/* 
 * mmap() example 3.
 * Create an anonymous area & inherit to a child, and use
 * a shared semaphore in it.
 *
 * G. Back CS 3214 Fall 2009
 */
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <assert.h>
#include <semaphore.h>

int
main(int ac, char *av[])
{
    size_t sz = getpagesize();
    int sharedflag = ac < 2 || strcmp(av[1], "-private") 
                        ?  MAP_SHARED : MAP_PRIVATE;
    void *addr = mmap(NULL, sz, 
                      PROT_READ|PROT_WRITE, 
                      MAP_ANONYMOUS | sharedflag, -1, 0);
    assert (addr != MAP_FAILED);
    printf("Memory mapped at %p\n", addr);

    sem_t *semp = (sem_t*) addr;
    assert(sem_init(semp, /* shared */1, /* initial value */ 0) == 0);
    
    int i, *ia = addr + sizeof(*semp);
    if (fork() == 0) {
        sleep(1);
        for (i = 0; i < 10; i++)
            ia[i] = i;
        sem_post(semp);
    } else {
        sem_wait(semp);
        for (i = 0; i < 10; i++)
            printf("%d ", ia[i]);
        printf("\n");
    }

    return 0;
}