/******************************************************************************
 * :CueCat (tm) Reader decoding program.                                      *
 * Copyright (C) 2000 Hal Duston                                              *
 *                                                                            *
 * This program is free software; you can redistribute it and/or modify       *
 * it under the terms of the GNU General Public License as published by       *
 * the Free Software Foundation; either version 2 of the License, or          *
 * (at your option) any later version.                                        *
 *                                                                            *
 * This program is distributed in the hope that it will be useful,            *
 * but WITHOUT ANT WARRANTY; without even the implied warranty of             *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the               *
 * GNU General Public License at http://www.fsf.org/copyleft/gpl.html         *
 * for more details.                                                          *
 *                                                                            *
 * :CueCat (tm) is a trademark of Digital:Convergence Corporation.            *
 *                                                                            *
 ******************************************************************************/
#include <ctype.h>
#include <unistd.h>

int main(int argc, char *arg[]);
static ssize_t decode(char *outbuf, const char *inbuf);

int main(int argc, char *arg[])
{
   char inbuf[512];
   char outbuf[512];
   ssize_t len;

   while((len = read(STDIN_FILENO, inbuf, sizeof(inbuf))) != 0)
   {
      inbuf[len] = '\0';
      len = decode(outbuf, inbuf);
      outbuf[len++] = 7; /* Ring the bell. */
      write(STDOUT_FILENO, outbuf, len);
   }
   _exit(0);
   return 0;
}

static ssize_t decode(char *outbuf, const char *inbuf)
{
   static int index_64[128] =
   {
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, 62, 63, -1, 63,
      52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
      -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
      15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
      -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
      41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
   };
   static char pad_64[4] = { 0x10, 0x34, 0x0d, 0x03 };
   const char *inptr = inbuf;
   char *outptr = outbuf;
   int ch = *inptr++;
   long n; /* Used as three byte integer. */
   int i;

   while(ch != '\0')
   {
      if(index_64[ch] < 0)
      {
         *outptr++ = ch;
         ch = *inptr++;
      }
      else
      {
         n = 0;
         for(i = 0; i < 4; ++i)
         {
            if(isalpha(ch))
            {
               ch ^= 0x20; /* Swap upper/lower case. */
            }
            if(index_64[ch] < 0)
            {
               n = n << 6 | pad_64[i]; /* Pad short runs. */
            }
            else
            {
               n = n << 6 | index_64[ch];
               ch = *inptr++;
            }
         }
         n ^= 0x434343; /* XOR with "ccc". */
         *outptr++ = (n >> 16) ? (n >> 16) : '\0';
         *outptr++ = (n >> 8 & 0xff) ? (n >> 8 & 0xff) : '\0';
         *outptr++ = (n & 0xff) ? (n & 0xff) : '\0';
      }
   }
   return outptr - outbuf;
}