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A mutex object facilitates protection against data races and allows thread-safe synchronization of data between threads. A thread obtains ownership of a mutex object by calling one of the lock functions and relinquishes ownership by calling the corresponding unlock function. Mutexes may be either recursive or non-recursive, and may grant simultaneous ownership to one or many threads. Boost.Thread supplies recursive and non-recursive mutexes with exclusive ownership semantics, along with a shared ownership (multiple-reader / single-writer) mutex.
Boost.Thread supports four basic concepts
for lockable objects: Lockable, TimedLockable, SharedLockable and UpgradeLockable. Each mutex type
implements one or more of these concepts, as do the various lock types.
The Lockable concept models exclusive
ownership. A type that implements the Lockable concept shall provide
the following member functions:
Lock ownership acquired through a call to lock()
or try_lock()
must be released through a call to unlock().
The current thread blocks until ownership can be obtained for the current thread.
The current thread owns *this.
boost::thread_resource_error if an error
occurs.
Attempt to obtain ownership for the current thread without blocking.
true if ownership
was obtained for the current thread, false
otherwise.
If the call returns true,
the current thread owns the *this.
boost::thread_resource_error if an error
occurs.
The current thread owns *this.
Releases ownership by the current thread.
The current thread no longer owns *this.
Nothing
The TimedLockable concept refines
the Lockable concept to add support
for timeouts when trying to acquire the lock.
A type that implements the TimedLockable concept shall meet
the requirements of the Lockable concept. In addition,
the following member functions must be provided:
Lock ownership acquired through a call to timed_lock()
must be released through a call to unlock().
Attempt to obtain ownership for the current thread. Blocks until
ownership can be obtained, or the specified time is reached. If
the specified time has already passed, behaves as try_lock().
true if ownership
was obtained for the current thread, false
otherwise.
If the call returns true,
the current thread owns *this.
boost::thread_resource_error if an error
occurs.
The SharedLockable concept is a refinement
of the TimedLockable concept that allows
for shared ownership as well as exclusive
ownership. This is the standard multiple-reader / single-write
model: at most one thread can have exclusive ownership, and if any thread
does have exclusive ownership, no other threads can have shared or exclusive
ownership. Alternatively, many threads may have shared ownership.
For a type to implement the SharedLockable concept, as well
as meeting the requirements of the TimedLockable concept, it must
also provide the following member functions:
Lock ownership acquired through a call to lock_shared(),
try_lock_shared()
or timed_lock_shared()
must be released through a call to unlock_shared().
The current thread blocks until shared ownership can be obtained for the current thread.
The current thread has shared ownership of *this.
boost::thread_resource_error if an error
occurs.
Attempt to obtain shared ownership for the current thread without blocking.
true if shared ownership
was obtained for the current thread, false
otherwise.
If the call returns true,
the current thread has shared ownership of *this.
boost::thread_resource_error if an error
occurs.
Attempt to obtain shared ownership for the current thread. Blocks
until shared ownership can be obtained, or the specified time is
reached. If the specified time has already passed, behaves as
try_lock_shared().
true if shared ownership
was acquired for the current thread, false
otherwise.
If the call returns true,
the current thread has shared ownership of *this.
boost::thread_resource_error if an error
occurs.
The current thread has shared ownership of *this.
Releases shared ownership of *this by the current thread.
The current thread no longer has shared ownership of *this.
Nothing
The UpgradeLockable concept is a refinement
of the SharedLockable concept that allows
for upgradable ownership as well as shared
ownership and exclusive ownership. This
is an extension to the multiple-reader / single-write model provided by
the SharedLockable concept: a single
thread may have upgradable ownership at the same time
as others have shared ownership. The thread with
upgradable ownership may at any time attempt to upgrade
that ownership to exclusive ownership. If no other
threads have shared ownership, the upgrade is completed immediately, and
the thread now has exclusive ownership, which must
be relinquished by a call to unlock(),
just as if it had been acquired by a call to lock().
If a thread with upgradable ownership tries to upgrade whilst other threads have shared ownership, the attempt will fail and the thread will block until exclusive ownership can be acquired.
Ownership can also be downgraded as well as upgraded:
exclusive ownership of an implementation of the UpgradeLockable concept can be
downgraded to upgradable ownership or shared ownership, and upgradable
ownership can be downgraded to plain shared ownership.
For a type to implement the UpgradeLockable concept, as well
as meeting the requirements of the SharedLockable concept, it must
also provide the following member functions:
Lock ownership acquired through a call to lock_upgrade()
must be released through a call to unlock_upgrade().
If the ownership type is changed through a call to one of the unlock_xxx_and_lock_yyy()
functions, ownership must be released through a call to the unlock function
corresponding to the new level of ownership.
The current thread blocks until upgrade ownership can be obtained for the current thread.
The current thread has upgrade ownership of *this.
boost::thread_resource_error if an error
occurs.
The current thread has upgrade ownership of *this.
Releases upgrade ownership of *this by the current thread.
The current thread no longer has upgrade ownership of *this.
Nothing
The current thread has upgrade ownership of *this.
Atomically releases upgrade ownership of *this by the current thread and acquires
exclusive ownership of *this. If any other threads have
shared ownership, blocks until exclusive ownership can be acquired.
The current thread has exclusive ownership of *this.
Nothing
The current thread has upgrade ownership of *this.
Atomically releases upgrade ownership of *this by the current thread and acquires
shared ownership of *this without blocking.
The current thread has shared ownership of *this.
Nothing
The current thread has exclusive ownership of *this.
Atomically releases exclusive ownership of *this by the current thread and acquires
upgrade ownership of *this without blocking.
The current thread has upgrade ownership of *this.
Nothing
#include <boost/thread/locks.hpp> struct defer_lock_t {}; struct try_to_lock_t {}; struct adopt_lock_t {}; const defer_lock_t defer_lock; const try_to_lock_t try_to_lock; const adopt_lock_t adopt_lock;
These tags are used in scoped locks constructors to specify a specific behavior.
defer_lock_t: is used
to construct the scoped lock without locking it.
try_to_lock_t: is used
to construct the scoped lock trying to lock it.
adopt_lock_t: is used
to construct the scoped lock without locking it but adopting ownership.
#include <boost/thread/locks.hpp> template<typename Lockable> class lock_guard { public: explicit lock_guard(Lockable& m_); lock_guard(Lockable& m_,boost::adopt_lock_t); ~lock_guard(); };
boost::lock_guard
is very simple: on construction it acquires ownership of the implementation
of the Lockable concept supplied as the
constructor parameter. On destruction, the ownership is released. This
provides simple RAII-style locking of a Lockable object, to facilitate
exception-safe locking and unlocking. In addition, the lock_guard(Lockable &
m,boost::adopt_lock_t)
constructor allows the boost::lock_guard object to take ownership
of a lock already held by the current thread.
The current thread owns a lock on m
equivalent to one obtained by a call to m.lock().
Stores a reference to m.
Takes ownership of the lock state of m.
Nothing.
Invokes m.unlock()
on the Lockable object passed
to the constructor.
Nothing.
unique_lock()unique_lock(Lockable &
m)unique_lock(Lockable &
m,boost::adopt_lock_t)unique_lock(Lockable &
m,boost::defer_lock_t)unique_lock(Lockable &
m,boost::try_to_lock_t)unique_lock(Lockable &
m,boost::system_time const& abs_time)~unique_lock()bool owns_lock() constLockable* mutex() constoperator unspecified-bool-type() constbool operator!() constLockable* release()#include <boost/thread/locks.hpp> template<typename Lockable> class unique_lock { public: unique_lock(); explicit unique_lock(Lockable& m_); unique_lock(Lockable& m_,adopt_lock_t); unique_lock(Lockable& m_,defer_lock_t); unique_lock(Lockable& m_,try_to_lock_t); unique_lock(Lockable& m_,system_time const& target_time); ~unique_lock(); unique_lock(detail::thread_move_t<unique_lock<Lockable> > other); unique_lock(detail::thread_move_t<upgrade_lock<Lockable> > other); operator detail::thread_move_t<unique_lock<Lockable> >(); detail::thread_move_t<unique_lock<Lockable> > move(); unique_lock& operator=(detail::thread_move_t<unique_lock<Lockable> > other); unique_lock& operator=(detail::thread_move_t<upgrade_lock<Lockable> > other); void swap(unique_lock& other); void swap(detail::thread_move_t<unique_lock<Lockable> > other); void lock(); bool try_lock(); template<typename TimeDuration> bool timed_lock(TimeDuration const& relative_time); bool timed_lock(::boost::system_time const& absolute_time); void unlock(); bool owns_lock() const; operator unspecified-bool-type() const; bool operator!() const; Lockable* mutex() const; Lockable* release(); };
boost::unique_lock is more complex than
boost::lock_guard:
not only does it provide for RAII-style locking, it also allows for deferring
acquiring the lock until the lock()
member function is called explicitly, or trying to acquire the lock in
a non-blocking fashion, or with a timeout. Consequently, unlock()
is only called in the destructor if the lock object has locked the Lockable object, or otherwise
adopted a lock on the Lockable object.
