lib/libTrie/TrieNode.h

   1 /*
   2  * Copyright (c) 2002,2003 Robert Collins <rbtcollins@hotmail.com>
   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 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, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  17  *
  18  */
  19
  20 #ifndef   LIBTRIE_TRIENODE_H
  21 #define   LIBTRIE_TRIENODE_H
  22
  23 #include "TrieCharTransform.h"
  24
  25 #include <sys/types.h>
  26 #include <utility>
  27
  28 /* TODO: parameterize this to be more generic -
  29 * i.e. M-ary internal node sizes etc
  30 */
  31
  32 class TrieNode
  33 {
  34
  35 public:
  36     TrieNode();
  37     ~TrieNode();
  38     TrieNode(TrieNode const &);
  39     TrieNode &operator= (TrieNode const &);
  40
  41     /* Find a string.
  42     * If found, return the private data.
  43     * If not found, return NULL.
  44     */
  45     inline void *find (char const *, size_t, TrieCharTransform *, bool const prefix) const;
  46
  47     /* Add a string.
  48     * returns false if the string is already
  49     * present or can't be added.
  50     */
  51
  52     bool add (char const *, size_t, void *, TrieCharTransform *);
  53
  54 private:
  55     /* 256-way Trie */
  56     /* The char index into internal is an
  57     * 8-bit prefix to a string in the trie.
  58     * internal[0] is the terminal node for
  59     * a string and may not be used
  60     */
  61     TrieNode * internal[256];
  62
  63     /* If a string ends here, non NULL */
  64     void *_privateData;
  65 };
  66
  67 /* recursive. TODO? make iterative */
  68 void *
  69 TrieNode::find (char const *aString, size_t theLength, TrieCharTransform *transform, bool const prefix) const
  70 {
  71     if (theLength) {
  72         int index = -1;
  73         unsigned char pos = transform ? (*transform) (*aString) : *aString;
  74
  75         if (internal[pos])
  76             index = pos;
  77
  78         if (index > -1) {
  79             void *result;
  80             result = internal[index]->find(aString + 1, theLength - 1, transform, prefix);
  81
  82             if (result)
  83                 return result;
  84         }
  85
  86         if (prefix)
  87             return _privateData;
  88
  89         return NULL;
  90     } else {
  91         /* terminal node */
  92         return _privateData;
  93     }
  94 }
  95 #endif /* LIBTRIE_TRIENODE_H */