locate/locatedb.h

   1 /* locatedb.h -- declarations for the locate database
   2    Copyright (C) 1994 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 2, or (at your option)
   7    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, write to the Free Software
  16    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  17    USA.
  18 */
  19
  20 #ifndef _LOCATEDB_H
  21 #define _LOCATEDB_H 1
  22
  23 #include <stdio.h>
  24
  25 /* The magic string at the start of a locate database, to make sure
  26    it's in the right format.  The 02 is the database format version number.
  27    This string has the same format as a database entry, but you can't
  28    concatenate databases even if you remove it, since the differential count
  29    in the first entry of the second database will be wrong.  */
  30 #define LOCATEDB_MAGIC "\0LOCATE02"
  31
  32 /* Common-prefix length differences in the ranges
  33    0..127, -127..-1 (0x00..0x7f, 0x81..0xff) fit into one byte.
  34    This value (which is -128) indicates that the difference is
  35    too large to fit into one byte, and a two-byte integer follows.  */
  36 #define LOCATEDB_ESCAPE 0x80
  37 #define LOCATEDB_ONEBYTE_MAX (127)
  38 #define LOCATEDB_ONEBYTE_MIN (-127)
  39
  40
  41 /* If it is ever possible to try to encode LOCATEDB_MAGIC as a
  42  * single-byte offset, then an unfortunate length of common prefix
  43  * will produce a spurious escape character, desynchronising the data
  44  * stream.  We use a compile-time check in the preprocessor to prevent
  45  * this.
  46  */
  47 #if LOCATEDB_ESCAPE <= LOCATEDB_ONEBYTE_MAX
  48 #error "You have a bad combination of LOCATEDB_ESCAPE and LOCATEDB_ONEBYTE_MAX, see above"
  49 #endif
  50
  51 /* These are used for old, bigram-encoded databases:  */
  52
  53 /* Means the differential count follows in a 2-byte int instead. */
  54 #define LOCATEDB_OLD_ESCAPE     30
  55
  56 /* Offset added to differential counts to encode them as positive numbers.  */
  57 #define LOCATEDB_OLD_OFFSET     14
  58
  59 # ifndef PARAMS
  60 #  if defined PROTOTYPES || (defined __STDC__ && __STDC__)
  61 #   define PARAMS(Args) Args
  62 #  else
  63 #   define PARAMS(Args) ()
  64 #  endif
  65 # endif
  66
  67 typedef enum
  68   {
  69     GetwordEndianStateInitial = 0,
  70     GetwordEndianStateNative  = 1,
  71     GetwordEndianStateSwab    = 2
  72   } GetwordEndianState;
  73
  74 int getword (FILE *fp, const char *filename,
  75              size_t minvalue, size_t maxvalue,
  76              GetwordEndianState *endian_state_flag);
  77
  78
  79 #define SLOCATE_DB_MAGIC_LEN 2
  80
  81 #endif /* !_LOCATEDB_H */