Chris@16: //////////////////////////////////////////////////////////////////////////////
Chris@16: //  Code based on Howard Hinnant's shared_mutex class
Chris@16: //
Chris@16: // (C) Copyright Howard Hinnant 2007-2010. Distributed under the Boost
Chris@16: // Software License, Version 1.0. (see http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: // (C) Copyright Ion Gaztanaga 2005-2012. Distributed under the Boost
Chris@16: // Software License, Version 1.0. (See accompanying file
Chris@16: // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: // See http://www.boost.org/libs/interprocess for documentation.
Chris@16: //
Chris@16: //////////////////////////////////////////////////////////////////////////////
Chris@16: 
Chris@16: #ifndef BOOST_INTERPROCESS_SHARABLE_MUTEX_HPP
Chris@16: #define BOOST_INTERPROCESS_SHARABLE_MUTEX_HPP
Chris@16: 
Chris@101: #ifndef BOOST_CONFIG_HPP
Chris@101: #  include <boost/config.hpp>
Chris@101: #endif
Chris@101: #
Chris@101: #if defined(BOOST_HAS_PRAGMA_ONCE)
Chris@16: #  pragma once
Chris@16: #endif
Chris@16: 
Chris@16: #include <boost/interprocess/detail/config_begin.hpp>
Chris@16: #include <boost/interprocess/detail/workaround.hpp>
Chris@16: #include <boost/interprocess/sync/scoped_lock.hpp>
Chris@16: #include <boost/interprocess/detail/posix_time_types_wrk.hpp>
Chris@16: #include <boost/interprocess/sync/interprocess_mutex.hpp>
Chris@16: #include <boost/interprocess/sync/interprocess_condition.hpp>
Chris@16: #include <climits>
Chris@16: 
Chris@16: 
Chris@16: //!\file
Chris@16: //!Describes interprocess_sharable_mutex class
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace interprocess {
Chris@16: 
Chris@16: //!Wraps a interprocess_sharable_mutex that can be placed in shared memory and can be
Chris@16: //!shared between processes. Allows timed lock tries
Chris@16: class interprocess_sharable_mutex
Chris@16: {
Chris@16:    //Non-copyable
Chris@16:    interprocess_sharable_mutex(const interprocess_sharable_mutex &);
Chris@16:    interprocess_sharable_mutex &operator=(const interprocess_sharable_mutex &);
Chris@16: 
Chris@16:    friend class interprocess_condition;
Chris@16:    public:
Chris@16: 
Chris@16:    //!Constructs the sharable lock.
Chris@16:    //!Throws interprocess_exception on error.
Chris@16:    interprocess_sharable_mutex();
Chris@16: 
Chris@16:    //!Destroys the sharable lock.
Chris@16:    //!Does not throw.
Chris@16:    ~interprocess_sharable_mutex();
Chris@16: 
Chris@16:    //Exclusive locking
Chris@16: 
Chris@16:    //!Effects: The calling thread tries to obtain exclusive ownership of the mutex,
Chris@16:    //!   and if another thread has exclusive or sharable ownership of
Chris@16:    //!   the mutex, it waits until it can obtain the ownership.
Chris@16:    //!Throws: interprocess_exception on error.
Chris@16:    void lock();
Chris@16: 
Chris@16:    //!Effects: The calling thread tries to acquire exclusive ownership of the mutex
Chris@16:    //!   without waiting. If no other thread has exclusive or sharable
Chris@16:    //!   ownership of the mutex this succeeds.
Chris@16:    //!Returns: If it can acquire exclusive ownership immediately returns true.
Chris@16:    //!   If it has to wait, returns false.
Chris@16:    //!Throws: interprocess_exception on error.
Chris@16:    bool try_lock();
Chris@16: 
Chris@16:    //!Effects: The calling thread tries to acquire exclusive ownership of the mutex
Chris@16:    //!   waiting if necessary until no other thread has exclusive or sharable
Chris@16:    //!   ownership of the mutex or abs_time is reached.
Chris@16:    //!Returns: If acquires exclusive ownership, returns true. Otherwise returns false.
Chris@16:    //!Throws: interprocess_exception on error.
