| /* |
| * Copyright (C) 2010, Google Inc. |
| * and other copyright owners as documented in the project's IP log. |
| * |
| * This program and the accompanying materials are made available |
| * under the terms of the Eclipse Distribution License v1.0 which |
| * accompanies this distribution, is reproduced below, and is |
| * available at http://www.eclipse.org/org/documents/edl-v10.php |
| * |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or |
| * without modification, are permitted provided that the following |
| * conditions are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * |
| * - Redistributions in binary form must reproduce the above |
| * copyright notice, this list of conditions and the following |
| * disclaimer in the documentation and/or other materials provided |
| * with the distribution. |
| * |
| * - Neither the name of the Eclipse Foundation, Inc. nor the |
| * names of its contributors may be used to endorse or promote |
| * products derived from this software without specific prior |
| * written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND |
| * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, |
| * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR |
| * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER |
| * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, |
| * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
| * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| package org.eclipse.jgit.diff; |
| |
| /** |
| * Equivalence function for a {@link org.eclipse.jgit.diff.Sequence} compared by |
| * difference algorithm. |
| * <p> |
| * Difference algorithms can use a comparator to compare portions of two |
| * sequences and discover the minimal edits required to transform from one |
| * sequence to the other sequence. |
| * <p> |
| * Indexes within a sequence are zero-based. |
| * |
| * @param <S> |
| * type of sequence the comparator supports. |
| */ |
| public abstract class SequenceComparator<S extends Sequence> { |
| /** |
| * Compare two items to determine if they are equivalent. |
| * |
| * It is permissible to compare sequence {@code a} with itself (by passing |
| * {@code a} again in position {@code b}). |
| * |
| * @param a |
| * the first sequence. |
| * @param ai |
| * item of {@code ai} to compare. |
| * @param b |
| * the second sequence. |
| * @param bi |
| * item of {@code bi} to compare. |
| * @return true if the two items are identical according to this function's |
| * equivalence rule. |
| */ |
| public abstract boolean equals(S a, int ai, S b, int bi); |
| |
| /** |
| * Get a hash value for an item in a sequence. |
| * |
| * If two items are equal according to this comparator's |
| * {@link #equals(Sequence, int, Sequence, int)} method, then this hash |
| * method must produce the same integer result for both items. |
| * |
| * It is not required for two items to have different hash values if they |
| * are are unequal according to the {@code equals()} method. |
| * |
| * @param seq |
| * the sequence. |
| * @param ptr |
| * the item to obtain the hash for. |
| * @return hash the hash value. |
| */ |
| public abstract int hash(S seq, int ptr); |
| |
| /** |
| * Modify the edit to remove common leading and trailing items. |
| * |
| * The supplied edit {@code e} is reduced in size by moving the beginning A |
| * and B points so the edit does not cover any items that are in common |
| * between the two sequences. The ending A and B points are also shifted to |
| * remove common items from the end of the region. |
| * |
| * @param a |
| * the first sequence. |
| * @param b |
| * the second sequence. |
| * @param e |
| * the edit to start with and update. |
| * @return {@code e} if it was updated in-place, otherwise a new edit |
| * containing the reduced region. |
| */ |
| public Edit reduceCommonStartEnd(S a, S b, Edit e) { |
| // Skip over items that are common at the start. |
| // |
| while (e.beginA < e.endA && e.beginB < e.endB |
| && equals(a, e.beginA, b, e.beginB)) { |
| e.beginA++; |
| e.beginB++; |
| } |
| |
| // Skip over items that are common at the end. |
| // |
| while (e.beginA < e.endA && e.beginB < e.endB |
| && equals(a, e.endA - 1, b, e.endB - 1)) { |
| e.endA--; |
| e.endB--; |
| } |
| |
| return e; |
| } |
| } |