jgit/org.eclipse.jgit/src/org/eclipse/jgit/diff/DiffAlgorithm.java

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package org.eclipse.jgit.diff;

/**
 * Compares two {@link Sequence}s to create an {@link EditList} of changes.
 *
 * 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 interface DiffAlgorithm {
	/**
	 * Compare two sequences and identify a list of edits between them.
	 * 
	 * @param <S>
	 *            type of sequence being compared.
	 * @param <C>
	 *            type of comparator to evaluate the sequence elements.
	 * @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, C extends SequenceComparator<? super S>> EditList diff(
			C cmp, S a, S b);
}