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