1 /*
2 * Copyright (C) 2010, Google Inc.
3 * and other copyright owners as documented in the project's IP log.
4 *
5 * This program and the accompanying materials are made available
6 * under the terms of the Eclipse Distribution License v1.0 which
7 * accompanies this distribution, is reproduced below, and is
8 * available at http://www.eclipse.org/org/documents/edl-v10.php
9 *
10 * All rights reserved.
11 *
12 * Redistribution and use in source and binary forms, with or
13 * without modification, are permitted provided that the following
14 * conditions are met:
15 *
16 * - Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 *
19 * - Redistributions in binary form must reproduce the above
20 * copyright notice, this list of conditions and the following
21 * disclaimer in the documentation and/or other materials provided
22 * with the distribution.
23 *
24 * - Neither the name of the Eclipse Foundation, Inc. nor the
25 * names of its contributors may be used to endorse or promote
26 * products derived from this software without specific prior
27 * written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
30 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
31 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
34 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
36 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
37 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
38 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42 */
43
44 package org.eclipse.jgit.diff;
45
46 /**
47 * Wraps two {@link Sequence} instances to cache their element hash codes.
48 * <p>
49 * This pair wraps two sequences that contain cached hash codes for the input
50 * sequences.
51 *
52 * @param <S>
53 * the base sequence type.
54 */
55 public class HashedSequencePair<S extends Sequence> {
56 private final SequenceComparator<? super S> cmp;
57
58 private final S baseA;
59
60 private final S baseB;
61
62 private HashedSequence<S> cachedA;
63
64 private HashedSequence<S> cachedB;
65
66 /**
67 * Construct a pair to provide fast hash codes.
68 *
69 * @param cmp
70 * the base comparator for the sequence elements.
71 * @param a
72 * the A sequence.
73 * @param b
74 * the B sequence.
75 */
76 public HashedSequencePair(SequenceComparator<? super S> cmp, S a, S b) {
77 this.cmp = cmp;
78 this.baseA = a;
79 this.baseB = b;
80 }
81
82 /** @return obtain a comparator that uses the cached hash codes. */
83 public HashedSequenceComparator<S> getComparator() {
84 return new HashedSequenceComparator<>(cmp);
85 }
86
87 /** @return wrapper around A that includes cached hash codes. */
88 public HashedSequence<S> getA() {
89 if (cachedA == null)
90 cachedA = wrap(baseA);
91 return cachedA;
92 }
93
94 /** @return wrapper around B that includes cached hash codes. */
95 public HashedSequence<S> getB() {
96 if (cachedB == null)
97 cachedB = wrap(baseB);
98 return cachedB;
99 }
100
101 private HashedSequence<S> wrap(S base) {
102 final int end = base.size();
103 final int[] hashes = new int[end];
104 for (int ptr = 0; ptr < end; ptr++)
105 hashes[ptr] = cmp.hash(base, ptr);
106 return new HashedSequence<>(base, hashes);
107 }
108 }