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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_UPGRADABLE_LOCK_HPP
 #define BOOST_INTERPROCESS_UPGRADABLE_LOCK_HPP
 
 #ifndef BOOST_CONFIG_HPP
 #  include <boost/config.hpp>
 #endif
 0023 ">#
 #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/detail/mpl.hpp>
 #include <boost/interprocess/detail/type_traits.hpp>
 
 #include <boost/interprocess/exceptions.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 {
 
 //!upgradable_lock is meant to carry out the tasks for read-locking, unlocking,
 //!try-read-locking and timed-read-locking (recursive or not) for the Mutex.
 //!Additionally the upgradable_lock can transfer ownership to a scoped_lock
 //!using transfer_lock syntax. The Mutex need not supply all of the functionality.
 //!If the client of upgradable_lock<Mutex> does not use functionality which the
 //!Mutex does not supply, no harm is done. Mutex ownership can be shared among
 //!read_locks, and a single upgradable_lock. upgradable_lock does not support
 //!copy semantics. However upgradable_lock supports ownership transfer from
 //!a upgradable_locks or scoped_locks via transfer_lock syntax.
 template <class UpgradableMutex>
 class upgradable_lock
 {
    public:
    typedef UpgradableMutex mutex_type;
    #if !defined(BOOST_INTERPROCESS_DOXYGEN_INVOKED)
    private:
    typedef upgradable_lock<UpgradableMutex> this_type;
    explicit upgradable_lock(scoped_lock<mutex_type>&);
    typedef bool this_type::*unspecified_bool_type;
    BOOST_MOVABLE_BUT_NOT_COPYABLE(upgradable_lock)
    #endif   //#ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED
    public:
 
    //!Effects: Default constructs a upgradable_lock.
    //!Postconditions: owns() == false and mutex() == 0.
    upgradable_lock() BOOST_NOEXCEPT
       : mp_mutex(0), m_locked(false)
    {}
 
    explicit upgradable_lock(mutex_type& m)
       : mp_mutex(&m), m_locked(false)
    {  mp_mutex->lock_upgradable();   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.
    upgradable_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 upgradable
    //!   locked. There is no effect required on the referenced mutex.
    upgradable_lock(mutex_type& m, accept_ownership_type)
       : mp_mutex(&m), m_locked(true)
    {}
 
    //!Effects: m.try_lock_upgradable().
    //!Postconditions: mutex() == &m. owns() == the return value of the
    //!   m.try_lock_upgradable() executed within the constructor.
    //!Notes: The constructor will take upgradable-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_upgradable, this constructor will fail at
    //!   compile time if instantiated, but otherwise have no effect.
    upgradable_lock(mutex_type& m, try_to_lock_type)
       : mp_mutex(&m), m_locked(false)
    {  m_locked = mp_mutex->try_lock_upgradable();   }
 
    //!Effects: m.timed_lock_upgradable(abs_time)
    //!Postconditions: mutex() == &m. owns() == the return value of the
    //!   m.timed_lock_upgradable() executed within the constructor.
    //!Notes: The constructor will take upgradable-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_upgradable, this constructor will fail
    //!   at compile time if instantiated, but otherwise have no effect.
    template<class TimePoint>
    upgradable_lock(mutex_type& m, const TimePoint& abs_time)
       : mp_mutex(&m), m_locked(false)
    {  m_locked = mp_mutex->timed_lock_upgradable(abs_time);  }
 
    //!Effects: No effects on the underlying mutex.
    //!Postconditions: mutex() == the value upgr.mutex() had before the
    //!   construction. upgr.mutex() == 0. owns() == upgr.owns() before the
    //!   construction. upgr.owns() == false.
    //!Notes: If upgr is locked, this constructor will lock this upgradable_lock
    //!   while unlocking upgr. If upgr is unlocked, then this upgradable_lock will
    //!   be unlocked as well. Only a moved upgradable_lock's will match this
    //!   signature. An non-moved upgradable_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.
    upgradable_lock(BOOST_RV_REF(upgradable_lock<mutex_type>) upgr) BOOST_NOEXCEPT
       : mp_mutex(0), m_locked(upgr.owns())
    {  mp_mutex = upgr.release(); }
 
