locate/locatedb.h

   1 /* locatedb.h -- declarations for the locate database
   2    Copyright (C) 1994, 2010 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 /* These are used for old, bigram-encoded databases:  */
  48
  49 /* Means the differential count follows in a 2-byte int instead. */
  50 #define LOCATEDB_OLD_ESCAPE     30
  51
  52 /* Offset added to differential counts to encode them as positive numbers.  */
  53 #define LOCATEDB_OLD_OFFSET     14
  54
  55 # ifndef PARAMS
  56 #  if defined PROTOTYPES || (defined __STDC__ && __STDC__)
  57 #   define PARAMS(Args) Args
  58 #  else
  59 #   define PARAMS(Args) ()
  60 #  endif
  61 # endif
  62
  63 typedef enum
  64   {
  65     GetwordEndianStateInitial = 0,
  66     GetwordEndianStateNative  = 1,
  67     GetwordEndianStateSwab    = 2
  68   } GetwordEndianState;
  69
  70 int getword (FILE *fp, const char *filename,
  71              size_t minvalue, size_t maxvalue,
  72              GetwordEndianState *endian_state_flag);
  73
  74 bool putword (FILE *fp, int word,
  75               GetwordEndianState endian_state_flag);
  76
  77
  78 #define SLOCATE_DB_MAGIC_LEN 2
  79
  80 #endif /* !_LOCATEDB_H */