Specializations of boost::unique_lock model the TimedLockable concept if the supplied
Lockable type itself models TimedLockable concept (e.g. boost::unique_lock<boost::timed_mutex>),
or the Lockable concept otherwise (e.g.
boost::unique_lock<boost::mutex>).
An instance of boost::unique_lock is said to own
the lock state of a Lockable m
if mutex()
returns a pointer to m
and owns_lock()
returns true. If an object
that owns the lock state of a Lockable object is destroyed,
then the destructor will invoke mutex()->unlock().
The member functions of boost::unique_lock are not thread-safe.
In particular, boost::unique_lock is intended to model
the ownership of a Lockable object by a particular
thread, and the member functions that release ownership of the lock state
(including the destructor) must be called by the same thread that acquired
ownership of the lock state.
Creates a lock object with no associated mutex.
owns_lock()
returns false. mutex()
returns NULL.
Nothing.
Stores a reference to m.
Invokes m.lock().
owns_lock()
returns true. mutex()
returns &m.
Any exception thrown by the call to m.lock().
The current thread owns an exclusive lock on m.
Stores a reference to m.
Takes ownership of the lock state of m.
owns_lock()
returns true. mutex()
returns &m.
Nothing.
Stores a reference to m.
owns_lock()
returns false. mutex()
returns &m.
Nothing.
Stores a reference to m.
Invokes m.try_lock(),
and takes ownership of the lock state if the call returns true.
mutex()
returns &m.
If the call to try_lock()
returned true, then
owns_lock()
returns true, otherwise
owns_lock()
returns false.
Nothing.
Stores a reference to m.
Invokes m.timed_lock(abs_time),
and takes ownership of the lock state if the call returns true.
mutex()
returns &m.
If the call to timed_lock()
returned true, then
owns_lock()
returns true, otherwise
owns_lock()
returns false.
Any exceptions thrown by the call to m.timed_lock(abs_time).
Invokes mutex()-> unlock()
if owns_lock()
returns true.
Nothing.
true if the *this
owns the lock on the Lockable object associated
with *this.
Nothing.
A pointer to the Lockable object associated
with *this,
or NULL if there
is no such object.
Nothing.
If owns_lock()
would return true,
a value that evaluates to true
in boolean contexts, otherwise a value that evaluates to false in boolean contexts.
Nothing.
! owns_lock().
Nothing.
The association between *this and the Lockable object is removed,
without affecting the lock state of the Lockable object. If owns_lock()
would have returned true,
it is the responsibility of the calling code to ensure that the
Lockable is correctly
unlocked.
A pointer to the Lockable object associated
with *this
at the point of the call, or NULL
if there is no such object.
Nothing.
*this
is no longer associated with any Lockable object. mutex()
returns NULL and
owns_lock()
returns false.
shared_lock()shared_lock(Lockable &
m)shared_lock(Lockable &
m,boost::adopt_lock_t)shared_lock(Lockable &
m,boost::defer_lock_t)shared_lock(Lockable &
m,boost::try_to_lock_t)shared_lock(Lockable &
m,boost::system_time const& abs_time)~shared_lock()bool owns_lock() constLockable* mutex() constoperator unspecified-bool-type() constbool operator!() constLockable* release()#include <boost/thread/locks.hpp> template<typename Lockable> class shared_lock { public: shared_lock(); explicit shared_lock(Lockable& m_); shared_lock(Lockable& m_,adopt_lock_t); shared_lock(Lockable& m_,defer_lock_t); shared_lock(Lockable& m_,try_to_lock_t); shared_lock(Lockable& m_,system_time const& target_time); shared_lock(detail::thread_move_t<shared_lock<Lockable> > other); shared_lock(detail::thread_move_t<unique_lock<Lockable> > other); shared_lock(detail::thread_move_t<upgrade_lock<Lockable> > other); ~shared_lock(); operator detail::thread_move_t<shared_lock<Lockable> >(); detail::thread_move_t<shared_lock<Lockable> > move(); shared_lock& operator=(detail::thread_move_t<shared_lock<Lockable> > other); shared_lock& operator=(detail::thread_move_t<unique_lock<Lockable> > other); shared_lock& operator=(detail::thread_move_t<upgrade_lock<Lockable> > other); void swap(shared_lock& other); void lock(); bool try_lock(); bool timed_lock(boost::system_time const& target_time); void unlock(); operator unspecified-bool-type() const; bool operator!() const; bool owns_lock() const; };
Like boost::unique_lock, boost::shared_lock models the Lockable concept, but rather than
acquiring unique ownership of the supplied Lockable object, locking an instance
of boost::shared_lock acquires shared ownership.
Like boost::unique_lock, not only does it
provide for RAII-style locking, it also allows for deferring acquiring
the lock until the lock()
member function is called explicitly, or trying to acquire the lock in
a non-blocking fashion, or with a timeout. Consequently, unlock()
is only called in the destructor if the lock object has locked the Lockable object, or otherwise
adopted a lock on the Lockable object.
An instance of boost::shared_lock is said to own
the lock state of a Lockable m
if mutex()
returns a pointer to m
and owns_lock()
returns true. If an object
that owns the lock state of a Lockable object is destroyed,
then the destructor will invoke mutex()->unlock_shared().
The member functions of boost::shared_lock are not thread-safe.
In particular, boost::shared_lock is intended to model
the shared ownership of a Lockable object by a particular
thread, and the member functions that release ownership of the lock state
(including the destructor) must be called by the same thread that acquired
ownership of the lock state.
Creates a lock object with no associated mutex.
owns_lock()
returns false. mutex()
returns NULL.
Nothing.
Stores a reference to m.
Invokes m.lock_shared().
owns_lock()
returns true. mutex()
returns &m.
Any exception thrown by the call to m.lock_shared().
The current thread owns an exclusive lock on m.
Stores a reference to m.
Takes ownership of the lock state of m.
owns_lock()
returns true. mutex()
returns &m.
Nothing.
Stores a reference to m.
owns_lock()
returns false. mutex()
returns &m.
Nothing.
Stores a reference to m.
Invokes m.try_lock_shared(),
and takes ownership of the lock state if the call returns true.
mutex()
returns &m.
If the call to try_lock_shared()
returned true, then
owns_lock()
returns true, otherwise
owns_lock()
returns false.
Nothing.
Stores a reference to m.
Invokes m.timed_lock(abs_time),
and takes ownership of the lock state if the call returns true.
mutex()
returns &m.
If the call to timed_lock_shared()
returned true, then
owns_lock()
returns true, otherwise
owns_lock()
returns false.
Any exceptions thrown by the call to m.timed_lock(abs_time).
Invokes mutex()-> unlock_shared()
if owns_lock()
returns true.
Nothing.
true if the *this
owns the lock on the Lockable object associated
with *this.
Nothing.
A pointer to the Lockable object associated
with *this,
or NULL if there
is no such object.
Nothing.
If owns_lock()
would return true,
a value that evaluates to true
in boolean contexts, otherwise a value that evaluates to false in boolean contexts.
Nothing.
! owns_lock().
Nothing.
The association between *this and the Lockable object is removed,
without affecting the lock state of the Lockable object. If owns_lock()
would have returned true,
it is the responsibility of the calling code to ensure that the
Lockable is correctly
unlocked.
A pointer to the Lockable object associated
with *this
at the point of the call, or NULL
if there is no such object.
Nothing.
*this
is no longer associated with any Lockable object. mutex()
returns NULL and
owns_lock()
returns false.
