usr.bin/file/ascmagic.c

/*
 * Ascii magic -- file types that we know based on keywords
 * that can appear anywhere in the file.
 *
 * Copyright (c) Ian F. Darwin, 1987.
 * Written by Ian F. Darwin.
 *
 * This software is not subject to any license of the American Telephone
 * and Telegraph Company or of the Regents of the University of California.
 *
 * Permission is granted to anyone to use this software for any purpose on
 * any computer system, and to alter it and redistribute it freely, subject
 * to the following restrictions:
 *
 * 1. The author is not responsible for the consequences of use of this
 *    software, no matter how awful, even if they arise from flaws in it.
 *
 * 2. The origin of this software must not be misrepresented, either by
 *    explicit claim or by omission.  Since few users ever read sources,
 *    credits must appear in the documentation.
 *
 * 3. Altered versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.  Since few users
 *    ever read sources, credits must appear in the documentation.
 *
 * 4. This notice may not be removed or altered.
 */

#include <stdio.h>
#include <ctype.h>
#include "file.h"
#include "names.h"

#ifndef lint
static char *moduleid =
        "@(#)$Header: ascmagic.c,v 1.5 87/09/16 14:44:45 ian Exp $";
#endif  /* lint */

char *ckfmsg = "write error on output";

                        /* an optimisation over plain strcmp() */
#define STREQ(a, b)     (*(a) == *(b) && strcmp((a), (b)) == 0)

ascmagic(buf)
register char   *buf;
{
        register int i;
        char    *s, *strtok(), *token;
        register struct names *p;
        extern int nbytes;
        short has_escapes = 0;

        /* these are easy, do them first */

        /*
         * for troff, look for . + letter + letter;
         * this must be done to disambiguate tar archives' ./file
         * and other trash from real troff input.
         */
        if (*buf == '.' &&
                isascii(*(buf+1)) && isalnum(*(buf+1)) &&
                isascii(*(buf+2)) && isalnum(*(buf+2))){
                ckfputs("troff or preprocessor input text", stdout);
                return 1;
        }
        if ((*buf == 'c' || *buf == 'C') &&
            isascii(*(buf + 1)) && isspace(*(buf + 1))) {
                ckfputs("fortran program text", stdout);
                return 1;
        }

        /* look for tokens from names.h - this is expensive! */
        s = buf;
        while ((token = strtok(s, " \t\n\r\f")) != NULL) {
                s = NULL;       /* make strtok() keep on tokin' */
                for (p = names; p < names + NNAMES; p++) {
                        if (STREQ(p->name, token)) {
                                ckfputs(types[p->type], stdout);
                                return 1;
                        }
                }
        }

        switch (is_tar(buf)) {
        case 1:
                ckfputs("tar archive", stdout);
                return 1;
        case 2:
                ckfputs("POSIX tar archive", stdout);
                return 1;
        }

        for (i = 0; i < nbytes; i++) {
                if (!isascii(*(buf+i)))
                        return 0;       /* not all ascii */
                if (*(buf+i) == '\033') /* ascii ESCAPE */
                        has_escapes ++;
        }

        /* all else fails, but it is ascii... */
        if (has_escapes){
                ckfputs("ascii text (with escape sequences)", stdout);
                }
        else {
                ckfputs("ascii text", stdout);
                }
        return 1;
}