonly) int ID;
+@property(nonatomic, assign, readonly) int32_t ID;
 
 @end
 

Firestore/Source/Local/FSTDocumentReference.m → Firestore/Source/Local/FSTDocumentReference.mm

@@ -16,14 +16,17 @@
 
 #import "Firestore/Source/Local/FSTDocumentReference.h"
 
+#include "Firestore/core/src/firebase/firestore/util/comparison.h"
+
 #import "Firestore/Source/Model/FSTDocumentKey.h"
-#import "Firestore/Source/Util/FSTComparison.h"
+
+using firebase::firestore::util::WrapCompare;
 
 NS_ASSUME_NONNULL_BEGIN
 
 @implementation FSTDocumentReference
 
-- (instancetype)initWithKey:(FSTDocumentKey *)key ID:(int)ID {
+- (instancetype)initWithKey:(FSTDocumentKey *)key ID:(int32_t)ID {
   self = [super init];
   if (self) {
     _key = key;
@@ -67,13 +70,13 @@ - (id)copyWithZone:(nullable NSZone *)zone {
       if (result != NSOrderedSame) {
         return result;
       }
-      return FSTCompareInts(left.ID, right.ID);
+      return WrapCompare<int32_t>(left.ID, right.ID);
     };
 
 /** Sorts document references by ID then key. */
 const NSComparator FSTDocumentReferenceComparatorByID =
     ^NSComparisonResult(FSTDocumentReference *left, FSTDocumentReference *right) {
-      NSComparisonResult result = FSTCompareInts(left.ID, right.ID);
+      NSComparisonResult result = WrapCompare<int32_t>(left.ID, right.ID);
       if (result != NSOrderedSame) {
         return result;
       }

Firestore/Source/Local/FSTMemoryMutationQueue.m → Firestore/Source/Local/FSTMemoryMutationQueue.mm

@@ -23,10 +23,13 @@
 #import "Firestore/Source/Model/FSTMutationBatch.h"
 #import "Firestore/Source/Model/FSTPath.h"
 #import "Firestore/Source/Util/FSTAssert.h"
-#import "Firestore/Source/Util/FSTComparison.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
+static const NSComparator NumberComparator = ^NSComparisonResult(NSNumber *left, NSNumber *right) {
+  return [left compare:right];
+};
+
 @interface FSTMemoryMutationQueue ()
 
 /**
@@ -260,7 +263,7 @@ - (nullable FSTMutationBatch *)nextMutationBatchAfterBatchID:(FSTBatchID)batchID
 
   // Find unique batchIDs referenced by all documents potentially matching the query.
   __block FSTImmutableSortedSet<NSNumber *> *uniqueBatchIDs =
-      [FSTImmutableSortedSet setWithComparator:FSTNumberComparator];
+      [FSTImmutableSortedSet setWithComparator:NumberComparator];
   FSTDocumentReferenceBlock block = ^(FSTDocumentReference *reference, BOOL *stop) {
     FSTResourcePath *rowKeyPath = reference.key.path;
     if (![prefix isPrefixOfPath:rowKeyPath]) {