123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180 |
- /*
- * 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;
-
- /**
- * Compares two {@link Sequence}s to create an {@link EditList} of changes.
- * <p>
- * An algorithm's {@code diff} method must be callable from concurrent threads
- * without data collisions. This permits some algorithms to use a singleton
- * pattern, with concurrent invocations using the same singleton. Other
- * algorithms may support parameterization, in which case the caller can create
- * a unique instance per thread.
- */
- public abstract class DiffAlgorithm {
- /**
- * Supported diff algorithm
- */
- public enum SupportedAlgorithm {
- /**
- * Myers diff algorithm
- */
- MYERS,
-
- /**
- * Histogram diff algorithm
- */
- HISTOGRAM
- }
-
- /**
- * @param alg
- * the diff algorithm for which an implementation should be
- * returned
- * @return an implementation of the specified diff algorithm
- */
- public static DiffAlgorithm getAlgorithm(SupportedAlgorithm alg) {
- switch (alg) {
- case MYERS:
- return MyersDiff.INSTANCE;
- case HISTOGRAM:
- return new HistogramDiff();
- default:
- throw new IllegalArgumentException();
- }
- }
-
- /**
- * Compare two sequences and identify a list of edits between them.
- *
- * @param <S>
- * type of sequence being compared.
- * @param cmp
- * the comparator supplying the element equivalence function.
- * @param a
- * the first (also known as old or pre-image) sequence. Edits
- * returned by this algorithm will reference indexes using the
- * 'A' side: {@link Edit#getBeginA()}, {@link Edit#getEndA()}.
- * @param b
- * the second (also known as new or post-image) sequence. Edits
- * returned by this algorithm will reference indexes using the
- * 'B' side: {@link Edit#getBeginB()}, {@link Edit#getEndB()}.
- * @return a modifiable edit list comparing the two sequences. If empty, the
- * sequences are identical according to {@code cmp}'s rules. The
- * result list is never null.
- */
- public <S extends Sequence> EditList diff(
- SequenceComparator<? super S> cmp, S a, S b) {
- Edit region = cmp.reduceCommonStartEnd(a, b, coverEdit(a, b));
-
- switch (region.getType()) {
- case INSERT:
- case DELETE:
- return EditList.singleton(region);
-
- case REPLACE: {
- if (region.getLengthA() == 1 && region.getLengthB() == 1)
- return EditList.singleton(region);
-
- SubsequenceComparator<S> cs = new SubsequenceComparator<S>(cmp);
- Subsequence<S> as = Subsequence.a(a, region);
- Subsequence<S> bs = Subsequence.b(b, region);
- EditList e = Subsequence.toBase(diffNonCommon(cs, as, bs), as, bs);
-
- // The last insertion may need to be shifted later if it
- // inserts elements that were previously reduced out as
- // common at the end.
- //
- Edit last = e.get(e.size() - 1);
- if (last.getType() == Edit.Type.INSERT) {
- while (last.endB < b.size()
- && cmp.equals(b, last.beginB, b, last.endB)) {
- last.beginA++;
- last.endA++;
- last.beginB++;
- last.endB++;
- }
- }
-
- return e;
- }
-
- case EMPTY:
- return new EditList(0);
-
- default:
- throw new IllegalStateException();
- }
- }
-
- private static <S extends Sequence> Edit coverEdit(S a, S b) {
- return new Edit(0, a.size(), 0, b.size());
- }
-
- /**
- * Compare two sequences and identify a list of edits between them.
- *
- * This method should be invoked only after the two sequences have been
- * proven to have no common starting or ending elements. The expected
- * elimination of common starting and ending elements is automatically
- * performed by the {@link #diff(SequenceComparator, Sequence, Sequence)}
- * method, which invokes this method using {@link Subsequence}s.
- *
- * @param <S>
- * type of sequence being compared.
- * @param cmp
- * the comparator supplying the element equivalence function.
- * @param a
- * the first (also known as old or pre-image) sequence. Edits
- * returned by this algorithm will reference indexes using the
- * 'A' side: {@link Edit#getBeginA()}, {@link Edit#getEndA()}.
- * @param b
- * the second (also known as new or post-image) sequence. Edits
- * returned by this algorithm will reference indexes using the
- * 'B' side: {@link Edit#getBeginB()}, {@link Edit#getEndB()}.
- * @return a modifiable edit list comparing the two sequences.
- */
- public abstract <S extends Sequence> EditList diffNonCommon(
- SequenceComparator<? super S> cmp, S a, S b);
- }
|