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 //////////////////////////////////////////////////////////////////////////////
 //
 // (C) Copyright Ion Gaztanaga 2005-2012. Distributed under the Boost
 // Software License, Version 1.0. (See accompanying file
 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 //
 // See http://www.boost.org/libs/interprocess for documentation.
 //
 //////////////////////////////////////////////////////////////////////////////
 //
 // This interface is inspired by Howard Hinnant's lock proposal.
 // http://home.twcny.rr.com/hinnant/cpp_extensions/threads_move.html
 //
 //////////////////////////////////////////////////////////////////////////////
 
 #ifndef BOOST_INTERPROCESS_SHARABLE_LOCK_HPP
 #define BOOST_INTERPROCESS_SHARABLE_LOCK_HPP
 
 #ifndef BOOST_CONFIG_HPP
 #  include <boost/config.hpp>
 #endif
 #
 #if defined(BOOST_HAS_PRAGMA_ONCE)
 #  pragma once
 #endif
 
 #include <boost/interprocess/detail/config_begin.hpp>
 #include <boost/interprocess/detail/workaround.hpp>
 #include <boost/interprocess/interprocess_fwd.hpp>
 #include <boost/interprocess/sync/lock_options.hpp>
 #include <boost/interprocess/exceptions.hpp>
 #include <boost/interprocess/detail/mpl.hpp>
 #include <boost/interprocess/detail/type_traits.hpp>
 #include <boost/interprocess/detail/simple_swap.hpp>
 #include <boost/move/utility_core.hpp>
 
 //!\file
 //!Describes the upgradable_lock class that serves to acquire the upgradable
 //!lock of a mutex.
 
 namespace boost {
 namespace interprocess {
 
 
 //!sharable_lock is meant to carry out the tasks for sharable-locking
 //!(such as read-locking), unlocking, try-sharable-locking and timed-sharable-locking
 //!(recursive or not) for the Mutex. The Mutex need not supply all of this
 //!functionality. If the client of sharable_lock<Mutex> does not use functionality which
 //!the Mutex does not supply, no harm is done. Mutex ownership can be shared among
 //!sharable_locks, and a single upgradable_lock. sharable_lock does not support
 //!copy semantics. But sharable_lock supports ownership transfer from an sharable_lock,
 //!upgradable_lock and scoped_lock via transfer_lock syntax.*/
 template <class SharableMutex>
 class sharable_lock
 {
    public:
    typedef SharableMutex mutex_type;
    #if !defined(BOOST_INTERPROCESS_DOXYGEN_INVOKED)
    private:
    typedef sharable_lock<SharableMutex> this_type;
    explicit sharable_lock(scoped_lock<mutex_type>&);
    typedef bool this_type::*unspecified_bool_type;
    BOOST_MOVABLE_BUT_NOT_COPYABLE(sharable_lock)
    #endif   //#ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED
    public:
 
    //!Effects: Default constructs a sharable_lock.
    //!Postconditions: owns() == false and mutex() == 0.
    sharable_lock() BOOST_NOEXCEPT
       : mp_mutex(0), m_locked(false)
    {}
 
    //!Effects: m.lock_sharable().
    //!Postconditions: owns() == true and mutex() == &m.
    //!Notes: The constructor will take sharable-ownership of the mutex. If
    //!   another thread already owns the mutex with exclusive ownership
    //!   (scoped_lock), this thread will block until the mutex is released.
    //!   If another thread owns the mutex with sharable or upgradable ownership,
    //!   then no blocking will occur. Whether or not this constructor handles
    //!   recursive locking depends upon the mutex.
    explicit sharable_lock(mutex_type& m)
       : mp_mutex(&m), m_locked(false)
    {  mp_mutex->lock_sharable();   m_locked = true;  }
 
    //!Postconditions: owns() == false, and mutex() == &m.
    //!Notes: The constructor will not take ownership of the mutex. There is no effect
    //!   required on the referenced mutex.
    sharable_lock(mutex_type& m, defer_lock_type)
       : mp_mutex(&m), m_locked(false)
    {}
 
    //!Postconditions: owns() == true, and mutex() == &m.
    //!Notes: The constructor will suppose that the mutex is already sharable
    //!   locked. There is no effect required on the referenced mutex.
    sharable_lock(mutex_type& m, accept_ownership_type)
       : mp_mutex(&m), m_locked(true)
    {}
 
    //!Effects: m.try_lock_sharable()
    //!Postconditions: mutex() == &m. owns() == the return value of the
    //!   m.try_lock_sharable() executed within the constructor.
    //!Notes: The constructor will take sharable-ownership of the mutex if it
    //!   can do so without waiting. Whether or not this constructor handles
    //!   recursive locking depends upon the mutex. If the mutex_type does not
    //!   support try_lock_sharable, this constructor will fail at compile
    //!   time if instantiated, but otherwise have no effect.
    sharable_lock(mutex_type& m, try_to_lock_type)
       : mp_mutex(&m), m_locked(false)
    {  m_locked = mp_mutex->try_lock_sharable();   }
 
