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Annotation of src/usr.bin/file/ascmagic.c, Revision 1.1.1.1

1.1       deraadt     1: /*
                      2:  * ASCII magic -- file types that we know based on keywords
                      3:  * that can appear anywhere in the file.
                      4:  *
                      5:  * Copyright (c) Ian F. Darwin, 1987.
                      6:  * Written by Ian F. Darwin.
                      7:  *
                      8:  * This software is not subject to any license of the American Telephone
                      9:  * and Telegraph Company or of the Regents of the University of California.
                     10:  *
                     11:  * Permission is granted to anyone to use this software for any purpose on
                     12:  * any computer system, and to alter it and redistribute it freely, subject
                     13:  * to the following restrictions:
                     14:  *
                     15:  * 1. The author is not responsible for the consequences of use of this
                     16:  *    software, no matter how awful, even if they arise from flaws in it.
                     17:  *
                     18:  * 2. The origin of this software must not be misrepresented, either by
                     19:  *    explicit claim or by omission.  Since few users ever read sources,
                     20:  *    credits must appear in the documentation.
                     21:  *
                     22:  * 3. Altered versions must be plainly marked as such, and must not be
                     23:  *    misrepresented as being the original software.  Since few users
                     24:  *    ever read sources, credits must appear in the documentation.
                     25:  *
                     26:  * 4. This notice may not be removed or altered.
                     27:  */
                     28:
                     29: #include <stdio.h>
                     30: #include <string.h>
                     31: #include <ctype.h>
                     32: #include <stdlib.h>
                     33: #include <unistd.h>
                     34: #include "file.h"
                     35: #include "names.h"
                     36:
                     37: #ifndef        lint
                     38: static char *moduleid =
                     39:        "@(#)$Id: ascmagic.c,v 1.8 1995/05/21 00:13:27 christos Exp $";
                     40: #endif /* lint */
                     41:
                     42:                        /* an optimisation over plain strcmp() */
                     43: #define        STREQ(a, b)     (*(a) == *(b) && strcmp((a), (b)) == 0)
                     44:
                     45: int
                     46: ascmagic(buf, nbytes)
                     47: unsigned char *buf;
                     48: int nbytes;    /* size actually read */
                     49: {
                     50:        int i, has_escapes = 0;
                     51:        unsigned char *s;
                     52:        char nbuf[HOWMANY+1];   /* one extra for terminating '\0' */
                     53:        char *token;
                     54:        register struct names *p;
                     55:
                     56:        /*
                     57:         * Do the tar test first, because if the first file in the tar
                     58:         * archive starts with a dot, we can confuse it with an nroff file.
                     59:         */
                     60:        switch (is_tar(buf, nbytes)) {
                     61:        case 1:
                     62:                ckfputs("tar archive", stdout);
                     63:                return 1;
                     64:        case 2:
                     65:                ckfputs("POSIX tar archive", stdout);
                     66:                return 1;
                     67:        }
                     68:
                     69:        /*
                     70:         * for troff, look for . + letter + letter or .\";
                     71:         * this must be done to disambiguate tar archives' ./file
                     72:         * and other trash from real troff input.
                     73:         */
                     74:        if (*buf == '.') {
                     75:                unsigned char *tp = buf + 1;
                     76:
                     77:                while (isascii(*tp) && isspace(*tp))
                     78:                        ++tp;   /* skip leading whitespace */
                     79:                if ((isascii(*tp) && (isalnum(*tp) || *tp=='\\') &&
                     80:                    isascii(tp[1]) && (isalnum(tp[1]) || tp[1] == '"'))) {
                     81:                        ckfputs("troff or preprocessor input text", stdout);
                     82:                        return 1;
                     83:                }
                     84:        }
                     85:        if ((*buf == 'c' || *buf == 'C') &&
                     86:            isascii(buf[1]) && isspace(buf[1])) {
                     87:                ckfputs("fortran program text", stdout);
                     88:                return 1;
                     89:        }
                     90:
                     91:        /* look for tokens from names.h - this is expensive! */
                     92:        /* make a copy of the buffer here because strtok() will destroy it */
                     93:        s = (unsigned char*) memcpy(nbuf, buf, nbytes);
                     94:        s[nbytes] = '\0';
                     95:        has_escapes = (memchr(s, '\033', nbytes) != NULL);
                     96:        while ((token = strtok((char *) s, " \t\n\r\f")) != NULL) {
                     97:                s = NULL;       /* make strtok() keep on tokin' */
                     98:                for (p = names; p < names + NNAMES; p++) {
                     99:                        if (STREQ(p->name, token)) {
                    100:                                ckfputs(types[p->type], stdout);
                    101:                                if (has_escapes)
                    102:                                        ckfputs(" (with escape sequences)",
                    103:                                                stdout);
                    104:                                return 1;
                    105:                        }
                    106:                }
                    107:        }
                    108:
                    109:
                    110:        for (i = 0; i < nbytes; i++) {
                    111:                if (!isascii(buf[i]))
                    112:                        return 0;       /* not all ASCII */
                    113:        }
                    114:
                    115:        /* all else fails, but it is ASCII... */
                    116:        ckfputs("ASCII text", stdout);
                    117:        if (has_escapes) {
                    118:                ckfputs(" (with escape sequences)", stdout);
                    119:        }
                    120:        return 1;
                    121: }
                    122:
                    123: