Example
Example 43 simulates a manufacturing operation where an
RWTPCValQueue is used to represent a warehouse of limited capacity that accepts widgets from a production function and then sends these widgets to a shipping function. The production of widgets occurs at a fixed rate, while the shipping rate of widgets varies from widget to widget. This difference in read and write rates eventually results in one function being forced to wait on the other.
Example 43 – Using a producer-consumer queue in a manufacturing operation
#include <stdlib.h> // For rand() and srand()
#include <rw/thread/RWThreadFunction.h>
#include <rw/itc/RWTPCValQueue.h>
#include <rw/functor/rwBind.h>
#include <rw/sync/RWMutexLock.h>
#include <rw/cstring.h>
#include <iostream>
using namespace std;
typedef int Widget;
void message(const RWCString& message) { // 1
static RWMutexLock mutex; // Make output operation atomic!
RWMutexLock::LockGuard lock(mutex);
cout << message << endl;
}
void produce(RWTPCValQueue<Widget>& warehouse, size_t runSize) {
for (size_t i=0; i<runSize; i++) {
if (!warehouse.canWrite()) // 2
message("Warehouse full!");
// Print bar graph of inventory size
message(RWCString('*',warehouse.entries()));
warehouse.write(Widget(i)); // 3
rwSleep(100); // Fixed time to produce widgets
}
warehouse.write(Widget(-1)); // Tell shipping the run is done!
message("Production done!");
}
void ship(RWTPCValQueue<Widget>& warehouse) {
// Seed random number sequence using thread id
::srand(rwThreadHash(rwThreadId()));
Widget widget;
do {
rwSleep(::rand()%200); // Random time for each shipment
if (!warehouse.canRead()) // 4
message("Warehouse empty!");
widget = warehouse.read(); // 5
} while (widget != -1);
message("Shipping done!");
}
void main() {
// The warehouse can hold only five widgets!
RWTPCValQueue<Widget> warehouse(5); // 6
RWThreadFunction production;
production = RWThreadFunction::make(rwBind(produce, rwRef(warehouse), 100));
RWThreadFunction shipping;
shipping = RWThreadFunction::make(rwBind(ship, rwRef(warehouse)));
production.start();
rwSleep(5*100); // Let production fill the warehouse!
shipping.start();
production.join();
shipping.join();
}
