c++-gtk-utils
Public Types | Public Member Functions
Cgu::AsyncQueue< T, Container > Class Template Reference

A thread-safe asynchronous queue. More...

#include <c++-gtk-utils/async_queue.h>

List of all members.

Public Types

typedef Container::value_type value_type
typedef Container::size_type size_type
typedef Container container_type

Public Member Functions

void push (const value_type &obj)
void push (value_type &&obj)
template<class... Args>
void emplace (Args &&...args)
void pop (value_type &obj)
void pop ()
bool empty () const
 AsyncQueue ()
 AsyncQueue (const AsyncQueue &)
AsyncQueueoperator= (const AsyncQueue &)
 ~AsyncQueue ()

Detailed Description

template<class T, class Container = std::list<T>>
class Cgu::AsyncQueue< T, Container >

A thread-safe asynchronous queue.

See also:
AsyncQueueDispatch

AsyncQueue is a class which provides some of the functionality of a std::queue object (but note that the AsyncQueue::pop(value_type& obj) method provides the pop()ed element by reference - see the comments on that method for the reason), except that it has mutex locking of the data container so as to permit push()ing and pop()ing from different threads. It is therefore useful for passing data between threads, perhaps in response to a signal being emitted from a Notifier object. Passing the data by means of a SharedLockPtr object, or an IntrusivePtr object referencing data derived from IntrusiveLockCounter, would be ideal.

By default the queue uses a std::list object as its container because in the kind of use mentioned above it is unlikely to hold many objects but it can be changed to, say, a std::deque object by specifying it as the second template parameter.

If the library is installed using the --with-glib-memory-slices-compat or --with-glib-memory-slices-no-compat configuration options, any AsyncQueue objects constructed on free store will be constructed in glib memory slices. This does not affect the queue container itself: to change the allocator of the C++ container, a custom allocator type can be provided when the AsyncQueue object is instantiated offering the standard allocator interface.


Member Typedef Documentation

template<class T , class Container = std::list<T>>
typedef Container Cgu::AsyncQueue< T, Container >::container_type
template<class T , class Container = std::list<T>>
typedef Container::size_type Cgu::AsyncQueue< T, Container >::size_type
template<class T , class Container = std::list<T>>
typedef Container::value_type Cgu::AsyncQueue< T, Container >::value_type

Constructor & Destructor Documentation

template<class T , class Container = std::list<T>>
Cgu::AsyncQueue< T, Container >::AsyncQueue ( )
Exceptions:
std::bad_allocThe constructor might throw std::bad_alloc if memory is exhausted and the system throws in that case.
Thread::MutexErrorThe constructor might throw Thread::MutexError if initialisation of the contained mutex fails. (It is often not worth checking for this, as it means either memory is exhausted or pthread has run out of other resources to create new mutexes.)
template<class T , class Container = std::list<T>>
Cgu::AsyncQueue< T, Container >::AsyncQueue ( const AsyncQueue< T, Container > &  )

This class cannot be copied. The copy constructor is deleted.

template<class T , class Container = std::list<T>>
Cgu::AsyncQueue< T, Container >::~AsyncQueue ( ) [inline]

The destructor does not throw unless the destructor of a contained item throws. It is thread safe (any thread may delete the AsyncQueue object).


Member Function Documentation

template<class T , class Container = std::list<T>>
template<class... Args>
void Cgu::AsyncQueue< T, Container >::emplace ( Args &&...  args) [inline]

Pushes an item onto the queue by constructing it in place: that is, by passing to this method the item's constructor's arguments, rather than the item itself. This method has strong exception safety if the container is a std::list or std::deque container (the default is std::list). (Technically, for a std::deque container, emplace() only offers the same exception guarantees as does push(), namely only the basic guarantee where a copy or move of the queue item throws during the call, but the purpose of emplace is to construct in place and any reasonable implementation will not copy or move the queue item.) It is thread safe.

Parameters:
argsThe constructor arguments for the item to be pushed onto the queue.
Exceptions:
std::bad_allocThe method might throw std::bad_alloc if memory is exhausted and the system throws in that case. It might also throw if the item's constructor (including any of its constructor arguments) might throw when constructing the item.
Note:
The constructor of the item pushed onto the queue must not access any of the methods of the same queue object, or a deadlock might occur.

