lock_guard.h

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// vim:set ft=cpp: -*- Mode: C++ -*-
/*
 * Copyright (C) 2025 Kernkonzept GmbH.
 * Author(s): Martin Decky <martin.decky@kernkonzept.com>
 *
 * License: see LICENSE.spdx (in this directory or the directories above)
 */

 
#pragma once
 
#include <pthread.h>
#include <stdlib.h>
 
namespace L4 {

class Lock_guard
{
public:
  Lock_guard() = delete;
  Lock_guard(const Lock_guard &) = delete;
  Lock_guard &operator=(const Lock_guard &) = delete;

  explicit Lock_guard(pthread_mutex_t &lock) : _lock(&lock)
  {
    _status = pthread_mutex_lock(_lock);
  }

  Lock_guard(Lock_guard &&guard) : _lock(guard._lock), _status(guard._status)
  {
    guard.release();
  }

  Lock_guard &operator=(Lock_guard &&guard)
  {
    // Unlock the currently associated mutex (if any).
    reset();
 
    // Move the state from the other guard.
    _lock = guard._lock;
    _status = guard._status;
 
    // Release the mutex from the other guard.
    guard.release();
 
    return *this;
  }

  int status() const
  {
    return _status;
  }

  ~Lock_guard()
  {
    reset();
  }
 
private:
  void release()
  {
    _lock = nullptr;
  }

  void reset()
  {
    // No mutex might be associated with this lock guard only if the mutex has
    // been moved to a different lock guard.
    if (_lock)
      {
        _status = pthread_mutex_unlock(_lock);
        release();
      }
  }
 
  pthread_mutex_t *_lock;
  int _status;
};
 
} // namespace L4