/usr/include/boost/interprocess/sync/interprocess_sharable_mutex.hpp is in libboost1.55-dev 1.55.0+dfsg-3.
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// Code based on Howard Hinnant's shared_mutex class
//
// (C) Copyright Howard Hinnant 2007-2010. Distributed under the Boost
// Software License, Version 1.0. (see http://www.boost.org/LICENSE_1_0.txt)
//
// (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.
//
//////////////////////////////////////////////////////////////////////////////
#ifndef BOOST_INTERPROCESS_SHARABLE_MUTEX_HPP
#define BOOST_INTERPROCESS_SHARABLE_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_sharable_mutex class
namespace boost {
namespace interprocess {
//!Wraps a interprocess_sharable_mutex that can be placed in shared memory and can be
//!shared between processes. Allows timed lock tries
class interprocess_sharable_mutex
{
//Non-copyable
interprocess_sharable_mutex(const interprocess_sharable_mutex &);
interprocess_sharable_mutex &operator=(const interprocess_sharable_mutex &);
friend class interprocess_condition;
public:
//!Constructs the sharable lock.
//!Throws interprocess_exception on error.
interprocess_sharable_mutex();
//!Destroys the sharable lock.
//!Does not throw.
~interprocess_sharable_mutex();
//Exclusive locking
//!Effects: The calling thread tries to obtain exclusive ownership of the mutex,
//! and if another thread has exclusive or sharable 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 or sharable
//! 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 or sharable
//! 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();
/// @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 num_shared : sizeof(unsigned)*CHAR_BIT-1;
} 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;
};
template<int Dummy>
struct base_constants_t
{
static const unsigned max_readers
= ~(unsigned(1) << (sizeof(unsigned)*CHAR_BIT-1));
};
typedef base_constants_t<0> constants;
/// @endcond
};
/// @cond
template <int Dummy>
const unsigned interprocess_sharable_mutex::base_constants_t<Dummy>::max_readers;
inline interprocess_sharable_mutex::interprocess_sharable_mutex()
{
this->m_ctrl.exclusive_in = 0;
this->m_ctrl.num_shared = 0;
}
inline interprocess_sharable_mutex::~interprocess_sharable_mutex()
{}
inline void interprocess_sharable_mutex::lock()
{
scoped_lock_t lck(m_mut);
//The exclusive lock must block in the first gate
//if an exclusive lock has been acquired
while (this->m_ctrl.exclusive_in){
this->m_first_gate.wait(lck);
}
//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_shared){
this->m_second_gate.wait(lck);
}
rollback.release();
}
inline bool interprocess_sharable_mutex::try_lock()
{
scoped_lock_t lck(m_mut, try_to_lock);
//If we can't lock or any has there is any exclusive
//or sharable mark return false;
if(!lck.owns()
|| this->m_ctrl.exclusive_in
|| this->m_ctrl.num_shared){
return false;
}
this->m_ctrl.exclusive_in = 1;
return true;
}
inline bool interprocess_sharable_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 lck(m_mut, abs_time);
if(!lck.owns()) return false;
//The exclusive lock must block in the first gate
//if an exclusive lock has been acquired
while (this->m_ctrl.exclusive_in){
if(!this->m_first_gate.timed_wait(lck, abs_time)){
if(this->m_ctrl.exclusive_in){
return false;
}
break;
}
}
//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_shared){
if(!this->m_second_gate.timed_wait(lck, abs_time)){
if(this->m_ctrl.num_shared){
return false;
}
break;
}
}
rollback.release();
return true;
}
inline void interprocess_sharable_mutex::unlock()
{
scoped_lock_t lck(m_mut);
this->m_ctrl.exclusive_in = 0;
this->m_first_gate.notify_all();
}
//Sharable locking
inline void interprocess_sharable_mutex::lock_sharable()
{
scoped_lock_t lck(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_shared == constants::max_readers){
this->m_first_gate.wait(lck);
}
//Increment sharable count
++this->m_ctrl.num_shared;
}
inline bool interprocess_sharable_mutex::try_lock_sharable()
{
scoped_lock_t lck(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(!lck.owns()
|| this->m_ctrl.exclusive_in
|| this->m_ctrl.num_shared == constants::max_readers){
return false;
}
//Increment sharable count
++this->m_ctrl.num_shared;
return true;
}
inline bool interprocess_sharable_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 lck(m_mut, abs_time);
if(!lck.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_shared == constants::max_readers){
if(!this->m_first_gate.timed_wait(lck, abs_time)){
if(this->m_ctrl.exclusive_in
|| this->m_ctrl.num_shared == constants::max_readers){
return false;
}
break;
}
}
//Increment sharable count
++this->m_ctrl.num_shared;
return true;
}
inline void interprocess_sharable_mutex::unlock_sharable()
{
scoped_lock_t lck(m_mut);
//Decrement sharable count
--this->m_ctrl.num_shared;
if (this->m_ctrl.num_shared == 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_shared == (constants::max_readers-1)){
this->m_first_gate.notify_all();
}
}
/// @endcond
} //namespace interprocess {
} //namespace boost {
#include <boost/interprocess/detail/config_end.hpp>
#endif //BOOST_INTERPROCESS_SHARABLE_MUTEX_HPP
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