#include <boost/thread/locks.hpp> template<typename Lockable> class upgrade_lock { public: explicit upgrade_lock(Lockable& m_); upgrade_lock(detail::thread_move_t<upgrade_lock<Lockable> > other); upgrade_lock(detail::thread_move_t<unique_lock<Lockable> > other); ~upgrade_lock(); operator detail::thread_move_t<upgrade_lock<Lockable> >(); detail::thread_move_t<upgrade_lock<Lockable> > move(); upgrade_lock& operator=(detail::thread_move_t<upgrade_lock<Lockable> > other); upgrade_lock& operator=(detail::thread_move_t<unique_lock<Lockable> > other); void swap(upgrade_lock& other); void lock(); void unlock(); operator unspecified-bool-type() const; bool operator!() const; bool owns_lock() const; };
Like boost::unique_lock, boost::upgrade_lock models the Lockable concept, but rather than
acquiring unique ownership of the supplied Lockable object, locking an instance
of boost::upgrade_lock acquires upgrade
ownership.
Like boost::unique_lock, not only does it
provide for RAII-style locking, it also allows for deferring acquiring
the lock until the lock()
member function is called explicitly, or trying to acquire the lock in
a non-blocking fashion, or with a timeout. Consequently, unlock()
is only called in the destructor if the lock object has locked the Lockable object, or otherwise
adopted a lock on the Lockable object.
An instance of boost::upgrade_lock is said to own
the lock state of a Lockable m
if mutex()
returns a pointer to m
and owns_lock()
returns true. If an object
that owns the lock state of a Lockable object is destroyed,
then the destructor will invoke mutex()->unlock_upgrade().
The member functions of boost::upgrade_lock are not thread-safe.
In particular, boost::upgrade_lock is intended to model
the upgrade ownership of a Lockable object by a particular
thread, and the member functions that release ownership of the lock state
(including the destructor) must be called by the same thread that acquired
ownership of the lock state.
#include <boost/thread/locks.hpp> template <class Lockable> class upgrade_to_unique_lock { public: explicit upgrade_to_unique_lock(upgrade_lock<Lockable>& m_); ~upgrade_to_unique_lock(); upgrade_to_unique_lock(detail::thread_move_t<upgrade_to_unique_lock<Lockable> > other); upgrade_to_unique_lock& operator=(detail::thread_move_t<upgrade_to_unique_lock<Lockable> > other); void swap(upgrade_to_unique_lock& other); operator unspecified-bool-type() const; bool operator!() const; bool owns_lock() const; };
boost::upgrade_to_unique_lock allows
for a temporary upgrade of an boost::upgrade_lock to exclusive ownership.
When constructed with a reference to an instance of boost::upgrade_lock, if that instance
has upgrade ownership on some Lockable object, that ownership
is upgraded to exclusive ownership. When the boost::upgrade_to_unique_lock instance
is destroyed, the ownership of the Lockable is downgraded back to
upgrade ownership.
class MutexType::scoped_try_lock { private: MutexType::scoped_try_lock(MutexType::scoped_try_lock<MutexType>& other); MutexType::scoped_try_lock& operator=(MutexType::scoped_try_lock<MutexType>& other); public: MutexType::scoped_try_lock(); explicit MutexType::scoped_try_lock(MutexType& m); MutexType::scoped_try_lock(MutexType& m_,adopt_lock_t); MutexType::scoped_try_lock(MutexType& m_,defer_lock_t); MutexType::scoped_try_lock(MutexType& m_,try_to_lock_t); MutexType::scoped_try_lock(MutexType::scoped_try_lock<MutexType>&& other); MutexType::scoped_try_lock& operator=(MutexType::scoped_try_lock<MutexType>&& other); void swap(MutexType::scoped_try_lock&& other); void lock(); bool try_lock(); void unlock(); bool owns_lock() const; MutexType* mutex() const; MutexType* release(); bool operator!() const; typedef unspecified-bool-type bool_type; operator bool_type() const; };
The member typedef scoped_try_lock
is provided for each distinct MutexType
as a typedef to a class with the preceding definition. The semantics of
each constructor and member function are identical to those of boost::unique_lock<MutexType>
for the same MutexType,
except that the constructor that takes a single reference to a mutex will
call m.try_lock() rather than m.lock().
template<typename Lockable1,typename Lockable2> void lock(Lockable1& l1,Lockable2& l2); template<typename Lockable1,typename Lockable2,typename Lockable3> void lock(Lockable1& l1,Lockable2& l2,Lockable3& l3); template<typename Lockable1,typename Lockable2,typename Lockable3,typename Lockable4> void lock(Lockable1& l1,Lockable2& l2,Lockable3& l3,Lockable4& l4); template<typename Lockable1,typename Lockable2,typename Lockable3,typename Lockable4,typename Lockable5> void lock(Lockable1& l1,Lockable2& l2,Lockable3& l3,Lockable4& l4,Lockable5& l5);
Locks the Lockable objects supplied
as arguments in an unspecified and indeterminate order in a way that
avoids deadlock. It is safe to call this function concurrently from
multiple threads with the same mutexes (or other lockable objects)
in different orders without risk of deadlock. If any of the lock()
or try_lock()
operations on the supplied Lockable objects throws
an exception any locks acquired by the function will be released
before the function exits.
Any exceptions thrown by calling lock()
or try_lock()
on the supplied Lockable objects.
All the supplied Lockable objects are locked
by the calling thread.
template<typename ForwardIterator> void lock(ForwardIterator begin,ForwardIterator end);
The value_type of
ForwardIterator must
implement the Lockable concept
Locks all the Lockable objects in the
supplied range in an unspecified and indeterminate order in a way
that avoids deadlock. It is safe to call this function concurrently
from multiple threads with the same mutexes (or other lockable objects)
in different orders without risk of deadlock. If any of the lock()
or try_lock()
operations on the Lockable objects in the
supplied range throws an exception any locks acquired by the function
will be released before the function exits.
Any exceptions thrown by calling lock()
or try_lock()
on the supplied Lockable objects.
All the Lockable objects in the
supplied range are locked by the calling thread.
template<typename Lockable1,typename Lockable2> int try_lock(Lockable1& l1,Lockable2& l2); template<typename Lockable1,typename Lockable2,typename Lockable3> int try_lock(Lockable1& l1,Lockable2& l2,Lockable3& l3); template<typename Lockable1,typename Lockable2,typename Lockable3,typename Lockable4> int try_lock(Lockable1& l1,Lockable2& l2,Lockable3& l3,Lockable4& l4); template<typename Lockable1,typename Lockable2,typename Lockable3,typename Lockable4,typename Lockable5> int try_lock(Lockable1& l1,Lockable2& l2,Lockable3& l3,Lockable4& l4,Lockable5& l5);
Calls try_lock()
on each of the Lockable objects supplied
as arguments. If any of the calls to try_lock()
returns false then all
locks acquired are released and the zero-based index of the failed
lock is returned.
If any of the try_lock()
operations on the supplied Lockable objects throws
an exception any locks acquired by the function will be released
before the function exits.
-1
if all the supplied Lockable objects are now
locked by the calling thread, the zero-based index of the object
which could not be locked otherwise.
Any exceptions thrown by calling try_lock()
on the supplied Lockable objects.
If the function returns -1, all the supplied Lockable objects are locked
by the calling thread. Otherwise any locks acquired by this function
will have been released.
template<typename ForwardIterator> ForwardIterator try_lock(ForwardIterator begin,ForwardIterator end);
The value_type of
ForwardIterator must
implement the Lockable concept
Calls try_lock()
on each of the Lockable objects in the
supplied range. If any of the calls to try_lock()
returns false then all
locks acquired are released and an iterator referencing the failed
lock is returned.
If any of the try_lock()
operations on the supplied Lockable objects throws
an exception any locks acquired by the function will be released
before the function exits.
end if all the supplied
Lockable objects are now
locked by the calling thread, an iterator referencing the object
which could not be locked otherwise.
Any exceptions thrown by calling try_lock()
on the supplied Lockable objects.
If the function returns end
then all the Lockable objects in the
supplied range are locked by the calling thread, otherwise all locks
acquired by the function have been released.
#include <boost/thread/mutex.hpp> class mutex: boost::noncopyable { public: mutex(); ~mutex(); void lock(); bool try_lock(); void unlock(); typedef platform-specific-type native_handle_type; native_handle_type native_handle(); typedef unique_lock<mutex> scoped_lock; typedef unspecified-type scoped_try_lock; };
boost::mutex implements the Lockable concept to provide an
exclusive-ownership mutex. At most one thread can own the lock on a given
instance of boost::mutex at any time. Multiple concurrent
calls to lock(),
try_lock()
and unlock()
shall be permitted.
typedef platform-specific-type native_handle_type; native_handle_type native_handle();
Returns an instance of native_handle_type
that can be used with platform-specific APIs to manipulate the
underlying implementation. If no such instance exists, native_handle()
and native_handle_type
are not present.
