| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| package org.apache.openjpa.lib.rop; |
| |
| import java.io.ObjectStreamException; |
| import java.util.ArrayList; |
| import java.util.Iterator; |
| import java.util.List; |
| |
| /** |
| * ResultList implementation that uses a forward-scrolling window of results. |
| * |
| * @author Abe White |
| */ |
| public class WindowResultList extends AbstractNonSequentialResultList { |
| |
| private static final int OPEN = 0; |
| private static final int FREED = 1; |
| private static final int CLOSED = 2; |
| |
| private final Object[] _window; |
| private int _pos = -1; |
| private ResultObjectProvider _rop = null; |
| private boolean _random = false; |
| private int _state = OPEN; |
| private int _size = -1; |
| |
| public WindowResultList(ResultObjectProvider rop) { |
| this(rop, 10); |
| } |
| |
| public WindowResultList(ResultObjectProvider rop, int windowSize) { |
| _rop = rop; |
| |
| if (windowSize <= 0) |
| windowSize = 10; |
| _window = new Object[windowSize]; |
| |
| try { |
| _rop.open(); |
| _random = _rop.supportsRandomAccess(); |
| } catch (RuntimeException re) { |
| close(); |
| throw re; |
| } catch (Exception e) { |
| close(); |
| _rop.handleCheckedException(e); |
| } |
| } |
| |
| @Override |
| public boolean isProviderOpen() { |
| return _state == OPEN; |
| } |
| |
| @Override |
| public boolean isClosed() { |
| return _state == CLOSED; |
| } |
| |
| @Override |
| public void close() { |
| if (_state != CLOSED) { |
| free(); |
| _state = CLOSED; |
| } |
| } |
| |
| @Override |
| public int size() { |
| assertOpen(); |
| if (_size != -1) |
| return _size; |
| try { |
| _size = _rop.size(); |
| return _size; |
| } catch (RuntimeException re) { |
| close(); |
| throw re; |
| } catch (Exception e) { |
| close(); |
| _rop.handleCheckedException(e); |
| return -1; |
| } |
| } |
| |
| @Override |
| public Object getInternal(int index) { |
| // out of range? |
| if (index < 0 || (_size != -1 && index >= _size)) |
| return PAST_END; |
| |
| try { |
| // if this is before window range, move window back |
| if (index < _pos) { |
| if (!_random || index == 0) |
| _rop.reset(); |
| _pos = -1; |
| } |
| |
| // if this is the first get or past window range, move window |
| if (_pos == -1 || index >= _pos + _window.length) { |
| // position result provider just before requested index |
| if (_random && index != 0) { |
| if (!_rop.absolute(index - 1)) |
| return PAST_END; |
| } else { |
| int begin = (_pos == -1) ? 0 : _pos + _window.length; |
| for (int i = begin; i < index; i++) |
| if (!_rop.next()) |
| return PAST_END; |
| } |
| |
| // create window starting at requested index |
| int end = -1; |
| for (int i = 0; i < _window.length; i++) { |
| if (end == -1 && !_rop.next()) |
| end = i; |
| _window[i] = (end == -1) ? _rop.getResultObject() |
| : PAST_END; |
| } |
| _pos = index; |
| |
| // if the window spans the entire result list, free |
| if (end != -1 && _pos == 0) { |
| _size = end; |
| free(); |
| } |
| } |
| |
| // grab result from window |
| return _window[index - _pos]; |
| } catch (RuntimeException re) { |
| close(); |
| throw re; |
| } catch (Exception e) { |
| close(); |
| _rop.handleCheckedException(e); |
| return null; |
| } |
| } |
| |
| private void free() { |
| if (_state == OPEN) { |
| try { |
| _rop.close(); |
| } catch (Exception e) { |
| } |
| _state = FREED; |
| } |
| } |
| |
| public Object writeReplace() throws ObjectStreamException { |
| if (_state != OPEN) |
| return this; |
| |
| // load results into list |
| List list = new ArrayList(); |
| for (Iterator itr = iterator(); itr.hasNext();) |
| list.add(itr.next()); |
| return list; |
| } |
| } |