/* slightly modified to avoid external references */

#include	<sys/types.h>
#include	<sys/stat.h>
#include	<sys/mman.h>	/* mmap() */
#include	<fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#define	FILE_MODE	(S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)
			/* default file access permissions for new files */

#ifndef	MAP_FILE	/* 44BSD defines this & requires it to mmap files */
#define	MAP_FILE   0	/* to compile under systems other than 44BSD */
#endif


int
main(int argc, char *argv[])
{
  int		fdin, fdout;
  char		*src, *dst;
  struct stat	statbuf;
  
  if (argc != 3) {
    fprintf(stderr, "usage: a.out <fromfile> <tofile>\n");
    exit(0);
  }
  
  if ( (fdin = open(argv[1], O_RDONLY)) < 0) {
    fprintf(stderr, "can't open %s for reading\n", argv[1]);
    exit(1);
  }
  
  if ( (fdout = open(argv[2], O_RDWR | O_CREAT | O_TRUNC,
		     FILE_MODE)) < 0) {
    fprintf(stderr, "usage: a.out <fromfile> <tofile>\n");
    exit(0);
  }
  
  if (fstat(fdin, &statbuf) < 0) { /* need size of input file */
    fprintf(stderr, "fstat error\n");
    exit(1);
  }
  
  /* set size of output file */
  if (lseek(fdout, statbuf.st_size - 1, SEEK_SET) == -1) {
    fprintf(stderr, "lseek error\n");
    exit(1);
  }
  
  if (write(fdout, " ", 1) != 1) {
    fprintf(stderr, "write error\n");
    exit(1);
  }
  
  if ( (src = mmap(0, statbuf.st_size, PROT_READ,
		   MAP_FILE | MAP_SHARED, fdin, 0)) == (caddr_t) -1) {
    fprintf(stderr, "mmap error for input\n");
    exit(1);
  }
  
  if ( (dst = mmap(0, statbuf.st_size, PROT_READ | PROT_WRITE,
		   MAP_FILE | MAP_SHARED, fdout, 0)) == (caddr_t) -1) {
    fprintf(stderr, "mmap error for output\n");
    exit(1);
  }
  
  memcpy(dst, src, statbuf.st_size);	/* does the file copy */
  
  exit(0);
}