Nothing.
#include <boost/thread/mutex.hpp> typedef mutex try_mutex;
boost::try_mutex is a typedef
to boost::mutex, provided for backwards
compatibility with previous releases of boost.
#include <boost/thread/mutex.hpp> class timed_mutex: boost::noncopyable { public: timed_mutex(); ~timed_mutex(); void lock(); void unlock(); bool try_lock(); bool timed_lock(system_time const & abs_time); template<typename TimeDuration> bool timed_lock(TimeDuration const & relative_time); typedef platform-specific-type native_handle_type; native_handle_type native_handle(); typedef unique_lock<timed_mutex> scoped_timed_lock; typedef unspecified-type scoped_try_lock; typedef scoped_timed_lock scoped_lock; };
boost::timed_mutex implements the TimedLockable concept to provide
an exclusive-ownership mutex. At most one thread can own the lock on a
given instance of boost::timed_mutex at any time. Multiple
concurrent calls to lock(),
try_lock(),
timed_lock(),
timed_lock()
and unlock()
shall be permitted.
typedef platform-specific-type native_handle_type; native_handle_type native_handle();
Returns an instance of native_handle_type
that can be used with platform-specific APIs to manipulate the
underlying implementation. If no such instance exists, native_handle()
and native_handle_type
are not present.
Nothing.
#include <boost/thread/recursive_mutex.hpp> class recursive_mutex: boost::noncopyable { public: recursive_mutex(); ~recursive_mutex(); void lock(); bool try_lock(); void unlock(); typedef platform-specific-type native_handle_type; native_handle_type native_handle(); typedef unique_lock<recursive_mutex> scoped_lock; typedef unspecified-type scoped_try_lock; };
boost::recursive_mutex implements the
Lockable concept to provide an
exclusive-ownership recursive mutex. At most one thread can own the lock
on a given instance of boost::recursive_mutex at any time. Multiple
concurrent calls to lock(),
try_lock()
and unlock()
shall be permitted. A thread that already has exclusive ownership of a
given boost::recursive_mutex instance can call
lock()
or try_lock()
to acquire an additional level of ownership of the mutex. unlock()
must be called once for each level of ownership acquired by a single thread
before ownership can be acquired by another thread.
typedef platform-specific-type native_handle_type; native_handle_type native_handle();
Returns an instance of native_handle_type
that can be used with platform-specific APIs to manipulate the
underlying implementation. If no such instance exists, native_handle()
and native_handle_type
are not present.
Nothing.
#include <boost/thread/recursive_mutex.hpp> typedef recursive_mutex recursive_try_mutex;
boost::recursive_try_mutex is a typedef to boost::recursive_mutex, provided for
backwards compatibility with previous releases of boost.
#include <boost/thread/recursive_mutex.hpp> class recursive_timed_mutex: boost::noncopyable { public: recursive_timed_mutex(); ~recursive_timed_mutex(); void lock(); bool try_lock(); void unlock(); bool timed_lock(system_time const & abs_time); template<typename TimeDuration> bool timed_lock(TimeDuration const & relative_time); typedef platform-specific-type native_handle_type; native_handle_type native_handle(); typedef unique_lock<recursive_timed_mutex> scoped_lock; typedef unspecified-type scoped_try_lock; typedef scoped_lock scoped_timed_lock; };
boost::recursive_timed_mutex implements
the TimedLockable concept to provide
an exclusive-ownership recursive mutex. At most one thread can own the
lock on a given instance of boost::recursive_timed_mutex at any time.
Multiple concurrent calls to lock(),
try_lock(),
timed_lock(),
timed_lock()
and unlock()
shall be permitted. A thread that already has exclusive ownership of a
given boost::recursive_timed_mutex instance
can call lock(),
timed_lock(),
timed_lock()
or try_lock()
to acquire an additional level of ownership of the mutex. unlock()
must be called once for each level of ownership acquired by a single thread
before ownership can be acquired by another thread.
typedef platform-specific-type native_handle_type; native_handle_type native_handle();
Returns an instance of native_handle_type
that can be used with platform-specific APIs to manipulate the
underlying implementation. If no such instance exists, native_handle()
and native_handle_type
are not present.
Nothing.
#include <boost/thread/shared_mutex.hpp> class shared_mutex { public: shared_mutex(); ~shared_mutex(); void lock_shared(); bool try_lock_shared(); bool timed_lock_shared(system_time const& timeout); void unlock_shared(); void lock(); bool try_lock(); bool timed_lock(system_time const& timeout); void unlock(); void lock_upgrade(); void unlock_upgrade(); void unlock_upgrade_and_lock(); void unlock_and_lock_upgrade(); void unlock_and_lock_shared(); void unlock_upgrade_and_lock_shared(); };
The class boost::shared_mutex provides an implementation
of a multiple-reader / single-writer mutex. It implements the UpgradeLockable concept.
Multiple concurrent calls to lock(),
try_lock(),
timed_lock(),
lock_shared(),
try_lock_shared()
and timed_lock_shared()
shall be permitted.
The classes condition_variable
and condition_variable_any
provide a mechanism for one thread to wait for notification from another
thread that a particular condition has become true. The general usage pattern
is that one thread locks a mutex and then calls wait
on an instance of condition_variable
or condition_variable_any.
When the thread is woken from the wait, then it checks to see if the appropriate
condition is now true, and continues if so. If the condition is not true,
then the thread then calls wait
again to resume waiting. In the simplest case, this condition is just a boolean
variable:
boost::condition_variable cond; boost::mutex mut; bool data_ready; void process_data(); void wait_for_data_to_process() { boost::unique_lock<boost::mutex> lock(mut); while(!data_ready) { cond.wait(lock); } process_data(); }
Notice that the lock is passed
to wait: wait
will atomically add the thread to the set of threads waiting on the condition
variable, and unlock the mutex. When the thread is woken, the mutex will
be locked again before the call to wait
returns. This allows other threads to acquire the mutex in order to update
the shared data, and ensures that the data associated with the condition
is correctly synchronized.
In the mean time, another thread sets the condition to true,
and then calls either notify_one
or notify_all on the condition
variable to wake one waiting thread or all the waiting threads respectively.
void retrieve_data(); void prepare_data(); void prepare_data_for_processing() { retrieve_data(); prepare_data(); { boost::lock_guard<boost::mutex> lock(mut); data_ready=true; } cond.notify_one(); }
Note that the same mutex is locked before the shared data is updated, but
that the mutex does not have to be locked across the call to notify_one.
This example uses an object of type condition_variable,
but would work just as well with an object of type condition_variable_any:
condition_variable_any is
more general, and will work with any kind of lock or mutex, whereas condition_variable requires that the lock
passed to wait is an instance
of boost::unique_lock<boost::mutex>.
This enables condition_variable
to make optimizations in some cases, based on the knowledge of the mutex
type; condition_variable_any
typically has a more complex implementation than condition_variable.
condition_variable()~condition_variable()void notify_one()void notify_all()void wait(boost::unique_lock<boost::mutex>& lock)template<typename predicate_type> void wait(boost::unique_lock<boost::mutex>&
lock,
predicate_type pred)bool timed_wait(boost::unique_lock<boost::mutex>& lock,boost::system_time
const&
abs_time)template<typename duration_type> bool timed_wait(boost::unique_lock<boost::mutex>&
lock,duration_type const& rel_time)template<typename predicate_type> bool timed_wait(boost::unique_lock<boost::mutex>&
lock,
boost::system_time const& abs_time, predicate_type
pred)#include <boost/thread/condition_variable.hpp> namespace boost { class condition_variable { public: condition_variable(); ~condition_variable(); void notify_one(); void notify_all(); void wait(boost::unique_lock<boost::mutex>& lock); template<typename predicate_type> void wait(boost::unique_lock<boost::mutex>& lock,predicate_type predicate); bool timed_wait(boost::unique_lock<boost::mutex>& lock,boost::system_time const& abs_time); template<typename duration_type> bool timed_wait(boost::unique_lock<boost::mutex>& lock,duration_type const& rel_time); template<typename predicate_type> bool timed_wait(boost::unique_lock<boost::mutex>& lock,boost::system_time const& abs_time,predicate_type predicate); template<typename duration_type,typename predicate_type> bool timed_wait(boost::unique_lock<boost::mutex>& lock,duration_type const& rel_time,predicate_type predicate); // backwards compatibility bool timed_wait(boost::unique_lock<boost::mutex>& lock,boost::xtime const& abs_time); template<typename predicate_type> bool timed_wait(boost::unique_lock<boost::mutex>& lock,boost::xtime const& abs_time,predicate_type predicate); }; }
Constructs an object of class condition_variable.
boost::thread_resource_error if an error
occurs.
