chore: import upstream snapshot with attribution

source/backend/cpu/ThreadPool.hpp

@@ -0,0 +1,58 @@
+//
+//  ThreadPool.hpp
+//  MNN
+//
+//  Created by MNN on 2019/06/30.
+//  Copyright © 2018, Alibaba Group Holding Limited
+//
+
+#ifndef CPU_INTHREADPOOL_H
+#define CPU_INTHREADPOOL_H
+#ifdef MNN_USE_THREAD_POOL
+#include <condition_variable>
+#include <functional>
+#include <mutex>
+#include <thread>
+#include <vector>
+#include <atomic>
+#include <MNN/MNNDefine.h>
+namespace MNN {
+
+class MNN_PUBLIC ThreadPool {
+public:
+    typedef std::pair<std::function<void(int)>, int> TASK;
+
+    int numberThread() const {
+        return mNumberThread;
+    }
+    void enqueue(TASK* task, int index);
+
+    void active();
+    void deactive();
+
+    int acquireWorkIndex();
+    void releaseWorkIndex(int index);
+
+    static int init(int numberThread, unsigned long cpuMask, ThreadPool*& threadPool);
+    static void destroy();
+
+private:
+    void enqueueInternal(TASK* task, int index);
+
+    ThreadPool(int numberThread = 0);
+    ~ThreadPool();
+
+    std::vector<std::thread> mWorkers;
+    std::vector<bool> mTaskAvailable;
+    std::atomic<bool> mStop = {false};
+
+    std::vector<std::pair<TASK*, std::vector<std::atomic_bool*>>> mTasks;
+    std::condition_variable mCondition;
+    std::mutex mQueueMutex;
+
+    int mNumberThread            = 0;
+    std::atomic_int mActiveCount = {0};
+};
+} // namespace MNN
+#endif
+#endif