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#include <stdio.h>

#include <fcntl.h>

#define USAGE   "USAGE: checkum -[vhcs] infile outfile\n\t-v\tverbose\n\

\t-h\thelp\n\t-c\tcheck checksum\n\t-s\tprint the ipl size"

static int verbose = 0;

static int verify  = 0;

static int size    = 0;

typedef int word_t;

#define WORDSIZE (sizeof(word_t))

main(argc, argv)

     int argc;

     char **argv;

{

  char   *infile;

  char   *outfile;

  int    infd;

  int    outfd;

  word_t checksum = 0;

  int    nbytes;

  word_t buf;

  int    i        = 1;

  int   filesize  = 0;

  while (*argv[i] == '-') {

      switch (*(argv[i]+1)) {

      case 'v':

        verbose++;

        break;

      case 'c':

        verify++;

        puts ("Sorry, unimplemented for now");

        exit(1);

        break;

      case 's':

        size++;

        break;

      case 'h':

        puts (USAGE);

        exit(0);

      default:

        printf ("\"%s\", Illegal option\n", argv[i]);

        puts (USAGE);

        exit(1);

    }

    i++;

  }

  infile = *(argv + i);

  outfile = *(argv + i+1);

  /* see it there were file names on the command line */

  if (infile == 0x0) {

    puts("Didn't specify an input file name");

    exit(1);

  }

  if (outfile == 0x0) {

    puts("Didn't specify an output file name");

     exit(1);

  }

  /* try to open the files */

  infd = open(infile, O_RDONLY);

  if (infd == -1) {

    printf("Couldn't open %s\n", infile);

    exit(1);

  }

  outfd = open(outfile, O_WRONLY|O_CREAT|O_TRUNC);

  if (outfd == -1) {

    printf("Couldn't open %s\n", outfile);

    exit(1);

  }

  if (verbose > 2)

    putchar('\n');

  /* calculate the checksum */

  while ((nbytes = read(infd, &buf, WORDSIZE)) == WORDSIZE) {

    if (verbose > 2)

      putchar('.');

    checksum+= buf;

    filesize+= WORDSIZE;

    if (write(outfd, &buf, WORDSIZE) != WORDSIZE) {

      puts("Couldn't write");

    }

    if (verbose > 3)

      putchar('+');

  }

  if (verbose > 2)

    putchar('\n');

  /* write the last byte read */

  if (nbytes > 0) {

    write(outfd, &buf, nbytes);

    checksum+= buf;                             /* calculate the last word */

    filesize+= nbytes;

  }

  /* write the checksum */

  buf = -checksum;

  write(outfd, &buf, WORDSIZE);

  filesize+= WORDSIZE;                          /* checksum increase the size */

  if (verbose > 0)

    printf("The calculated checksum is:\n\t0x%x,\n\t%u\n", -checksum, -checksum);

  /* calculate the extra 2K here */

  buf = 0;

  while ((filesize % 2048) !=0) {

    filesize+=WORDSIZE;

    write(outfd, &buf, WORDSIZE);

  }

  if (size > 0) {

    printf ("%u is the new file size\n", filesize);

  }

  close(outfd);

  close(infd);

  exit(0);

}

#if 0

/* Calculate a simple checksum and concatenate it to the end of BUF.  */

void

compute_and_concatenate_checksum (word *buf, size_t bufsize_in_words)

{

  size_t i;

  word sum;

  sum = buf[0]

  for (i = 1; i < bufsize_in_words; i++)

    sum += buf[i];

  buf[bufsize_in_words] = -sum;

}

/* Calculate a simple checksum and verify it.  NOTE: bufsize_in_words should

   include the checksum, i.e., it should be one larger than when the

   checksum was calculated using compute_and_concatenate_checksum!  */

int

compute_and_and_verify_checksum (word *buf, size_t bufsize_in_words)

{

  size_t i;

  word sum;

  sum = buf[0];

  for (i = 1; i < bufsize_in_words; i++)

    sum += buf[i];

  if (sum != 0)

    return ERROR;

  return SUCCESS;

}

#endif