YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

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#ifndef YB_UTIL_COUNTDOWN_LATCH_H

#define YB_UTIL_COUNTDOWN_LATCH_H

#include <atomic>

#include "yb/util/condition_variable.h"

#include "yb/util/monotime.h"

#include "yb/util/mutex.h"

namespace yb {

// This is a C++ implementation of the Java CountDownLatch

// class.

// See http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/CountDownLatch.html

class CountDownLatch {

 public:

  // Initialize the latch with the given initial count.

  explicit CountDownLatch(uint64_t count);

  ~CountDownLatch();

  // Decrement the count of this latch by 'amount'

  // If the new count is less than or equal to zero, then all waiting threads are woken up.

  // If the count is already zero, this has no effect.

  void CountDown(uint64_t amount);

  // Decrement the count of this latch.

  // If the new count is zero, then all waiting threads are woken up.

  // If the count is already zero, this has no effect.

  void CountDown() {

    CountDown(1);

  }

  // Wait until the count on the latch reaches zero.

  // If the count is already zero, this returns immediately.

  void Wait() const;

  // Waits for the count on the latch to reach zero, or until 'when' time is reached.

  // Returns true if the count became zero, false otherwise.

  bool WaitUntil(MonoTime when) const;

  bool WaitUntil(CoarseTimePoint when) const;

  // Waits for the count on the latch to reach zero, or until 'delta' time elapses.

  // Returns true if the count became zero, false otherwise.

  bool WaitFor(MonoDelta delta) const;

  // Reset the latch with the given count. This is equivalent to reconstructing

  // the latch. If 'count' is 0, and there are currently waiters, those waiters

  // will be triggered as if you counted down to 0.

  void Reset(uint64_t count);

  uint64_t count() const;

  auto CountDownCallback() {

    return [this] {

      this->CountDown();

    };

  }

 private:

  mutable Mutex lock_;

  ConditionVariable cond_;

  std::atomic<uint64_t> count_;

  DISALLOW_COPY_AND_ASSIGN(CountDownLatch);

};

// Utility class which calls latch->CountDown() in its destructor.

class CountDownOnScopeExit {

 public:

  explicit CountDownOnScopeExit(CountDownLatch *latch) : latch_(latch) {}

  ~CountDownOnScopeExit() {

    latch_->CountDown();

  }

 private:

  CountDownLatch *latch_;

  DISALLOW_COPY_AND_ASSIGN(CountDownOnScopeExit);

};

} // namespace yb

#endif // YB_UTIL_COUNTDOWN_LATCH_H