Implement RC1 optimization

Author: ndossche

ext/spl/spl_iterators.c

@@ -3081,11 +3081,25 @@ static zend_result spl_iterator_zip_valid(zend_object_iterator *iter)
 	return SUCCESS;
 }
 
+/* Invariant: returned array is packed and has all UNDEF elements. */
 static zend_array *spl_iterator_zip_reset_array(spl_zip_iterator *zip_iterator)
 {
 	zval *array_zv = &zip_iterator->intern.data;
 
-	// TODO: optimize: reuse array if RC1
+	/* Reuse array if it's RC1 */
+	if (!Z_ISUNDEF_P(array_zv) && Z_REFCOUNT_P(array_zv) == 1) {
+		zend_array *array = Z_ARR_P(array_zv);
+		if (HT_IS_PACKED(array)
+		 && array->nNumUsed == zip_iterator->iterator_count
+		 && array->nNumOfElements == zip_iterator->iterator_count) {
+			array->nNextFreeElement = zip_iterator->iterator_count;
+			for (uint32_t i = 0; i < zip_iterator->iterator_count; i++) {
+				zval_ptr_dtor(&array->arPacked[i]);
+				ZVAL_UNDEF(&array->arPacked[i]);
+			}
+			return array;
+		}
+	}
 
 	zval_ptr_dtor(array_zv);