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/** @file decvalwtsource.cc
* @brief A posting source which returns decreasing weights from a value.
*/
/* Copyright (C) 2009 Lemur Consulting Ltd
* Copyright (C) 2011,2012,2015,2016 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
*/
#include <config.h>
#include "xapian/postingsource.h"
#include "xapian/error.h"
#include "net/length.h"
#include "serialise-double.h"
#include <cmath>
using namespace Xapian;
DecreasingValueWeightPostingSource::DecreasingValueWeightPostingSource(
Xapian::valueno slot_,
Xapian::docid range_start_,
Xapian::docid range_end_)
: Xapian::ValueWeightPostingSource(slot_),
range_start(range_start_),
range_end(range_end_)
{
}
double
DecreasingValueWeightPostingSource::get_weight() const {
return curr_weight;
}
Xapian::DecreasingValueWeightPostingSource *
DecreasingValueWeightPostingSource::clone() const {
return new DecreasingValueWeightPostingSource(get_slot(), range_start,
range_end);
}
std::string
DecreasingValueWeightPostingSource::name() const {
return "Xapian::DecreasingValueWeightPostingSource";
}
std::string
DecreasingValueWeightPostingSource::serialise() const {
std::string result;
result += encode_length(get_slot());
result += encode_length(range_start);
result += encode_length(range_end);
return result;
}
Xapian::DecreasingValueWeightPostingSource *
DecreasingValueWeightPostingSource::unserialise(const std::string &s) const {
const char * pos = s.data();
const char * end = pos + s.size();
Xapian::valueno new_slot;
Xapian::docid new_range_start, new_range_end;
decode_length(&pos, end, new_slot);
decode_length(&pos, end, new_range_start);
decode_length(&pos, end, new_range_end);
if (pos != end)
throw Xapian::NetworkError("Junk at end of serialised "
"DecreasingValueWeightPostingSource");
return new DecreasingValueWeightPostingSource(new_slot, new_range_start,
new_range_end);
}
void
DecreasingValueWeightPostingSource::init(const Xapian::Database & db_) {
Xapian::ValueWeightPostingSource::init(db_);
if (range_end == 0 || get_database().get_doccount() <= range_end)
items_at_end = false;
else
items_at_end = true;
}
void
DecreasingValueWeightPostingSource::skip_if_in_range(double min_wt)
{
if (ValueWeightPostingSource::at_end()) return;
curr_weight = Xapian::ValueWeightPostingSource::get_weight();
Xapian::docid docid = Xapian::ValueWeightPostingSource::get_docid();
if (docid >= range_start && (range_end == 0 || docid <= range_end)) {
if (items_at_end) {
if (curr_weight < min_wt) {
// skip to end of range.
ValueWeightPostingSource::skip_to(range_end + 1, min_wt);
if (!ValueWeightPostingSource::at_end())
curr_weight = Xapian::ValueWeightPostingSource::get_weight();
}
} else {
if (curr_weight < min_wt) {
// terminate early.
done();
} else {
// Update max_weight.
set_maxweight(curr_weight);
}
}
}
}
void
DecreasingValueWeightPostingSource::next(double min_wt) {
if (get_maxweight() < min_wt) {
done();
return;
}
Xapian::ValueWeightPostingSource::next(min_wt);
skip_if_in_range(min_wt);
}
void
DecreasingValueWeightPostingSource::skip_to(Xapian::docid min_docid,
double min_wt) {
if (get_maxweight() < min_wt) {
done();
return;
}
Xapian::ValueWeightPostingSource::skip_to(min_docid, min_wt);
skip_if_in_range(min_wt);
}
bool
DecreasingValueWeightPostingSource::check(Xapian::docid min_docid,
double min_wt) {
if (get_maxweight() < min_wt) {
done();
return true;
}
bool valid = Xapian::ValueWeightPostingSource::check(min_docid, min_wt);
if (valid) {
skip_if_in_range(min_wt);
}
return valid;
}
std::string
DecreasingValueWeightPostingSource::get_description() const {
return "DecreasingValueWeightPostingSource()";
}
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