Handle empty bulk enqueue

Author: caomengxuan666

include/daking/MPSC_queue.hpp

@@ -486,6 +486,9 @@ namespace daking {
         DAKING_ALWAYS_INLINE void enqueue_bulk(const_reference value, size_type n) {
             // N times thread_local operation, One time CAS operation.
             // So it is more efficient than N times enqueue.
+            if (n == 0) {
+                return;
+            }
 
             node_t* first_new_node = _allocate();
             node_t* prev_node = first_new_node;
@@ -511,6 +514,9 @@ namespace daking {
                 "Iterator must be at least input iterator.");
             static_assert(std::is_same_v<typename std::iterator_traits<InputIt>::value_type, value_type>,
                 "The value type of iterator must be same as MPSC_queue::value_type.");
+            if (n == 0) {
+                return;
+            }
 
             node_t* first_new_node = _allocate();
             node_t* prev_node = first_new_node;
@@ -743,4 +749,4 @@ namespace daking {
     };
 }
 
-#endif // !DAKING_MPSC_QUEUE_HPP
+#endif // !DAKING_MPSC_QUEUE_HPP

tests/test_MPSC.cpp

@@ -133,6 +133,21 @@ TEST(MPSCQueueBulkTest, EnqueueBulk_InputIterator) {
 	EXPECT_TRUE(queue.empty());
 }
 
+TEST(MPSCQueueBulkTest, EnqueueBulk_EmptyRangeIsNoOp) {
+	TestQueue queue;
+	const int value = 99;
+	std::vector<int> data;
+
+	queue.enqueue_bulk(value, 0);
+	EXPECT_TRUE(queue.empty());
+
+	queue.enqueue_bulk(data.begin(), data.size());
+	EXPECT_TRUE(queue.empty());
+
+	queue.enqueue_bulk(data.begin(), data.end());
+	EXPECT_TRUE(queue.empty());
+}
+
 TEST(MPSCQueueBulkTest, TryDequeueBulk_Partial) {
 	TestQueue queue;
 	queue.enqueue(1);
@@ -306,4 +321,4 @@ TEST(MPSCQueueBlockTest, DequeueBulk_BlockAndWait) {
 	EXPECT_EQ(results[2], 3);
 	EXPECT_TRUE(queue.empty());
 }
-#endif
+#endif