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/** @file multivaluelist.h
* @brief Class for merging ValueList objects from subdatabases.
*/
/* Copyright (C) 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_MULTIVALUELIST_H
#define XAPIAN_INCLUDED_MULTIVALUELIST_H
#include "valuelist.h"
#include "database.h"
#include <string>
#include <vector>
struct SubValueList;
/// Class for merging ValueList objects from subdatabases.
class MultiValueList : public ValueList {
/// Don't allow assignment.
void operator=(const MultiValueList &);
/// Don't allow copying.
MultiValueList(const MultiValueList &);
/// Current docid (or 0 if we haven't started yet).
Xapian::docid current_docid;
/// Vector of sub-valuelists which we use as a heap.
std::vector<SubValueList *> valuelists;
/// The value slot we're iterating over.
Xapian::valueno slot;
size_t multiplier;
public:
/// Constructor.
MultiValueList(const std::vector<Xapian::Internal::intrusive_ptr<Xapian::Database::Internal> > & dbs,
Xapian::valueno slot_);
/// Destructor.
~MultiValueList();
/// Return the docid at the current position.
Xapian::docid get_docid() const;
/// Return the value at the current position.
std::string get_value() const;
/// Return the value slot for the current position/this iterator.
Xapian::valueno get_valueno() const;
/// Return true if the current position is past the last entry in this list.
bool at_end() const;
/** Advance the current position to the next document in the value stream.
*
* The list starts before the first entry in the list, so next()
* must be called before any methods which need the context of
* the current position.
*/
void next();
/** Skip forward to the specified docid.
*
* If the specified docid isn't in the list, position ourselves on the
* first document after it (or at_end() if no greater docids are present).
*/
void skip_to(Xapian::docid);
/** Check if the specified docid occurs in this valuestream.
*
* The caller is required to ensure that the specified @a docid actually
* exists in the database.
*
* This method acts like skip_to() if that can be done at little extra
* cost, in which case it then sets @a valid to true.
*
* Otherwise it simply checks if a particular docid is present. If it
* is, it returns true. If it isn't, it returns false, and leaves the
* position unspecified (and hence the result of calling methods which
* depends on the current position, such as get_docid(), are also
* unspecified). In this state, next() will advance to the first matching
* position after @a docid, and skip_to() will act as it would if the
* position was the first matching position after @a docid.
*
* The default implementation calls skip_to().
*/
bool check(Xapian::docid did);
/// Return a string description of this object.
std::string get_description() const;
};
#endif // XAPIAN_INCLUDED_MULTIVALUELIST_H
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