jgit/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/filter/ObjectFilter.java

/**
 * Copyright (C) 2015, 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.
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 * - 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
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 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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package org.eclipse.jgit.revwalk.filter;

import java.io.IOException;

import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.revwalk.ObjectWalk;

/**
 * Selects interesting objects when walking.
 * <p>
 * Applications should install the filter on an ObjectWalk by
 * {@link org.eclipse.jgit.revwalk.ObjectWalk#setObjectFilter(ObjectFilter)}
 * prior to starting traversal.
 *
 * @since 4.0
 */
public abstract class ObjectFilter {
	/** Default filter that always returns true. */
	public static final ObjectFilter ALL = new AllFilter();

	private static final class AllFilter extends ObjectFilter {
		@Override
		public boolean include(ObjectWalk walker, AnyObjectId o) {
			return true;
		}
	}

	/**
	 * Determine if the named object should be included in the walk.
	 *
	 * @param walker
	 *            the active walker this filter is being invoked from within.
	 * @param objid
	 *            the object currently being tested.
	 * @return {@code true} if the named object should be included in the walk.
	 * @throws org.eclipse.jgit.errors.MissingObjectException
	 *             an object the filter needed to consult to determine its
	 *             answer was missing
	 * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
	 *             an object the filter needed to consult to determine its
	 *             answer was of the wrong type
	 * @throws java.io.IOException
	 *             an object the filter needed to consult to determine its
	 *             answer could not be read.
	 */
	public abstract boolean include(ObjectWalk walker, AnyObjectId objid)
			throws MissingObjectException, IncorrectObjectTypeException,
			       IOException;
}