aca-tasks/task3/main-bonus-task-rd.cpp

/***************************************************************************
 *
 * main.cpp:    Code to solve Barlas Exersice 3-12.
 *
 * Version      0.5 by Hartmut Weber: Just a template. 3-11 not solved.
 *              1.0 by Robin Dietzel: Add QSemaphores to apply rules from 3-11 task
 *
 * Statemet of Version 1.0 Authorship:
 *              All added code to the template originates from my own.
 *
 **************************************************************************/
#include <QCoreApplication>
#include <QTimer>
#include <QThread>
#include <stdio.h>
#include <QSemaphore>
#include <QRandomGenerator>

using namespace std;

#define CHAR_COUNT_MAX 500
#define TIME_FACTOR 2

int charCount = 0;
QSemaphore semCharCount(1);
QRandomGenerator *randg = QRandomGenerator::global();

QSemaphore lockBC_(0);
QSemaphore lockC_(0);

class AThread : public QThread {
private:
    int ID;
public:
    AThread(int i) : ID(i) {}

    void run() {
        while (charCount < CHAR_COUNT_MAX) {
            lockBC_.release(1);
            printf("A");
            fflush(stdout);
            semCharCount.acquire();
            charCount++;
            semCharCount.release();
            msleep((randg->generate() % 3 + 1) * TIME_FACTOR);
        }
        return;
    }
};

class BThread : public QThread {
private:
    int ID;
public:
    BThread(int i) : ID(i) {}

    void run() {
        while (charCount < CHAR_COUNT_MAX) {
            if (lockBC_.tryAcquire(1)) {
                if (lockC_.available() == 0) {
                    lockC_.release(1);
                }
                printf("B");
                fflush(stdout);
                semCharCount.acquire();
                charCount++;
                semCharCount.release();
            };
            msleep((randg->generate() % 3 + 1) * TIME_FACTOR);
        }
        return;
    }
};

class CThread : public QThread {
private:
    int ID;
public:
    CThread(int i) : ID(i) {}

    void run() {
        while (charCount < CHAR_COUNT_MAX) {
            if (lockC_.tryAcquire(1) && lockBC_.tryAcquire(1)) {
                printf("C");
                fflush(stdout);
                semCharCount.acquire();
                charCount++;
                semCharCount.release();
            }
            msleep((randg->generate() % 3 + 1) * TIME_FACTOR);
        }
        return;
    }
};

int main(int argc, char *argv[]) {
    QCoreApplication a(argc, argv);

    printf("START\n\n");
    fflush(stdout);
    AThread *pTa = new AThread(1);
    BThread *pTb = new BThread(2);
    CThread *pTc = new CThread(3);

    pTa->start();
    pTb->start();
    pTc->start();

    pTa->wait();
    pTb->wait();
    pTc->wait();
    printf("\n\n");
    fflush(stdout);

    // Let event loop do at least one turn. (https:/stackoverflow.com/questions/4180394)
    QTimer::singleShot(0, &a, &QCoreApplication::quit); // Let event loop do at least one turn.

    return a.exec();
}