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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.
+//
+//////////////////////////////////////////////////////////////////////////////
+
+#ifndef BOOST_INTERPROCESS_UPGRADABLE_MUTEX_HPP
+#define BOOST_INTERPROCESS_UPGRADABLE_MUTEX_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/sync/scoped_lock.hpp>
+#include <boost/interprocess/detail/posix_time_types_wrk.hpp>
+#include <boost/interprocess/sync/interprocess_mutex.hpp>
+#include <boost/interprocess/sync/interprocess_condition.hpp>
+#include <climits>
+
+
+//!\file
+//!Describes interprocess_upgradable_mutex class
+
+namespace boost {
+namespace interprocess {
+
+//!Wraps a interprocess_upgradable_mutex that can be placed in shared memory and can be
+//!shared between processes. Allows timed lock tries
+class interprocess_upgradable_mutex
+{
+ //Non-copyable
+ interprocess_upgradable_mutex(const interprocess_upgradable_mutex &);
+ interprocess_upgradable_mutex &operator=(const interprocess_upgradable_mutex &);
+
+ friend class interprocess_condition;
+ public:
+
+ //!Constructs the upgradable lock.
+ //!Throws interprocess_exception on error.
+ interprocess_upgradable_mutex();
+
+ //!Destroys the upgradable lock.
+ //!Does not throw.
+ ~interprocess_upgradable_mutex();
+
+ //Exclusive locking
+
+ //!Effects: The calling thread tries to obtain exclusive ownership of the mutex,
+ //! and if another thread has exclusive, sharable or upgradable ownership of
+ //! the mutex, it waits until it can obtain the ownership.
+ //!Throws: interprocess_exception on error.
+ void lock();
+
+ //!Effects: The calling thread tries to acquire exclusive ownership of the mutex
+ //! without waiting. If no other thread has exclusive, sharable or upgradable
+ //! ownership of the mutex this succeeds.
+ //!Returns: If it can acquire exclusive ownership immediately returns true.
+ //! If it has to wait, returns false.
+ //!Throws: interprocess_exception on error.
+ bool try_lock();
+
+ //!Effects: The calling thread tries to acquire exclusive ownership of the mutex
+ //! waiting if necessary until no other thread has exclusive, sharable or
+ //! upgradable ownership of the mutex or abs_time is reached.
+ //!Returns: If acquires exclusive ownership, returns true. Otherwise returns false.
+ //!Throws: interprocess_exception on error.
+ bool timed_lock(const boost::posix_time::ptime &abs_time);
+
+ //!Precondition: The thread must have exclusive ownership of the mutex.
+ //!Effects: The calling thread releases the exclusive ownership of the mutex.
+ //!Throws: An exception derived from interprocess_exception on error.
+ void unlock();
+
+ //Sharable locking
+
+ //!Effects: The calling thread tries to obtain sharable ownership of the mutex,
+ //! and if another thread has exclusive ownership of the mutex,
+ //! waits until it can obtain the ownership.
+ //!Throws: interprocess_exception on error.
+ void lock_sharable();
+
+ //!Effects: The calling thread tries to acquire sharable ownership of the mutex
+ //! without waiting. If no other thread has exclusive ownership
+ //! of the mutex this succeeds.
+ //!Returns: If it can acquire sharable ownership immediately returns true. If it
+ //! has to wait, returns false.
+ //!Throws: interprocess_exception on error.
+ bool try_lock_sharable();
+
+ //!Effects: The calling thread tries to acquire sharable ownership of the mutex
+ //! waiting if necessary until no other thread has exclusive
+ //! ownership of the mutex or abs_time is reached.
+ //!Returns: If acquires sharable ownership, returns true. Otherwise returns false.
+ //!Throws: interprocess_exception on error.
+ bool timed_lock_sharable(const boost::posix_time::ptime &abs_time);
+
+ //!Precondition: The thread must have sharable ownership of the mutex.
+ //!Effects: The calling thread releases the sharable ownership of the mutex.
+ //!Throws: An exception derived from interprocess_exception on error.