Chris@16:    bool timed_lock(const boost::posix_time::ptime &abs_time);
Chris@16: 
Chris@16:    //!Precondition: The thread must have exclusive ownership of the mutex.
Chris@16:    //!Effects: The calling thread releases the exclusive ownership of the mutex.
Chris@16:    //!Throws: An exception derived from interprocess_exception on error.
Chris@16:    void unlock();
Chris@16: 
Chris@16:    //Sharable locking
Chris@16: 
Chris@16:    //!Effects: The calling thread tries to obtain sharable ownership of the mutex,
Chris@16:    //!   and if another thread has exclusive ownership of the mutex,
Chris@16:    //!   waits until it can obtain the ownership.
Chris@16:    //!Throws: interprocess_exception on error.
Chris@16:    void lock_sharable();
Chris@16: 
Chris@16:    //!Effects: The calling thread tries to acquire sharable ownership of the mutex
Chris@16:    //!   without waiting. If no other thread has exclusive ownership
Chris@16:    //!   of the mutex this succeeds.
Chris@16:    //!Returns: If it can acquire sharable ownership immediately returns true. If it
Chris@16:    //!   has to wait, returns false.
Chris@16:    //!Throws: interprocess_exception on error.
Chris@16:    bool try_lock_sharable();
Chris@16: 
Chris@16:    //!Effects: The calling thread tries to acquire sharable ownership of the mutex
Chris@16:    //!   waiting if necessary until no other thread has exclusive
Chris@16:    //!   ownership of the mutex or abs_time is reached.
Chris@16:    //!Returns: If acquires sharable ownership, returns true. Otherwise returns false.
Chris@16:    //!Throws: interprocess_exception on error.
Chris@16:    bool timed_lock_sharable(const boost::posix_time::ptime &abs_time);
Chris@16: 
Chris@16:    //!Precondition: The thread must have sharable ownership of the mutex.
Chris@16:    //!Effects: The calling thread releases the sharable ownership of the mutex.
Chris@16:    //!Throws: An exception derived from interprocess_exception on error.
Chris@16:    void unlock_sharable();
Chris@16: 
Chris@101:    #if !defined(BOOST_INTERPROCESS_DOXYGEN_INVOKED)
Chris@16:    private:
Chris@16:    typedef scoped_lock<interprocess_mutex> scoped_lock_t;
Chris@16: 
Chris@16:    //Pack all the control data in a word to be able
Chris@16:    //to use atomic instructions in the future
Chris@16:    struct control_word_t
Chris@16:    {
Chris@16:       unsigned exclusive_in   : 1;
Chris@16:       unsigned num_shared     : sizeof(unsigned)*CHAR_BIT-1;
Chris@16:    }                       m_ctrl;
Chris@16: 
Chris@16:    interprocess_mutex      m_mut;
Chris@16:    interprocess_condition  m_first_gate;
Chris@16:    interprocess_condition  m_second_gate;
Chris@16: 
Chris@16:    private:
Chris@16:    //Rollback structures for exceptions or failure return values
Chris@16:    struct exclusive_rollback
Chris@16:    {
Chris@16:       exclusive_rollback(control_word_t         &ctrl
Chris@16:                         ,interprocess_condition &first_gate)
Chris@16:          :  mp_ctrl(&ctrl), m_first_gate(first_gate)
Chris@16:       {}
Chris@16: 
Chris@16:       void release()
Chris@16:       {  mp_ctrl = 0;   }
Chris@16: 
Chris@16:       ~exclusive_rollback()
Chris@16:       {
Chris@16:          if(mp_ctrl){
Chris@16:             mp_ctrl->exclusive_in = 0;
Chris@16:             m_first_gate.notify_all();
Chris@16:          }
Chris@16:       }
Chris@16:       control_word_t          *mp_ctrl;
Chris@16:       interprocess_condition  &m_first_gate;
Chris@16:    };
Chris@16: 
Chris@16:    template<int Dummy>
Chris@16:    struct base_constants_t
