scoped_lock.hpp

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   #ifndef BOOST_INTERPROCESS_RVALUE_REFERENCE
   scoped_lock(detail::moved_object<upgradable_lock<Mutex> > upgr
              ,boost::posix_time::ptime &abs_time)
      : mp_mutex(0), m_locked(false)
   {
      upgradable_lock<mutex_type> &u_lock = upgr.get();
      if(u_lock.owns()){
         if((m_locked = u_lock.mutex()->timed_unlock_upgradable_and_lock(abs_time)) == true){
            mp_mutex = u_lock.release();
         }
      }
      else{
         u_lock.release();
      }
   }
   #else
   scoped_lock(upgradable_lock<Mutex> &&upgr
              ,boost::posix_time::ptime &abs_time)
      : mp_mutex(0), m_locked(false)
   {
      upgradable_lock<mutex_type> &u_lock = upgr;
      if(u_lock.owns()){
         if((m_locked = u_lock.mutex()->timed_unlock_upgradable_and_lock(abs_time)) == true){
            mp_mutex = u_lock.release();
         }
      }
      else{
         u_lock.release();
      }
   }
   #endif

   //!Effects: If shar.owns() then calls try_unlock_sharable_and_lock() on the
   //!referenced mutex. 
   //!   a)if try_unlock_sharable_and_lock() returns true then mutex() obtains
   //!      the value from shar.release() and owns() is set to true. 
   //!   b)if try_unlock_sharable_and_lock() returns false then shar is
   //!      unaffected and this scoped_lock construction has the same
   //!      effects as a default construction. 
   //!   c)Else shar.owns() is false. mutex() obtains the value from
   //!      shar.release() and owns() is set to false 
   //!Notes: This construction will not block. It will try to obtain mutex
   //!   ownership from shar immediately, while changing the lock type from a
   //!   "read lock" to a "write lock". If the "read lock" isn't held in the
   //!   first place, the mutex merely changes type to an unlocked "write lock".
   //!   If the "read lock" is held, then mutex transfer occurs only if it can
   //!   do so in a non-blocking manner.
   #ifndef BOOST_INTERPROCESS_RVALUE_REFERENCE
   scoped_lock(detail::moved_object<sharable_lock<Mutex> > shar
              ,detail::try_to_lock_type)
      : mp_mutex(0), m_locked(false)
   {
      sharable_lock<mutex_type> &s_lock = shar.get();
      if(s_lock.owns()){
         if((m_locked = s_lock.mutex()->try_unlock_sharable_and_lock()) == true){
            mp_mutex = s_lock.release();
         }
      }
      else{
         s_lock.release();
      }
   }
   #else
   scoped_lock(sharable_lock<Mutex> &&shar
              ,detail::try_to_lock_type)
      : mp_mutex(0), m_locked(false)
   {
      sharable_lock<mutex_type> &s_lock = shar;
      if(s_lock.owns()){
         if((m_locked = s_lock.mutex()->try_unlock_sharable_and_lock()) == true){
            mp_mutex = s_lock.release();
         }
      }
      else{
         s_lock.release();
      }
   }
   #endif

   //!Effects: if (owns()) mp_mutex->unlock().
   //!Notes: The destructor behavior ensures that the mutex lock is not leaked.*/
   ~scoped_lock()
   {
      try{  if(m_locked && mp_mutex)   mp_mutex->unlock();  }
      catch(...){}
   }

   //!Effects: If owns() before the call, then unlock() is called on mutex().
   //!   *this gets the state of scop and scop gets set to a default constructed state. 
   //!Notes: With a recursive mutex it is possible that both this and scop own
   //!   the same mutex before the assignment. In this case, this will own the
   //!   mutex after the assignment (and scop will not), but the mutex's lock
   //!   count will be decremented by one.
   #ifndef BOOST_INTERPROCESS_RVALUE_REFERENCE
   scoped_lock &operator=(detail::moved_object<scoped_lock> scop)
   {  
      if(this->owns())
         this->unlock();
      m_locked = scop.get().owns();
      mp_mutex = scop.get().release();
      return *this;
   }
   #else
   scoped_lock &operator=(scoped_lock &&scop)
   {  
      if(this->owns())
         this->unlock();
      m_locked = scop.owns();
      mp_mutex = scop.release();
      return *this;
   }
   #endif

