diff --git a/CMakeLists.txt b/CMakeLists.txt
index c1f0190..6a9fc6d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -145,6 +145,7 @@ set(SOURCE_FILE_HEADERS
     http_client.h
     stack.h
     linked_stack.h
+    circular_queue.h
 )
 
 if (NOT HAVE_STRPTIME)
@@ -194,8 +195,8 @@ if (ENABLE_UTILS_TESTING)
     set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
     add_subdirectory(googletest)
     enable_testing()
-    add_executable(stack_test test/stack_test.cpp)
-    target_link_libraries(stack_test GTest::gtest_main utils)
+    add_executable(unittest test/stack_test.cpp test/queue_test.cpp)
+    target_link_libraries(unittest GTest::gtest_main utils)
     include(GoogleTest)
-    gtest_discover_tests(stack_test)
+    gtest_discover_tests(unittest)
 endif()
diff --git a/circular_queue.h b/circular_queue.h
new file mode 100644
index 0000000..750ce11
--- /dev/null
+++ b/circular_queue.h
@@ -0,0 +1,131 @@
+#ifndef _UTIL_CIRCULAR_QUEUE_H
+#define _UTIL_CIRCULAR_QUEUE_H
+#include <functional>
+#include <malloc.h>
+#include <stddef.h>
+
+template <typename T>
+struct CircularQueue {
+    T* base;
+    size_t front;
+    size_t rear;
+    size_t size;
+};
+
+template <typename T>
+bool init_circular_queue(struct CircularQueue<T>& queue, size_t size) {
+    if (size < 2) {
+        return false;
+    }
+    queue.base = (T*)malloc(size * sizeof(T));
+    if (!queue.base) {
+        return false;
+    }
+    queue.front = 0;
+    queue.rear = 0;
+    queue.size = size;
+    return true;
+}
+
+template <typename T>
+void free_circular_queue(struct CircularQueue<T>& queue, std::function<void(T)> free_func = std::function<void(T)>()) {
+    if (!queue.base) return;
+    if (queue.front == queue.rear) return;
+    if (free_func) {
+        circular_queue_iter(queue, free_func);
+    }
+    free(queue.base);
+    queue.base = nullptr;
+    queue.front = 0;
+    queue.rear = 0;
+    queue.size = 0;
+}
+
+template <typename T, class F>
+inline void free_circular_queue(struct CircularQueue<T>& queue, F free_func) {
+    free_circular_queue(queue, std::function<void(T)>(free_func));
+}
+
+template <typename T>
+void circular_queue_clear(struct CircularQueue<T>& queue, std::function<void(T)> free_func = std::function<void(T)>()) {
+    if (!queue.base) return;
+    if (free_func && queue.front != queue.rear) {
+        circular_queue_iter(queue, free_func);
+    }
+    queue.front = 0;
+    queue.rear = 0;
+}
+
+template <typename T, class F>
+inline void circular_queue_clear(struct CircularQueue<T>& queue, F free_func) {
+    circular_queue_clear(queue, std::function<void(T)>(free_func));
+}
+
+template <typename T>
+bool circular_queue_is_empty(struct CircularQueue<T>& queue) {
+    if (!queue.base) return true;
+    return queue.front == queue.rear;
+}
+
+template <typename T>
+bool circular_queue_is_full(struct CircularQueue<T>& queue) {
+    if (!queue.base) return false;
+    return (queue.rear + 1) % queue.size == queue.front;
+}
+
+template <typename T>
+size_t circular_queue_length(struct CircularQueue<T>& queue) {
+    if (!queue.base) return 0;
+    return queue.rear >= queue.front ? queue.rear - queue.front : queue.rear + queue.size - queue.front;
+}
+
+template <typename T>
+bool circular_queue_get_head(struct CircularQueue<T>& queue, T& head) {
+    if (!queue.base || queue.rear == queue.front) return false;
+    head = queue.base[queue.front];
+    return true;
+}
+
+template <typename T>
+bool circular_queue_get_back(struct CircularQueue<T>& queue, T& back) {
+    if (!queue.base || queue.rear == queue.front) return false;
+    size_t pos = queue.rear ? queue.rear - 1 : queue.size - 1;
+    back = queue.base[pos];
+    return true;
+}
+
+template <typename T>
+bool circular_queue_push(struct CircularQueue<T>& queue, T data) {
+    if (!queue.base) return false;
+    if ((queue.rear + 1) % queue.size == queue.front) return false;
+    queue.base[queue.rear++] = data;
+    queue.rear %= queue.size;
+    return true;
+}
+
+template <typename T>
+bool circular_queue_pop(struct CircularQueue<T>& queue, T& data) {
+    if (!queue.base) return false;
+    if (queue.rear == queue.front) return false;
+    data = queue.base[queue.front++];
+    queue.front %= queue.size;
+    return true;
+}
+
+template <typename T, typename ... Args>
+void circular_queue_iter(struct CircularQueue<T>& queue, std::function<void(T, Args...)> callback, Args... args) {
+    if (!queue.base || !callback) return;
+    if (queue.front == queue.rear) return;
+    size_t now = queue.front;
+    while (now != queue.rear) {
+        callback(queue.base[now], args...);
+        now = (now + 1) % queue.size;
+    }
+}
+
+template <typename T, class F, typename ... Args>
+inline void circular_queue_iter(struct CircularQueue<T>& queue, F callback, Args... args) {
+    circular_queue_iter(queue, std::function<void(T, Args...)>(callback), args...);
+}
+
+#endif
diff --git a/linked_stack.h b/linked_stack.h
index 09dfa1f..c8c2317 100644
--- a/linked_stack.h
+++ b/linked_stack.h
@@ -37,7 +37,7 @@ void linked_stack_clear(struct LinkedStack<T>*& top, std::function<void(T)> free
 }
 
 template <typename T, class F>
-void linked_stack_clear(struct LinkedStack<T>*& top, F free_func) {
+inline void linked_stack_clear(struct LinkedStack<T>*& top, F free_func) {
     linked_stack_clear(top, std::function<void(T)>(free_func));
 }
 
