#include <sys/mman.h>  /* for mmap     */
#include <stdlib.h>    /* for exit     */
#include <stdio.h>     /* for fprintf  */
#include <string.h>    /* for strerror */
#include <unistd.h>    /* for fork     */
#include <errno.h>     /* for errno    */

#include "mem.h"

#define NAME_MAX 64


int parse_args(int argc,  char *argv[ ], int *np){
  if ( (argc != 2) || ((*np = atoi (argv[1])) <= 0) ) {
	fprintf (stderr, "Usage: %s nprocs\n", argv[0]);
	return(-1); };
  return(0);
}

int main(int argc, char *argv[]){
  int fd, i, nprocs, *count;
  pid_t child;
  void *start_addr;
  char self[NAME_MAX];
  size_t size = sizeof(int);
  
  if(parse_args(argc, argv, &nprocs) < 0)
	exit(EXIT_FAILURE);
  /* does the file exist (and is the right size)? if not make it!  */
  if(init_shared_file(&fd, "sharedFile", size) != 0){
	exit(EXIT_FAILURE);
  }
  /* map it to memory                                              */
  start_addr =
	mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
  if(start_addr == MAP_FAILED){
	perror("mmap failed");
	exit(EXIT_FAILURE);
  }
  fprintf(stderr, "mmap returned %ld\n", (long)start_addr);
  count = (int *)start_addr;
  *count = 0;
  for(i = 0; i < nprocs; i++){
	child = fork();
	if(child < 0){
	  fprintf(stderr, "%s: fork failed -- %s\n",
		argv[0], strerror(errno));
	  exit(EXIT_FAILURE);
	}
	if(child > 0) break;
  }
  /* name myself                                                   */
  sprintf(self, "process %d", i);

  while(1){
	 count = (int *)start_addr;
	fprintf(stderr, "%s: count before = %d\n", self, *count);
	(*count)++;
	sleep(1);
	fprintf(stderr, "%s: count after = %d\n", self, *count);
	
  }

  exit(EXIT_SUCCESS);

}