/* * 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 #include #include #include #include #include "file.h" #include "names.h" #ifndef lint static char *moduleid = "@(#)$Id: ascmagic.c,v 1.1.1.1 1994/09/03 19:16:22 csgr Exp $"; #endif /* lint */ /* an optimisation over plain strcmp() */ #define STREQ(a, b) (*(a) == *(b) && strcmp((a), (b)) == 0) int ascmagic(buf, nbytes) unsigned char *buf; int nbytes; /* size actually read */ { int i, isblock, has_escapes = 0; unsigned char *s; char nbuf[HOWMANY+1]; /* one extra for terminating '\0' */ char *token; register struct names *p; /* these are easy, do them first */ /* * for troff, look for . + letter + letter or .\"; * this must be done to disambiguate tar archives' ./file * and other trash from real troff input. */ if (*buf == '.') { unsigned char *tp = buf + 1; while (isascii(*tp) && isspace(*tp)) ++tp; /* skip leading whitespace */ if ((isascii(*tp) && (isalnum(*tp) || *tp=='\\') && isascii(*(tp+1)) && (isalnum(*(tp+1)) || *tp=='"'))) { 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! */ /* make a copy of the buffer here because strtok() will destroy it */ s = (unsigned char*) memcpy(nbuf, buf, nbytes); s[nbytes] = '\0'; has_escapes = (memchr(s, '\033', nbytes) != NULL); while ((token = strtok((char*)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); if (has_escapes) ckfputs(" (with escape sequences)", stdout); return 1; } } } switch (is_tar(buf, nbytes)) { 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 */ } /* all else fails, but it is ascii... */ ckfputs("ascii text", stdout); if (has_escapes) { ckfputs(" (with escape sequences)", stdout); } return 1; }