////////////////////////////////////////////////////////////////////////////// | |
// | |
// (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_SHARABLE_LOCK_HPP | |
#define BOOST_INTERPROCESS_SHARABLE_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/exceptions.hpp> | |
#include <boost/interprocess/detail/mpl.hpp> | |
#include <boost/interprocess/detail/type_traits.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 { | |
//!sharable_lock is meant to carry out the tasks for sharable-locking | |
//!(such as read-locking), unlocking, try-sharable-locking and timed-sharable-locking | |
//!(recursive or not) for the Mutex. The Mutex need not supply all of this | |
//!functionality. If the client of sharable_lock<Mutex> does not use functionality which | |
//!the Mutex does not supply, no harm is done. Mutex ownership can be shared among | |
//!sharable_locks, and a single upgradable_lock. sharable_lock does not support | |
//!copy semantics. But sharable_lock supports ownership transfer from an sharable_lock, | |
//!upgradable_lock and scoped_lock via transfer_lock syntax.*/ | |
template <class SharableMutex> | |
class sharable_lock | |
{ | |
public: | |
typedef SharableMutex mutex_type; | |
/// @cond | |
private: | |
typedef sharable_lock<SharableMutex> this_type; | |
explicit sharable_lock(scoped_lock<mutex_type>&); | |
typedef bool this_type::*unspecified_bool_type; | |
BOOST_INTERPROCESS_MOVABLE_BUT_NOT_COPYABLE(sharable_lock) | |
/// @endcond | |
public: | |
//!Effects: Default constructs a sharable_lock. | |
//!Postconditions: owns() == false and mutex() == 0. | |
sharable_lock() | |
: mp_mutex(0), m_locked(false) | |
{} | |
//!Effects: m.lock_sharable(). | |
//!Postconditions: owns() == true and mutex() == &m. | |
//!Notes: The constructor will take sharable-ownership of the mutex. If | |
//! another thread already owns the mutex with exclusive ownership | |
//! (scoped_lock), this thread will block until the mutex is released. | |
//! If another thread owns the mutex with sharable or upgradable ownership, | |
//! then no blocking will occur. Whether or not this constructor handles | |
//! recursive locking depends upon the mutex. | |
explicit sharable_lock(mutex_type& m) | |
: mp_mutex(&m), m_locked(false) | |
{ mp_mutex->lock_sharable(); 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. | |
sharable_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 sharable | |
//! locked. There is no effect required on the referenced mutex. | |
sharable_lock(mutex_type& m, accept_ownership_type) | |
: mp_mutex(&m), m_locked(true) | |
{} | |
//!Effects: m.try_lock_sharable() | |
//!Postconditions: mutex() == &m. owns() == the return value of the | |
//! m.try_lock_sharable() executed within the constructor. | |
//!Notes: The constructor will take sharable-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_sharable, this constructor will fail at compile | |
//! time if instantiated, but otherwise have no effect. | |
sharable_lock(mutex_type& m, try_to_lock_type) | |
: mp_mutex(&m), m_locked(false) | |
{ m_locked = mp_mutex->try_lock_sharable(); } | |
//!Effects: m.timed_lock_sharable(abs_time) | |
//!Postconditions: mutex() == &m. owns() == the return value of the | |
//! m.timed_lock_sharable() executed within the constructor. | |
//!Notes: The constructor will take sharable-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_sharable, this constructor will fail at | |
//! compile time if instantiated, but otherwise have no effect. | |
sharable_lock(mutex_type& m, const boost::posix_time::ptime& abs_time) | |
: mp_mutex(&m), m_locked(false) | |
{ m_locked = mp_mutex->timed_lock_sharable(abs_time); } | |
//!Postconditions: mutex() == upgr.mutex(). owns() == the value of upgr.owns() | |
//! before the construction. upgr.owns() == false after the construction. | |
//!Notes: If the upgr sharable_lock owns the mutex, ownership is moved to this | |
//! sharable_lock with no blocking. If the upgr sharable_lock does not own the mutex, then | |
//! neither will this sharable_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);". This constructor does not alter the state of the mutex, | |
