dict/lookup.c

   1 /*
   2  * Copyright (C) 1994-1998, Index Data I/S
   3  * All rights reserved.
   4  * Sebastian Hammer, Adam Dickmeiss
   5  *
   6  * $Log: lookup.c,v $
   7  * Revision 1.8  1998-03-05 08:17:24  adam
   8  * Added a few comments - no code changed.
   9  *
  10  * Revision 1.7  1996/02/02 13:43:51  adam
  11  * The public functions simply use char instead of Dict_char to represent
  12  * search strings. Dict_char is used internally only.
  13  *
  14  * Revision 1.6  1995/12/11  09:04:50  adam
  15  * Bug fix: the lookup/scan/lookgrep didn't handle empty dictionary.
  16  *
  17  * Revision 1.5  1995/09/04  09:09:15  adam
  18  * String arg in lookup is const.
  19  *
  20  * Revision 1.4  1994/10/05  12:16:51  adam
  21  * Pagesize is a resource now.
  22  *
  23  * Revision 1.3  1994/09/26  10:17:25  adam
  24  * Minor changes.
  25  *
  26  * Revision 1.2  1994/09/16  15:39:14  adam
  27  * Initial code of lookup - not tested yet.
  28  *
  29  * Revision 1.1  1994/08/16  16:26:48  adam
  30  * Added dict.
  31  *
  32  */
  33
  34 #include <stdlib.h>
  35 #include <string.h>
  36 #include <stdio.h>
  37 #include <assert.h>
  38
  39 #include <dict.h>
  40
  41 static char *dict_look (Dict dict, const Dict_char *str)
  42 {
  43     Dict_ptr ptr = 1;
  44     int mid, lo, hi;
  45     int cmp;
  46     void *p;
  47     short *indxp;
  48     char *info;
  49
  50     dict_bf_readp (dict->dbf, ptr, &p);
  51     mid = lo = 0;
  52     hi = DICT_nodir(p)-1;
  53     indxp = (short*) ((char*) p+DICT_pagesize(dict)-sizeof(short));
  54     while (lo <= hi)
  55     {
  56         mid = (lo+hi)/2;
  57         if (indxp[-mid] > 0)
  58         {
  59             /* string (Dict_char *) DICT_EOS terminated */
  60             /* unsigned char        length of information */
  61             /* char *               information */
  62             info = (char*)p + indxp[-mid];
  63             cmp = dict_strcmp((Dict_char*) info, str);
  64             if (!cmp)
  65                 return info+(dict_strlen ((Dict_char*) info)+1)
  66                     *sizeof(Dict_char);
  67         }
  68         else
  69         {
  70             Dict_char dc;
  71             Dict_ptr subptr;
  72
  73             /* Dict_ptr             subptr */
  74             /* Dict_char            sub char */
  75             /* unsigned char        length of information */
  76             /* char *               information */
  77             info = (char*)p - indxp[-mid];
  78             memcpy (&dc, info+sizeof(Dict_ptr), sizeof(Dict_char));
  79             cmp = dc- *str;
  80             if (!cmp)
  81             {
  82                 memcpy (&subptr, info, sizeof(Dict_ptr));
  83                 if (*++str == DICT_EOS)
  84                 {
  85                     if (info[sizeof(Dict_ptr)+sizeof(Dict_char)])
  86                         return info+sizeof(Dict_ptr)+sizeof(Dict_char);
  87                     return NULL;
  88                 }
  89                 else
  90                 {
  91                     if (subptr == 0)
  92                         return NULL;
  93                     ptr = subptr;
  94                     dict_bf_readp (dict->dbf, ptr, &p);
  95                     mid = lo = 0;
  96                     hi = DICT_nodir(p)-1;
  97                     indxp = (short*) ((char*) p+DICT_pagesize(dict)
  98                                       -sizeof(short));
  99                     continue;
 100                 }
 101             }
 102         }
 103         if (cmp < 0)
 104             lo = mid+1;
 105         else
 106             hi = mid-1;
 107     }
 108     return NULL;
 109 }
 110
 111 char *dict_lookup (Dict dict, const char *p)
 112 {
 113     if (dict->head.last <= 1)
 114         return NULL;
 115     return dict_look (dict, (const Dict_char *) p);
 116 }
 117
 118