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/* (C) Copyright 1993,1994 by Carnegie Mellon University |
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* All Rights Reserved. |
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* |
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* Permission to use, copy, modify, distribute, and sell this software |
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* and its documentation for any purpose is hereby granted without |
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* fee, provided that the above copyright notice appear in all copies |
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* and that both that copyright notice and this permission notice |
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* appear in supporting documentation, and that the name of Carnegie |
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* Mellon University not be used in advertising or publicity |
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* pertaining to distribution of the software without specific, |
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* written prior permission. Carnegie Mellon University makes no |
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* representations about the suitability of this software for any |
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* purpose. It is provided "as is" without express or implied |
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* warranty. |
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* |
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* CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO |
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* THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY |
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* AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE |
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* FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN |
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* AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING |
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* OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS |
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* SOFTWARE. |
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*/ |
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#include <stdio.h> |
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#include <string.h> |
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|
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/* Description of the various file formats and their magic numbers */ |
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struct magic { |
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char *name; /* Name of the file format */ |
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char *num; /* The magic number */ |
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int len; /* Length of same (0 means strlen(magicnum)) */ |
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}; |
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|
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/* The magic numbers of the file formats we know about */ |
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static struct magic magic[] = { |
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{ "image/gif", "GIF", 0 }, |
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{ "image/jpeg", "\377\330\377", 0 }, |
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{ "video/mpeg", "\0\0\001\263", 4 }, |
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{ "application/postscript", "%!", 0 }, |
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}; |
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static int num_magic = (sizeof(magic)/sizeof(magic[0])); |
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static char *default_type = "application/octet-stream"; |
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|
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/* The longest magic number */ |
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static int max_magiclen = 0; |
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|
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/* |
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* Determins the format of the file "inputf". The name |
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* of the file format (or NULL on error) is returned. |
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*/ |
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char *magic_look(FILE *infile) |
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{ |
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int i, j; |
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char buf[80]; |
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int numread = 0; |
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|
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if (max_magiclen == 0) { |
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for (i=0; i<num_magic; i++) { |
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if (magic[i].len == 0) magic[i].len = strlen(magic[i].num); |
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if (magic[i].len > max_magiclen) max_magiclen = magic[i].len; |
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} |
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} |
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|
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numread = fread(buf, 1, max_magiclen, infile); |
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rewind(infile); |
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|
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for (i=0; i<num_magic; i++) { |
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if (numread >= magic[i].len) { |
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for (j=0; j<magic[i].len; j++) { |
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if (buf[j] != magic[i].num[j]) break; |
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} |
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if (j == magic[i].len) return magic[i].name; |
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} |
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} |
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|
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return default_type; |
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} |