mpack_src/mpack-1.6-4/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	jmc	1.1	/* (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			}