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/*
* libpinyin
* Library to deal with pinyin.
*
* Copyright (C) 2006-2007 Peng Wu
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#ifndef NGRAM_H
#define NGRAM_H
#include <db.h>
namespace pinyin{
class Bigram;
/* Note:
* When transfer from system ngram to user ngram,
* if user ngram doesn't exist,
* copy total freq from system ngram to user ngram,
* so the total freq exists.
* if item freq don't exist, copy item freq from system to user ngram,
* so the item freq exists.
* if user ngram already exists(always true), increases the total freq,
* if item ngram already exists(always true), increases the freq.
*/
class SingleGram{
friend class Bigram;
friend bool merge_single_gram(SingleGram * merged,
const SingleGram * system,
const SingleGram * user);
private:
MemoryChunk m_chunk;
SingleGram(void * buffer, size_t length);
public:
/* Null Constructor */
SingleGram();
/* retrieve all items */
bool retrieve_all(/* out */ BigramPhraseWithCountArray array) const;
/* search method */
/* the array result contains many items */
bool search(/* in */ PhraseIndexRange * range,
/* out */ BigramPhraseArray array) const;
/* insert_freq method
*/
bool insert_freq(/* in */ phrase_token_t token,
/* in */ guint32 freq);
/* remove_freq method
*/
bool remove_freq(/* in */ phrase_token_t token,
/* out */ guint32 & freq);
/* get_freq method
*/
bool get_freq(/* in */ phrase_token_t token,
/* out */ guint32 & freq) const;
/* set_freq method
*/
bool set_freq(/* in */ phrase_token_t token,
/* in */ guint32 freq);
/* get_total_freq method
* used in user bigram table
*/
bool get_total_freq(guint32 & total) const;
/* set_total_freq method
* used in user bigram table
*/
bool set_total_freq(guint32 total);
/* prune one method
* only used in training
*/
bool prune();
};
class Bigram{
private:
DB * m_db;
void reset(){
if ( m_db ){
m_db->sync(m_db, 0);
m_db->close(m_db, 0);
m_db = NULL;
}
}
public:
Bigram(){
m_db = NULL;
}
~Bigram(){
reset();
}
/* load/save berkeley db in memory. */
bool load_db(const char * dbfile);
bool save_db(const char * dbfile);
/* attach bi-gram */
bool attach(const char * dbfile, guint32 flags);
/* load/store one single gram */
bool load(/* in */ phrase_token_t index,
/* out */ SingleGram * & single_gram);
bool store(/* in */ phrase_token_t index,
/* in */ SingleGram * single_gram);
/* array of phrase_token_t items, for parameter estimation. */
bool get_all_items(/* out */ GArray * items);
};
bool merge_single_gram(SingleGram * merged, const SingleGram * system,
const SingleGram * user);
};
#endif
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