//! only potentially who owns it. | |
sharable_lock(BOOST_INTERPROCESS_RV_REF(sharable_lock<mutex_type>) upgr) | |
: mp_mutex(0), m_locked(upgr.owns()) | |
{ mp_mutex = upgr.release(); } | |
//!Effects: If upgr.owns() then calls unlock_upgradable_and_lock_sharable() on the | |
//! referenced mutex. | |
//!Postconditions: mutex() == the value upgr.mutex() had before the construction. | |
//! upgr.mutex() == 0 owns() == the value of upgr.owns() before construction. | |
//! upgr.owns() == false after the construction. | |
//!Notes: If upgr is locked, this constructor will lock this sharable_lock while | |
//! unlocking upgr. Only a moved sharable_lock's will match this | |
//! signature. An non-moved upgradable_lock can be moved with the expression: | |
//! "boost::interprocess::move(lock);".*/ | |
template<class T> | |
sharable_lock(BOOST_INTERPROCESS_RV_REF(upgradable_lock<T>) upgr | |
, typename detail::enable_if< detail::is_same<T, SharableMutex> >::type * = 0) | |
: mp_mutex(0), m_locked(false) | |
{ | |
upgradable_lock<mutex_type> &u_lock = upgr; | |
if(u_lock.owns()){ | |
u_lock.mutex()->unlock_upgradable_and_lock_sharable(); | |
m_locked = true; | |
} | |
mp_mutex = u_lock.release(); | |
} | |
//!Effects: If scop.owns() then calls unlock_and_lock_sharable() on the | |
//! referenced mutex. | |
//!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 a sharable-ownership of this sharable_lock. | |
//! Only a moved scoped_lock's will match this | |
//! signature. An non-moved scoped_lock can be moved with the expression: | |
//! "boost::interprocess::move(lock);". | |
template<class T> | |
sharable_lock(BOOST_INTERPROCESS_RV_REF(scoped_lock<T>) scop | |
, typename detail::enable_if< detail::is_same<T, SharableMutex> >::type * = 0) | |
: mp_mutex(0), m_locked(false) | |
{ | |
scoped_lock<mutex_type> &e_lock = scop; | |
if(e_lock.owns()){ | |
e_lock.mutex()->unlock_and_lock_sharable(); | |
m_locked = true; | |
} | |
mp_mutex = e_lock.release(); | |
} | |
//!Effects: if (owns()) mp_mutex->unlock_sharable(). | |
//!Notes: The destructor behavior ensures that the mutex lock is not leaked. | |
~sharable_lock() | |
{ | |
try{ | |
if(m_locked && mp_mutex) mp_mutex->unlock_sharable(); | |
} | |
catch(...){} | |
} | |
//!Effects: If owns() before the call, then unlock_sharable() 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 lock count will be decremented by one. | |
sharable_lock &operator=(BOOST_INTERPROCESS_RV_REF(sharable_lock<mutex_type>) upgr) | |
{ | |
if(this->owns()) | |
this->unlock(); | |
m_locked = upgr.owns(); | |
mp_mutex = upgr.release(); | |
return *this; | |
} | |
//!Effects: If mutex() == 0 or already locked, throws a lock_exception() | |
//! exception. Calls lock_sharable() 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_sharable(); | |
m_locked = true; | |
} | |
//!Effects: If mutex() == 0 or already locked, throws a lock_exception() | |
//! exception. Calls try_lock_sharable() on the referenced mutex. | |
//!Postconditions: owns() == the value returned from | |
//! mutex()->try_lock_sharable(). | |
//!Notes: The sharable_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_sharable(), 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_sharable(); | |
return m_locked; | |
} | |
//!Effects: If mutex() == 0 or already locked, throws a lock_exception() | |
//! exception. Calls timed_lock_sharable(abs_time) on the referenced mutex. | |
//!Postconditions: owns() == the value returned from | |
//! mutex()->timed_lock_sharable(elps_time). | |
//!Notes: The sharable_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 interval. If the mutex_type does not support | |
//! timed_lock_sharable(), 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_sharable(abs_time); | |
return m_locked; | |
} | |
//!Effects: If mutex() == 0 or not locked, throws a lock_exception() exception. | |
//! Calls unlock_sharable() on the referenced mutex. | |
//!Postconditions: owns() == false. | |
//!Notes: The sharable_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_sharable(); | |
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(sharable_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_SHARABLE_LOCK_HPP |