    //!Effects: m.timed_lock_sharable(abs_time)
    //!Postconditions: mutex() == &m. owns() == the return value of the
    //!   m.timed_lock_sharable() executed within the constructor.
    //!Notes: The constructor will take sharable-ownership of the mutex if it
    //!   can do so within the time specified. Whether or not this constructor
    //!   handles recursive locking depends upon the mutex. If the mutex_type
    //!   does not support timed_lock_sharable, this constructor will fail at
    //!   compile time if instantiated, but otherwise have no effect.
    template<class TimePoint>
    sharable_lock(mutex_type& m, const TimePoint& abs_time)
       : mp_mutex(&m), m_locked(false)
    {  m_locked = mp_mutex->timed_lock_sharable(abs_time);  }
 
    //!Postconditions: mutex() == upgr.mutex(). owns() == the value of upgr.owns()
    //!   before the construction. upgr.owns() == false after the construction.
    //!Notes: If the upgr sharable_lock owns the mutex, ownership is moved to this
    //!   sharable_lock with no blocking. If the upgr sharable_lock does not own the mutex, then
    //!   neither will this sharable_lock. Only a moved sharable_lock's will match this
    //!   signature. An non-moved sharable_lock can be moved with the expression:
    //!   "boost::move(lock);". This constructor does not alter the state of the mutex,
    //!   only potentially who owns it.
    sharable_lock(BOOST_RV_REF(sharable_lock<mutex_type>) upgr) BOOST_NOEXCEPT
       : mp_mutex(0), m_locked(upgr.owns())
    {  mp_mutex = upgr.release(); }
 
    //!Effects: If upgr.owns() then calls unlock_upgradable_and_lock_sharable() on the
    //!   referenced mutex.
    //!Postconditions: mutex() == the value upgr.mutex() had before the construction.
    //!   upgr.mutex() == 0 owns() == the value of upgr.owns() before construction.
    //!   upgr.owns() == false after the construction.
    //!Notes: If upgr is locked, this constructor will lock this sharable_lock while
    //!   unlocking upgr. Only a moved sharable_lock's will match this
    //!   signature. An non-moved upgradable_lock can be moved with the expression:
    //!   "boost::move(lock);".*/
    template<class T>
    sharable_lock(BOOST_RV_REF(upgradable_lock<T>) upgr
       , typename ipcdetail::enable_if< ipcdetail::is_same<T, SharableMutex> >::type * = 0)
       : mp_mutex(0), m_locked(false)
    {
       upgradable_lock<mutex_type> &u_lock = upgr;
       if(u_lock.owns()){
          u_lock.mutex()->unlock_upgradable_and_lock_sharable();
          m_locked = true;
       }
       mp_mutex = u_lock.release();
    }
 
    //!Effects: If scop.owns() then calls unlock_and_lock_sharable() on the
    //!   referenced mutex.
    //!Postconditions: mutex() == the value scop.mutex() had before the construction.
    //!   scop.mutex() == 0 owns() == scop.owns() before the constructor. After the
    //!   construction, scop.owns() == false.
    //!Notes: If scop is locked, this constructor will transfer the exclusive ownership
    //!   to a sharable-ownership of this sharable_lock.
    //!   Only a moved scoped_lock's will match this
    //!   signature. An non-moved scoped_lock can be moved with the expression:
    //!   "boost::move(lock);".
    template<class T>
    sharable_lock(BOOST_RV_REF(scoped_lock<T>) scop
                , typename ipcdetail::enable_if< ipcdetail::is_same<T, SharableMutex> >::type * = 0)
       : mp_mutex(0), m_locked(false)
    {
       scoped_lock<mutex_type> &e_lock = scop;
       if(e_lock.owns()){
          e_lock.mutex()->unlock_and_lock_sharable();
          m_locked = true;
       }
       mp_mutex = e_lock.release();
    }
 
    //!Effects: if (owns()) mp_mutex->unlock_sharable().
    //!Notes: The destructor behavior ensures that the mutex lock is not leaked.
    ~sharable_lock()
    {
       BOOST_TRY{
          if(m_locked && mp_mutex)   mp_mutex->unlock_sharable();
       }
       BOOST_CATCH(...){} BOOST_CATCH_END
    }
 
    //!Effects: If owns() before the call, then unlock_sharable() is called on mutex().
    //!   *this gets the state of upgr and upgr gets set to a default constructed state.
    //!Notes: With a recursive mutex it is possible that both this and upgr own the mutex
    //!   before the assignment. In this case, this will own the mutex after the assignment
    //!   (and upgr will not), but the mutex's lock count will be decremented by one.
    sharable_lock &operator=(BOOST_RV_REF(sharable_lock<mutex_type>) upgr)
    {
       if(this->owns())
          this->unlock();
       m_locked = upgr.owns();
       mp_mutex = upgr.release();
       return *this;
    }
 
