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//
// NearQuery.cc
//
// NearQuery: An operator query that filters matches by proximity.
//
// Part of the ht://Dig package <http://www.htdig.org/>
// Copyright (c) 1995-2004 The ht://Dig Group
// For copyright details, see the file COPYING in your distribution
// or the GNU Library General Public License (LGPL) version 2 or later
// <http://www.gnu.org/copyleft/lgpl.html>
//
// $Id: NearQuery.cc,v 1.4 2004/05/28 13:15:24 lha Exp $
//
#include "NearQuery.h"
String
NearQuery::OperatorString() const
{
String s;
s << "near/" << distance;
return s;
}
//
// l r nextTo
// -----------------------
// 0 0 0
// 0 b 0
// 0 x 0
// a 0 0
// a b near(a, b)
// a x a
// x 0 0
// x b b
// x x x
//
ResultList *
NearQuery::Evaluate()
{
ResultList *result = 0;
Query *left = (Query *)operands[0];
Query *right = (Query *)operands[1];
if(left && right)
{
ResultList *l = left->GetResults();
if(l)
{
ResultList *r = right->GetResults();
if(r)
{
if(l->IsIgnore())
{
result = new ResultList(*r);
}
else if(r->IsIgnore())
{
result = new ResultList(*l);
}
else
{
result = Near(*l, *r);
}
}
}
}
return result;
}
ResultList *
NearQuery::Near(const ResultList &l, const ResultList &r)
{
ResultList *result = 0;
DictionaryCursor c;
l.Start_Get(c);
DocMatch *match = (DocMatch *)l.Get_NextElement(c);
while(match)
{
DocMatch *confirm = r.find(match->GetId());
if(confirm)
{
List *locations = MergeLocations(
*match->GetLocations(),
*confirm->GetLocations());
if(locations)
{
if(!result)
{
result = new ResultList;
}
DocMatch *copy = new DocMatch(*match);
copy->SetLocations(locations);
result->add(copy);
}
}
match = (DocMatch *)l.Get_NextElement(c);
}
return result;
}
//
//: merge match positions in a 'near' operation
// all combinations are tested; the pairs of positions near enough are kept
//
List *
NearQuery::MergeLocations(const List &p, const List &q)
{
List *result = 0;
ListCursor pc;
p.Start_Get(pc);
const Location *left = (const Location *)p.Get_Next(pc);
while(left)
{
ListCursor qc;
q.Start_Get(qc);
const Location *right = (const Location *)q.Get_Next(qc);
while(right)
{
int dist = right->from - left->to;
if(dist < 1)
{
dist = left->from - right->to;
if(dist < 1)
{
dist = 0;
}
}
if(unsigned(dist) <= distance)
{
if(!result)
{
result = new List;
}
result->Add(new Location(*left));
result->Add(new Location(*right));
}
right = (const Location *)q.Get_Next(qc);
}
left = (const Location *)p.Get_Next(pc);
}
return result;
}
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