Reapply "lab6 bash exercises"

This reverts commit 8aea945eed.

include/buffer.h

@@ -1,28 +0,0 @@
-//
-// Created by lumijiez on 11/16/24.
-//
-
-#ifndef BUFFER_H
-#define BUFFER_H
-
-#include <queue>
-#include <mutex>
-#include <condition_variable>
-
-class Buffer {
-public:
-    explicit Buffer(int size);
-    void produce(int producerId, int item);
-    int consume(int consumerId);
-    bool isEmpty() const;
-    bool isFull() const;
-
-private:
-    std::queue<int> items;
-    const int maxSize;
-    mutable std::mutex mtx;
-    std::condition_variable notFull;
-    std::condition_variable notEmpty;
-};
-
-#endif //BUFFER_H