    //!Effects: If mutex() == 0 or already locked, throws a lock_exception()
    //!   exception. Calls lock_sharable() on the referenced mutex.
    //!Postconditions: owns() == true.
    //!Notes: The sharable_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_sharable();
       m_locked = true;
    }
 
    //!Effects: If mutex() == 0 or already locked, throws a lock_exception()
    //!   exception. Calls try_lock_sharable() on the referenced mutex.
    //!Postconditions: owns() == the value returned from
    //!   mutex()->try_lock_sharable().
    //!Notes: The sharable_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_sharable(), 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_sharable();
       return m_locked;
    }
 
    //!Effects: If mutex() == 0 or already locked, throws a lock_exception()
    //!   exception. Calls timed_lock_sharable(abs_time) on the referenced mutex.
    //!Postconditions: owns() == the value returned from
    //!   mutex()->timed_lock_sharable(elps_time).
    //!Notes: The sharable_lock changes from a state of not owning the mutex,
    //!   to owning the mutex, but only if it can obtain ownership within the
    //!   specified time interval. If the mutex_type does not support
    //!   timed_lock_sharable(), this function will fail at compile time if
    //!   instantiated, but otherwise have no effect.
    template<class TimePoint>
    bool timed_lock(const TimePoint& abs_time)
    {
       if(!mp_mutex || m_locked)
          throw lock_exception();
       m_locked = mp_mutex->timed_lock_sharable(abs_time);
       return m_locked;
    }
 
    //!Effects: If mutex() == 0 or already locked, throws a lock_exception()
    //!   exception. Calls try_lock_shared_until(abs_time) on the referenced mutex.
    //!Postconditions: owns() == the value returned from
    //!   mutex()->timed_lock_sharable(elps_time).
    //!Notes: The sharable_lock changes from a state of not owning the mutex,
    //!   to owning the mutex, but only if it can obtain ownership within the
    //!   specified time interval. If the mutex_type does not support
    //!   timed_lock_sharable(), this function will fail at compile time if
    //!   instantiated, but otherwise have no effect.
    //!
    //!Note: Similar to timed_lock, but with a std-like interface
    template<class TimePoint>
    bool try_lock_until(const TimePoint& abs_time)
    {
       if(!mp_mutex || m_locked)
          throw lock_exception();
       m_locked = mp_mutex->try_lock_shared_until(abs_time);
       return m_locked;
    }
 
    //!Effects: If mutex() == 0 or already locked, throws a lock_exception()
    //!   exception. Calls try_lock_shared_until(abs_time) on the referenced mutex.
    //!Postconditions: owns() == the value returned from
    //!   mutex()->timed_lock_sharable(elps_time).
    //!Notes: The sharable_lock changes from a state of not owning the mutex,
    //!   to owning the mutex, but only if it can obtain ownership within the
    //!   specified time interval. If the mutex_type does not support
    //!   timed_lock_sharable(), this function will fail at compile time if
    //!   instantiated, but otherwise have no effect.
    //!
    //!Note: Similar to timed_lock, but with a std-like interface
    template<class Duration>
    bool try_lock_for(const Duration& dur)
    {
       if(!mp_mutex || m_locked)
          throw lock_exception();
       m_locked = mp_mutex->try_lock_shared_for(dur);
       return m_locked;
    }
 
    //!Effects: If mutex() == 0 or not locked, throws a lock_exception() exception.
    //!   Calls unlock_sharable() on the referenced mutex.
    //!Postconditions: owns() == false.
    //!Notes: The sharable_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_sharable();
       m_locked = false;
    }
 
    //!Effects: Returns true if this scoped_lock has
    //!acquired the referenced mutex.
    bool owns() const BOOST_NOEXCEPT
    {  return m_locked && mp_mutex;  }
 
    //!Conversion to bool.
    //!Returns owns().
    operator unspecified_bool_type() const BOOST_NOEXCEPT
    {  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 BOOST_NOEXCEPT
    {  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() BOOST_NOEXCEPT
    {
       mutex_type *mut = mp_mutex;
       mp_mutex = 0;
       m_locked = false;
       return mut;
    }
 
    //!Effects: Swaps state with moved lock.
    //!Throws: Nothing.
    void swap(sharable_lock<mutex_type> &other) BOOST_NOEXCEPT
    {
       (simple_swap)(mp_mutex, other.mp_mutex);
       (simple_swap)(m_locked, other.m_locked);
    }
 
    #if !defined(BOOST_INTERPROCESS_DOXYGEN_INVOKED)
    private:
    mutex_type *mp_mutex;
    bool        m_locked;
    #endif   //#ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED
 };
 
 } // namespace interprocess
 } // namespace boost
 
 #include <boost/interprocess/detail/config_end.hpp>
 
 #endif // BOOST_INTERPROCESS_SHARABLE_LOCK_HPP

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