RWTPCValQueueGuardedPrioritized< Type > Class Template Reference
[Interthread Communication]

First-in-first-out (FIFO) queue that provides producer-consumer synchronization semantics for exchanging guarded and prioritized values between cooperating threads. More...

#include <rw/itc/RWTPCValQueueGuardedPrioritized.h>

Inheritance diagram for RWTPCValQueueGuardedPrioritized< Type >:

List of all members.

Public Member Functions
	RWTPCValQueueGuardedPrioritized (size_t maxCapacity=0, bool isOpen=true)
	~RWTPCValQueueGuardedPrioritized (void)

---

Detailed Description

template<class Type>
class RWTPCValQueueGuardedPrioritized< Type >

RWTPCValQueueGuardedPrioritized<Type> is a first-in-first-out (FIFO) queue that provides producer-consumer synchronization semantics for exchanging guarded and 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 guard functor and priority value to each data value prior to storing that value in an internal buffer. The guard functor is used during read operations to determine whether the associated value is currently eligible for retrieval from the buffer. The priority value is used during 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, except when the retrieval of the older values is prohibited by their guard functors.

Examples

 #include <rw/itc/RWTPCValQueueGuardedPrioritized.h>
 #include <rw/thread/RWThreadFunction.h>  // for RWThreadFunction
 #include <rw/functor/functorR0.h>        // for RWTFunctorR0<>
 #include <iostream.h>
 
 enum Command
      {RUN,STOP,PROCESS_HIGH,PROCESS_MED,PROCESS_LOW,EXIT};
 
 RWTPCValQueueGuardedPrioritized<Command>  pcQueue;
 bool isRunning = false;
 
 // The guard function
 bool canProcess() { return isRunning; }
 
 void reader(void)
 {
    // Get commands from queue, update state, 
    // and write to stdout.
    Command command;
    while (EXIT != (command = pcQueue.read())) {
       switch(command) {
          case RUN: cout<<"RUN"<<endl; isRunning=true; break;
          case STOP: cout<<"STOP"<<endl; isRunning=false; break;
          case PROCESS_HIGH: cout<<"PROCESS_HIGH"<<endl; break;
          case PROCESS_MED: cout<<"PROCESS_MED"<<endl; break;
          case PROCESS_LOW: cout<<"PROCESS_LOW"<<endl; break;
       }
    }
    cout<<"EXIT"<<endl;
 }
      
 int main()
 {
    RWThread thread = rwtMakeThreadFunctionG(void,reader);
    RWTFunctorR0<bool> guard =
              rwtMakeFunctorR0G(bool,bool,canProcess);
 
    thread.start();
    pcQueue.write(1,PROCESS_LOW,guard);
    pcQueue.write(2,PROCESS_MED,guard);
    pcQueue.write(1,PROCESS_LOW,guard);
    pcQueue.write(1,PROCESS_LOW,guard);
    pcQueue.write(3,PROCESS_HIGH,guard);
    pcQueue.write(4,RUN);
    pcQueue.write(2,PROCESS_MED,guard);
    pcQueue.write(1,PROCESS_LOW,guard);
    pcQueue.write(1,PROCESS_LOW,guard);
    pcQueue.write(1,PROCESS_LOW,guard);
    pcQueue.write(3,PROCESS_HIGH,guard);
    pcQueue.write(4,STOP);
    pcQueue.write(3,PROCESS_HIGH,guard);
    pcQueue.write(1,PROCESS_LOW,guard);
    pcQueue.write(4,RUN);
    pcQueue.write(0,EXIT);
    thread.join();
    return 0;
 }

* This code produces the following output:

 RUN
 PROCESS_HIGH
 PROCESS_MED
 PROCESS_MED
 PROCESS_LOW
 PROCESS_LOW
 PROCESS_LOW
 PROCESS_LOW
 PROCESS_LOW
 PROCESS_LOW
 STOP
 RUN
 PROCESS_HIGH
 PROCESS_HIGH
 PROCESS_LOW
 EXIT

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Constructor & Destructor Documentation

template<class Type >

RWTPCValQueueGuardedPrioritized< Type >::RWTPCValQueueGuardedPrioritized	(	size_t	maxCapacity = 0,
		bool	isOpen = true
	)			[inline]

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

The parameter maxCapacity specifies the maximum number of unread entries allowed 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.

template<class Type >

RWTPCValQueueGuardedPrioritized< Type >::~RWTPCValQueueGuardedPrioritized

(

void

)

[inline]

Destructor.