159 lines
3.9 KiB
C++
159 lines
3.9 KiB
C++
/*
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----
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This file is part of SECONDO.
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Copyright (C) 2004, University in Hagen, Department of Computer Science,
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Database Systems for New Applications.
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SECONDO is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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SECONDO is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with SECONDO; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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----
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Author: David Ullrich
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*/
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#include "BPTreeSearchEnumerator.h"
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namespace fialgebra {
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// ctor
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BPTreeSearchEnumerator::BPTreeSearchEnumerator(
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BPTree* tree,
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BPTreeNode* startNode,
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const Attribute* minValue,
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const Attribute* maxValue ) :
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// Members initialisieren
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_tree( tree ),
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_currentNode( startNode ),
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_currentIndex( -1 ),
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_minValue( minValue ),
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_maxValue( maxValue ) { }
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BPTreeSearchEnumerator::~BPTreeSearchEnumerator() {
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if ( _currentNode ) {
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delete _currentNode;
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_currentNode = NULL;
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} // if
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}
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BPTree* BPTreeSearchEnumerator::GetTree() {
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return _tree;
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}
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// Liefert das aktuelle Element in der Ergebnisliste.
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size_t BPTreeSearchEnumerator::GetCurrentId() {
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size_t id = _currentNode->GetIDAt( _currentIndex );
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return id;
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}
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const Attribute& BPTreeSearchEnumerator::GetCurrentValue() {
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Attribute& value = _currentNode->GetValueAt( _currentIndex );
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return value;
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}
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// Springt zum naechsten Element in der Ergebnisliste;
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// Liefert bei Erfolg true, am Ende der Liste false.
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bool BPTreeSearchEnumerator::MoveNext() {
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while ( true ) {
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_currentIndex++;
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// Wenn wir am Ende eines Blatts ankommen, muessen wir
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// in das naechste Blatt springen.
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if ( (unsigned long)_currentIndex >=
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_currentNode->GetValueCount() ) {
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// Wenn es kein NextLeaf mehr gibt, sind wir fertig.
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size_t nextLeaf = _currentNode->GetNextLeaf();
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if ( nextLeaf == 0 ) break;
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// cleanup
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delete _currentNode;
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_currentIndex = -1;
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_currentNode = _tree->GetNodefromPageNumber( nextLeaf );
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continue;
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} // if
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Attribute& curValue = _currentNode->GetValueAt( _currentIndex );
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// -1 : curValue < minValue
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// 0 : curValue = minValue
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// 1 : curValue > minValue
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// Wenn kein minValue angegeben ist, sind alle Werte groesser.
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int compMin = 1;
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if ( _minValue != NULL ) compMin = curValue.Compare( _minValue );
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// -1 : curValue < maxValue
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// 0 : curValue = maxValue
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// 1 : curValue > maxValue
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// Wenn kein maxValue angegeben ist, sind alle Werte kleiner.
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int compMax = -1;
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if ( _maxValue != NULL ) compMax = curValue.Compare( _maxValue );
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// Wenn der aktuelle Key groesser als der max. Key ist,
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// sind wir fertig.
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if ( compMax > 0 ) break;
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// Wenn der aktuelle Key im min/max-Intervall liegt,
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// haben wir einen Treffer.
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if ( compMin >= 0 && compMax <= 0 ) return true;
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// Wenn wir bis hier hin kommen, ist der aktuelle Value
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// kleiner als der minValue. Wir laufen so lange weiter,
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// bis wir ins [min,max]-Intervall kommen.
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} // while
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return false;
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}
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} // namespace fialgebra
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