jgit/org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/CachedPack.java

/*
 * Copyright (C) 2011, 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.
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 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
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 * - Redistributions of source code must retain the above copyright
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 * - Redistributions in binary form must reproduce the above
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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package org.eclipse.jgit.storage.pack;

import java.io.IOException;
import java.util.Set;

import org.eclipse.jgit.lib.ObjectId;

/** Describes a pack file {@link ObjectReuseAsIs} can append onto a stream. */
public abstract class CachedPack {
	/**
	 * Objects that start this pack.
	 * <p>
	 * All objects reachable from the tips are contained within this pack. If
	 * {@link PackWriter} is going to include everything reachable from all of
	 * these objects, this cached pack is eligible to be appended directly onto
	 * the output pack stream.
	 *
	 * @return the tip objects that describe this pack.
	 */
	public abstract Set<ObjectId> getTips();

	/**
	 * Get the number of objects in this pack.
	 *
	 * @return the total object count for the pack.
	 * @throws IOException
	 *             if the object count cannot be read.
	 */
	public abstract long getObjectCount() throws IOException;

	/**
	 * Determine if the pack contains the requested objects.
	 *
	 * @param <T>
	 *            any type of ObjectId to search for.
	 * @param toFind
	 *            the objects to search for.
	 * @return the objects contained in the pack.
	 * @throws IOException
	 *             the pack cannot be accessed
	 */
	public abstract <T extends ObjectId> Set<ObjectId> hasObject(
			Iterable<T> toFind) throws IOException;
}