#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
#include <stdio.h>
#include <errno.h>
#include <fcntl.h>

#define PAGEPROT PROT_READ|PROT_WRITE
#define MAPFLAGS MAP_PRIVATE|MAP_ANONYMOUS

static int syspagesize = 0, pagemask, offmask, error_cnt = 0;

void sigsegv(int unused)
{
  _exit(0);
}

caddr_t femmap(int fd, off_t foff, size_t syz, int prot, u_char *msg) {
  /* femmap() and femunmap() take care of the need to allocate
     on page boundaries and in multiples of pages. */
  off_t pfoff;  /* foff on a page boundary */
  size_t psyz; /* syz rounded up to full pages */
  int chopped;
  caddr_t rslt;
  if (syspagesize == 0) {
    syspagesize = getpagesize();
    offmask = syspagesize - 1;
    pagemask = ~offmask;
    if (1) printf("--- Syspagesize %d, pagemask %X, offmask %X\n",
        syspagesize, pagemask, offmask);
  }
  printf("foff is %d\n", foff);
  printf("--- Syspagesize %d, pagemask %X, offmask %X\n",
        syspagesize, pagemask, offmask);
  pfoff = foff & pagemask;
  printf("pfoff is %d\n", pfoff);
  chopped = foff & offmask;
  psyz = (syz + chopped + syspagesize - 1) & pagemask;

  printf("**** Vars just before mmap call ****\n");
  printf("psyz = %d\nprot = %d\nfd = %d\npfoff = %d\n", psyz, prot, fd, (int)pfoff);

  if ((rslt = mmap(0, psyz, prot, MAP_SHARED, fd, pfoff))  ==MAP_FAILED) {
  /* if ((rslt = mmap(0, psyz, prot, MAP_SHARED, fd, 0))  ==MAP_FAILED) {
  */
    printf("perror reports errno of %d\n", errno);
    printf("   Mapping %d at %X <---> %d (%s\n", psyz, (int)rslt, (int)pfoff,
      msg);
    error_cnt++;
    exit(1);
  }
  if (1)
    printf("   Mapping %d at %X <---> %d (%s\n", psyz, (int)rslt, (int)pfoff,
      msg);
  return (rslt + chopped);
  /* return (rslt + chopped + pfoff);
  */
}
     
int main(int argc, char **argv)
{
  int fh;
  off_t foff;
  size_t syz;
  int prot;
  u_char *msg;
  int i;
  off_t size;
  u_char *result = NULL;

  struct stat finfo;

  foff = atoi(argv[1]);
  printf("Offset is %d\n", foff);

  for (i=2; i<argc; i++)
  {
     fh = open(argv[i], O_RDONLY);

     fstat(fh, &finfo);

     size = finfo.st_size;

     printf("File %s opened on descriptor %d.  It is %ld bytes long\n",
             argv[i], fh, (u_long) size);

     result = (u_char *)femmap(fh, foff, (int) size, PROT_READ, "mapping fh");

     printf("Result from femmap is %X\n", result);
     printf("Byte is %d\n", *result);

     close(fh);
  }


  return 0;
}