    //!Effects: If scop.owns(), m_.unlock_and_lock_upgradable().
    //!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 an upgradable-ownership of this upgradable_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);".
    template<class T>
    upgradable_lock(BOOST_RV_REF(scoped_lock<T>) scop
                   , typename ipcdetail::enable_if< ipcdetail::is_same<T, UpgradableMutex> >::type * = 0)
       : mp_mutex(0), m_locked(false)
    {
       scoped_lock<mutex_type> &u_lock = scop;
       if(u_lock.owns()){
          u_lock.mutex()->unlock_and_lock_upgradable();
          m_locked = true;
       }
       mp_mutex = u_lock.release();
    }
 
    //!Effects: If shar.owns() then calls try_unlock_sharable_and_lock_upgradable()
    //!   on the referenced mutex.
    //!   a)if try_unlock_sharable_and_lock_upgradable() returns true then mutex()
    //!      obtains the value from shar.release() and owns() is set to true.
    //!   b)if try_unlock_sharable_and_lock_upgradable() returns false then shar is
    //!      unaffected and this upgradable_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 an "upgradable lock". If the "read lock" isn't held
    //!   in the first place, the mutex merely changes type to an unlocked
    //!   "upgradable lock". If the "read lock" is held, then mutex transfer
    //!   occurs only if it can do so in a non-blocking manner.
    template<class T>
    upgradable_lock( BOOST_RV_REF(sharable_lock<T>) shar, try_to_lock_type
                   , typename ipcdetail::enable_if< ipcdetail::is_same<T, UpgradableMutex> >::type * = 0)
       : 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_upgradable()) == true){
             mp_mutex = s_lock.release();
          }
       }
       else{
          s_lock.release();
       }
    }
 
    //!Effects: if (owns()) m_->unlock_upgradable().
    //!Notes: The destructor behavior ensures that the mutex lock is not leaked.
    ~upgradable_lock()
    {
       BOOST_INTERPROCESS_TRY{
          if(m_locked && mp_mutex)   mp_mutex->unlock_upgradable();
       }
       BOOST_INTERPROCESS_CATCH(...){} BOOST_INTERPROCESS_CATCH_END
    }
 
    //!Effects: If owns(), then unlock_upgradable() 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 upgradable lock
    //!   count will be decremented by one.
    upgradable_lock &operator=(BOOST_RV_REF(upgradable_lock) upgr)
    {
       if(this->owns())
          this->unlock();
       m_locked = upgr.owns();
       mp_mutex = upgr.release();
       return *this;
    }
 
    //!Effects: If mutex() == 0 or if already locked, throws a lock_exception()
    //!   exception. Calls lock_upgradable() 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_upgradable();
       m_locked = true;
    }
 
    //!Effects: If mutex() == 0 or if already locked, throws a lock_exception()
    //!   exception. Calls try_lock_upgradable() on the referenced mutex.
    //!Postconditions: owns() == the value returned from
    //!   mutex()->try_lock_upgradable().
    //!Notes: The upgradable_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_upgradable(), 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_upgradable();
       return m_locked;
    }
 
    //!Effects: If mutex() == 0 or if already locked, throws a lock_exception()
    //!   exception. Calls timed_lock_upgradable(abs_time) on the referenced mutex.
    //!Postconditions: owns() == the value returned from
    //!   mutex()->timed_lock_upgradable(abs_time).
    //!Notes: The upgradable_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. If the mutex_type does not support
    //!   timed_lock_upgradable(abs_time), 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_upgradable(abs_time);
       return m_locked;
    }
 
    //!Effects: If mutex() == 0 or if not locked, throws a lock_exception()
    //!   exception. Calls unlock_upgradable() on the referenced mutex.
    //!Postconditions: owns() == false.
    //!Notes: The upgradable_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_upgradable();
       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(upgradable_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_UPGRADABLE_LOCK_HPP

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