All threads waiting on *this have been notified by a call
to notify_one or
notify_all (though
the respective calls to wait
or timed_wait need
not have returned).
Destroys the object.
Nothing.
If any threads are currently blocked waiting
on *this
in a call to wait
or timed_wait,
unblocks one of those threads.
Nothing.
If any threads are currently blocked waiting
on *this
in a call to wait
or timed_wait,
unblocks all of those threads.
Nothing.
lock is locked
by the current thread, and either no other thread is currently
waiting on *this,
or the execution of the mutex() member function on the lock objects supplied in the
calls to wait or
timed_wait in all
the threads currently waiting on *this would return the same value
as lock->mutex()
for this call to wait.
Atomically call lock.unlock() and blocks the current thread.
The thread will unblock when notified by a call to this->notify_one()
or this->notify_all(),
or spuriously. When the thread is unblocked (for whatever reason),
the lock is reacquired by invoking lock.lock() before the call to wait returns. The lock is also
reacquired by invoking lock.lock() if the function exits with an
exception.
lock is locked
by the current thread.
boost::thread_resource_error if an error
occurs. boost::thread_interrupted if the wait
was interrupted by a call to interrupt()
on the boost::thread object associated
with the current thread of execution.
As-if
while(!pred()) { wait(lock); }
lock is locked
by the current thread, and either no other thread is currently
waiting on *this,
or the execution of the mutex() member function on the lock objects supplied in the
calls to wait or
timed_wait in all
the threads currently waiting on *this would return the same value
as lock->mutex()
for this call to wait.
Atomically call lock.unlock() and blocks the current thread.
The thread will unblock when notified by a call to this->notify_one()
or this->notify_all(),
when the time as reported by boost::get_system_time() would be equal to or later than
the specified abs_time,
or spuriously. When the thread is unblocked (for whatever reason),
the lock is reacquired by invoking lock.lock() before the call to wait returns. The lock is also
reacquired by invoking lock.lock() if the function exits with an
exception.
false if the call
is returning because the time specified by abs_time
was reached, true
otherwise.
lock is locked
by the current thread.
boost::thread_resource_error if an error
occurs. boost::thread_interrupted if the wait
was interrupted by a call to interrupt()
on the boost::thread object associated
with the current thread of execution.
lock is locked
by the current thread, and either no other thread is currently
waiting on *this,
or the execution of the mutex() member function on the lock objects supplied in the
calls to wait or
timed_wait in all
the threads currently waiting on *this would return the same value
as lock->mutex()
for this call to wait.
Atomically call lock.unlock() and blocks the current thread.
The thread will unblock when notified by a call to this->notify_one()
or this->notify_all(),
after the period of time indicated by the rel_time
argument has elapsed, or spuriously. When the thread is unblocked
(for whatever reason), the lock is reacquired by invoking lock.lock()
before the call to wait
returns. The lock is also reacquired by invoking lock.lock()
if the function exits with an exception.
false if the call
is returning because the time period specified by rel_time has elapsed, true otherwise.
lock is locked
by the current thread.
boost::thread_resource_error if an error
occurs. boost::thread_interrupted if the wait
was interrupted by a call to interrupt()
on the boost::thread object associated
with the current thread of execution.
![[Note]](../../../doc/src/images/note.png) |
Note |
|---|---|
The duration overload of timed_wait is difficult to use correctly. The overload taking a predicate should be preferred in most cases. |
As-if
while(!pred()) { if(!timed_wait(lock,abs_time)) { return pred(); } } return true;
condition_variable_any()~condition_variable_any()void notify_one()void notify_all()template<typename lock_type> void wait(lock_type&
lock)template<typename lock_type,typename predicate_type>
void wait(lock_type& lock, predicate_type
pred)template<typename lock_type> bool timed_wait(lock_type&
lock,boost::system_time const& abs_time)template<typename lock_type,typename duration_type>
bool timed_wait(lock_type& lock,duration_type
const&
rel_time)template<typename lock_type,typename predicate_type>
bool timed_wait(lock_type& lock, boost::system_time
const&
abs_time,
predicate_type pred)#include <boost/thread/condition_variable.hpp> namespace boost { class condition_variable_any { public: condition_variable_any(); ~condition_variable_any(); void notify_one(); void notify_all(); template<typename lock_type> void wait(lock_type& lock); template<typename lock_type,typename predicate_type> void wait(lock_type& lock,predicate_type predicate); template<typename lock_type> bool timed_wait(lock_type& lock,boost::system_time const& abs_time); template<typename lock_type,typename duration_type> bool timed_wait(lock_type& lock,duration_type const& rel_time); template<typename lock_type,typename predicate_type> bool timed_wait(lock_type& lock,boost::system_time const& abs_time,predicate_type predicate); template<typename lock_type,typename duration_type,typename predicate_type> bool timed_wait(lock_type& lock,duration_type const& rel_time,predicate_type predicate); // backwards compatibility template<typename lock_type> bool timed_wait(lock_type>& lock,boost::xtime const& abs_time); template<typename lock_type,typename predicate_type> bool timed_wait(lock_type& lock,boost::xtime const& abs_time,predicate_type predicate); }; }
Constructs an object of class condition_variable_any.
boost::thread_resource_error if an error
occurs.
All threads waiting on *this have been notified by a call
to notify_one or
notify_all (though
the respective calls to wait
or timed_wait need
not have returned).
Destroys the object.
Nothing.
If any threads are currently blocked waiting
on *this
in a call to wait
or timed_wait,
unblocks one of those threads.
Nothing.
If any threads are currently blocked waiting
on *this
in a call to wait
or timed_wait,
unblocks all of those threads.
Nothing.
Atomically call lock.unlock() and blocks the current thread.
The thread will unblock when notified by a call to this->notify_one()
or this->notify_all(),
or spuriously. When the thread is unblocked (for whatever reason),
the lock is reacquired by invoking lock.lock() before the call to wait returns. The lock is also
reacquired by invoking lock.lock() if the function exits with an
exception.
lock is locked
by the current thread.
boost::thread_resource_error if an error
occurs. boost::thread_interrupted if the wait
was interrupted by a call to interrupt()
on the boost::thread object associated
with the current thread of execution.
As-if
while(!pred()) { wait(lock); }
Atomically call lock.unlock() and blocks the current thread.
The thread will unblock when notified by a call to this->notify_one()
or this->notify_all(),
when the time as reported by boost::get_system_time() would be equal to or later than
the specified abs_time,
or spuriously. When the thread is unblocked (for whatever reason),
the lock is reacquired by invoking lock.lock() before the call to wait returns. The lock is also
reacquired by invoking lock.lock() if the function exits with an
exception.
false if the call
is returning because the time specified by abs_time
was reached, true
otherwise.
lock is locked
by the current thread.
boost::thread_resource_error if an error
occurs. boost::thread_interrupted if the wait
was interrupted by a call to interrupt()
on the boost::thread object associated
with the current thread of execution.
Atomically call lock.unlock() and blocks the current thread.
The thread will unblock when notified by a call to this->notify_one()
or this->notify_all(),
after the period of time indicated by the rel_time
argument has elapsed, or spuriously. When the thread is unblocked
(for whatever reason), the lock is reacquired by invoking lock.lock()
before the call to wait
returns. The lock is also reacquired by invoking lock.lock()
if the function exits with an exception.
false if the call
is returning because the time period specified by rel_time has elapsed, true otherwise.
lock is locked
by the current thread.
boost::thread_resource_error if an error
occurs. boost::thread_interrupted if the wait
was interrupted by a call to interrupt()
on the boost::thread object associated
with the current thread of execution.
|
Note |
|---|---|
The duration overload of timed_wait is difficult to use correctly. The overload taking a predicate should be preferred in most cases. |
As-if
while(!pred()) { if(!timed_wait(lock,abs_time)) { return pred(); } } return true;
#include <boost/thread/condition.hpp> typedef condition_variable_any condition;
The typedef condition is
provided for backwards compatibility with previous boost releases.
boost::call_once provides a mechanism for ensuring
that an initialization routine is run exactly once without data races or
deadlocks.
