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/** @file glass_termlist.h
* @brief A TermList in a glass database.
*/
/* Copyright (C) 2007,2008,2009,2010,2011 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_GLASS_TERMLIST_H
#define XAPIAN_INCLUDED_GLASS_TERMLIST_H
#include <string>
#include "xapian/intrusive_ptr.h"
#include <xapian/positioniterator.h>
#include <xapian/types.h>
namespace Xapian {
namespace Internal {
class ExpandStats;
}
}
#include "glass_database.h"
#include "api/termlist.h"
#include "glass_table.h"
/// A TermList in a glass database.
class GlassTermList : public TermList {
/// Don't allow assignment.
void operator=(const GlassTermList &);
/// Don't allow copying.
GlassTermList(const GlassTermList &);
/// The database we're reading data from.
Xapian::Internal::intrusive_ptr<const GlassDatabase> db;
/// The document id that this TermList is for.
Xapian::docid did;
/// The length of document @a did.
Xapian::termcount doclen;
/// The number of entries in this termlist.
Xapian::termcount termlist_size;
/// The tag value from the termlist table which holds the encoded termlist.
std::string data;
/** Current position with the encoded tag value held in @a data.
*
* If we've iterated to the end of the list, this gets set to NULL.
*/
const char *pos;
/// Pointer to the end of the encoded tag value.
const char *end;
/// The termname at the current position.
std::string current_term;
/// The wdf for the term at the current position.
Xapian::termcount current_wdf;
/** The term frequency for the term at the current position.
*
* This will have the value 0 if the term frequency has not yet been
* looked up in the database (so it needs to be mutable).
*/
mutable Xapian::doccount current_termfreq;
public:
/// Create a new GlassTermList object for document @a did_ in DB @a db_
GlassTermList(Xapian::Internal::intrusive_ptr<const GlassDatabase> db_,
Xapian::docid did_);
/** Return the length of this document.
*
* This is a non-virtual method, used by GlassDatabase.
*/
Xapian::termcount get_doclength() const;
/** Return approximate size of this termlist.
*
* For a GlassTermList, this value will always be exact.
*/
Xapian::termcount get_approx_size() const;
/// Collate weighting information for the current term.
void accumulate_stats(Xapian::Internal::ExpandStats & stats) const;
/// Return the termname at the current position.
std::string get_termname() const;
/// Return the wdf for the term at the current position.
Xapian::termcount get_wdf() const;
/** Return the term frequency for the term at the current position.
*
* In order to be able to support updating databases efficiently, we can't
* store this value in the termlist table, so it has to be read from the
* postlist table, which is relatively expensive (compared to reading the
* wdf for example).
*/
Xapian::doccount get_termfreq() const;
/** Advance the current position to the next term in the termlist.
*
* The list starts before the first term in the list, so next()
* must be called before any methods which need the context of
* the current position.
*
* @return Always returns 0 for a GlassTermList.
*/
TermList * next();
TermList * skip_to(const std::string & term);
/// Return true if the current position is past the last term in this list.
bool at_end() const;
/// Return the length of the position list for the current position.
Xapian::termcount positionlist_count() const;
/// Return a PositionIterator for the current position.
Xapian::PositionIterator positionlist_begin() const;
};
#endif // XAPIAN_INCLUDED_GLASS_TERMLIST_H
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