RWTPCValQueuePrioritized<Type>

Module:  Threads   Package:  Interthread Communication

RWTPCValQueuePrioritized<Type>  
   RWTPCValBufferBasePrioritized<Type,RWTPriorityDecorator<Type>>

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• Public Constructor
• Public Destructor
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Members

RWTPCValQueuePrioritized()

~RWTPCValQueuePrioritized()

#include <rw/itc/RWTPCValQueuePrioritized.h> 

RWTPCValQueuePrioritized<Type> is a first-in-first-out (FIFO) queue that provides producer-consumer synchronization semantics for exchanging prioritized values between cooperating threads.

In the producer-consumer synchronization model, reader threads (consumers) are blocked while the queue is empty, and writer threads (producers) are blocked while the queue is full. The queue is considered full when the number of unread entries equals or exceeds some user-specified maximum capacity.

The write operations inherited by this class bind a priority value to each data value prior to storing that value in an internal buffer. The priority value is used by these write operations to determine a value's insertion point within the queue, such that the set of unread values will be retrieved in priority order when they are eventually read from the queue. A new value is retrieved after any previously inserted values of the same priority.

#include <rw/itc/RWTPCValQueuePrioritized.h>
#include <rw/thread/RWThreadFunction.h>  // for RWThreadFunction
#include <rw/cstring.h>                  // for RWCString
#include <iostream.h>

RWTPCValQueuePrioritized<RWCString>  pcQueue();

void reader(void)
{
   // Get values from queue and write to stdout.
   RWCString message;
   while ("Exit" != (message = pcQueue.read())) {
      cout << message << endl;
      rwSleep(100); // Let the messages pile up
   }
   cout << "EXIT" << endl;
}
     
int main()
{
   RWThread thread = rwtMakeThreadFunctionG(void,reader);
   RWCString high("High"), medium("Medium"), low("Low");

   thread.start();
   pcQueue.write(1,low); 
   pcQueue.write(1,low);
   pcQueue.write(2,medium); 
   pcQueue.write(1,low);
   pcQueue.write(3,high);
   pcQueue.write(2,medium); 
   pcQueue.write(1,low);
   pcQueue.write(1,low);
   pcQueue.write(3,high);
   pcQueue.write(1,low);
   pcQueue.write(2,medium); 
   pcQueue.write(2,medium); 
   pcQueue.write(0,"Exit"); 
   thread.join();
   return 0;
}

This code produces the following output:

High
High
Medium
Medium
Medium
Medium
Low
Low
Low
Low
Low
Low
EXIT

RWTPCValQueuePrioritized(size_t maxCapacity=0,
                        bool isOpen=true);

Constructs a value-based, prioritized, producer-consumer queue instance.

The parameter maxCapacity specifies the maximum number of unread entries to allow to accumulate within the queue. Once the number of entries in the queue equals this number, any thread attempting to write an additional entry is blocked until an entry is removed by a read operation, or until the capacity is increased. A capacity of zero, the default, indicates that the queue has no size limit, except as imposed by memory limitations, and that all write operations should complete without blocking.

The parameter isOpen is a bool value that specifies whether the queue should be initialized in the open state (true, the default) or the closed state (false).

~RWTPCValQueuePrioritized();

Destructor.

RWTPCValBufferBasePrioritized<Type,PriorityDecorator>, RWTPCValStackPrioritized<Type>, RWTPCValQueueGuardedPrioritized<Type>

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