@@ -74,7 +74,7 @@ void linked_stack_iter(struct LinkedStack<T>* top, std::function<void(T, Args...
 }
 
 template <typename T, class F, typename ... Args>
-void linked_stack_iter(struct LinkedStack<T>* top, F callback, Args... args) {
+inline void linked_stack_iter(struct LinkedStack<T>* top, F callback, Args... args) {
     linked_stack_iter(top, std::function<void(T, Args...)>(callback), args...);
 }
 
diff --git a/test/queue_test.cpp b/test/queue_test.cpp
new file mode 100644
index 0000000..2ba430d
--- /dev/null
+++ b/test/queue_test.cpp
@@ -0,0 +1,83 @@
+#include "gtest/gtest.h"
+#include "circular_queue.h"
+#include <string>
+
+TEST(Queue_Test, CircularQueue1) {
+    struct CircularQueue<int> queue;
+    EXPECT_EQ(init_circular_queue(queue, 3), true);
+    EXPECT_EQ(circular_queue_is_empty(queue), true);
+    int v;
+    EXPECT_EQ(circular_queue_get_back(queue, v), false);
+    EXPECT_EQ(circular_queue_get_head(queue, v), false);
+    EXPECT_EQ(circular_queue_pop(queue, v), false);
+    EXPECT_EQ(circular_queue_push(queue, 1), true);
+    EXPECT_EQ(circular_queue_push(queue, 2), true);
+    EXPECT_EQ(circular_queue_is_full(queue), true);
+    EXPECT_EQ(circular_queue_is_empty(queue), false);
+    EXPECT_EQ(circular_queue_push(queue, 3), false);
+    EXPECT_EQ(circular_queue_pop(queue, v), true);
+    EXPECT_EQ(v, 1);
+    EXPECT_EQ(circular_queue_is_full(queue), false);
+    EXPECT_EQ(circular_queue_push(queue, 3), true);
+    EXPECT_EQ(circular_queue_get_head(queue, v), true);
+    EXPECT_EQ(v, 2);
+    EXPECT_EQ(circular_queue_get_back(queue, v), true);
+    EXPECT_EQ(v, 3);
+    EXPECT_EQ(circular_queue_length(queue), 2);
+    EXPECT_EQ(queue.front, 1);
+    EXPECT_EQ(queue.rear, 0);
+    std::string text;
+    circular_queue_iter(queue, [&text](int ele) {
+        if (!text.empty()) {
+            text += ",";
+        }
+        text += std::to_string(ele);
+    });
+    EXPECT_EQ(text, "2,3");
+    EXPECT_EQ(circular_queue_pop(queue, v), true);
+    EXPECT_EQ(v, 2);
+    EXPECT_EQ(queue.front, 2);
+    EXPECT_EQ(circular_queue_length(queue), 1);
+    EXPECT_EQ(circular_queue_push(queue, 4), true);
+    EXPECT_EQ(circular_queue_pop(queue, v), true);
+    EXPECT_EQ(v, 3);
+    EXPECT_EQ(queue.front, 0);
+    EXPECT_EQ(queue.rear, 1);
+    circular_queue_clear(queue);
+    EXPECT_EQ(queue.rear, 0);
+    EXPECT_EQ(circular_queue_is_empty(queue), true);
+    free_circular_queue(queue);
+}
+
+TEST(Queue_Test, CircularQueue2) {
+    struct CircularQueue<int> queue;
+    EXPECT_EQ(init_circular_queue(queue, 5), true);
+    EXPECT_EQ(circular_queue_push(queue, 1), true);
+    EXPECT_EQ(circular_queue_push(queue, 2), true);
+    EXPECT_EQ(circular_queue_push(queue, 3), true);
+    EXPECT_EQ(circular_queue_push(queue, 4), true);
+    std::string text;
+    circular_queue_iter(queue, [&text](int ele) {
+        if (!text.empty()) {
+            text += ",";
+        }
+        text += std::to_string(ele);
+    });
+    EXPECT_EQ(text, "1,2,3,4");
+    int v;
+    EXPECT_EQ(circular_queue_pop(queue, v), true);
+    EXPECT_EQ(v, 1);
+    EXPECT_EQ(circular_queue_push(queue, 5), true);
+    EXPECT_EQ(circular_queue_length(queue), 4);
+    EXPECT_EQ(queue.front, 1);
+    EXPECT_EQ(queue.rear, 0);
+    text = "";
+    circular_queue_iter(queue, [&text](int ele) {
+        if (!text.empty()) {
+            text += ",";
+        }
+        text += std::to_string(ele);
+    });
+    EXPECT_EQ(text, "2,3,4,5");
+    free_circular_queue(queue);
+}