readwritelock.h

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#ifndef ION_BASE_READWRITELOCK_H_
#define ION_BASE_READWRITELOCK_H_

#include "ion/port/atomic.h"
#include "ion/port/mutex.h"
#include "ion/port/semaphore.h"

namespace ion {
namespace base {

class ION_API ReadWriteLock {
 public:
  ReadWriteLock();
  ~ReadWriteLock();

  void LockForRead();
  void UnlockForRead();
  void LockForWrite();
  void UnlockForWrite();

  int GetReaderCount() const { return reader_count_; }
  int GetWriterCount() const { return writer_count_; }

 private:
  std::atomic<int> reader_count_;
  std::atomic<int> writer_count_;
  port::Semaphore room_empty_;
  port::Mutex turnstile_;

  DISALLOW_COPY_AND_ASSIGN(ReadWriteLock);
};

class ION_API ReadLock {
 public:
  explicit ReadLock(ReadWriteLock* lock) : lock_(*lock) {}
  ~ReadLock() {}
  void Lock() { lock_.LockForRead(); }
  void Unlock() { lock_.UnlockForRead(); }
  bool IsLocked() const { return lock_.GetReaderCount() > 0; }

 private:
  ReadWriteLock& lock_;

  DISALLOW_IMPLICIT_CONSTRUCTORS(ReadLock);
};

class ION_API WriteLock {
 public:
  explicit WriteLock(ReadWriteLock* lock) : lock_(*lock) {}
  ~WriteLock() {}
  void Lock() { lock_.LockForWrite(); }
  void Unlock() { lock_.UnlockForWrite(); }
  bool IsLocked() const { return lock_.GetWriterCount() > 0; }

 private:
  ReadWriteLock& lock_;

  DISALLOW_IMPLICIT_CONSTRUCTORS(WriteLock);
};

}  // namespace base
}  // namespace ion

#endif  // ION_BASE_READWRITELOCK_H_