/**
 *  Copyright (c) 2021 by Contributors
 * @file semaphore_wrapper.h
 * @brief A simple corss platform semaphore wrapper
 */
#ifndef DGL_RUNTIME_SEMAPHORE_WRAPPER_H_
#define DGL_RUNTIME_SEMAPHORE_WRAPPER_H_

#ifdef _WIN32
#include <windows.h>
#else
#include <semaphore.h>
#endif

namespace dgl {
namespace runtime {

/**
 * @brief A simple crossplatform Semaphore wrapper
 */
class Semaphore {
 public:
  /**
   * @brief Semaphore constructor
   */
  Semaphore();
  /**
   * @brief blocking wait, decrease semaphore by 1
   */
  void Wait();
  /**
   * @brief timed wait, decrease semaphore by 1 or returns if times out
   * @param timeout The timeout value in milliseconds. If zero, wait
   * indefinitely.
   */
  bool TimedWait(int timeout);
  /**
   * @brief increase semaphore by 1
   */
  void Post();

 private:
#ifdef _WIN32
  HANDLE sem_;
#else
  sem_t sem_;
#endif
  enum {
    MILLISECONDS_PER_SECOND = 1000,
    NANOSECONDS_PER_MILLISECOND = 1000 * 1000,
    NANOSECONDS_PER_SECOND = 1000 * 1000 * 1000
  };
};

}  // namespace runtime
}  // namespace dgl

#endif  // DGL_RUNTIME_SEMAPHORE_WRAPPER_H_