125 lines
3.5 KiB
C
125 lines
3.5 KiB
C
/*
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* ASCII magic -- file types that we know based on keywords
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* that can appear anywhere in the file.
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*
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* Copyright (c) Ian F. Darwin, 1987.
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* Written by Ian F. Darwin.
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*
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* This software is not subject to any license of the American Telephone
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* and Telegraph Company or of the Regents of the University of California.
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*
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* Permission is granted to anyone to use this software for any purpose on
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* any computer system, and to alter it and redistribute it freely, subject
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* to the following restrictions:
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*
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* 1. The author is not responsible for the consequences of use of this
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* software, no matter how awful, even if they arise from flaws in it.
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*
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* 2. The origin of this software must not be misrepresented, either by
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* explicit claim or by omission. Since few users ever read sources,
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* credits must appear in the documentation.
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*
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* 3. Altered versions must be plainly marked as such, and must not be
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* misrepresented as being the original software. Since few users
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* ever read sources, credits must appear in the documentation.
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*
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* 4. This notice may not be removed or altered.
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*/
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#include <stdio.h>
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#include <string.h>
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#include <ctype.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include "file.h"
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#include "names.h"
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#ifndef lint
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static char *moduleid =
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"@(#)$Id: ascmagic.c,v 1.21 1997/01/15 17:23:24 christos Exp $";
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#endif /* lint */
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/* an optimisation over plain strcmp() */
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#define STREQ(a, b) (*(a) == *(b) && strcmp((a), (b)) == 0)
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int
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ascmagic(buf, nbytes)
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unsigned char *buf;
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int nbytes; /* size actually read */
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{
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int i, has_escapes = 0;
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unsigned char *s;
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char nbuf[HOWMANY+1]; /* one extra for terminating '\0' */
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char *token;
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register struct names *p;
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/*
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* Do the tar test first, because if the first file in the tar
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* archive starts with a dot, we can confuse it with an nroff file.
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*/
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switch (is_tar(buf, nbytes)) {
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case 1:
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ckfputs("tar archive", stdout);
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return 1;
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case 2:
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ckfputs("POSIX tar archive", stdout);
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return 1;
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}
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/*
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* for troff, look for . + letter + letter or .\";
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* this must be done to disambiguate tar archives' ./file
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* and other trash from real troff input.
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*/
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if (*buf == '.') {
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unsigned char *tp = buf + 1;
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while (isascii(*tp) && isspace(*tp))
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++tp; /* skip leading whitespace */
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if ((isascii(*tp) && (isalnum(*tp) || *tp=='\\') &&
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isascii(tp[1]) && (isalnum(tp[1]) || tp[1] == '"'))) {
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ckfputs("troff or preprocessor input text", stdout);
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return 1;
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}
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}
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if ((*buf == 'c' || *buf == 'C') &&
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isascii(buf[1]) && isspace(buf[1])) {
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ckfputs("fortran program text", stdout);
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return 1;
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}
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/* Make sure we are dealing with ascii text before looking for tokens */
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for (i = 0; i < nbytes; i++) {
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if (!isascii(buf[i]))
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return 0; /* not all ASCII */
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}
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/* look for tokens from names.h - this is expensive! */
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/* make a copy of the buffer here because strtok() will destroy it */
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s = (unsigned char*) memcpy(nbuf, buf, nbytes);
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s[nbytes] = '\0';
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has_escapes = (memchr(s, '\033', nbytes) != NULL);
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while ((token = strtok((char *) s, " \t\n\r\f")) != NULL) {
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s = NULL; /* make strtok() keep on tokin' */
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for (p = names; p < names + NNAMES; p++) {
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if (STREQ(p->name, token)) {
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ckfputs(types[p->type], stdout);
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if (has_escapes)
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ckfputs(" (with escape sequences)",
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stdout);
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return 1;
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}
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}
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}
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/* all else fails, but it is ASCII... */
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ckfputs("ASCII text", stdout);
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if (has_escapes) {
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ckfputs(" (with escape sequences)", stdout);
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}
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return 1;
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}
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