Add arch tagline
[emacs.git] / msdos / is_exec.c
blobab627956cb728946830593f28a2187d0a4732d1c
1 /* IS_EXEC.C
3 * Copyright (C) 1995 DJ Delorie
4 * Copyright (C) 1994 Eli Zaretskii <eliz@is.elta.co.il>
6 * (See the README file in this directory for the copyright and license
7 * history of this file.)
9 * This file is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 3, or (at your option)
12 * any later version.
14 * This file is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
19 * You should have received a copy of the GNU General Public License
20 * along with this file; see the file COPYING. If not, write to
21 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
22 * Boston, MA 02110-1301, USA.
24 * Commentary:
26 * Given a filename or a file handle, and the extension of the file,
27 * determine if the file is executable.
28 * First, the file extension is checked in case it uniquely identifies
29 * the file as either an executable or not. Failing this, the first
30 * two bytes of the file are tested for known signatures of executable
31 * files.
35 #include <libc/stubs.h>
36 #include <stdio.h>
37 #include <string.h>
38 #include <ctype.h>
39 #include <errno.h>
40 #include <dpmi.h>
41 #include <go32.h>
42 #include <io.h>
43 #include <libc/farptrgs.h>
44 #include <libc/dosio.h>
46 extern unsigned short _djstat_flags;
47 unsigned short _get_magic(const char *, int);
48 int _is_executable(const char *, int, const char *);
51 * Read a MAGIC NUMBER from a given file. These are the first
52 * two bytes of the file, if we look at them as an unsigned short. */
54 #define _STAT_EXEC_EXT 2 /* get execute bits from file extension? */
55 #define _STAT_EXEC_MAGIC 4 /* get execute bits from magic signature? */
57 unsigned short
58 _get_magic(const char *s, int fh)
60 __dpmi_regs regs;
61 unsigned short retval;
62 unsigned short fpos_high = 0, fpos_low = 0;
63 int read_fail = 0;
65 /* If given a pathname, open the file. */
66 if (s)
68 int handle;
69 if((handle = _open(s,0)) == -1)
70 return 0;
71 regs.x.bx = handle;
73 /* Else file already open. Remember its current file position
74 and move to beginning of file. */
75 else
77 regs.x.ax = 0x4201; /* set pointer from current position */
78 regs.x.bx = fh;
79 regs.x.cx = regs.x.dx = 0; /* move 0 bytes (i.e., stay put) */
80 __dpmi_int(0x21, &regs);
81 if (regs.x.flags & 1)
83 errno = __doserr_to_errno(regs.x.ax);
84 return 0;
86 fpos_high = regs.x.dx; /* got current position */
87 fpos_low = regs.x.ax;
89 regs.x.ax = 0x4200; /* set pointer from the beginning of file */
90 regs.x.cx = regs.x.dx = 0; /* move to beginning of file */
91 __dpmi_int(0x21, &regs);
92 if (regs.x.flags & 1)
94 errno = __doserr_to_errno(regs.x.ax);
95 return 0;
98 regs.x.ds = __tb_segment;
99 regs.x.dx = __tb_offset;
101 /* Read 2 bytes from the file. */
102 regs.x.ax = 0x3f00;
103 regs.x.cx = 2;
104 __dpmi_int(0x21, &regs);
106 /* We can either (1) succeed, (2) read less than 2 bytes,
107 or (3) fail to read at all. */
108 if (regs.x.ax != 2)
109 read_fail = (regs.x.flags & 1) ? regs.x.ax : -1;
111 /* If called with filename, close the file. */
112 if (s)
114 regs.x.ax = 0x3e00;
115 __dpmi_int(0x21, &regs);
116 if (regs.x.flags & 1)
117 errno = __doserr_to_errno(regs.x.ax);
