dispatch timer

dispatch-timer.c

//
//  dispatch-timer.c
//
//  Created by Shon Frazier on 4/22/13.
//  Copyright (c) 2013 Shon Frazier. All rights reserved.
//

#include <stdio.h>
#include <dispatch/dispatch.h>


#define FREQ  (1000.)

int main(int argc, const char * argv[])
{
    __block uint64_t count = 0;
    uint64_t interval = (1./FREQ) * NSEC_PER_SEC;
    uint64_t leeway = 0.5 * NSEC_PER_SEC;
    
    dispatch_time_t start = dispatch_time(DISPATCH_TIME_NOW, 0);
    
    dispatch_queue_t queue = dispatch_get_main_queue();
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    
    dispatch_source_set_event_handler(timer, ^{
        if(!(count % (uint64_t)FREQ)) fprintf(stdout, "%lli\n", count);
        fflush(stdout);
            count ++;
    });
    
    dispatch_source_set_timer(timer, start, interval, leeway);
    dispatch_resume(timer);
    
    dispatch_main();
    
    return 0;
}