+ void unlock_sharable();
+
+ //Upgradable locking
+
+ //!Effects: The calling thread tries to obtain upgradable ownership of the mutex,
+ //! and if another thread has exclusive or upgradable ownership of the mutex,
+ //! waits until it can obtain the ownership.
+ //!Throws: interprocess_exception on error.
+ void lock_upgradable();
+
+ //!Effects: The calling thread tries to acquire upgradable ownership of the mutex
+ //! without waiting. If no other thread has exclusive or upgradable ownership
+ //! of the mutex this succeeds.
+ //!Returns: If it can acquire upgradable ownership immediately returns true.
+ //! If it has to wait, returns false.
+ //!Throws: interprocess_exception on error.
+ bool try_lock_upgradable();
+
+ //!Effects: The calling thread tries to acquire upgradable ownership of the mutex
+ //! waiting if necessary until no other thread has exclusive or upgradable
+ //! ownership of the mutex or abs_time is reached.
+ //!Returns: If acquires upgradable ownership, returns true. Otherwise returns false.
+ //!Throws: interprocess_exception on error.
+ bool timed_lock_upgradable(const boost::posix_time::ptime &abs_time);
+
+ //!Precondition: The thread must have upgradable ownership of the mutex.
+ //!Effects: The calling thread releases the upgradable ownership of the mutex.
+ //!Throws: An exception derived from interprocess_exception on error.
+ void unlock_upgradable();
+
+ //Demotions
+
+ //!Precondition: The thread must have exclusive ownership of the mutex.
+ //!Effects: The thread atomically releases exclusive ownership and acquires
+ //! upgradable ownership. This operation is non-blocking.
+ //!Throws: An exception derived from interprocess_exception on error.
+ void unlock_and_lock_upgradable();
+
+ //!Precondition: The thread must have exclusive ownership of the mutex.
+ //!Effects: The thread atomically releases exclusive ownership and acquires
+ //! sharable ownership. This operation is non-blocking.
+ //!Throws: An exception derived from interprocess_exception on error.
+ void unlock_and_lock_sharable();
+
+ //!Precondition: The thread must have upgradable ownership of the mutex.
+ //!Effects: The thread atomically releases upgradable ownership and acquires
+ //! sharable ownership. This operation is non-blocking.
+ //!Throws: An exception derived from interprocess_exception on error.
+ void unlock_upgradable_and_lock_sharable();
+
+ //Promotions
+
+ //!Precondition: The thread must have upgradable ownership of the mutex.
+ //!Effects: The thread atomically releases upgradable ownership and acquires
+ //! exclusive ownership. This operation will block until all threads with
+ //! sharable ownership release their sharable lock.
+ //!Throws: An exception derived from interprocess_exception on error.
+ void unlock_upgradable_and_lock();
+
+ //!Precondition: The thread must have upgradable ownership of the mutex.
+ //!Effects: The thread atomically releases upgradable ownership and tries to
+ //! acquire exclusive ownership. This operation will fail if there are threads
+ //! with sharable ownership, but it will maintain upgradable ownership.
+ //!Returns: If acquires exclusive ownership, returns true. Otherwise returns false.
+ //!Throws: An exception derived from interprocess_exception on error.
+ bool try_unlock_upgradable_and_lock();
+
+ //!Precondition: The thread must have upgradable ownership of the mutex.
+ //!Effects: The thread atomically releases upgradable ownership and tries to acquire
+ //! exclusive ownership, waiting if necessary until abs_time. This operation will
+ //! fail if there are threads with sharable ownership or timeout reaches, but it
+ //! will maintain upgradable ownership.
+ //!Returns: If acquires exclusive ownership, returns true. Otherwise returns false.
+ //!Throws: An exception derived from interprocess_exception on error. */
+ bool timed_unlock_upgradable_and_lock(const boost::posix_time::ptime &abs_time);
+
+ //!Precondition: The thread must have sharable ownership of the mutex.
+ //!Effects: The thread atomically releases sharable ownership and tries to acquire
+ //! exclusive ownership. This operation will fail if there are threads with sharable
+ //! or upgradable ownership, but it will maintain sharable ownership.
+ //!Returns: If acquires exclusive ownership, returns true. Otherwise returns false.
