1/*-
2 * Copyright (c) 1994 Søren Schmidt
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer,
10 *    in this position and unchanged.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 * 3. The name of the author may not be used to endorse or promote products
15 *    derived from this software without specific prior written permission
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#ifndef lint
30static const char rcsid[] =
31  "$FreeBSD$";
32#endif /* not lint */
33
34#include <stdio.h>
35#include <string.h>
36#include "decode.h"
37
38int decode(FILE *fd, char *buffer, int len)
39{
40	int n, pos = 0, tpos;
41	char *bp, *p;
42	char tbuffer[3];
43	char temp[128];
44
45#define	DEC(c)	(((c) - ' ') & 0x3f)
46
47	do {
48		if (!fgets(temp, sizeof(temp), fd))
49			return(0);
50	} while (strncmp(temp, "begin ", 6));
51	sscanf(temp, "begin %o %s", (unsigned *)&n, temp);
52	bp = buffer;
53	for (;;) {
54		if (!fgets(p = temp, sizeof(temp), fd))
55			return(0);
56		if ((n = DEC(*p)) <= 0)
57			break;
58		for (++p; n > 0; p += 4, n -= 3) {
59			tpos = 0;
60			if (n >= 3) {
61				tbuffer[tpos++] = DEC(p[0])<<2 | DEC(p[1])>>4;
62				tbuffer[tpos++] = DEC(p[1])<<4 | DEC(p[2])>>2;
63				tbuffer[tpos++] = DEC(p[2])<<6 | DEC(p[3]);
64			}
65			else {
66				if (n >= 1) {
67					tbuffer[tpos++] =
68						DEC(p[0])<<2 | DEC(p[1])>>4;
69				}
70				if (n >= 2) {
71					tbuffer[tpos++] =
72						DEC(p[1])<<4 | DEC(p[2])>>2;
73				}
74				if (n >= 3) {
75					tbuffer[tpos++] =
76						DEC(p[2])<<6 | DEC(p[3]);
77				}
78			}
79			if (tpos == 0)
80				continue;
81			if (tpos + pos > len) {
82				tpos = len - pos;
83				/*
84				 * Arrange return value > len to indicate
85				 * overflow.
86				 */
87				pos++;
88			}
89			bcopy(tbuffer, bp, tpos);
90			pos += tpos;
91			bp += tpos;
92			if (pos > len)
93				return(pos);
94		}
95	}
96	if (!fgets(temp, sizeof(temp), fd) || strcmp(temp, "end\n"))
97		return(0);
98	return(pos);
99}
100