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Editing: sharable_lock.hpp
////////////////////////////////////////////////////////////////////////////// // // (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> #include <boost/interprocess/detail/posix_time_types_wrk.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() : 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. sharable_lock(mutex_type& m, const boost::posix_time::ptime& 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) : 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() { try{ if(m_locked && mp_mutex) mp_mutex->unlock_sharable(); } catch(...){} } //!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. bool timed_lock(const boost::posix_time::ptime& 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 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 { 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. void swap(sharable_lock<mutex_type> &other) { (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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