1  /* locatedb.h -- declarations for the locate database
       2     Copyright (C) 1994-2022 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 <https://www.gnu.org/licenses/>.
      16  */
      17  
      18  #ifndef INC_LOCATEDB_H
      19  # define INC_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  typedef enum
      56    {
      57      GetwordEndianStateInitial = 0,
      58      GetwordEndianStateNative  = 1,
      59      GetwordEndianStateSwab    = 2
      60    } GetwordEndianState;
      61  
      62  int getword (FILE *fp, const char *filename,
      63  	     size_t maxvalue,
      64  	     GetwordEndianState *endian_state_flag);
      65  
      66  # define SLOCATE_DB_MAGIC_LEN 2
      67  
      68  #endif /* !INC_LOCATEDB_H */