Chris@16:    {
Chris@16:       static const unsigned max_readers
Chris@16:          = ~(unsigned(1) << (sizeof(unsigned)*CHAR_BIT-1));
Chris@16:    };
Chris@16:    typedef base_constants_t<0> constants;
Chris@101:    #endif   //#ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED
Chris@16: };
Chris@16: 
Chris@101: #if !defined(BOOST_INTERPROCESS_DOXYGEN_INVOKED)
Chris@16: 
Chris@16: template <int Dummy>
Chris@16: const unsigned interprocess_sharable_mutex::base_constants_t<Dummy>::max_readers;
Chris@16: 
Chris@16: inline interprocess_sharable_mutex::interprocess_sharable_mutex()
Chris@16: {
Chris@16:    this->m_ctrl.exclusive_in  = 0;
Chris@16:    this->m_ctrl.num_shared   = 0;
Chris@16: }
Chris@16: 
Chris@16: inline interprocess_sharable_mutex::~interprocess_sharable_mutex()
Chris@16: {}
Chris@16: 
Chris@16: inline void interprocess_sharable_mutex::lock()
Chris@16: {
Chris@16:    scoped_lock_t lck(m_mut);
Chris@16: 
Chris@16:    //The exclusive lock must block in the first gate
Chris@16:    //if an exclusive lock has been acquired
Chris@16:    while (this->m_ctrl.exclusive_in){
Chris@16:       this->m_first_gate.wait(lck);
Chris@16:    }
Chris@16: 
Chris@16:    //Mark that exclusive lock has been acquired
Chris@16:    this->m_ctrl.exclusive_in = 1;
Chris@16: 
Chris@16:    //Prepare rollback
Chris@16:    exclusive_rollback rollback(this->m_ctrl, this->m_first_gate);
Chris@16: 
Chris@16:    //Now wait until all readers are gone
Chris@16:    while (this->m_ctrl.num_shared){
Chris@16:       this->m_second_gate.wait(lck);
Chris@16:    }
Chris@16:    rollback.release();
Chris@16: }
Chris@16: 
Chris@16: inline bool interprocess_sharable_mutex::try_lock()
Chris@16: {
Chris@16:    scoped_lock_t lck(m_mut, try_to_lock);
Chris@16: 
Chris@16:    //If we can't lock or any has there is any exclusive
Chris@16:    //or sharable mark return false;
Chris@16:    if(!lck.owns()
Chris@16:       || this->m_ctrl.exclusive_in
Chris@16:       || this->m_ctrl.num_shared){
Chris@16:       return false;
Chris@16:    }
Chris@16:    this->m_ctrl.exclusive_in = 1;
Chris@16:    return true;
Chris@16: }
Chris@16: 
Chris@16: inline bool interprocess_sharable_mutex::timed_lock
Chris@16:    (const boost::posix_time::ptime &abs_time)
Chris@16: {
Chris@16:    scoped_lock_t lck(m_mut, abs_time);
Chris@16:    if(!lck.owns())   return false;
Chris@16: 
Chris@16:    //The exclusive lock must block in the first gate
Chris@16:    //if an exclusive lock has been acquired
Chris@16:    while (this->m_ctrl.exclusive_in){
Chris@101:       //Mutexes and condvars handle just fine infinite abs_times
Chris@101:       //so avoid checking it here
Chris@16:       if(!this->m_first_gate.timed_wait(lck, abs_time)){
Chris@16:          if(this->m_ctrl.exclusive_in){
Chris@16:             return false;
Chris@16:          }
Chris@16:          break;
Chris@16:       }
Chris@16:    }
Chris@16: 
Chris@16:    //Mark that exclusive lock has been acquired
Chris@16:    this->m_ctrl.exclusive_in = 1;
Chris@16: 
Chris@16:    //Prepare rollback
Chris@16:    exclusive_rollback rollback(this->m_ctrl, this->m_first_gate);
Chris@16: 
Chris@16:    //Now wait until all readers are gone
Chris@16:    while (this->m_ctrl.num_shared){
Chris@101:       //Mutexes and condvars handle just fine infinite abs_times
Chris@101:       //so avoid checking it here
Chris@16:       if(!this->m_second_gate.timed_wait(lck, abs_time)){
Chris@16:          if(this->m_ctrl.num_shared){
Chris@16:             return false;
Chris@16:          }
Chris@16:          break;
Chris@16:       }
Chris@16:    }
