mutex.cpp

mutex.cpp

//http://www.libsdl.org/ install instructions tutorials
#include <SDL/SDL.h>
#include <SDL/SDL_thread.h>

#include <iostream>
#include <stdlib.h>
using namespace std;

bool quit = false, consumed = true;
int a = 0, b = 0;

SDL_mutex *mutex_a, *mutex_b; //Declares an SDL_mutex pointer, mutex_a and mutex_b:

int thread_a(void *data) {
	char *thread_name = (char *) data;
	while (!quit) {
		//if thread_a reach inside while, begins action

		printf("I am %s. \n", thread_name);
		printf("I am %s. \n", &thread_name);
		SDL_mutexP(mutex_a); //Lock the mutex_a before PROCESSING a
		printf("%s has locked a\n", thread_name);
		printf("%s has locked a\n", &thread_name);

		++a; //instruction

		SDL_Delay(10); //Wait 10 milliseconds before return

		SDL_mutexP(mutex_b); //Lock the mutex_b before ACCESSING b
		printf("%s has locked b\n", thread_name);
		printf("%s has locked b\n", &thread_name);
		a += b++;

		SDL_mutexV(mutex_b); //Unlock the mutex_b
		SDL_mutexV(mutex_a); //Unlock the mutex_a

		SDL_Delay(rand() * 3000 + 1000); //Wait a period >= 1000
	}
	printf("%s quits\n", thread_name);
	printf("%s quits\n", &thread_name);
	return 0;
}

int thread_b(void *data) {
	char *thread_name = (char *) data;
	while (!quit) {
		//if thread_b reach inside while, begins action

		printf("I am %s. \n", thread_name);
		printf("I am %s. \n", &thread_name);
		SDL_mutexP(mutex_a); //Lock the mutex_a before PROCESSING a
		printf("%s has locked a\n", thread_name);
		printf("%s has locked a\n", &thread_name);

		a += b; //instruction

		SDL_mutexP(mutex_b); //Lock the mutex_b before ACCESSING b
		printf("%s has locked b\n", thread_name);
		printf("%s has locked b\n", &thread_name);
		b++;

		SDL_Delay(10); //Wait 10 milliseconds before return

		SDL_mutexV(mutex_b); //Unlock the mutex_b
		SDL_mutexV(mutex_a); //Unlock the mutex_a

		SDL_Delay(rand() * 3000 + 2000); //Wait a period >= 2000
	}
	printf("%s quits\n", thread_name);
	printf("%s quits\n", &thread_name);
	return 0;
}

int main() {
	cout << "Starting..." << endl; // prints Starting...
	SDL_Thread *id_a, *id_b; //Thread's IDS
	char *thread_name[2] = { "LOST_IN_SOUND", "PERSONA_FORMAX_SNIDER" }; //Thread's NAMES

	mutex_a = SDL_CreateMutex();
	mutex_b = SDL_CreateMutex();

	//create the threads
	id_a = SDL_CreateThread(thread_a, thread_name[0]);
	id_b = SDL_CreateThread(thread_b, thread_name[1]);

	//experiment with 20 seconds
	for (int i = 0; i < 10; i++) {
		SDL_Delay(2000);
	}

	quit = true; //signal the threads to return

	//wait for the threads to exit
	SDL_WaitThread(id_a, NULL);
	SDL_WaitThread(id_b, NULL);

	return 0;
}