1 /**
2 * Copyright (c) 2011, University of Konstanz, Distributed Systems Group
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 * * Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * * Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * * Neither the name of the University of Konstanz nor the
13 * names of its contributors may be used to endorse or promote products
14 * derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
19 * DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
20 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
21 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
22 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
23 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
25 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 package org.treetank.service.xml.xpath.axis;
29
30 import java.util.HashSet;
31 import java.util.Set;
32
33 import org.treetank.api.INodeReadTrx;
34 import org.treetank.axis.AbsAxis;
35 import org.treetank.service.xml.xpath.XPathError;
36 import org.treetank.service.xml.xpath.XPathError.ErrorType;
37
38 /**
39 * <h1>IntersectAxis</h1>
40 * <p>
41 * Returns an intersection of two operands. This axis takes two node sequences as operands and returns a
42 * sequence containing all the nodes that occur in both operands.
43 * </p>
44 */
45 public class IntersectAxis extends AbsAxis {
46
47 /** First operand sequence. */
48 private final AbsAxis mOp1;
49
50 /** Second operand sequence. */
51 private final AbsAxis mOp2;
52
53 /** Set to decide, if an item is contained in both sequences. */
54 private final Set<Long> mDupSet;
55
56 /**
57 * Constructor. Initializes the internal state.
58 *
59 * @param rtx
60 * Exclusive (immutable) trx to iterate with.
61 * @param mOperand1
62 * First operand
63 * @param mOperand2
64 * Second operand
65 */
66 public IntersectAxis(final INodeReadTrx rtx, final AbsAxis mOperand1, final AbsAxis mOperand2) {
67
68 super(rtx);
69 mOp1 = mOperand1;
70 mOp2 = mOperand2;
71 mDupSet = new HashSet<Long>();
72
73 }
74
75 /**
76 * {@inheritDoc}
77 */
78 @Override
79 public void reset(final long mNodeKey) {
80
81 super.reset(mNodeKey);
82
83 if (mDupSet != null) {
84 mDupSet.clear();
85 }
86
87 if (mOp1 != null) {
88 mOp1.reset(mNodeKey);
89 }
90 if (mOp2 != null) {
91 mOp2.reset(mNodeKey);
92 }
93 }
94
95 /**
96 * {@inheritDoc}
97 */
98 @Override
99 public boolean hasNext() {
100
101 // store all item keys of the first sequence to the set.
102 while (mOp1.hasNext()) {
103 if (getNode().getDataKey() < 0) { // only nodes are
104 // allowed
105 throw new XPathError(ErrorType.XPTY0004);
106 }
107
108 mDupSet.add(getNode().getDataKey());
109 }
110
111 while (mOp2.hasNext()) {
112
113 if (getNode().getDataKey() < 0) { // only nodes are
114 // allowed
115 throw new XPathError(ErrorType.XPTY0004);
116 }
117
118 // return true, if item key is already in the set -> item is
119 // contained in
120 // both input sequences.
121 if (!mDupSet.add(getNode().getDataKey())) {
122 return true;
123 }
124 }
125
126 return false;
127 }
128
129 }