#include <boost/thread/once.hpp> typedef platform-specific-type once_flag; #define BOOST_ONCE_INIT platform-specific-initializer
Objects of type boost::once_flag shall be initialized with
BOOST_ONCE_INIT:
boost::once_flag f=BOOST_ONCE_INIT;
#include <boost/thread/once.hpp> template<typename Callable> void call_once(once_flag& flag,Callable func);
Callable is CopyConstructible. Copying func shall have no side effects,
and the effect of calling the copy shall be equivalent to calling
the original.
Calls to call_once
on the same once_flag
object are serialized. If there has been no prior effective call_once on the same once_flag object, the argument
func (or a copy thereof)
is called as-if by invoking func(), and the invocation of call_once is effective if and only
if func()
returns without exception. If an exception is thrown, the exception
is propagated to the caller. If there has been a prior effective
call_once on the
same once_flag object,
the call_once returns
without invoking func.
The completion of an effective call_once
invocation on a once_flag
object, synchronizes with all subsequent call_once
invocations on the same once_flag
object.
thread_resource_error
when the effects cannot be achieved. or any exception propagated
from func.
The function passed to call_once
must not also call call_once
passing the same once_flag
object. This may cause deadlock, or invoking the passed function
a second time. The alternative is to allow the second call to return
immediately, but that assumes the code knows it has been called recursively,
and can proceed even though the call to call_once
didn't actually call the function, in which case it could also avoid
calling call_once
recursively.
void call_once(void (*func)(),once_flag& flag);
This second overload is provided for backwards compatibility. The effects
of call_once(func,flag)
shall be the same as those of call_once(flag,func).
A barrier is a simple concept. Also known as a rendezvous,
it is a synchronization point between multiple threads. The barrier is configured
for a particular number of threads (n),
and as threads reach the barrier they must wait until all n
threads have arrived. Once the n-th
thread has reached the barrier, all the waiting threads can proceed, and
the barrier is reset.
#include <boost/thread/barrier.hpp> class barrier { public: barrier(unsigned int count); ~barrier(); bool wait(); };
Instances of boost::barrier are not copyable or movable.
barrier(unsigned int count);
Construct a barrier for count
threads.
boost::thread_resource_error if an error
occurs.
~barrier();
No threads are waiting on *this.
Destroys *this.
Nothing.
wait
bool wait();
Block until count
threads have called wait
on *this.
When the count-th
thread calls wait,
all waiting threads are unblocked, and the barrier is reset.
true for exactly one
thread from each batch of waiting threads, false
otherwise.
boost::thread_resource_error if an error
occurs.
The futures library provides a means of handling synchronous future values, whether those values are generated by another thread, or on a single thread in response to external stimuli, or on-demand.
This is done through the provision of four class templates: boost::unique_future and boost::shared_future which are used to
retrieve the asynchronous results, and boost::promise and boost::packaged_task which are used to
generate the asynchronous results.
An instance of boost::unique_future holds the one and
only reference to a result. Ownership can be transferred between instances
using the move constructor or move-assignment operator, but at most one
instance holds a reference to a given asynchronous result. When the result
is ready, it is returned from boost::unique_future<R>::get()
by rvalue-reference to allow the result to be moved or copied as appropriate
for the type.
On the other hand, many instances of boost::shared_future may reference the
same result. Instances can be freely copied and assigned, and boost::shared_future<R>::get()
returns a const reference
so that multiple calls to boost::shared_future<R>::get()
are safe. You can move an instance of boost::unique_future into an instance
of boost::shared_future, thus transferring
ownership of the associated asynchronous result, but not vice-versa.
You can wait for futures either individually or with one of the boost::wait_for_any()
and boost::wait_for_all()
functions.
You can set the value in a future with either a boost::promise or a boost::packaged_task. A boost::packaged_task is a callable object
that wraps a function or callable object. When the packaged task is invoked,
it invokes the contained function in turn, and populates a future with
the return value. This is an answer to the perennial question: "how
do I return a value from a thread?": package the function you wish
to run as a boost::packaged_task and pass the packaged
task to the thread constructor. The future retrieved from the packaged
task can then be used to obtain the return value. If the function throws
an exception, that is stored in the future in place of the return value.
int calculate_the_answer_to_life_the_universe_and_everything() { return 42; } boost::packaged_task<int> pt(calculate_the_answer_to_life_the_universe_and_everything); boost::unique_future<int> fi=pt.get_future(); boost::thread task(boost::move(pt)); // launch task on a thread fi.wait(); // wait for it to finish assert(fi.is_ready()); assert(fi.has_value()); assert(!fi.has_exception()); assert(fi.get_state()==boost::future_state::ready); assert(fi.get()==42);
A boost::promise is a bit more low level:
it just provides explicit functions to store a value or an exception in
the associated future. A promise can therefore be used where the value
may come from more than one possible source, or where a single operation
may produce multiple values.
boost::promise<int> pi; boost::unique_future<int> fi; fi=pi.get_future(); pi.set_value(42); assert(fi.is_ready()); assert(fi.has_value()); assert(!fi.has_exception()); assert(fi.get_state()==boost::future_state::ready); assert(fi.get()==42);
Both boost::promise and boost::packaged_task support wait
callbacks that are invoked when a thread blocks in a call to
wait()
or timed_wait()
on a future that is waiting for the result from the boost::promise or boost::packaged_task, in the thread that
is doing the waiting. These can be set using the set_wait_callback() member function on the boost::promise or boost::packaged_task in question.
This allows lazy futures where the result is not actually
computed until it is needed by some thread. In the example below, the call
to f.get()
invokes the callback invoke_lazy_task,
which runs the task to set the value. If you remove the call to f.get(), the task is not ever run.
int calculate_the_answer_to_life_the_universe_and_everything() { return 42; } void invoke_lazy_task(boost::packaged_task<int>& task) { try { task(); } catch(boost::task_already_started&) {} } int main() { boost::packaged_task<int> task(calculate_the_answer_to_life_the_universe_and_everything); task.set_wait_callback(invoke_lazy_task); boost::unique_future<int> f(task.get_future()); assert(f.get()==42); }
namespace future_state { enum state {uninitialized, waiting, ready}; }
template <typename R> class unique_future { unique_future(unique_future & rhs);// = delete; unique_future& operator=(unique_future& rhs);// = delete; public: typedef future_state::state state; unique_future(); ~unique_future(); // move support unique_future(unique_future && other); unique_future& operator=(unique_future && other); void swap(unique_future& other); // retrieving the value R&& get(); // functions to check state state get_state() const; bool is_ready() const; bool has_exception() const; bool has_value() const; // waiting for the result to be ready void wait() const; template<typename Duration> bool timed_wait(Duration const& rel_time) const; bool timed_wait_until(boost::system_time const& abs_time) const; };
unique_future();
Constructs an uninitialized future.
this->is_ready returns false. this->get_state()
returns boost::future_state::uninitialized.
Nothing.
unique_future(unique_future && other);
Constructs a new future, and transfers ownership of the asynchronous
result associated with other
to *this.
this->get_state()
returns the value of other->get_state() prior to the call. other->get_state()
returns boost::future_state::uninitialized. If other was associated with an
asynchronous result, that result is now associated with *this.
other is not
associated with any asynchronous result.
Nothing.
If the compiler does not support rvalue-references, this is implemented using the boost.thread move emulation.
unique_future& operator=(unique_future && other);
Transfers ownership of the asynchronous result associated with
other to *this.
this->get_state()
returns the value of other->get_state() prior to the call. other->get_state()
returns boost::future_state::uninitialized. If other was associated with an
asynchronous result, that result is now associated with *this.
other is not
associated with any asynchronous result. If *this was associated with an asynchronous
result prior to the call, that result no longer has an associated
boost::unique_future instance.
Nothing.
If the compiler does not support rvalue-references, this is implemented using the boost.thread move emulation.
void swap(unique_future & other);
Swaps ownership of the asynchronous results associated with
other and *this.
this->get_state()
returns the value of other->get_state() prior to the call. other->get_state()
returns the value of this->get_state() prior to the call. If other was associated with an
asynchronous result, that result is now associated with *this,
otherwise *this
has no associated result. If *this was associated with an asynchronous
result, that result is now associated with other,
otherwise other
has no associated result.
