1 /* $NetBSD: is_simh.c,v 1.1.1.1 2023/08/18 18:36:49 christos Exp $ */
2
3 /*-
4 * Copyright (c) 2023 Christos Zoulas
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 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 /*
30 * Parse SIM-H tape files
31 * http://simh.trailing-edge.com/docs/simh_magtape.pdf
32 */
33
34 #ifndef TEST
35 #include "file.h"
36
37 #ifndef lint
38 #if 0
39 FILE_RCSID("@(#)$File: is_simh.c,v 1.10 2023/07/27 19:39:55 christos Exp $")
40 #else
41 __RCSID("$NetBSD: is_simh.c,v 1.1.1.1 2023/08/18 18:36:49 christos Exp $");
42 #endif
43 #endif
44
45 #include <string.h>
46 #include <stddef.h>
47 #include "magic.h"
48 #else
49 #include <stdint.h>
50 #include <sys/types.h>
51 #include <string.h>
52 #include <stddef.h>
53 #define CAST(a, b) (a)(b)
54 #endif
55
56
57 #ifdef DEBUG
58 #include <stdio.h>
59 #define DPRINTF(fmt, ...) printf(fmt, __VA_ARGS__)
60 #else
61 #define DPRINTF(fmt, ...)
62 #endif
63
64 /*
65 * if SIMH_TAPEMARKS == 0:
66 * check all the records and tapemarks
67 * otherwise:
68 * check only up-to the number of tapemarks specified
69 */
70 #ifndef SIMH_TAPEMARKS
71 #define SIMH_TAPEMARKS 10
72 #endif
73
74 typedef union {
75 char s[4];
76 uint32_t u;
77 } myword;
78
79 static myword simh_bo;
80
81 #define NEED_SWAP (simh_bo.u == CAST(uint32_t, 0x01020304))
82
83 /*
84 * swap an int
85 */
86 static uint32_t
swap4(uint32_t sv)87 swap4(uint32_t sv)
88 {
89 myword d, s;
90 s.u = sv;
91 d.s[0] = s.s[3];
92 d.s[1] = s.s[2];
93 d.s[2] = s.s[1];
94 d.s[3] = s.s[0];
95 return d.u;
96 }
97
98
99 static uint32_t
getlen(const unsigned char ** uc)100 getlen(const unsigned char **uc)
101 {
102 uint32_t n;
103 memcpy(&n, *uc, sizeof(n));
104 *uc += sizeof(n);
105 if (NEED_SWAP)
106 n = swap4(n);
107 if (n == 0xffffffff) /* check for End of Medium */
108 return n;
109 n &= 0x00ffffff; /* keep only the record len */
110 if (n & 1)
111 n++;
112 return n;
113 }
114
115 static int
simh_parse(const unsigned char * uc,const unsigned char * ue)116 simh_parse(const unsigned char *uc, const unsigned char *ue)
117 {
118 uint32_t nbytes, cbytes;
119 const unsigned char *orig_uc = uc;
120 size_t nt = 0, nr = 0;
121
122 (void)memcpy(simh_bo.s, "\01\02\03\04", 4);
123
124 while (ue - uc >= CAST(ptrdiff_t, sizeof(nbytes))) {
125 nbytes = getlen(&uc);
126 if ((nt > 0 || nr > 0) && nbytes == 0xFFFFFFFF)
127 /* EOM after at least one record or tapemark */
128 break;
129 if (nbytes == 0) {
130 nt++; /* count tapemarks */
131 #if SIMH_TAPEMARKS
132 if (nt == SIMH_TAPEMARKS)
133 break;
134 #endif
135 continue;
136 }
137 /* handle a data record */
138 uc += nbytes;
139 if (ue - uc < CAST(ptrdiff_t, sizeof(nbytes)))
140 break;
141 cbytes = getlen(&uc);
142 if (nbytes != cbytes)
143 return 0;
144 nr++;
145 }
146 if (nt * sizeof(uint32_t) == CAST(size_t, uc - orig_uc))
147 return 0; /* All examined data was tapemarks (0) */
148 if (nr == 0) /* No records */
149 return 0;
150 return 1;
151 }
152
153 #ifndef TEST
154 int
file_is_simh(struct magic_set * ms,const struct buffer * b)155 file_is_simh(struct magic_set *ms, const struct buffer *b)
156 {
157 const unsigned char *uc = CAST(const unsigned char *, b->fbuf);
158 const unsigned char *ue = uc + b->flen;
159 int mime = ms->flags & MAGIC_MIME;
160
161 if ((ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION)) != 0)
162 return 0;
163
164 if (!simh_parse(uc, ue))
165 return 0;
166
167 if (mime == MAGIC_MIME_ENCODING)
168 return 1;
169
170 if (mime) {
171 if (file_printf(ms, "application/SIMH-tape-data") == -1)
172 return -1;
173 return 1;
174 }
175
176 if (file_printf(ms, "SIMH tape data") == -1)
177 return -1;
178
179 return 1;
180 }
181
182 #else
183
184 #include <sys/types.h>
185 #include <sys/stat.h>
186 #include <stdio.h>
187 #include <fcntl.h>
188 #include <unistd.h>
189 #include <stdlib.h>
190 #include <stdint.h>
191 #include <err.h>
192
193 int
main(int argc,char * argv[])194 main(int argc, char *argv[])
195 {
196 int fd;
197 struct stat st;
198 unsigned char *p;
199
200 if ((fd = open(argv[1], O_RDONLY)) == -1)
201 err(EXIT_FAILURE, "Can't open `%s'", argv[1]);
202
203 if (fstat(fd, &st) == -1)
204 err(EXIT_FAILURE, "Can't stat `%s'", argv[1]);
205
206 if ((p = CAST(char *, malloc(st.st_size))) == NULL)
207 err(EXIT_FAILURE, "Can't allocate %jd bytes",
208 (intmax_t)st.st_size);
209 if (read(fd, p, st.st_size) != st.st_size)
210 err(EXIT_FAILURE, "Can't read %jd bytes",
211 (intmax_t)st.st_size);
212 printf("is simh %d\n", simh_parse(p, p + st.st_size));
213 return 0;
214 }
215 #endif
216