+ //!Throws: An exception derived from interprocess_exception on error.
+ bool try_unlock_sharable_and_lock();
+
+ //!Precondition: The thread must have sharable ownership of the mutex.
+ //!Effects: The thread atomically releases sharable ownership and tries to acquire
+ //! upgradable ownership. This operation will fail if there are threads with sharable
+ //! or upgradable ownership, but it will maintain sharable ownership.
+ //!Returns: If acquires upgradable ownership, returns true. Otherwise returns false.
+ //!Throws: An exception derived from interprocess_exception on error.
+ bool try_unlock_sharable_and_lock_upgradable();
+
+ /// @cond
+ private:
+ typedef scoped_lock<interprocess_mutex> scoped_lock_t;
+
+ //Pack all the control data in a word to be able
+ //to use atomic instructions in the future
+ struct control_word_t
+ {
+ unsigned exclusive_in : 1;
+ unsigned upgradable_in : 1;
+ unsigned num_upr_shar : sizeof(unsigned)*CHAR_BIT-2;
+ } m_ctrl;
+
+ interprocess_mutex m_mut;
+ interprocess_condition m_first_gate;
+ interprocess_condition m_second_gate;
+
+ private:
+ //Rollback structures for exceptions or failure return values
+ struct exclusive_rollback
+ {
+ exclusive_rollback(control_word_t &ctrl
+ ,interprocess_condition &first_gate)
+ : mp_ctrl(&ctrl), m_first_gate(first_gate)
+ {}
+
+ void release()
+ { mp_ctrl = 0; }
+
+ ~exclusive_rollback()
+ {
+ if(mp_ctrl){
+ mp_ctrl->exclusive_in = 0;
+ m_first_gate.notify_all();
+ }
+ }
+ control_word_t *mp_ctrl;
+ interprocess_condition &m_first_gate;
+ };
+
+ struct upgradable_to_exclusive_rollback
+ {
+ upgradable_to_exclusive_rollback(control_word_t &ctrl)
+ : mp_ctrl(&ctrl)
+ {}
+
+ void release()
+ { mp_ctrl = 0; }
+
+ ~upgradable_to_exclusive_rollback()
+ {
+ if(mp_ctrl){
+ //Recover upgradable lock
+ mp_ctrl->upgradable_in = 1;
+ ++mp_ctrl->num_upr_shar;
+ //Execute the second half of exclusive locking
+ mp_ctrl->exclusive_in = 0;
+ }
+ }
+ control_word_t *mp_ctrl;
+ };
+
+ template<int Dummy>
+ struct base_constants_t
+ {
+ static const unsigned max_readers
+ = ~(unsigned(3) << (sizeof(unsigned)*CHAR_BIT-2));
+ };
+ typedef base_constants_t<0> constants;
+ /// @endcond
+};
+
+/// @cond
+
+template <int Dummy>
+const unsigned interprocess_upgradable_mutex::base_constants_t<Dummy>::max_readers;
+
+inline interprocess_upgradable_mutex::interprocess_upgradable_mutex()
+{
+ this->m_ctrl.exclusive_in = 0;
+ this->m_ctrl.upgradable_in = 0;
+ this->m_ctrl.num_upr_shar = 0;
+}
+
+inline interprocess_upgradable_mutex::~interprocess_upgradable_mutex()
+{}
+
+inline void interprocess_upgradable_mutex::lock()
+{
+ scoped_lock_t lock(m_mut);
+
+ //The exclusive lock must block in the first gate
+ //if an exclusive or upgradable lock has been acquired
+ while (this->m_ctrl.exclusive_in || this->m_ctrl.upgradable_in){
+ this->m_first_gate.wait(lock);
+ }
+
+ //Mark that exclusive lock has been acquired
+ this->m_ctrl.exclusive_in = 1;
+
+ //Prepare rollback
+ exclusive_rollback rollback(this->m_ctrl, this->m_first_gate);
+
+ //Now wait until all readers are gone
+ while (this->m_ctrl.num_upr_shar){
+ this->m_second_gate.wait(lock);
+ }
+ rollback.release();
+}
+
+inline bool interprocess_upgradable_mutex::try_lock()
+{
+ scoped_lock_t lock(m_mut, try_to_lock);
+
+ //If we can't lock or any has there is any exclusive, upgradable
+ //or sharable mark return false;
+ if(!lock.owns()
+ || this->m_ctrl.exclusive_in
