uLib/src/Core/Monitor.h

/*//////////////////////////////////////////////////////////////////////////////
// CMT Cosmic Muon Tomography project //////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

  Copyright (c) 2014, Universita' degli Studi di Padova, INFN sez. di Padova
  All rights reserved

  Authors: Andrea Rigoni Garola < andrea.rigoni@pd.infn.it >

  ------------------------------------------------------------------
  This library is free software;  you  can  redistribute  it  and/or
  modify it  under the  terms  of  the  GNU  Lesser  General  Public
  License as published  by  the  Free  Software  Foundation;  either
  version 3.0 of the License, or (at your option) any later version.

  This library is  distributed in  the hope that it will  be useful,
  but  WITHOUT ANY WARRANTY;  without  even  the implied warranty of
  MERCHANTABILITY  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of  the GNU Lesser General  Public
  License along with this library.

//////////////////////////////////////////////////////////////////////////////*/

#ifndef U_CORE_MONITOR_H
#define U_CORE_MONITOR_H

#include <mutex>
#include <condition_variable>
#include <chrono>
#include <utility>

namespace uLib {

/**
 * @brief Mutex class wraps std::timed_mutex and is used for thread synchronization.
 */
class Mutex {
public:
  Mutex() = default;
  ~Mutex() = default;

  /** @brief Locks the mutex, blocking if necessary. */
  void Lock() { m_Mutex.lock(); }

  /** @brief Unlocks the mutex. */
  void Unlock() { m_Mutex.unlock(); }

  /** @brief Tries to lock the mutex without blocking. */
  bool TryLock() { return m_Mutex.try_lock(); }

  /** @brief Tries to lock the mutex within a timeout in milliseconds. */
  bool TryLockFor(int timeout_ms) {
      if (timeout_ms < 0) { Lock(); return true; }
      return m_Mutex.try_lock_for(std::chrono::milliseconds(timeout_ms));
  }

  /** @brief RAII helper for scoped locking. */
  class ScopedLock {
  public:
    ScopedLock(Mutex &mutex) : m_Mutex(mutex) { m_Mutex.Lock(); }
    ~ScopedLock() { m_Mutex.Unlock(); }
  private:
    Mutex &m_Mutex;
    // Non-copyable
    ScopedLock(const ScopedLock&) = delete;
    ScopedLock& operator=(const ScopedLock&) = delete;
  };

  /** @brief Returns the underlying std::timed_mutex. */
  std::timed_mutex& GetNative() { return m_Mutex; }

private:
  std::timed_mutex m_Mutex;
  // Non-copyable
  Mutex(const Mutex &) = delete;
  Mutex &operator=(const Mutex &) = delete;
};

namespace detail {

/** @brief Internal implementation for the ULIB_MUTEX_LOCK macros. */
class ScopedTimedLock {
public:
    ScopedTimedLock(Mutex& mutex, int timeout_ms) 
        : m_RawMutex(nullptr), m_MutexWrapper(&mutex), m_Locked(false) {
        m_Locked = m_MutexWrapper->TryLockFor(timeout_ms);
    }
    
    ScopedTimedLock(std::timed_mutex& mutex, int timeout_ms) 
        : m_RawMutex(&mutex), m_MutexWrapper(nullptr), m_Locked(false) {
        if (timeout_ms < 0) { m_RawMutex->lock(); m_Locked = true; }
        else m_Locked = m_RawMutex->try_lock_for(std::chrono::milliseconds(timeout_ms));
    }

    ~ScopedTimedLock() {
        if (m_Locked) {
            if (m_RawMutex) m_RawMutex->unlock();
            else if (m_MutexWrapper) m_MutexWrapper->Unlock();
        }
    }
    
    operator bool() const { return m_Locked; }
    void unlock() { if (m_Locked) { 
        if (m_RawMutex) m_RawMutex->unlock();
        else if (m_MutexWrapper) m_MutexWrapper->Unlock();
        m_Locked = false; 
    } }

private:
    std::timed_mutex* m_RawMutex = nullptr;
    Mutex* m_MutexWrapper = nullptr;
    bool m_Locked;
    
    // Non-copyable/movable to be safe in the 'for' loop
    ScopedTimedLock(const ScopedTimedLock&) = delete;
    ScopedTimedLock& operator=(const ScopedTimedLock&) = delete;
    ScopedTimedLock(ScopedTimedLock&&) = default; 
};

inline ScopedTimedLock makeScopedMutexLock(Mutex& mutex, int timeout_ms) {
    return ScopedTimedLock(mutex, timeout_ms);
}

inline ScopedTimedLock makeScopedMutexLock(std::timed_mutex& mutex, int timeout_ms) {
    return ScopedTimedLock(mutex, timeout_ms);
}

} // namespace detail

/**
 * @brief Macro for block-scoped locking of a static mutex.
 * @param timeout Timeout in ms (-1 for infinite).
 */
#define ULIB_STATIC_LOCK(timeout) \
    static std::timed_mutex __ulib_static_mutex; \
    for (auto __ulib_lock = uLib::detail::makeScopedMutexLock(__ulib_static_mutex, timeout); \
         __ulib_lock; \
         __ulib_lock.unlock())

/**
 * @brief Macro for block-scoped locking of a provided mutex.
 * @param mutex The uLib::Mutex or std::timed_mutex to lock.
 * @param timeout Timeout in ms (-1 for infinite).
 */
#define ULIB_MUTEX_LOCK(mutex, timeout) \
    for (auto __ulib_lock = uLib::detail::makeScopedMutexLock(mutex, timeout); \
         __ulib_lock; \
         __ulib_lock.unlock())

/**
 * @brief Monitor class provides a base for objects that need thread-safe access.
 */
template <typename T>
class Monitor {
protected:
  T* m_Resource;
  Mutex m_Mutex;

public:
  Monitor(T* resource) : m_Resource(resource) {}
  virtual ~Monitor() { delete m_Resource; }

  /** @brief Thread-safe access to the resource through a lambda. */
  template <typename F>
  auto Access(F f) -> decltype(f(*m_Resource)) {
    Mutex::ScopedLock lock(m_Mutex);
    return f(*m_Resource);
  }
};

} // namespace uLib

#endif // U_CORE_MONITOR_H