backends/chert/chert_synonym.h

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/* Copyright (C) 2005,2007,2008,2009 Olly Betts
 *
 * 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 St, Fifth Floor, Boston, MA  02110-1301 USA
 */

#ifndef XAPIAN_INCLUDED_CHERT_SYNONYM_H
#define XAPIAN_INCLUDED_CHERT_SYNONYM_H

#include <xapian/types.h>

#include "alltermslist.h"
#include "database.h"
#include "chert_lazytable.h"
#include "termlist.h"

#include <set>
#include <string>

class ChertSynonymTable : public ChertLazyTable {
    mutable std::string last_term;

    mutable std::set<std::string> last_synonyms;

  public:
    ChertSynonymTable(const std::string & dbdir, bool readonly)
        : ChertLazyTable("synonym", dbdir + "/synonym.", readonly,
                         Z_DEFAULT_STRATEGY) { }

    // Merge in batched-up changes.
    void merge_changes();

    // Discard batched-up changes.
    void discard_changes() {
        last_term.resize(0);
        last_synonyms.clear();
    }

    void add_synonym(const std::string & term, const std::string & synonym);

    void remove_synonym(const std::string & term, const std::string & synonym);

    void clear_synonyms(const std::string & term);

    TermList * open_termlist(const std::string & term);

    bool is_modified() const {
        return !last_term.empty() || ChertTable::is_modified();
    }

    void flush_db() {
        merge_changes();
        ChertTable::flush_db();
    }

    void cancel() {
        discard_changes();
        ChertTable::cancel();
    }

    // @}
};

class ChertCursor;

class ChertSynonymTermList : public AllTermsList {
    ChertSynonymTermList(const ChertSynonymTermList &);

    void operator=(const ChertSynonymTermList &);

    Xapian::Internal::RefCntPtr<const Xapian::Database::Internal> database;

    ChertCursor * cursor;

    string prefix;

  public:
    ChertSynonymTermList(Xapian::Internal::RefCntPtr<const Xapian::Database::Internal> database_,
                      ChertCursor * cursor_,
                      const string & prefix_)
            : database(database_), cursor(cursor_), prefix(prefix_)
    {
        // Position the cursor on the highest key before the first key we want,
        // so that the first call to next() will put us on the first key we
        // want.
        if (prefix.empty()) {
            cursor->find_entry(string());
        } else {
            // Seek to the first key before one with the desired prefix.
            cursor->find_entry_lt(prefix);
        }
    }

    ~ChertSynonymTermList();

    string get_termname() const;

    Xapian::doccount get_termfreq() const;

    Xapian::termcount get_collection_freq() const;

    TermList * next();

    TermList * skip_to(const string &tname);

    bool at_end() const;
};

#endif // XAPIAN_INCLUDED_CHERT_SYNONYM_H

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