1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1994 Søren 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
decode(FILE * fd,char * buffer,int len)35 int 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