+ || this->m_ctrl.num_upr_shar){
+ return false;
+ }
+ this->m_ctrl.exclusive_in = 1;
+ return true;
+}
+
+inline bool interprocess_upgradable_mutex::timed_lock
+ (const boost::posix_time::ptime &abs_time)
+{
+ if(abs_time == boost::posix_time::pos_infin){
+ this->lock();
+ return true;
+ }
+ scoped_lock_t lock(m_mut, abs_time);
+ if(!lock.owns()) return false;
+
+ //The exclusive lock must block in the first gate
+ //if an exclusive or upgradable lock has been acquired
+ while (this->m_ctrl.exclusive_in || this->m_ctrl.upgradable_in){
+ if(!this->m_first_gate.timed_wait(lock, abs_time))
+ return !(this->m_ctrl.exclusive_in || this->m_ctrl.upgradable_in);
+ }
+
+ //Mark that exclusive lock has been acquired
+ this->m_ctrl.exclusive_in = 1;
+
+ //Prepare rollback
+ exclusive_rollback rollback(this->m_ctrl, this->m_first_gate);
+
+ //Now wait until all readers are gone
+ while (this->m_ctrl.num_upr_shar){
+ if(!this->m_second_gate.timed_wait(lock, abs_time)){
+ return !(this->m_ctrl.num_upr_shar);
+ }
+ }
+ rollback.release();
+ return true;
+}
+
+inline void interprocess_upgradable_mutex::unlock()
+{
+ scoped_lock_t lock(m_mut);
+ this->m_ctrl.exclusive_in = 0;
+ this->m_first_gate.notify_all();
+}
+
+//Upgradable locking
+
+inline void interprocess_upgradable_mutex::lock_upgradable()
+{
+ scoped_lock_t lock(m_mut);
+
+ //The upgradable lock must block in the first gate
+ //if an exclusive or upgradable lock has been acquired
+ //or there are too many sharable locks
+ while(this->m_ctrl.exclusive_in || this->m_ctrl.upgradable_in
+ || this->m_ctrl.num_upr_shar == constants::max_readers){
+ this->m_first_gate.wait(lock);
+ }
+
+ //Mark that upgradable lock has been acquired
+ //And add upgradable to the sharable count
+ this->m_ctrl.upgradable_in = 1;
+ ++this->m_ctrl.num_upr_shar;
+}
+
+inline bool interprocess_upgradable_mutex::try_lock_upgradable()
+{
+ scoped_lock_t lock(m_mut, try_to_lock);
+
+ //The upgradable lock must fail
+ //if an exclusive or upgradable lock has been acquired
+ //or there are too many sharable locks
+ if(!lock.owns()
+ || this->m_ctrl.exclusive_in
+ || this->m_ctrl.upgradable_in
+ || this->m_ctrl.num_upr_shar == constants::max_readers){
+ return false;
+ }
+
+ //Mark that upgradable lock has been acquired
+ //And add upgradable to the sharable count
+ this->m_ctrl.upgradable_in = 1;
+ ++this->m_ctrl.num_upr_shar;
+ return true;
+}
+
+inline bool interprocess_upgradable_mutex::timed_lock_upgradable
+ (const boost::posix_time::ptime &abs_time)
+{
+ if(abs_time == boost::posix_time::pos_infin){
+ this->lock_upgradable();
+ return true;
+ }
+ scoped_lock_t lock(m_mut, abs_time);
+ if(!lock.owns()) return false;
+
+ //The upgradable lock must block in the first gate
+ //if an exclusive or upgradable lock has been acquired
+ //or there are too many sharable locks
+ while(this->m_ctrl.exclusive_in
+ || this->m_ctrl.upgradable_in
+ || this->m_ctrl.num_upr_shar == constants::max_readers){
+ if(!this->m_first_gate.timed_wait(lock, abs_time)){
+ return!(this->m_ctrl.exclusive_in
+ || this->m_ctrl.upgradable_in
+ || this->m_ctrl.num_upr_shar == constants::max_readers);
+ }
+ }
+
+ //Mark that upgradable lock has been acquired
+ //And add upgradable to the sharable count
+ this->m_ctrl.upgradable_in = 1;
+ ++this->m_ctrl.num_upr_shar;
+ return true;
+}
+
+inline void interprocess_upgradable_mutex::unlock_upgradable()
+{
+ scoped_lock_t lock(m_mut);
