test/testsem.c

/* Simple test of the SDL semaphore code */

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>

#include "SDL.h"
#include "SDL_thread.h"

#define NUM_THREADS 10

static SDL_sem *sem;
int alive = 1;

int SDLCALL ThreadFunc(void *data)
{
	int threadnum = (int)(uintptr_t)data;
	while ( alive ) {
		SDL_SemWait(sem);
		fprintf(stderr, "Thread number %d has got the semaphore (value = %d)!\n", threadnum, SDL_SemValue(sem));
		SDL_Delay(200);
		SDL_SemPost(sem);
		fprintf(stderr, "Thread number %d has released the semaphore (value = %d)!\n", threadnum, SDL_SemValue(sem));
		SDL_Delay(1); /* For the scheduler */
	}
	printf("Thread number %d exiting.\n", threadnum);
	return 0;
}

static void killed(int sig)
{
	alive = 0;
}

static void TestWaitTimeout(void)
{
	Uint32 start_ticks;
	Uint32 end_ticks;
	Uint32 duration;

	sem = SDL_CreateSemaphore(0);
	printf("Waiting 2 seconds on semaphore\n");

	start_ticks = SDL_GetTicks();
	SDL_SemWaitTimeout(sem, 2000);
	end_ticks = SDL_GetTicks();

	duration = end_ticks - start_ticks;
	
	/* Accept a little offset in the effective wait */
	if (duration > 1900 && duration < 2050)
		printf("Wait done.\n");
	else
		fprintf(stderr, "Wait took %d milliseconds\n", duration);
}

int main(int argc, char **argv)
{
	SDL_Thread *threads[NUM_THREADS];
	uintptr_t i;
	int init_sem;

	if(argc < 2) {
		fprintf(stderr,"Usage: %s init_value\n", argv[0]);
		return(1);
	}

	/* Load the SDL library */
	if ( SDL_Init(0) < 0 ) {
		fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError());
		return(1);
	}
	signal(SIGTERM, killed);
	signal(SIGINT, killed);
	
	init_sem = atoi(argv[1]);
	sem = SDL_CreateSemaphore(init_sem);
	
	printf("Running %d threads, semaphore value = %d\n", NUM_THREADS, init_sem);
	/* Create all the threads */
	for( i = 0; i < NUM_THREADS; ++i ) {
		threads[i] = SDL_CreateThread(ThreadFunc, (void*)i);
	}

	/* Wait 10 seconds */
	SDL_Delay(10 * 1000);

	/* Wait for all threads to finish */
	printf("Waiting for threads to finish\n");
	alive = 0;
	for( i = 0; i < NUM_THREADS; ++i ) {
		SDL_WaitThread(threads[i], NULL);
	}
	printf("Finished waiting for threads\n");

	SDL_DestroySemaphore(sem);

	TestWaitTimeout();

	SDL_Quit();
	return(0);
}