Nothing.
R&& get(); R& unique_future<R&>::get(); void unique_future<void>::get();
If *this
is associated with an asynchronous result, waits until the result
is ready as-if by a call to boost::unique_future<R>::wait(),
and retrieves the result (whether that is a value or an exception).
If the result type R
is a reference, returns the stored reference. If R is void,
there is no return value. Otherwise, returns an rvalue-reference
to the value stored in the asynchronous result.
this->is_ready()
returns true. this->get_state()
returns boost::future_state::ready.
boost::future_uninitialized if *this
is not associated with an asynchronous result. boost::thread_interrupted if the result
associated with *this is not ready at the point
of the call, and the current thread is interrupted. Any exception
stored in the asynchronous result in place of a value.
get()
is an interruption point.
void wait();
If *this
is associated with an asynchronous result, waits until the result
is ready. If the result is not ready on entry, and the result
has a wait callback set, that callback is
invoked prior to waiting.
boost::future_uninitialized if *this
is not associated with an asynchronous result. boost::thread_interrupted if the result
associated with *this is not ready at the point
of the call, and the current thread is interrupted. Any exception
thrown by the wait callback if such a callback
is called.
this->is_ready()
returns true. this->get_state()
returns boost::future_state::ready.
wait()
is an interruption point.
template<typename Duration> bool timed_wait(Duration const& wait_duration);
If *this
is associated with an asynchronous result, waits until the result
is ready, or the time specified by wait_duration
has elapsed. If the result is not ready on entry, and the result
has a wait callback set, that callback is
invoked prior to waiting.
true if *this
is associated with an asynchronous result, and that result is
ready before the specified time has elapsed, false
otherwise.
boost::future_uninitialized if *this
is not associated with an asynchronous result. boost::thread_interrupted if the result
associated with *this is not ready at the point
of the call, and the current thread is interrupted. Any exception
thrown by the wait callback if such a callback
is called.
If this call returned true,
then this->is_ready()
returns true and
this->get_state()
returns boost::future_state::ready.
timed_wait()
is an interruption point. Duration must be a type that
meets the Boost.DateTime time duration requirements.
bool timed_wait(boost::system_time const& wait_timeout);
If *this
is associated with an asynchronous result, waits until the result
is ready, or the time point specified by wait_timeout
has passed. If the result is not ready on entry, and the result
has a wait callback set, that callback is
invoked prior to waiting.
true if *this
is associated with an asynchronous result, and that result is
ready before the specified time has passed, false
otherwise.
boost::future_uninitialized if *this
is not associated with an asynchronous result. boost::thread_interrupted if the result
associated with *this is not ready at the point
of the call, and the current thread is interrupted. Any exception
thrown by the wait callback if such a callback
is called.
If this call returned true,
then this->is_ready()
returns true and
this->get_state()
returns boost::future_state::ready.
timed_wait()
is an interruption point.
bool is_ready();
Checks to see if the asynchronous result associated with *this
is set.
true if *this
is associated with an asynchronous result, and that result is
ready for retrieval, false
otherwise.
Nothing.
bool has_value();
Checks to see if the asynchronous result associated with *this
is set with a value rather than an exception.
true if *this
is associated with an asynchronous result, that result is ready
for retrieval, and the result is a stored value, false otherwise.
Nothing.
bool has_exception();
Checks to see if the asynchronous result associated with *this
is set with an exception rather than a value.
true if *this
is associated with an asynchronous result, that result is ready
for retrieval, and the result is a stored exception, false otherwise.
Nothing.
future_state::state get_state();
Determine the state of the asynchronous result associated with
*this,
if any.
boost::future_state::uninitialized if *this
is not associated with an asynchronous result. boost::future_state::ready if the asynchronous
result associated with *this is ready for retrieval,
boost::future_state::waiting otherwise.
Nothing.
template <typename R> class shared_future { public: typedef future_state::state state; shared_future(); ~shared_future(); // copy support shared_future(shared_future const& other); shared_future& operator=(shared_future const& other); // move support shared_future(shared_future && other); shared_future(unique_future<R> && other); shared_future& operator=(shared_future && other); shared_future& operator=(unique_future<R> && other); void swap(shared_future& other); // retrieving the value R get(); // functions to check state, and wait for ready state get_state() const; bool is_ready() const; bool has_exception() const; bool has_value() const; // waiting for the result to be ready void wait() const; template<typename Duration> bool timed_wait(Duration const& rel_time) const; bool timed_wait_until(boost::system_time const& abs_time) const; };
shared_future();
Constructs an uninitialized future.
this->is_ready returns false. this->get_state()
returns boost::future_state::uninitialized.
Nothing.
const R& get();
If *this
is associated with an asynchronous result, waits until the result
is ready as-if by a call to boost::shared_future<R>::wait(),
and returns a const
reference to the result.
If the result type R
is a reference, returns the stored reference. If R is void,
there is no return value. Otherwise, returns a const reference to the value stored
in the asynchronous result.
boost::future_uninitialized if *this
is not associated with an asynchronous result. boost::thread_interrupted if the result
associated with *this is not ready at the point
of the call, and the current thread is interrupted.
get()
is an interruption point.
void wait();
If *this
is associated with an asynchronous result, waits until the result
is ready. If the result is not ready on entry, and the result
has a wait callback set, that callback is
invoked prior to waiting.
boost::future_uninitialized if *this
is not associated with an asynchronous result. boost::thread_interrupted if the result
associated with *this is not ready at the point
of the call, and the current thread is interrupted. Any exception
thrown by the wait callback if such a callback
is called.
this->is_ready()
returns true. this->get_state()
returns boost::future_state::ready.
wait()
is an interruption point.
template<typename Duration> bool timed_wait(Duration const& wait_duration);
If *this
is associated with an asynchronous result, waits until the result
is ready, or the time specified by wait_duration
has elapsed. If the result is not ready on entry, and the result
has a wait callback set, that callback is
invoked prior to waiting.
true if *this
is associated with an asynchronous result, and that result is
ready before the specified time has elapsed, false
otherwise.
boost::future_uninitialized if *this
is not associated with an asynchronous result. boost::thread_interrupted if the result
associated with *this is not ready at the point
of the call, and the current thread is interrupted. Any exception
thrown by the wait callback if such a callback
is called.
If this call returned true,
then this->is_ready()
returns true and
this->get_state()
returns boost::future_state::ready.
timed_wait()
is an interruption point. Duration must be a type that
meets the Boost.DateTime time duration requirements.
bool timed_wait(boost::system_time const& wait_timeout);
If *this
is associated with an asynchronous result, waits until the result
is ready, or the time point specified by wait_timeout
has passed. If the result is not ready on entry, and the result
has a wait callback set, that callback is
invoked prior to waiting.
true if *this
is associated with an asynchronous result, and that result is
ready before the specified time has passed, false
otherwise.
boost::future_uninitialized if *this
is not associated with an asynchronous result. boost::thread_interrupted if the result
associated with *this is not ready at the point
of the call, and the current thread is interrupted. Any exception
thrown by the wait callback if such a callback
is called.
If this call returned true,
then this->is_ready()
returns true and
this->get_state()
returns boost::future_state::ready.
timed_wait()
is an interruption point.
bool is_ready();
Checks to see if the asynchronous result associated with *this
is set.
true if *this
is associated with an asynchronous result, and that result is
ready for retrieval, false
otherwise.
Nothing.
bool has_value();
Checks to see if the asynchronous result associated with *this
is set with a value rather than an exception.
true if *this
is associated with an asynchronous result, that result is ready
for retrieval, and the result is a stored value, false otherwise.
Nothing.
bool has_exception();
Checks to see if the asynchronous result associated with *this
is set with an exception rather than a value.
true if *this
is associated with an asynchronous result, that result is ready
for retrieval, and the result is a stored exception, false otherwise.
Nothing.
future_state::state get_state();
Determine the state of the asynchronous result associated with
*this,
if any.
boost::future_state::uninitialized if *this
is not associated with an asynchronous result. boost::future_state::ready if the asynchronous
result associated with *this is ready for retrieval,
boost::future_state::waiting otherwise.
