/* atob: version 4.0jp
 * stream filter to change printable ascii from "btoa" back into 8 bit bytes
 * if bad chars, or Csums do not match: exit(1) [and NO output]
 *
 *  Paul Rutter		Joe Orost
 *  philabs!per		petsd!joe
 *
 * Modified by Jef Poskanzer <jef@mail.acme.com> to get rid of the annoying
 * and wasteful no-output stuff.  This makes it run twice as fast.  Still
 * does exit(1), of course.
 */

#include <stdio.h>

#define reg register

#define streq(s0, s1)  strcmp(s0, s1) == 0

#define times85(x)	((((((x<<2)+x)<<2)+x)<<2)+x)

long int Ceor = 0;
long int Csum = 0;
long int Crot = 0;
long int word = 0;
int bcount = 0;
long int prevword;
int prevfull = 0;

fatal() {
  fprintf(stderr, "bad format or Csum to atob\n");
  exit(1);
}

#define DE(c) ((c) - '!')

decode(c)
  reg c;
{
  if (c == 'z') {
    if (bcount != 0)
      fatal();
    word = 0;
    wordout();
  } else if ((c >= '!') && (c < ('!' + 85))) {
    if (bcount == 0) {
      word = DE(c);
      ++bcount;
    } else if (bcount < 4) {
      word = times85(word);
      word += DE(c);
      ++bcount;
    } else {
      word = times85(word) + DE(c);
      wordout();
      word = 0;
      bcount = 0;
    }
  } else
    fatal();
}

wordout()
{
  /*write out previous word, if any*/
  if (prevfull) {
    byteout((int)((prevword >> 24) & 255), 1);
    byteout((int)((prevword >> 16) & 255), 1);
    byteout((int)((prevword >> 8) & 255), 1);
    byteout((int)(prevword & 255), 1);
  }
  /*save word for later output*/
  prevword = word;
  prevfull = 1;
}

byteout(c, really)
  reg c;
  int really;
{
  Ceor ^= c;
  Csum += c;
  Csum += 1;
  if ((Crot & 0x80000000)) {
    Crot <<= 1;
    Crot += 1;
  } else
    Crot <<= 1;
  Crot += c;
  if (really)
    putc(c, stdout);
}

main(argc, argv)
  char **argv;
{
  reg c;
  reg long int i;
  char buf[100];
  long int n1, n2, oeor, osum, orot;

  if (argc != 1) {
    fprintf(stderr,"bad args to %s\n", argv[0]);
    exit(2);
  }
  /*search for header line*/
  for (;;) {
    if (fgets(buf, sizeof buf, stdin) == NULL)
      fatal();
     if (streq(buf, "xbtoa Begin\n"))
      break;
  }

  while ((c = getchar()) != EOF) {
    if (c == '\n')
      continue;
    if (c == 'x')
      break;
    decode(c);
  }
  if(scanf("btoa End N %ld %lx E %lx S %lx R %lx\n",
         &n1, &n2, &oeor, &osum, &orot) != 5)
    fatal();
  if (n1 != n2)
    fatal();
  if (prevfull) {
    switch (n1 % 4) {
      case 0:
      byteout((int)((prevword >> 24) & 255), 1);
      byteout((int)((prevword >> 16) & 255), 1);
      byteout((int)((prevword >> 8) & 255), 1);
      byteout((int)(prevword & 255), 1);
      break;
      case 1:
      byteout((int)((prevword >> 24) & 255), 1);
      byteout((int)((prevword >> 16) & 255), 0);
      byteout((int)((prevword >> 8) & 255), 0);
      byteout((int)(prevword & 255), 0);
      break;
      case 2:
      byteout((int)((prevword >> 24) & 255), 1);
      byteout((int)((prevword >> 16) & 255), 1);
      byteout((int)((prevword >> 8) & 255), 0);
      byteout((int)(prevword & 255), 0);
      break;
      case 3:
      byteout((int)((prevword >> 24) & 255), 1);
      byteout((int)((prevword >> 16) & 255), 1);
      byteout((int)((prevword >> 8) & 255), 1);
      byteout((int)(prevword & 255), 0);
      break;
    }
  }
  if (oeor != Ceor || osum != Csum || orot != Crot)
    fatal();
  exit(0);
}