+ //Mark that upgradable lock has been acquired
+ //And add upgradable to the sharable count
+ this->m_ctrl.upgradable_in = 0;
+ --this->m_ctrl.num_upr_shar;
+ this->m_first_gate.notify_all();
+}
+
+//Sharable locking
+
+inline void interprocess_upgradable_mutex::lock_sharable()
+{
+ scoped_lock_t lock(m_mut);
+
+ //The sharable lock must block in the first gate
+ //if an exclusive lock has been acquired
+ //or there are too many sharable locks
+ while(this->m_ctrl.exclusive_in
+ || this->m_ctrl.num_upr_shar == constants::max_readers){
+ this->m_first_gate.wait(lock);
+ }
+
+ //Increment sharable count
+ ++this->m_ctrl.num_upr_shar;
+}
+
+inline bool interprocess_upgradable_mutex::try_lock_sharable()
+{
+ scoped_lock_t lock(m_mut, try_to_lock);
+
+ //The sharable lock must fail
+ //if an exclusive lock has been acquired
+ //or there are too many sharable locks
+ if(!lock.owns()
+ || this->m_ctrl.exclusive_in
+ || this->m_ctrl.num_upr_shar == constants::max_readers){
+ return false;
+ }
+
+ //Increment sharable count
+ ++this->m_ctrl.num_upr_shar;
+ return true;
+}
+
+inline bool interprocess_upgradable_mutex::timed_lock_sharable
+ (const boost::posix_time::ptime &abs_time)
+{
+ if(abs_time == boost::posix_time::pos_infin){
+ this->lock_sharable();
+ return true;
+ }
+ scoped_lock_t lock(m_mut, abs_time);
+ if(!lock.owns()) return false;
+
+ //The sharable lock must block in the first gate
+ //if an exclusive lock has been acquired
+ //or there are too many sharable locks
+ while (this->m_ctrl.exclusive_in
+ || this->m_ctrl.num_upr_shar == constants::max_readers){
+ if(!this->m_first_gate.timed_wait(lock, abs_time)){
+ return!(this->m_ctrl.exclusive_in
+ || this->m_ctrl.num_upr_shar == constants::max_readers);
+ }
+ }
+
+ //Increment sharable count
+ ++this->m_ctrl.num_upr_shar;
+ return true;
+}
+
+inline void interprocess_upgradable_mutex::unlock_sharable()
+{
+ scoped_lock_t lock(m_mut);
+ //Decrement sharable count
+ --this->m_ctrl.num_upr_shar;
+ if (this->m_ctrl.num_upr_shar == 0){
+ this->m_second_gate.notify_one();
+ }
+ //Check if there are blocked sharables because of
+ //there were too many sharables
+ else if(this->m_ctrl.num_upr_shar == (constants::max_readers-1)){
+ this->m_first_gate.notify_all();
+ }
+}
+
+//Downgrading
+
+inline void interprocess_upgradable_mutex::unlock_and_lock_upgradable()
+{
+ scoped_lock_t lock(m_mut);
+ //Unmark it as exclusive
+ this->m_ctrl.exclusive_in = 0;
+ //Mark it as upgradable
+ this->m_ctrl.upgradable_in = 1;
+ //The sharable count should be 0 so increment it
+ this->m_ctrl.num_upr_shar = 1;
+ //Notify readers that they can enter
+ m_first_gate.notify_all();
+}
+
+inline void interprocess_upgradable_mutex::unlock_and_lock_sharable()
+{
+ scoped_lock_t lock(m_mut);
+ //Unmark it as exclusive
+ this->m_ctrl.exclusive_in = 0;
+ //The sharable count should be 0 so increment it
+ this->m_ctrl.num_upr_shar = 1;
+ //Notify readers that they can enter
+ m_first_gate.notify_all();
+}
+
+inline void interprocess_upgradable_mutex::unlock_upgradable_and_lock_sharable()
+{
+ scoped_lock_t lock(m_mut);
+ //Unmark it as upgradable (we don't have to decrement count)
+ this->m_ctrl.upgradable_in = 0;
+ //Notify readers/upgradable that they can enter
+ m_first_gate.notify_all();
+}
+
+//Upgrading
+
+inline void interprocess_upgradable_mutex::unlock_upgradable_and_lock()
+{
+ scoped_lock_t lock(m_mut);
+ //Simulate unlock_upgradable() without
+ //notifying sharables.