Since 2.0.0-rc5

template<class T , class Container = std::list<T>>
bool Cgu::AsyncQueue< T, Container >::empty ( ) const [inline]
Returns:
Whether the queue is empty. It will not throw assuming that the empty() method of the container type does not throw, as it will not on any sane implementation.
Note:
This method is thread safe, but the return value may not be valid if another thread has pushed to or popped from the queue before the value returned by the method is acted on. It is provided as a utility, but may not be meaningful, depending on the intended usage.
template<class T , class Container = std::list<T>>
AsyncQueue& Cgu::AsyncQueue< T, Container >::operator= ( const AsyncQueue< T, Container > &  )

This class cannot be copied. The assignment operator is deleted.

template<class T , class Container = std::list<T>>
void Cgu::AsyncQueue< T, Container >::pop ( ) [inline]

Discards the item at the front of the queue. This method has strong exception safety if the container is a std::deque or std::list container (the default is std::list), provided the destructor of a contained item does not throw. It is thread safe.

Exceptions:
AsyncQueuePopErrorIf the queue is empty when a pop is attempted, this method will throw AsyncQueuePopError. It might also throw if the destructor of the queue item might throw (but that should never happen), or if the empty() method of the container type throws (which would not happen on any sane implementation).
template<class T , class Container = std::list<T>>
void Cgu::AsyncQueue< T, Container >::pop ( value_type obj) [inline]

Pops an item from the queue. This method has strong exception safety if the container is a std::deque or std::list container (the default is std::list), provided the destructor of a contained item does not throw. It is thread safe.

Parameters:
objA value type reference to which the item at the front of the queue will be assigned.
Exceptions:
AsyncQueuePopErrorIf the queue is empty when a pop is attempted, this method will throw AsyncQueuePopError. It might also throw if the assignment operator of the queue item might throw. In order to complete pop() operations atomically under a single lock and to retain strong exception safety, the object into which the pop()ed data is to be placed is passed as an argument by reference (this avoids a copy from a temporary object after the data has been extracted from the queue, which would occur if the item extracted were returned by value). It might also throw if the destructor of the queue item might throw (but that should never happen), or if the empty() method of the container type throws (which would not happen on any sane implementation).
template<class T , class Container = std::list<T>>
void Cgu::AsyncQueue< T, Container >::push ( const value_type obj) [inline]

Pushes an item onto the queue. This method has strong exception safety if the container is a std::list or std::deque container (the default is std::list), except that if std::deque is used as the container and the copy constructor, move constructor, assignment operator or move assignment operator of the queue item throws, it only gives the basic exception guarantee (and the basic guarantee is not given by std::deque if the queue item's move constructor throws and it uses a non-default allocator which does not provide for it to be CopyInsertable). It is thread safe.

Parameters:
objThe item to be pushed onto the queue.
Exceptions:
std::bad_allocThe method might throw std::bad_alloc if memory is exhausted and the system throws in that case. It might also throw if the copy constructor, move constructor, assignment operator or move assignment operator of the queue item might throw.
template<class T , class Container = std::list<T>>
void Cgu::AsyncQueue< T, Container >::push ( value_type &&  obj) [inline]

Pushes an item onto the queue. This method has strong exception safety if the container is a std::list or std::deque container (the default is std::list), except that if std::deque is used as the container and the copy constructor, move constructor, assignment operator or move assignment operator of the queue item throws, it only gives the basic exception guarantee (and the basic guarantee is not given by std::deque if the queue item's move constructor throws and it uses a non-default allocator which does not provide for it to be CopyInsertable). It is thread safe.

Parameters:
objThe item to be pushed onto the queue.
Exceptions:
std::bad_allocThe method might throw std::bad_alloc if memory is exhausted and the system throws in that case. It might also throw if the copy constructor, move constructor, assignment operator or move assignment operator of the queue item might throw.

Since 2.0.0-rc5


The documentation for this class was generated from the following file: