sdl-threading.c

linux下的一些小游戏编程

/* Example of SDL's portable threading API. */

#include <stdio.h>
#include <stdlib.h>
#include <SDL/SDL.h>

/* We must include SDL_thread.h separately. */
#include <SDL/SDL_thread.h>

static int counter = 0;
SDL_mutex *counter_mutex;

/* The three threads will run until this flag is set. */
static int exit_flag = 0;

/* This function is a thread entry point. */
int ThreadEntryPoint(void *data)
{
    char *threadname;

    /* Anything can be passed as thread data.
       We will use it as a thread name. */
    threadname = (char *) data;

    /* Loop until main() sets the exit flag. */
    while (exit_flag == 0) {
	printf("This is %s! ", threadname);

	/* Get a lock on the counter variable. */
	SDL_mutexP(counter_mutex);

	/* We can now safely modify the counter. */
	printf("The counter is currently %i\n", counter);
	counter++;

	/* Release the lock on the counter variable. */
	SDL_mutexV(counter_mutex);

	/* Delay for a random amount of time. */
	SDL_Delay(rand() % 3000);
    }

    printf("%s is now exiting.\n", threadname);

    return 0;
}

int main()
{
    SDL_Thread *thread1, *thread2, *thread3;

    /* Create a mutex to protect the counter. */
    counter_mutex = SDL_CreateMutex();

    printf("Press Ctrl-C to exit the program.\n");

    /* Create three threads. Give each thread a name
       as its data. */
    thread1 = SDL_CreateThread(ThreadEntryPoint, "Thread 1");
    thread2 = SDL_CreateThread(ThreadEntryPoint, "Thread 2");
    thread3 = SDL_CreateThread(ThreadEntryPoint, "Thread 3");

    /* Let the threads run until the counter reaches 20. */
    while (counter < 20)
	SDL_Delay(1000);

    /* Signal the threads to exit. */
    exit_flag = 1;
    printf("exit_flag has been set by main().\n");

    /* Give them time to notice the flag and exit. */
    SDL_Delay(3500);

    /* Destroy the counter mutex. */
    SDL_DestroyMutex(counter_mutex);

    return 0;
}