+ this->m_ctrl.upgradable_in = 0;
+ --this->m_ctrl.num_upr_shar;
+ //Execute the second half of exclusive locking
+ this->m_ctrl.exclusive_in = 1;
+
+ //Prepare rollback
+ upgradable_to_exclusive_rollback rollback(m_ctrl);
+
+ while (this->m_ctrl.num_upr_shar){
+ this->m_second_gate.wait(lock);
+ }
+ rollback.release();
+}
+
+inline bool interprocess_upgradable_mutex::try_unlock_upgradable_and_lock()
+{
+ scoped_lock_t lock(m_mut, try_to_lock);
+ //Check if there are no readers
+ if(!lock.owns()
+ || this->m_ctrl.num_upr_shar != 1){
+ return false;
+ }
+ //Now unlock upgradable and mark exclusive
+ this->m_ctrl.upgradable_in = 0;
+ --this->m_ctrl.num_upr_shar;
+ this->m_ctrl.exclusive_in = 1;
+ return true;
+}
+
+inline bool interprocess_upgradable_mutex::timed_unlock_upgradable_and_lock
+ (const boost::posix_time::ptime &abs_time)
+{
+ scoped_lock_t lock(m_mut, abs_time);
+ if(!lock.owns()) return false;
+
+ //Simulate unlock_upgradable() without
+ //notifying sharables.
+ this->m_ctrl.upgradable_in = 0;
+ --this->m_ctrl.num_upr_shar;
+ //Execute the second half of exclusive locking
+ this->m_ctrl.exclusive_in = 1;
+
+ //Prepare rollback
+ upgradable_to_exclusive_rollback rollback(m_ctrl);
+
+ while (this->m_ctrl.num_upr_shar){
+ if(!this->m_second_gate.timed_wait(lock, abs_time)){
+ return !(this->m_ctrl.num_upr_shar);
+ }
+ }
+ rollback.release();
+ return true;
+}
+
+inline bool interprocess_upgradable_mutex::try_unlock_sharable_and_lock()
+{
+ scoped_lock_t lock(m_mut, try_to_lock);
+
+ //If we can't lock or any has there is any exclusive, upgradable
+ //or sharable mark return false;
+ if(!lock.owns()
+ || this->m_ctrl.exclusive_in
+ || this->m_ctrl.upgradable_in
+ || this->m_ctrl.num_upr_shar != 1){
+ return false;
+ }
+ this->m_ctrl.exclusive_in = 1;
+ this->m_ctrl.num_upr_shar = 0;
+ return true;
+}
+
+inline bool interprocess_upgradable_mutex::try_unlock_sharable_and_lock_upgradable()
+{
+ scoped_lock_t lock(m_mut, try_to_lock);
+
+ //The upgradable lock must fail
+ //if an exclusive or upgradable lock has been acquired
+ if(!lock.owns()
+ || this->m_ctrl.exclusive_in
+ || this->m_ctrl.upgradable_in){
+ return false;
+ }
+
+ //Mark that upgradable lock has been acquired
+ this->m_ctrl.upgradable_in = 1;
+ return true;
+}
+
+/// @endcond
+
+} //namespace interprocess {
+} //namespace boost {
+
+
+#include <boost/interprocess/detail/config_end.hpp>
+
+#endif //BOOST_INTERPROCESS_UPGRADABLE_MUTEX_HPP