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 a {@link org.eclipse.jgit.diff.Sequence} to have a narrower range of
48 * elements.
49 * <p>
50 * This sequence acts as a proxy for the real sequence, translating element
51 * indexes on the fly by adding {@code begin} to them. Sequences of this type
52 * must be used with a {@link org.eclipse.jgit.diff.SubsequenceComparator}.
53 *
54 * @param <S>
55 * the base sequence type.
56 */
57 public final class Subsequence<S extends Sequence> extends Sequence {
58 /**
59 * Construct a subsequence around the A region/base sequence.
60 *
61 * @param a
62 * the A sequence.
63 * @param region
64 * the region of {@code a} to create a subsequence around.
65 * @return subsequence of {@code base} as described by A in {@code region}.
66 */
67 public static <S extends Sequence> Subsequence<S> a(S a, Edit region) {
68 return new Subsequence<>(a, region.beginA, region.endA);
69 }
70
71 /**
72 * Construct a subsequence around the B region/base sequence.
73 *
74 * @param b
75 * the B sequence.
76 * @param region
77 * the region of {@code b} to create a subsequence around.
78 * @return subsequence of {@code base} as described by B in {@code region}.
79 */
80 public static <S extends Sequence> Subsequence<S> b(S b, Edit region) {
81 return new Subsequence<>(b, region.beginB, region.endB);
82 }
83
84 /**
85 * Adjust the Edit to reflect positions in the base sequence.
86 *
87 * @param e
88 * edit to adjust in-place. Prior to invocation the indexes are
89 * in terms of the two subsequences; after invocation the indexes
90 * are in terms of the base sequences.
91 * @param a
92 * the A sequence.
93 * @param b
94 * the B sequence.
95 */
96 public static <S extends Sequence> void toBase(Edit e, Subsequence<S> a,
97 Subsequence<S> b) {
98 e.beginA += a.begin;
99 e.endA += a.begin;
100
101 e.beginB += b.begin;
102 e.endB += b.begin;
103 }
104
105 /**
106 * Adjust the Edits to reflect positions in the base sequence.
107 *
108 * @param edits
109 * edits to adjust in-place. Prior to invocation the indexes are
110 * in terms of the two subsequences; after invocation the indexes
111 * are in terms of the base sequences.
112 * @param a
113 * the A sequence.
114 * @param b
115 * the B sequence.
116 * @return always {@code edits} (as the list was updated in-place).
117 */
118 public static <S extends Sequence> EditList toBase(EditList edits,
119 Subsequence<S> a, Subsequence<S> b) {
120 for (Edit e : edits)
121 toBase(e, a, b);
122 return edits;
123 }
124
125 final S base;
126
127 final int begin;
128
129 private final int size;
130
131 /**
132 * Construct a subset of another sequence.
133 *
134 * The size of the subsequence will be {@code end - begin}.
135 *
136 * @param base
137 * the real sequence.
138 * @param begin
139 * First element index of {@code base} that will be part of this
140 * new subsequence. The element at {@code begin} will be this
141 * sequence's element 0.
142 * @param end
143 * One past the last element index of {@code base} that will be
144 * part of this new subsequence.
145 */
146 public Subsequence(S base, int begin, int end) {
147 this.base = base;
148 this.begin = begin;
149 this.size = end - begin;
150 }
151
152 /** {@inheritDoc} */
153 @Override
154 public int size() {
155 return size;
156 }
157 }