Simplify usage of diffing API

AsyncDisplayKit/ASDisplayNode.mm

@@ -21,6 +21,7 @@
 #import "_ASCoreAnimationExtras.h"
 #import "ASDisplayNodeExtras.h"
 #import "ASEqualityHelpers.h"
+#import "NSArray+Diffing.h"
 
 #import "ASInternalHelpers.h"
 #import "ASLayout.h"

AsyncDisplayKit/Private/NSArray+Diffing.h

@@ -13,6 +13,6 @@
 /**
  * Uses a bottom-up memoized longest common subsequence solution to identify differences. Runs in O(mn) complexity.
  */
-- (void)asdk_diffWithArray:(NSArray *)array insertions:(NSMutableIndexSet **)insertions deletions:(NSMutableIndexSet **)deletions;
+- (void)asdk_diffWithArray:(NSArray *)array insertions:(NSIndexSet **)insertions deletions:(NSIndexSet **)deletions;
 
 @end

AsyncDisplayKit/Private/NSArray+Diffing.m

@@ -10,28 +10,32 @@
 
 @implementation NSArray (Diffing)
 
-- (void)asdk_diffWithArray:(NSArray *)array insertions:(NSMutableIndexSet **)insertions deletions:(NSMutableIndexSet **)deletions
+- (void)asdk_diffWithArray:(NSArray *)array insertions:(NSIndexSet **)insertions deletions:(NSIndexSet **)deletions
 {
   NSIndexSet *commonIndexes = [self _asdk_commonIndexesWithArray:array];
   
   if (insertions) {
     NSArray *commonObjects = [self objectsAtIndexes:commonIndexes];
+    NSMutableIndexSet *insertionIndexes = [NSMutableIndexSet indexSet];
     for (NSInteger i = 0, j = 0; i < commonObjects.count || j < array.count;) {
       if (i < commonObjects.count && j < array.count && [commonObjects[i] isEqual:array[j]]) {
         i++; j++;
       } else {
-        [*insertions addIndex:j];
+        [insertionIndexes addIndex:j];
         j++;
       }
     }
+    *insertions = insertionIndexes;
   }
   
   if (deletions) {
+    NSMutableIndexSet *deletionIndexes = [NSMutableIndexSet indexSet];
     for (NSInteger i = 0; i < self.count; i++) {
       if (![commonIndexes containsIndex:i]) {
-        [*deletions addIndex:i];
+        [deletionIndexes addIndex:i];
       }
     }
+    *deletions = deletionIndexes;
   }
 }
 

AsyncDisplayKitTests/ArrayDiffingTests.m

@@ -57,8 +57,7 @@
   ];
   
   for (NSArray *test in tests) {
-    NSMutableIndexSet *insertions = [NSMutableIndexSet indexSet];
-    NSMutableIndexSet *deletions = [NSMutableIndexSet indexSet];
+    NSIndexSet *insertions, *deletions;
     [test[0] asdk_diffWithArray:test[1] insertions:&insertions deletions:&deletions];
     for (NSNumber *index in (NSArray *)test[2]) {
       XCTAssert([insertions containsIndex:[index integerValue]]);