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+//////////////////////////////////////////////////////////////////////////////
+//
+// (C) Copyright Ion Gaztanaga 2005-2011. 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/move/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_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::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)
+ : 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()
+ {
+ 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_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