119 /* Else leave file pointer where we found it. */
120 else
122 regs.x.ax = 0x4200; /* set pointer from the beginning of file */
123 regs.x.bx = fh;
124 regs.x.cx = fpos_high;
125 regs.x.dx = fpos_low;
126 __dpmi_int(0x21, &regs);
127 if (regs.x.flags & 1)
129 errno = __doserr_to_errno(regs.x.ax);
130 return 0;
134 if (read_fail == 0)
135 retval = _farpeekw(_dos_ds, __tb);
136 else
138 /* The file couldn't be read: assume non-executable. If the file
139 *is* executable, but was passed as a file-handle, and the user
140 opened it in write-only mode, they lose... */
141 retval = 0;
142 if (read_fail != -1)
143 errno = __doserr_to_errno(read_fail);
146 return retval;
149 /* A list of extensions which designate executable files. These
150 are NOT tested for the magic number. */
151 static char executables[] = "|EXE|COM|BAT|BTM|DLL|VXD|";
153 /* A list of extensions which belong to files known to NEVER be
154 executables. These exist to minimize read()'ing files while
155 detecting executables by magic number. You are welcome to
156 add to this list, but remember: only extensions which could
157 NEVER be present in executables should go here. */
158 static char non_executables[] = "\
159 |A|A01|A02|A03|A04|A05|ADL|ARC|ARJ|ASC|ASM|AUX|AWK\
160 |BAS|BIB|BGI|BMP\
161 |C|CC|CFG|CGZ|CH3|CHR|CI|CLP|CMF|CPI|CPP|CXX\
162 |DAT|DBF|DIZ|DOC|DVI\
163 |E|EL|ELC\
164 |F77|FN3\
165 |GIF|GZ\
166 |H|HLP|HPP|HXX\
167 |ICO|IN|INC|INF|INI\
168 |JPG\
169 |L|LEX|LF|LIB|LOG|LST|LZH\
170 |M|MAK|MAP|MF|MID|MPG\
171 |O|OBJ\
172 |PAK|PAS|PBM|PCD|PCX|PDS|PIC|PIF|PN3|PRJ|PS\
173 |RAS|RGB|RLE\
174 |S|SND|SY3\
175 |TAR|TAZ|TEX|TGA|TGZ|TIF|TXH|TXI|TXT\
176 |VOC\
177 |WAV|WK1|WK3|WKB|WQ1|WQ3|WQ4|WQ5|WQ6|WQ!\
178 |XBM\
180 |ZIP|ZOO|";
183 _is_executable(const char *filename, int fhandle, const char *extension)
185 if (!extension && filename)
187 const char *cp, *ep=0;
188 for (cp=filename; *cp; cp++)
190 if (*cp == '.')
191 ep = cp;
192 if (*cp == '/' || *cp == '\\' || *cp == ':')
193 ep = 0;
195 extension = ep;
197 if ((_djstat_flags & _STAT_EXEC_EXT) == 0
198 && extension
199 && *extension
200 && strlen(extension) <= ((extension[0]=='.') ? 4 : 3))
202 /* Search the list of extensions in executables[]. */
203 char tmp_buf[6], *tp = tmp_buf;
205 *tp++ = '|';
206 if (*extension == '.')
207 extension++;
208 while (*extension)
209 *tp++ = toupper (*extension++);
210 *tp++ = '|';
211 *tp = '\0';
212 if (strstr(non_executables, tmp_buf))
213 return 0;
214 else if (strstr(executables, tmp_buf))
215 return 1;
218 /* No extension, or extension doesn't define execute
219 bits unambiguously. We are in for some dirty work.
220 Read the first two bytes of the file and see if they
221 are any of the known magic numbers which designate
222 executable files.
223 Unix-like shells, which have executable shell scripts
224 without extensions and DON'T have "#!" as their FIRST
225 TWO CHARACTERS, lose here. Sorry, folks. */
226 if ( (_djstat_flags & _STAT_EXEC_MAGIC) == 0 )
228 switch (_get_magic(filename, fhandle))
230 case 0x5a4d: /* "MZ" */
231 case 0x010b:
232 case 0x014c:
233 case 0x2123: /* "#!" */
234 return 1;
238 return 0;
241 /* arch-tag: b0965811-8c3e-4bc4-8d81-4447a3594785
242 (do not change this comment) */