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/** @file chert_positionlist.h
* @brief A position list in a chert database.
*/
/* Copyright (C) 2005,2006,2008,2009,2010,2011,2013 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_HGUARD_CHERT_POSITIONLIST_H
#define XAPIAN_HGUARD_CHERT_POSITIONLIST_H
#include <xapian/types.h>
#include "bitstream.h"
#include "chert_lazytable.h"
#include "pack.h"
#include "backends/positionlist.h"
#include <string>
using namespace std;
class ChertPositionListTable : public ChertLazyTable {
public:
static string make_key(Xapian::docid did, const string & term) {
string key;
C_pack_uint_preserving_sort(key, did);
key += term;
return key;
}
/** Create a new ChertPositionListTable object.
*
* This method does not create or open the table on disk - you
* must call the create() or open() methods respectively!
*
* @param dbdir The directory the chert database is stored in.
* @param readonly true if we're opening read-only, else false.
*/
ChertPositionListTable(const string & dbdir, bool readonly)
: ChertLazyTable("position", dbdir + "/position.", readonly,
DONT_COMPRESS) { }
/** Set the position list for term tname in document did.
*
* @param check_for_update If true, check if the new list is the same as
* the existing list (if there is one).
*/
void set_positionlist(Xapian::docid did, const string & tname,
Xapian::PositionIterator pos,
const Xapian::PositionIterator &pos_end,
bool check_for_update);
/// Delete the position list for term tname in document did.
void delete_positionlist(Xapian::docid did, const string & tname) {
del(make_key(did, tname));
}
/// Return the number of entries in specified position list.
Xapian::termcount positionlist_count(Xapian::docid did,
const string & term) const;
};
/** A position list in a chert database. */
class ChertPositionList : public PositionList {
/// Interpolative decoder.
BitReader rd;
/// Current entry.
Xapian::termpos current_pos;
/// Last entry.
Xapian::termpos last;
/// Number of entries.
Xapian::termcount size;
/// Have we started iterating yet?
bool have_started;
/// Copying is not allowed.
ChertPositionList(const ChertPositionList &);
/// Assignment is not allowed.
void operator=(const ChertPositionList &);
public:
/// Default constructor.
ChertPositionList() { }
/// Construct and initialise with data.
ChertPositionList(const ChertTable * table, Xapian::docid did,
const string & tname) {
(void)read_data(table, did, tname);
}
/** Fill list with data, and move the position to the start.
*
* @return true if position data was read.
*/
bool read_data(const ChertTable * table, Xapian::docid did,
const string & tname);
/// Returns size of position list.
Xapian::termcount get_size() const;
/** Returns current position.
*
* Either next() or skip_to() must have been called before this
* method can be called.
*/
Xapian::termpos get_position() const;
/// Advance to the next term position in the list.
void next();
/// Advance to the first term position which is at least termpos.
void skip_to(Xapian::termpos termpos);
/// True if we're off the end of the list
bool at_end() const;
};
#endif /* XAPIAN_HGUARD_CHERT_POSITIONLIST_H */
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