Chris@16:    rollback.release();
Chris@16:    return true;
Chris@16: }
Chris@16: 
Chris@16: inline void interprocess_sharable_mutex::unlock()
Chris@16: {
Chris@16:    scoped_lock_t lck(m_mut);
Chris@16:    this->m_ctrl.exclusive_in = 0;
Chris@16:    this->m_first_gate.notify_all();
Chris@16: }
Chris@16: 
Chris@16: //Sharable locking
Chris@16: 
Chris@16: inline void interprocess_sharable_mutex::lock_sharable()
Chris@16: {
Chris@16:    scoped_lock_t lck(m_mut);
Chris@16: 
Chris@16:    //The sharable lock must block in the first gate
Chris@16:    //if an exclusive lock has been acquired
Chris@16:    //or there are too many sharable locks
Chris@16:    while(this->m_ctrl.exclusive_in
Chris@16:         || this->m_ctrl.num_shared == constants::max_readers){
Chris@16:       this->m_first_gate.wait(lck);
Chris@16:    }
Chris@16: 
Chris@16:    //Increment sharable count
Chris@16:    ++this->m_ctrl.num_shared;
Chris@16: }
Chris@16: 
Chris@16: inline bool interprocess_sharable_mutex::try_lock_sharable()
Chris@16: {
Chris@16:    scoped_lock_t lck(m_mut, try_to_lock);
Chris@16: 
Chris@16:    //The sharable lock must fail
Chris@16:    //if an exclusive lock has been acquired
Chris@16:    //or there are too many sharable locks
Chris@16:    if(!lck.owns()
Chris@16:       || this->m_ctrl.exclusive_in
Chris@16:       || this->m_ctrl.num_shared == constants::max_readers){
Chris@16:       return false;
Chris@16:    }
Chris@16: 
Chris@16:    //Increment sharable count
Chris@16:    ++this->m_ctrl.num_shared;
Chris@16:    return true;
Chris@16: }
Chris@16: 
Chris@16: inline bool interprocess_sharable_mutex::timed_lock_sharable
Chris@16:    (const boost::posix_time::ptime &abs_time)
Chris@16: {
Chris@16:    scoped_lock_t lck(m_mut, abs_time);
Chris@16:    if(!lck.owns())   return false;
Chris@16: 
Chris@16:    //The sharable lock must block in the first gate
Chris@16:    //if an exclusive lock has been acquired
Chris@16:    //or there are too many sharable locks
Chris@16:    while (this->m_ctrl.exclusive_in
Chris@16:          || this->m_ctrl.num_shared == constants::max_readers){
Chris@101:       //Mutexes and condvars handle just fine infinite abs_times
Chris@101:       //so avoid checking it here
Chris@16:       if(!this->m_first_gate.timed_wait(lck, abs_time)){
Chris@16:          if(this->m_ctrl.exclusive_in
Chris@16:                || this->m_ctrl.num_shared == constants::max_readers){
Chris@16:             return false;
Chris@16:          }
Chris@16:          break;
Chris@16:       }
Chris@16:    }
Chris@16: 
Chris@16:    //Increment sharable count
Chris@16:    ++this->m_ctrl.num_shared;
Chris@16:    return true;
Chris@16: }
Chris@16: 
Chris@16: inline void interprocess_sharable_mutex::unlock_sharable()
Chris@16: {
Chris@16:    scoped_lock_t lck(m_mut);
Chris@16:    //Decrement sharable count
Chris@16:    --this->m_ctrl.num_shared;
Chris@16:    if (this->m_ctrl.num_shared == 0){
Chris@16:       this->m_second_gate.notify_one();
Chris@16:    }
Chris@16:    //Check if there are blocked sharables because of
Chris@16:    //there were too many sharables
Chris@16:    else if(this->m_ctrl.num_shared == (constants::max_readers-1)){
Chris@16:       this->m_first_gate.notify_all();
Chris@16:    }
Chris@16: }
Chris@16: 
Chris@101: #endif   //#ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED
Chris@16: 
Chris@16: }  //namespace interprocess {
Chris@16: }  //namespace boost {
Chris@16: 
Chris@16: #include <boost/interprocess/detail/config_end.hpp>
Chris@16: 
Chris@16: #endif   //BOOST_INTERPROCESS_SHARABLE_MUTEX_HPP