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[unix-history] / usr.bin / vidcontrol / decode.c

/*-
* Copyright (c) 1994 Søren Schmidt
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
*    derived from this software withough specific prior written permission
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*      $Id$
*/

#include <stdio.h>

int decode(FILE *fd, char *buffer)
{
       int n, pos = 0;
       char *p;
       char temp[128];

#define DEC(c)  (((c) - ' ') & 0x3f)

       do {
               if (!fgets(temp, sizeof(temp), fd)) 
                       return(0);
       } while (strncmp(temp, "begin ", 6));
       sscanf(temp, "begin %o %s", &n, temp);
       for (;;) {
               if (!fgets(p = temp, sizeof(temp), fd))
                       return(0);
               if ((n = DEC(*p)) <= 0)
                       break;
               for (++p; n > 0; p += 4, n -= 3)
                       if (n >= 3) {
                               buffer[pos++] = DEC(p[0])<<2 | DEC(p[1])>>4;
                               buffer[pos++] = DEC(p[1])<<4 | DEC(p[2])>>2;
                               buffer[pos++] = DEC(p[2])<<6 | DEC(p[3]);
                       }
                       else {
                               if (n >= 1) {
                                       buffer[pos++] =
                                               DEC(p[0])<<2 | DEC(p[1])>>4;
                               }
                               if (n >= 2) {
                                       buffer[pos++] = 
                                               DEC(p[1])<<4 | DEC(p[2])>>2;
                               }
                               if (n >= 3) {
                                       buffer[pos++] =
                                               DEC(p[2])<<6 | DEC(p[3]);
                               }
                       }
       }
       if (!fgets(temp, sizeof(temp), fd) || strcmp(temp, "end\n"))
               return(0);
       return(pos);
}