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

3 files changed, 14 insertions, 8 deletions

diff --git a/Firestore/Source/Local/FSTDocumentReference.h b/Firestore/Source/Local/FSTDocumentReference.h
index eff60e4..04b8416 100644
--- a/Firestore/Source/Local/FSTDocumentReference.h
+++ b/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
 
diff --git a/Firestore/Source/Local/FSTDocumentReference.m b/Firestore/Source/Local/FSTDocumentReference.mm
index 25a5935..4310baa 100644
--- a/Firestore/Source/Local/FSTDocumentReference.m
+++ b/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 @@ const NSComparator FSTDocumentReferenceComparatorByKey =
       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;
       }
diff --git a/Firestore/Source/Local/FSTMemoryMutationQueue.m b/Firestore/Source/Local/FSTMemoryMutationQueue.mm
index b155264..702f614 100644
--- a/Firestore/Source/Local/FSTMemoryMutationQueue.m
+++ b/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 @@ NS_ASSUME_NONNULL_BEGIN
 
   // 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]) {