Get differences between two NSArrays (for animating table view changes)

arrayDiff.m

void arrayDiff(NSArray *array1, NSArray *array2, NSSet **objectsToAdd, NSSet **objectsToRemove, NSSet **objectsInBoth) {
    if (array1 == nil) {
        *objectsToAdd = [NSSet setWithArray:array2];
        *objectsToRemove = [NSSet set];
        *objectsInBoth = [NSSet set];
    }

    else if (array2 == nil) {
        *objectsToAdd = [NSSet set];
        *objectsToRemove = [NSSet setWithArray:array1];
        *objectsInBoth = [NSSet set];
    }

    else {
        NSMutableArray *toAdd = [array2 mutableCopy];
        [toAdd removeObjectsInArray:array1];
        *objectsToAdd = [NSSet setWithArray:toAdd];

        NSMutableArray *toRemove = [array1 mutableCopy];
        [toRemove removeObjectsInArray:array2];
        *objectsToRemove = [NSSet setWithArray:toRemove];

        NSMutableArray *inBoth = [array2 mutableCopy];
        [inBoth removeObjectsInArray:toAdd];
        *objectsInBoth = [NSSet setWithArray:inBoth];
    }
}