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

int main(int argc, char ** argv)
{
  int fd = 0;
  int pagesize = 0;
  unsigned int delta = 0;
  int retval = 0;
  size_t count = 0;
  size_t size = 0;
  char* addr = 0;

  pagesize = getpagesize();

  srand(time(0));
  delta = rand() % pagesize;
  if (argc > 1)
    delta = 0xf96;
  
  fprintf (stderr, "pagesize %d\n", pagesize);
  fprintf (stderr, "using delta %06d, %06x\n", delta, delta);


  fd = open ("/tmp/MemMapTest1.data", O_RDWR|O_CREAT);
  if (fd == -1)
    {
      fprintf (stderr, "Unable to create file: %s\n", strerror (errno));
      exit (1);
    }
  if (unlink ("/tmp/MemMapTest1.data") == -1)
    {
      fprintf (stderr, "Unable to unlink file: %s\n", strerror (errno));
      exit (1);
    }

  retval = ftruncate (fd, delta);
  if (retval == -1)
    {
      fprintf (stderr, "Unable to resize file: %s\n", strerror (errno));
      exit (1);
    }

  size = delta;
  addr = (char*) mmap (0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
  if (addr == MAP_FAILED)
    {
      fprintf (stderr, "Unable to map file: %s\n", strerror (errno));
      exit (1);
    }

  fprintf (stderr, "%03d address: %p, size: %06d, %06x, new size: %06d, %06x\n",
           count, addr, size, size, size + delta, size + delta);
  
  while (count < 500)
    {
      if (munmap(addr, size) == -1)
        {
          fprintf (stderr, "Unable to unmap file: %s\n", strerror (errno));
          exit (1);
        }

      size += delta;
      retval = ftruncate (fd, size);
      if (retval == -1)
        {
          fprintf (stderr, "Unable to resize file: %s\n", strerror (errno));
          exit (1);
        }
      addr = (char*) mmap (addr, size, PROT_READ|PROT_WRITE,
                           MAP_SHARED|MAP_FIXED, fd, 0);
      if (addr == MAP_FAILED)
        {
          fprintf (stderr, "Unable to map file: %s\n", strerror (errno));
          exit (1);
        }

      ++count;
      fprintf (stderr, "%03d address: %p, size: %06d, %06x, new size: %06d, %06x\n",
               count, addr, size, size, size + delta, size + delta);
    }
  fprintf (stderr, "%03d exited loop\n", count);
  return 0;
}