asyncqueue.h

Pegasus is an open-source implementationof the DMTF CIM and WBEM standards. It is designed to be por

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#ifndef Pegasus_AsyncQueue_h
#define Pegasus_AsyncQueue_h

#include <Pegasus/Common/Linkage.h>
#include <Pegasus/Common/List.h>
#include <Pegasus/Common/Condition.h>

PEGASUS_NAMESPACE_BEGIN

/** AsyncQueue implementation (formerly AsyncDQueue).
*/
template<class ElemType>
class AsyncQueue
{
public:

    /** Constructor (zero means unlimited capacity).
    */
    AsyncQueue(size_t capacity = 0);

    /** Destructor.
    */
    virtual ~AsyncQueue();

    /** Close the queue so that subsequent enqueue() and dequeue() requests
        result in ListClosed() exceptions.
    */
    void close();

    /** Enqueue an element at the back of queue.
    */
    void enqueue(ElemType *element);

    /** Enqueue an element at the back of queue (wait if the queue is full).
    */
    void enqueue_wait(ElemType *element);

    /** Dequeue an element from the front of the queue. Return null immediately
        if queue is empty.
    */
    ElemType *dequeue();

    /** Dequeue an element from the front of the queue (wait if the queue is
        empty).
    */
    ElemType *dequeue_wait();

    /** Discard all the elements on the list. The size becomes zero afterwards.
    */
    void clear();

    /** Return number of element in queue.
    */
    Uint32 count() const { return _size.get(); }

    /** Get capacity.
    */
    Uint32 capacity() const { return _capacity.get(); }

    /** Return number of element in queue.
    */
    Uint32 size() const { return _size.get(); }

    /** Return true is queue is empty (has zero elements).
    */
    Boolean is_empty() const { return _size.get() == 0; }

    /** Return true if the queue is full.
    */
    Boolean is_full() const { return _size.get() == _capacity.get(); }

    /** Return true if the queue has been closed (in which case no new
        elements may be enqueued).
    */
    Boolean is_closed() const { return _closed.get(); }

private:

    Mutex _mutex;
    Condition _not_empty;
    Condition _not_full;
    AtomicInt _capacity;
    AtomicInt _size;
    AtomicInt _closed;
    typedef List<ElemType,NullLock> Rep;
    Rep _rep;
};

template<class ElemType>
AsyncQueue<ElemType>::AsyncQueue(size_t capacity) :
    _mutex(Mutex::NON_RECURSIVE), _capacity(capacity)
{
    if (capacity == 0)
        _capacity.set(0x7FFFFFFF);
}

template<class ElemType>
AsyncQueue<ElemType>::~AsyncQueue()
{
}

template<class ElemType>
void AsyncQueue<ElemType>::close()
{
    AutoMutex auto_mutex(_mutex);

    if (!is_closed())
    {
        _closed++;
        _not_full.signal();
        _not_empty.signal();
    }
}

template<class ElemType>
void AsyncQueue<ElemType>::enqueue(ElemType *element)
{
    if (element)
    {
        AutoMutex auto_mutex(_mutex);

        if (is_closed())
            throw ListClosed();

        if (is_full())
            throw ListFull(_capacity.get());

        _rep.insert_back(element);
        _size++;
        _not_empty.signal();
    }
}

template<class ElemType>
void AsyncQueue<ElemType>::enqueue_wait(ElemType *element)
{
    if (element)
    {
        AutoMutex auto_mutex(_mutex);

        while (is_full())
        {
            if (is_closed())
                throw ListClosed();

            _not_full.wait(_mutex);
        }

        if (is_closed())
            throw ListClosed();

        _rep.insert_back(element);
        _size++;
        _not_empty.signal();
    }
}

template<class ElemType>
void AsyncQueue<ElemType>::clear()
{
    AutoMutex auto_mutex(_mutex);
    _rep.clear();
    _size = 0;
    _not_full.signal();
}

template<class ElemType>
ElemType* AsyncQueue<ElemType>::dequeue()
{
    AutoMutex auto_mutex(_mutex);

    if (is_closed())
        throw ListClosed();

    ElemType* p = _rep.remove_front();

    if (p)
    {
        _size--;
        _not_full.signal();
    }

    return p;
}

template<class ElemType>
ElemType* AsyncQueue<ElemType>::dequeue_wait()
{
    AutoMutex auto_mutex(_mutex);

    while (is_empty())
    {
        if (is_closed())
            throw ListClosed();

        _not_empty.wait(_mutex);
    }

    if (is_closed())
        throw ListClosed();

    ElemType* p = _rep.remove_front();
    PEGASUS_DEBUG_ASSERT(p != 0);
    _size--;
    _not_full.signal();

    return p;
}

PEGASUS_NAMESPACE_END

#endif /* Pegasus_AsyncQueue_h */