Nothing.
template <typename R> class promise { promise(promise & rhs);// = delete; promise & operator=(promise & rhs);// = delete; public: // template <class Allocator> explicit promise(Allocator a); promise(); ~promise(); // Move support promise(promise && rhs); promise & operator=(promise&& rhs); void swap(promise& other); // Result retrieval unique_future<R> get_future(); // Set the value void set_value(R& r); void set_value(R&& r); void set_exception(boost::exception_ptr e); template<typename F> void set_wait_callback(F f); };
promise();
Constructs a new boost::promise with no associated
result.
Nothing.
promise(promise && other);
Constructs a new boost::promise, and transfers
ownership of the result associated with other
to *this,
leaving other
with no associated result.
Nothing.
If the compiler does not support rvalue-references, this is implemented using the boost.thread move emulation.
promise& operator=(promise && other);
Transfers ownership of the result associated with other to *this, leaving other
with no associated result. If there was already a result associated
with *this,
and that result was not ready, sets any
futures associated with that result to ready
with a boost::broken_promise
exception as the result.
Nothing.
If the compiler does not support rvalue-references, this is implemented using the boost.thread move emulation.
~promise();
Destroys *this.
If there was a result associated with *this, and that result is not
ready, sets any futures associated with
that task to ready with a boost::broken_promise exception as
the result.
Nothing.
unique_future<R> get_future();
If *this
was not associated with a result, allocate storage for a new
asynchronous result and associate it with *this. Returns a boost::unique_future associated
with the result associated with *this.
boost::future_already_retrieved if
the future associated with the task has already been retrieved.
std::bad_alloc if any memory necessary
could not be allocated.
void set_value(R&& r); void set_value(const R& r); void promise<R&>::set_value(R& r); void promise<void>::set_value();
If *this
was not associated with a result, allocate storage for a new
asynchronous result and associate it with *this. Store the value r in the asynchronous result
associated with *this. Any threads blocked waiting
for the asynchronous result are woken.
All futures waiting on the asynchronous result are ready
and boost::unique_future<R>::has_value()
or boost::shared_future<R>::has_value()
for those futures shall return true.
boost::promise_already_satisfied if
the result associated with *this is already ready.
std::bad_alloc if the memory required
for storage of the result cannot be allocated. Any exception
thrown by the copy or move-constructor of R.
void set_exception(boost::exception_ptr e);
If *this
was not associated with a result, allocate storage for a new
asynchronous result and associate it with *this. Store the exception e in the asynchronous result
associated with *this. Any threads blocked waiting
for the asynchronous result are woken.
All futures waiting on the asynchronous result are ready
and boost::unique_future<R>::has_exception()
or boost::shared_future<R>::has_exception()
for those futures shall return true.
boost::promise_already_satisfied if
the result associated with *this is already ready.
std::bad_alloc if the memory required
for storage of the result cannot be allocated.
template<typename F> void set_wait_callback(F f);
The expression f(t) where t
is a lvalue of type boost::promise shall be well-formed.
Invoking a copy of f
shall have the same effect as invoking f
Store a copy of f
with the asynchronous result associated with *this as a wait callback.
This will replace any existing wait callback store alongside
that result. If a thread subsequently calls one of the wait functions
on a boost::unique_future or boost::shared_future associated
with this result, and the result is not ready,
f(*this)
shall be invoked.
std::bad_alloc if memory cannot
be allocated for the required storage.
template<typename R> class packaged_task { packaged_task(packaged_task&);// = delete; packaged_task& operator=(packaged_task&);// = delete; public: // construction and destruction template <class F> explicit packaged_task(F const& f); explicit packaged_task(R(*f)()); template <class F> explicit packaged_task(F&& f); // template <class F, class Allocator> // explicit packaged_task(F const& f, Allocator a); // template <class F, class Allocator> // explicit packaged_task(F&& f, Allocator a); ~packaged_task() {} // move support packaged_task(packaged_task&& other); packaged_task& operator=(packaged_task&& other); void swap(packaged_task& other); // result retrieval unique_future<R> get_future(); // execution void operator()(); template<typename F> void set_wait_callback(F f); };
template<typename F> packaged_task(F const &f); packaged_task(R(*f)()); template<typename F> packaged_task(F&&f);
f()
is a valid expression with a return type convertible to R. Invoking a copy of f shall behave the same as
invoking f.
Constructs a new boost::packaged_task with a
copy of f stored
as the associated task.
Any exceptions thrown by the copy (or move) constructor of f. std::bad_alloc
if memory for the internal data structures could not be allocated.
packaged_task(packaged_task && other);
Constructs a new boost::packaged_task, and transfers
ownership of the task associated with other
to *this,
leaving other
with no associated task.
Nothing.
If the compiler does not support rvalue-references, this is implemented using the boost.thread move emulation.
packaged_task& operator=(packaged_task && other);
Transfers ownership of the task associated with other to *this, leaving other
with no associated task. If there was already a task associated
with *this,
and that task has not been invoked, sets any futures associated
with that task to ready with a boost::broken_promise exception as
the result.
Nothing.
If the compiler does not support rvalue-references, this is implemented using the boost.thread move emulation.
~packaged_task();
Destroys *this.
If there was a task associated with *this, and that task has not been
invoked, sets any futures associated with that task to ready
with a boost::broken_promise
exception as the result.
Nothing.
unique_future<R> get_future();
Returns a boost::unique_future associated
with the result of the task associated with *this.
boost::task_moved if ownership of
the task associated with *this has been moved to another
instance of boost::packaged_task. boost::future_already_retrieved if
the future associated with the task has already been retrieved.
void operator()();
Invoke the task associated with *this and store the result in the
corresponding future. If the task returns normally, the return
value is stored as the asynchronous result, otherwise the exception
thrown is stored. Any threads blocked waiting for the asynchronous
result associated with this task are woken.
All futures waiting on the asynchronous result are ready
boost::task_moved if ownership of
the task associated with *this has been moved to another
instance of boost::packaged_task. boost::task_already_started if the
task has already been invoked.
template<typename F> void set_wait_callback(F f);
The expression f(t) where t
is a lvalue of type boost::packaged_task shall
be well-formed. Invoking a copy of f
shall have the same effect as invoking f
Store a copy of f
with the task associated with *this as a wait callback.
This will replace any existing wait callback store alongside
that task. If a thread subsequently calls one of the wait functions
on a boost::unique_future or boost::shared_future associated
with this task, and the result of the task is not ready,
f(*this)
shall be invoked.
boost::task_moved if ownership of
the task associated with *this has been moved to another
instance of boost::packaged_task.
template<typename Iterator> Iterator wait_for_any(Iterator begin,Iterator end); template<typename F1,typename F2> unsigned wait_for_any(F1& f1,F2& f2); template<typename F1,typename F2,typename F3> unsigned wait_for_any(F1& f1,F2& f2,F3& f3); template<typename F1,typename F2,typename F3,typename F4> unsigned wait_for_any(F1& f1,F2& f2,F3& f3,F4& f4); template<typename F1,typename F2,typename F3,typename F4,typename F5> unsigned wait_for_any(F1& f1,F2& f2,F3& f3,F4& f4,F5& f5);
The types Fn shall
be specializations of boost::unique_future or boost::shared_future, and Iterator shall be a forward iterator
with a value_type
which is a specialization of boost::unique_future or boost::shared_future.
Waits until at least one of the specified futures is ready.
The range-based overload returns an Iterator
identifying the first future in the range that was detected as
ready. The remaining overloads return the
zero-based index of the first future that was detected as ready
(first parameter => 0, second parameter => 1, etc.).
boost::thread_interrupted if the current
thread is interrupted. Any exception thrown by the wait
callback associated with any of the futures being waited
for. std::bad_alloc if memory could not
be allocated for the internal wait structures.
wait_for_any()
is an interruption point.
template<typename Iterator> void wait_for_all(Iterator begin,Iterator end); template<typename F1,typename F2> void wait_for_all(F1& f1,F2& f2); template<typename F1,typename F2,typename F3> void wait_for_all(F1& f1,F2& f2,F3& f3); template<typename F1,typename F2,typename F3,typename F4> void wait_for_all(F1& f1,F2& f2,F3& f3,F4& f4); template<typename F1,typename F2,typename F3,typename F4,typename F5> void wait_for_all(F1& f1,F2& f2,F3& f3,F4& f4,F5& f5);
The types Fn shall
be specializations of boost::unique_future or boost::shared_future, and Iterator shall be a forward iterator
with a value_type
which is a specialization of boost::unique_future or boost::shared_future.
Waits until all of the specified futures are ready.
Any exceptions thrown by a call to wait() on the specified futures.
wait_for_all()
is an interruption point.