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/** @file
* @brief Abstract base class for termlists.
*/
/* Copyright (C) 2007,2010,2013,2020,2024 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, see
* <https://www.gnu.org/licenses/>.
*/
#ifndef XAPIAN_INCLUDED_TERMLIST_H
#define XAPIAN_INCLUDED_TERMLIST_H
#include "api/smallvector.h"
#include "backends/positionlist.h"
#include <string>
#include <string_view>
#include "xapian/intrusive_ptr.h"
#include <xapian/types.h>
#include <xapian/termiterator.h>
namespace Xapian {
namespace Internal {
class ExpandStats;
}
}
/// Abstract base class for termlists.
class Xapian::TermIterator::Internal : public Xapian::Internal::intrusive_base {
/// Don't allow assignment.
void operator=(const Internal &) = delete;
/// Don't allow copying.
Internal(const Internal &) = delete;
protected:
/// Only constructable as a base class for derived classes.
Internal() { }
/// The current term.
std::string current_term;
public:
/** We have virtual methods and want to be able to delete derived classes
* using a pointer to the base class, so we need a virtual destructor.
*/
virtual ~Internal();
/// Return approximate size of this termlist.
virtual Xapian::termcount get_approx_size() const = 0;
/// Collate weighting information for the current term.
virtual void accumulate_stats(Xapian::Internal::ExpandStats & stats) const;
/// Return the termname at the current position.
const std::string& get_termname() const {
return current_term;
}
/// Return the wdf for the term at the current position.
virtual Xapian::termcount get_wdf() const = 0;
/// Return the term frequency for the term at the current position.
virtual Xapian::doccount get_termfreq() const = 0;
/** Advance the current position to the next term in the termlist.
*
* The list starts before the first term in the list, so next(), skip_to()
* or check() must be called before any methods which need the context of
* the current position.
*
* @return Normally returns NULL to indicate success. If the end has been
* reached, returns this; if another non-NULL pointer is
* returned then the caller should substitute the returned pointer
* for its pointer to us, and then delete us. This "pruning" can
* only happen for a non-leaf subclass of this class.
*/
virtual Internal * next() = 0;
/** Skip forward to the specified term.
*
* If the specified term isn't in the list, position ourselves on the
* first term after term.
*
* @return Normally returns NULL to indicate success. If no terms after
* term exist, returns this; if another non-NULL pointer is
* returned then the caller should substitute the returned pointer
* for its pointer to us, and then delete us. This "pruning" can
* only happen for a non-leaf subclass of this class.
*/
virtual Internal* skip_to(std::string_view term) = 0;
/// Return the length of the position list for the current position.
virtual Xapian::termcount positionlist_count() const = 0;
/** Get pointer to VecCOW<termpos> if that's the internal representation.
*
* This avoids unnecessary copying of positions in the common cases - the
* case it doesn't help with is adding a document back with unmodified
* positions *AND* a different docid, which is an unusual thing to do.
*
* @return Pointer to VecCOW<termpos> or NULL.
*/
virtual const Xapian::VecCOW<Xapian::termpos> * get_vec_termpos() const;
/// Return PositionList for the current position.
virtual PositionList* positionlist_begin() const = 0;
/** Which shard of a multidatabase this is from.
*
* Used by Enquire::get_eset().
*/
size_t shard_index = 0;
};
// In the external API headers, this class is Xapian::TermIterator::Internal,
// but in the library code it's still known as "TermList" in most places.
typedef Xapian::TermIterator::Internal TermList;
#endif // XAPIAN_INCLUDED_TERMLIST_H
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