| 1 | /* locatedb.h -- declarations for the locate database
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| 2 | Copyright (C) 1994 Free Software Foundation, Inc.
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| 3 |
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| 4 | This program is free software; you can redistribute it and/or modify
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| 5 | it under the terms of the GNU General Public License as published by
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| 6 | the Free Software Foundation; either version 2, or (at your option)
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| 7 | any later version.
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| 8 |
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| 9 | This program is distributed in the hope that it will be useful,
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| 10 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 12 | GNU General Public License for more details.
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| 13 |
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| 14 | You should have received a copy of the GNU General Public License
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| 15 | along with this program; if not, write to the Free Software
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| 16 | Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
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| 17 | USA.
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| 18 | */
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| 19 |
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| 20 | #ifndef _LOCATEDB_H
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| 21 | #define _LOCATEDB_H 1
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| 22 |
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| 23 | /* The magic string at the start of a locate database, to make sure
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| 24 | it's in the right format. The 02 is the database format version number.
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| 25 | This string has the same format as a database entry, but you can't
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| 26 | concatenate databases even if you remove it, since the differential count
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| 27 | in the first entry of the second database will be wrong. */
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| 28 | #define LOCATEDB_MAGIC "\0LOCATE02"
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| 29 |
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| 30 | /* Common-prefix length differences in the ranges
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| 31 | 0..127, -127..-1 (0x00..0x7f, 0x81..0xff) fit into one byte.
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| 32 | This value (which is -128) indicates that the difference is
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| 33 | too large to fit into one byte, and a two-byte integer follows. */
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| 34 | #define LOCATEDB_ESCAPE 0x80
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| 35 | #define LOCATEDB_ONEBYTE_MAX (127)
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| 36 | #define LOCATEDB_ONEBYTE_MIN (-127)
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| 37 |
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| 38 |
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| 39 | /* If it is ever possible to try to encode LOCATEDB_MAGIC as a
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| 40 | * single-byte offset, then an unfortunate length of common prefix
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| 41 | * will produce a spurious escape character, desynchronising the data
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| 42 | * stream. We use a compile-time check in the preprocessor to prevent
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| 43 | * this.
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| 44 | */
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| 45 | #if LOCATEDB_ESCAPE <= LOCATEDB_ONEBYTE_MAX
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| 46 | #error "You have a bad combination of LOCATEDB_ESCAPE and LOCATEDB_ONEBYTE_MAX, see above"
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| 47 | #endif
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| 48 |
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| 49 | /* These are used for old, bigram-encoded databases: */
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| 50 |
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| 51 | /* Means the differential count follows in a 2-byte int instead. */
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| 52 | #define LOCATEDB_OLD_ESCAPE 30
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| 53 |
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| 54 | /* Offset added to differential counts to encode them as positive numbers. */
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| 55 | #define LOCATEDB_OLD_OFFSET 14
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| 56 |
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| 57 | # ifndef PARAMS
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| 58 | # if defined PROTOTYPES || (defined __STDC__ && __STDC__)
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| 59 | # define PARAMS(Args) Args
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| 60 | # else
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| 61 | # define PARAMS(Args) ()
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| 62 | # endif
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| 63 | # endif
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| 64 |
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| 65 |
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| 66 | #define SLOCATE_DB_MAGIC_LEN 2
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| 67 |
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| 68 | #endif /* !_LOCATEDB_H */
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