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

1 files changed, 86 insertions, 0 deletions

diff --git a/Firestore/Source/Local/FSTDocumentReference.mm b/Firestore/Source/Local/FSTDocumentReference.mm
new file mode 100644
index 0000000..4310baa
--- /dev/null
+++ b/Firestore/Source/Local/FSTDocumentReference.mm
@@ -0,0 +1,86 @@
+/*
+ * 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.
+ */
+
+#import "Firestore/Source/Local/FSTDocumentReference.h"
+
+#include "Firestore/core/src/firebase/firestore/util/comparison.h"
+
+#import "Firestore/Source/Model/FSTDocumentKey.h"
+
+using firebase::firestore::util::WrapCompare;
+
+NS_ASSUME_NONNULL_BEGIN
+
+@implementation FSTDocumentReference
+
+- (instancetype)initWithKey:(FSTDocumentKey *)key ID:(int32_t)ID {
+  self = [super init];
+  if (self) {
+    _key = key;
+    _ID = ID;
+  }
+  return self;
+}
+
+- (BOOL)isEqual:(id)other {
+  if (other == self) return YES;
+  if (![[other class] isEqual:[self class]]) return NO;
+
+  FSTDocumentReference *reference = (FSTDocumentReference *)other;
+
+  return [self.key isEqualToKey:reference.key] && self.ID == reference.ID;
+}
+
+- (NSUInteger)hash {
+  NSUInteger result = [self.key hash];
+  result = result * 31u + self.ID;
+  return result;
+}
+
+- (NSString *)description {
+  return [NSString stringWithFormat:@"<FSTDocumentReference: key=%@, ID=%d>", self.key, self.ID];
+}
+
+- (id)copyWithZone:(nullable NSZone *)zone {
+  // FSTDocumentReference is immutable
+  return self;
+}
+
+@end
+
+#pragma mark Comparators
+
+/** Sorts document references by key then ID. */
+const NSComparator FSTDocumentReferenceComparatorByKey =
+    ^NSComparisonResult(FSTDocumentReference *left, FSTDocumentReference *right) {
+      NSComparisonResult result = FSTDocumentKeyComparator(left.key, right.key);
+      if (result != NSOrderedSame) {
+        return result;
+      }
+      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 = WrapCompare<int32_t>(left.ID, right.ID);
+      if (result != NSOrderedSame) {
+        return result;
+      }
+      return FSTDocumentKeyComparator(left.key, right.key);
+    };
+
+NS_ASSUME_NONNULL_END