1/* locatedb.h -- declarations for the locate database
2   Copyright (C) 1994, 2003, 2006 Free Software Foundation, Inc.
3
4   This program is free software: you can redistribute it and/or modify
5   it under the terms of the GNU General Public License as published by
6   the Free Software Foundation, either version 3 of the License, or
7   (at your option) any later version.
8
9   This program is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12   GNU General Public License for more details.
13
14   You should have received a copy of the GNU General Public License
15   along with this program.  If not, see <http://www.gnu.org/licenses/>.
16*/
17
18#ifndef _LOCATEDB_H
19#define _LOCATEDB_H 1
20
21/* The magic string at the start of a locate database, to make sure
22   it's in the right format.  The 02 is the database format version number.
23   This string has the same format as a database entry, but you can't
24   concatenate databases even if you remove it, since the differential count
25   in the first entry of the second database will be wrong.  */
26#define LOCATEDB_MAGIC "\0LOCATE02"
27
28/* Common-prefix length differences in the ranges
29   0..127, -127..-1 (0x00..0x7f, 0x81..0xff) fit into one byte.
30   This value (which is -128) indicates that the difference is
31   too large to fit into one byte, and a two-byte integer follows.  */
32#define	LOCATEDB_ESCAPE 0x80
33#define LOCATEDB_ONEBYTE_MAX (127)
34#define LOCATEDB_ONEBYTE_MIN (-127)
35
36
37/* If it is ever possible to try to encode LOCATEDB_MAGIC as a
38 * single-byte offset, then an unfortunate length of common prefix
39 * will produce a spurious escape character, desynchronising the data
40 * stream.  We use a compile-time check in the preprocessor to prevent
41 * this.
42 */
43#if LOCATEDB_ESCAPE <= LOCATEDB_ONEBYTE_MAX
44#error "You have a bad combination of LOCATEDB_ESCAPE and LOCATEDB_ONEBYTE_MAX, see above"
45#endif
46
47
48
49/* These are used for old, bigram-encoded databases:  */
50
51/* Means the differential count follows in a 2-byte int instead. */
52#define	LOCATEDB_OLD_ESCAPE	30
53
54/* Offset added to differential counts to encode them as positive numbers.  */
55#define	LOCATEDB_OLD_OFFSET	14
56
57# ifndef PARAMS
58#  if defined PROTOTYPES || (defined __STDC__ && __STDC__)
59#   define PARAMS(Args) Args
60#  else
61#   define PARAMS(Args) ()
62#  endif
63# endif
64
65#endif /* !_LOCATEDB_H */
66