| ////////////////////////////////////////////////////////////////////////////// |
| // |
| // (C) Copyright Ion Gaztanaga 2005-2009. 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 |
| |
| #if (defined _MSC_VER) && (_MSC_VER >= 1200) |
| # 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/interprocess/detail/move.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 { |
| |
| //!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; |
| /// @cond |
| private: |
| typedef upgradable_lock<UpgradableMutex> this_type; |
| explicit upgradable_lock(scoped_lock<mutex_type>&); |
| typedef bool this_type::*unspecified_bool_type; |
| BOOST_INTERPROCESS_MOVABLE_BUT_NOT_COPYABLE(upgradable_lock) |
| /// @endcond |
| public: |
| |
| //!Effects: Default constructs a upgradable_lock. |
| //!Postconditions: owns() == false and mutex() == 0. |
| upgradable_lock() |
| : 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. |
| upgradable_lock(mutex_type& m, const boost::posix_time::ptime& 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::interprocess::move(lock);". This constructor does not alter the |
| //! state of the mutex, only potentially who owns it. |
| upgradable_lock(BOOST_INTERPROCESS_RV_REF(upgradable_lock<mutex_type>) upgr) |
| : 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::interprocess::move(lock);". |
| template<class T> |
| upgradable_lock(BOOST_INTERPROCESS_RV_REF(scoped_lock<T>) scop |
| , typename detail::enable_if< detail::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_INTERPROCESS_RV_REF(sharable_lock<T>) shar, try_to_lock_type |
| , typename detail::enable_if< detail::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() |
| { |
| try{ |
| if(m_locked && mp_mutex) mp_mutex->unlock_upgradable(); |
| } |
| catch(...){} |
| } |
| |
| //!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_INTERPROCESS_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. |
| bool timed_lock(const boost::posix_time::ptime& 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 |
| { 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(upgradable_lock<mutex_type> &other) |
| { |
| std::swap(mp_mutex, other.mp_mutex); |
| std::swap(m_locked, other.m_locked); |
| } |
| |
| /// @cond |
| private: |
| mutex_type *mp_mutex; |
| bool m_locked; |
| /// @endcond |
| }; |
| |
| } // namespace interprocess |
| } // namespace boost |
| |
| #include <boost/interprocess/detail/config_end.hpp> |
| |
| #endif // BOOST_INTERPROCESS_UPGRADABLE_LOCK_HPP |