tools/mpack-1.6/magic.c

/* (C) Copyright 1993,1994 by Carnegie Mellon University
 * All Rights Reserved.
 *
 * Permission to use, copy, modify, distribute, and sell this software
 * and its documentation for any purpose is hereby granted without
 * fee, provided that the above copyright notice appear in all copies
 * and that both that copyright notice and this permission notice
 * appear in supporting documentation, and that the name of Carnegie
 * Mellon University not be used in advertising or publicity
 * pertaining to distribution of the software without specific,
 * written prior permission.  Carnegie Mellon University makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied
 * warranty.
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 */
#include <stdio.h>
#include <string.h>

/* Description of the various file formats and their magic numbers */
struct magic {
    char *name;                 /* Name of the file format */
    char *num;          /* The magic number */
    int len;            /* Length of same (0 means strlen(magicnum)) */
};

/* The magic numbers of the file formats we know about */
static struct magic magic[] = {
    { "image/gif", "GIF", 0 },
    { "image/jpeg", "\377\330\377", 0 },
    { "video/mpeg", "\0\0\001\263", 4 },
    { "application/postscript", "%!", 0 },
};
static int num_magic = (sizeof(magic)/sizeof(magic[0]));
static char *default_type = "application/octet-stream";

/* The longest magic number */
static int max_magiclen = 0;

/*
 * Determins the format of the file "inputf".  The name
 * of the file format (or NULL on error) is returned.
 */
char *magic_look(FILE *infile)
{
    int i, j;
    char buf[80];
    int numread = 0;

    if (max_magiclen == 0) {
        for (i=0; i<num_magic; i++) {
            if (magic[i].len == 0) magic[i].len = strlen(magic[i].num);
            if (magic[i].len > max_magiclen) max_magiclen = magic[i].len;
        }
    }

    numread = fread(buf, 1, max_magiclen, infile);
    rewind(infile);

    for (i=0; i<num_magic; i++) {
        if (numread >= magic[i].len) {
            for (j=0; j<magic[i].len; j++) {
                if (buf[j] != magic[i].num[j]) break;
            }
            if (j == magic[i].len) return magic[i].name;
        }
    }

    return default_type;
}
1	/* (C) Copyright 1993,1994 by Carnegie Mellon University
2	* All Rights Reserved.
3	*
4	* Permission to use, copy, modify, distribute, and sell this software
5	* and its documentation for any purpose is hereby granted without
6	* fee, provided that the above copyright notice appear in all copies
7	* and that both that copyright notice and this permission notice
8	* appear in supporting documentation, and that the name of Carnegie
9	* Mellon University not be used in advertising or publicity
10	* pertaining to distribution of the software without specific,
11	* written prior permission. Carnegie Mellon University makes no
12	* representations about the suitability of this software for any
13	* purpose. It is provided "as is" without express or implied
14	* warranty.
15	*
16	* CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
17	* THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
18	* AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
19	* FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
20	* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
21	* AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
22	* OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
23	* SOFTWARE.
24	*/
25	#include <stdio.h>
26	#include <string.h>
27
28	/* Description of the various file formats and their magic numbers */
29	struct magic {
30	char name; / Name of the file format */
31	char num; / The magic number */
32	int len; /* Length of same (0 means strlen(magicnum)) */
33	};
34
35	/* The magic numbers of the file formats we know about */
36	static struct magic magic[] = {
37	{ "image/gif", "GIF", 0 },
38	{ "image/jpeg", "\377\330\377", 0 },
39	{ "video/mpeg", "\0\0\001\263", 4 },
40	{ "application/postscript", "%!", 0 },
41	};
42	static int num_magic = (sizeof(magic)/sizeof(magic[0]));
43	static char *default_type = "application/octet-stream";
44
45	/* The longest magic number */
46	static int max_magiclen = 0;
47
48	/*
49	* Determins the format of the file "inputf". The name
50	* of the file format (or NULL on error) is returned.
51	*/
52	char magic_look(FILE infile)
53	{
54	int i, j;
55	char buf[80];
56	int numread = 0;
57
58	if (max_magiclen == 0) {
59	for (i=0; i<num_magic; i++) {
60	if (magic[i].len == 0) magic[i].len = strlen(magic[i].num);
61	if (magic[i].len > max_magiclen) max_magiclen = magic[i].len;
62	}
63	}
64
65	numread = fread(buf, 1, max_magiclen, infile);
66	rewind(infile);
67
68	for (i=0; i<num_magic; i++) {
69	if (numread >= magic[i].len) {
70	for (j=0; j<magic[i].len; j++) {
71	if (buf[j] != magic[i].num[j]) break;
72	}
73	if (j == magic[i].len) return magic[i].name;
74	}
75	}
76
77	return default_type;
78	}