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 *
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 * modification, are permitted provided that the following conditions are
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 *
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 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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#include <grpc++/impl/sync.h>
#include <grpc++/impl/thd.h>

#include "src/cpp/server/thread_pool.h"

namespace grpc {

void ThreadPool::ThreadFunc() {
  for (;;) {
    // Wait until work is available or we are shutting down.
    grpc::unique_lock<grpc::mutex> lock(mu_);
    if (!shutdown_ && callbacks_.empty()) {
      cv_.wait(lock);
    }
    // Drain callbacks before considering shutdown to ensure all work
    // gets completed.
    if (!callbacks_.empty()) {
      auto cb = callbacks_.front();
      callbacks_.pop();
      lock.unlock();
      cb();
    } else if (shutdown_) {
      return;
    }
  }
}

ThreadPool::ThreadPool(int num_threads) : shutdown_(false) {
  for (int i = 0; i < num_threads; i++) {
    threads_.push_back(grpc::thread(&ThreadPool::ThreadFunc, this));
  }
}

ThreadPool::~ThreadPool() {
  {
    grpc::lock_guard<grpc::mutex> lock(mu_);
    shutdown_ = true;
    cv_.notify_all();
  }
  for (auto t = threads_.begin(); t != threads_.end(); t++) {
    t->join();
  }
}

void ThreadPool::ScheduleCallback(const std::function<void()>& callback) {
  grpc::lock_guard<grpc::mutex> lock(mu_);
  callbacks_.push(callback);
  cv_.notify_one();
}

}  // namespace grpc