   //!Effects: If mutex() == 0 or if already locked, throws a lock_exception()
   //!   exception. Calls lock() on the referenced mutex.
   //!Postconditions: owns() == true.
   //!Notes: The scoped_lock changes from a state of not owning the mutex, to
   //!   owning the mutex, blocking if necessary.
   void lock()
   {
      if(!mp_mutex || m_locked)
         throw lock_exception();
      mp_mutex->lock();
      m_locked = true;
   }

   //!Effects: If mutex() == 0 or if already locked, throws a lock_exception()
   //!   exception. Calls try_lock() on the referenced mutex. 
   //!Postconditions: owns() == the value returned from mutex()->try_lock().
   //!Notes: The scoped_lock changes from a state of not owning the mutex, to
   //!   owning the mutex, but only if blocking was not required. If the
   //!   mutex_type does not support try_lock(), this function will fail at
   //!   compile time if instantiated, but otherwise have no effect.*/
   bool try_lock()
   {
      if(!mp_mutex || m_locked)
         throw lock_exception();
      m_locked = mp_mutex->try_lock();
      return m_locked;
   }

   //!Effects: If mutex() == 0 or if already locked, throws a lock_exception()
   //!   exception. Calls timed_lock(abs_time) on the referenced mutex.
   //!Postconditions: owns() == the value returned from mutex()-> timed_lock(abs_time).
   //!Notes: The scoped_lock changes from a state of not owning the mutex, to
   //!   owning the mutex, but only if it can obtain ownership by the specified
   //!   time. If the mutex_type does not support timed_lock (), this function
   //!   will fail at compile time if instantiated, but otherwise have no effect.*/
   bool timed_lock(const boost::posix_time::ptime& abs_time)
   {
      if(!mp_mutex || m_locked)
         throw lock_exception();
      m_locked = mp_mutex->timed_lock(abs_time);
      return m_locked;
   }

   //!Effects: If mutex() == 0 or if not locked, throws a lock_exception()
   //!   exception. Calls unlock() on the referenced mutex.
   //!Postconditions: owns() == false.
   //!Notes: The scoped_lock changes from a state of owning the mutex, to not
   //!   owning the mutex.*/
   void unlock()
   {
      if(!mp_mutex || !m_locked)
         throw lock_exception();
      mp_mutex->unlock();
      m_locked = false;
   }

   //!Effects: Returns true if this scoped_lock has acquired
   //!the referenced mutex.
   bool owns() const
   {  return m_locked && mp_mutex;  }

   //!Conversion to bool.
   //!Returns owns().
   operator unspecified_bool_type() const
   {  return m_locked? &this_type::m_locked : 0;   }

   //!Effects: Returns a pointer to the referenced mutex, or 0 if
   //!there is no mutex to reference.
   mutex_type* mutex() const
   {  return  mp_mutex;  }

   //!Effects: Returns a pointer to the referenced mutex, or 0 if there is no
   //!   mutex to reference.
   //!Postconditions: mutex() == 0 and owns() == false.
   mutex_type* release()
   {
      mutex_type *mut = mp_mutex;
      mp_mutex = 0;
      m_locked = false;
      return mut;
   }
 
   //!Effects: Swaps state with moved lock. 
   //!Throws: Nothing.
   #ifndef BOOST_INTERPROCESS_RVALUE_REFERENCE
   void swap(detail::moved_object<scoped_lock<mutex_type> > other)
   {
      std::swap(mp_mutex, other.get().mp_mutex);
      std::swap(m_locked, other.get().m_locked);
   }
   #else
   void swap(scoped_lock<mutex_type> &&other)
   {
      std::swap(mp_mutex, other.mp_mutex);
      std::swap(m_locked, other.m_locked);
   }
   #endif

   /// @cond
   private:
   mutex_type *mp_mutex; 
   bool        m_locked;
   /// @endcond
};

/// @cond

//!This class is movable
template <class M>
struct is_movable<scoped_lock<M> >
{
   enum {   value = true };
};
/// @endcond

} // namespace interprocess
} // namespace boost

#include <boost/interprocess/detail/config_end.hpp>

#endif // BOOST_INTERPROCESS_SCOPED_LOCK_HPP