| /* |
| * 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.util.Comparator; |
| |
| |
| /** |
| * A result object provider that merges multiple result object provider |
| * delegates. Support exists for maintaining ordering of the internally held |
| * results, provided that each of the individual results is itself ordered. |
| * |
| * @author Abe White |
| * @author Marc Prud'hommeaux |
| */ |
| public class MergedResultObjectProvider implements ResultObjectProvider { |
| |
| private static final byte UNOPENED = 0; |
| private static final byte OPENED = 1; |
| private static final byte VALUE = 2; |
| private static final byte DONE = 3; |
| |
| private final ResultObjectProvider[] _rops; |
| private final Comparator _comp; |
| private final byte[] _status; |
| private Object[] _values; |
| private Object[] _orderValues; |
| private Object _cur = null; |
| private int _size = -1; |
| |
| /** |
| * Constructor. Provide delegates. |
| */ |
| public MergedResultObjectProvider(ResultObjectProvider[] rops) { |
| this(rops, null); |
| } |
| |
| /** |
| * Constructor. Provide delegates and optional comparator. |
| */ |
| public MergedResultObjectProvider(ResultObjectProvider[] rops, |
| Comparator comp) { |
| _rops = rops; |
| _comp = comp; |
| _status = new byte[rops.length]; |
| _values = (comp == null) ? null : new Object[rops.length]; |
| _orderValues = (comp == null) ? null : new Object[rops.length]; |
| } |
| |
| @Override |
| public boolean supportsRandomAccess() { |
| return false; |
| } |
| |
| @Override |
| public void open() throws Exception { |
| // if we have a comparator, then open all; else open first |
| int len = (_comp != null) ? _rops.length : 1; |
| for (int i = 0; i < len; i++) { |
| _rops[i].open(); |
| _status[i] = OPENED; |
| } |
| } |
| |
| @Override |
| public boolean absolute(int pos) throws Exception { |
| throw new UnsupportedOperationException(); |
| } |
| |
| @Override |
| public int size() throws Exception { |
| if (_size != -1) |
| return _size; |
| |
| // have to open all to get sizes |
| for (int i = 0; i < _status.length; i++) { |
| if (_status[i] == UNOPENED) { |
| _rops[i].open(); |
| _status[i] = OPENED; |
| } |
| } |
| |
| int total = 0; |
| int size; |
| for (ResultObjectProvider rop : _rops) { |
| size = rop.size(); |
| if (size == Integer.MAX_VALUE) { |
| total = size; |
| break; |
| } |
| total += size; |
| } |
| _size = total; |
| return _size; |
| } |
| |
| @Override |
| public void reset() throws Exception { |
| for (int i = 0; i < _rops.length; i++) |
| if (_status[i] != UNOPENED) |
| _rops[i].reset(); |
| clear(); |
| } |
| |
| @Override |
| public void close() throws Exception { |
| Exception err = null; |
| for (int i = 0; i < _rops.length; i++) { |
| try { |
| if (_status[i] != UNOPENED) |
| _rops[i].close(); |
| } catch (Exception e) { |
| if (err == null) |
| err = e; |
| } |
| } |
| |
| clear(); |
| if (err != null) |
| throw err; |
| } |
| |
| private void clear() { |
| _cur = null; |
| for (int i = 0; i < _rops.length; i++) { |
| _status[i] = OPENED; |
| if (_values != null) |
| _values[i] = null; |
| if (_orderValues != null) |
| _orderValues[i] = null; |
| } |
| } |
| |
| @Override |
| public void handleCheckedException(Exception e) { |
| if (_rops.length == 0) |
| throw new RuntimeException(e); |
| _rops[0].handleCheckedException(e); |
| } |
| |
| @Override |
| public boolean next() throws Exception { |
| // initialize all rops with the latest values |
| boolean hasValue = false; |
| for (int i = 0; i < _status.length; i++) { |
| switch (_status[i]) { |
| case UNOPENED: |
| // this will only ever be the case if we aren't ordering |
| _rops[i].open(); |
| _status[i] = OPENED; |
| // no break |
| case OPENED: |
| // if this rop has a value, cache it; if we're not ordering, |
| // then that's the value to return |
| if (_rops[i].next()) { |
| if (_comp == null) { |
| _cur = _rops[i].getResultObject(); |
| return true; |
| } else { |
| hasValue = true; |
| _status[i] = VALUE; |
| _values[i] = _rops[i].getResultObject(); |
| _orderValues[i] = getOrderingValue(_values[i], |
| i, _rops[i]); |
| } |
| } else |
| _status[i] = DONE; |
| break; |
| case VALUE: |
| // we only use this state when ordering |
| hasValue = true; |
| break; |
| } |
| } |
| |
| // if we get to this point without a comparator, it means none |
| // of our rops have any more values |
| if (_comp == null || !hasValue) |
| return false; |
| |
| // for all the rops with values, find the 'least' one according to |
| // the comparator |
| int least = -1; |
| Object orderVal = null; |
| for (int i = 0; i < _orderValues.length; i++) { |
| if (_status[i] != VALUE) |
| continue; |
| if (least == -1 || _comp.compare(_orderValues[i], orderVal) < 0) { |
| least = i; |
| orderVal = _orderValues[i]; |
| } |
| } |
| |
| // assign the least value to the current one, and clear the cached |
| // value for that rop so that we know to get the next value for |
| // the next comparison |
| _cur = _values[least]; |
| _values[least] = null; |
| _orderValues[least] = null; |
| _status[least] = OPENED; |
| return true; |
| } |
| |
| @Override |
| public Object getResultObject() throws Exception { |
| return _cur; |
| } |
| |
| /** |
| * Return the value to use for ordering on the given result value. Returns |
| * the result value by default. |
| * |
| * @param val the result value |
| * @param idx the index of the result object provider in the array |
| * given on construction that produced the result value |
| * @param rop the result object provider that produced the result value |
| */ |
| protected Object getOrderingValue(Object val, int idx, |
| ResultObjectProvider rop) { |
| return val; |
| } |
| } |