EST_StringTrie.cc

/*************************************************************************/
/*                                                                       */
/*                Centre for Speech Technology Research                  */
/*                     University of Edinburgh, UK                       */
/*                         Copyright (c) 1996                            */
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/*************************************************************************/
/*                     Author :  Alan W Black                            */
/*                     Date   :  June 1996                               */
/*-----------------------------------------------------------------------*/
/*                                                                       */
/* A class for building EST_String (char-based) tries for indexing       */
/* arbitrary objects by Strings                                          */
/*                                                                       */
/*=======================================================================*/
#include "EST_String.h"
#include "EST_StringTrie.h"
#include <cstring>

#define TRIEWIDTH 256

static void (* trie_delete_function)(void *n) = 0;

static inline int char2idx(unsigned char k)
{
//    return k & 0x7f;  // only seven significant bits;
    return k;
}

EST_TrieNode::EST_TrieNode(const int width)
{
    // Initialise a node of given width
    w=width; 
    d= new EST_TrieNode *[w]; 
    contents=0;
    memset(d,0,w*sizeof(EST_TrieNode *));
}

EST_TrieNode::~EST_TrieNode()
{
    int i;

    if (trie_delete_function != 0)   /* user supplied delete function */
    trie_delete_function(contents);
    for (i=0; i<w; i++)
    delete d[i];
    delete [] d;
}
    
void *EST_TrieNode::lookup(const unsigned char *key) const
{
    // find key in EST_TrieNode, 0 if not found 

    if (*key == '\0')
    return contents;  // base case
    else
    {
    int idx = char2idx(*key);
    if (d[idx] == 0)
        return 0;     // not there
    else
        return d[idx]->lookup(key+1);
    }
}

void EST_TrieNode::copy_into(EST_StringTrie &trie,
                 const EST_String &path) const
{
    // find all items and add them to trie

    if (contents != 0)
    trie.add(path,contents);

    for (int i=0; i < w; i++)
    {
    if (d[i] != 0)
    {
        char tail[2];
        tail[0] = (char)i;
        tail[1] = '\0';
        d[i]->copy_into(trie,path+tail);
    }
    }
}

void EST_TrieNode::add(const unsigned char *key,void *value)
{
    // add this value

    if (*key == '\0')
    contents = value;
    else
    {
    int idx = char2idx(*key);
    if (d[idx] == 0) // need new subnode
        d[idx] = new EST_TrieNode(w);
    d[idx]->add(key+1,value);
    }
}

EST_StringTrie::EST_StringTrie()
{
    tree = new EST_TrieNode(TRIEWIDTH);
}

void EST_StringTrie::copy(const EST_StringTrie &trie)
{
    // This can't work because of the void* pointers in contents
    delete tree;
    tree = new EST_TrieNode(TRIEWIDTH);
    trie.tree->copy_into(*this,"");
}

EST_StringTrie::~EST_StringTrie()
{
    delete tree;
}

void *EST_StringTrie::lookup(const EST_String &key) const
{
    const unsigned char *ckey = (const unsigned char *)(void *)(const char *)key;
    return tree->lookup(ckey);
}

void EST_StringTrie::add(const EST_String &key,void *item)
{
    const unsigned char *ckey = (const unsigned char *)(void *)(const char *)key;
    tree->add(ckey,item);
    return;
}
    
void EST_StringTrie::clear(void)
{
    delete tree;
    tree = new EST_TrieNode(TRIEWIDTH);
}

void EST_StringTrie::clear(void (*deletenode)(void *n))
{
    // This wont work if we go multi-thread
    trie_delete_function = deletenode;
    delete tree;
    trie_delete_function = 0;
    tree = new EST_TrieNode(TRIEWIDTH);
}