/*
 * Copyright (C) 2011, Google Inc. and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.internal.storage.pack;

import java.io.IOException;

Describes a pack file ObjectReuseAsIs can append onto a stream. /**
 * Describes a pack file
 * {@link org.eclipse.jgit.internal.storage.pack.ObjectReuseAsIs} can append
 * onto a stream.
 */
public abstract class CachedPack {
	
Get the number of objects in this pack.
Throws:
IOException – 
            if the object count cannot be read.
Returns:
the total object count for the pack./**
	 * Get the number of objects in this pack.
	 *
	 * @return the total object count for the pack.
	 * @throws java.io.IOException
	 *             if the object count cannot be read.
	 */
	public abstract long getObjectCount() throws IOException;

	
Get the number of delta objects stored in this pack.
 This is an optional method, not every cached pack storage system knows the precise number of deltas stored within the pack. This number must be smaller than getObjectCount() as deltas are not supposed to span across pack files. 

This method must be fast, if the only way to determine delta counts is to
scan the pack file's contents one object at a time, implementors should
return 0 and avoid the high cost of the scan.
Throws:
IOException – 
            if the delta count cannot be read.
Returns:
the number of deltas; 0 if the number is not known or there are
        no deltas./**
	 * Get the number of delta objects stored in this pack.
	 * <p>
	 * This is an optional method, not every cached pack storage system knows
	 * the precise number of deltas stored within the pack. This number must be
	 * smaller than {@link #getObjectCount()} as deltas are not supposed to span
	 * across pack files.
	 * <p>
	 * This method must be fast, if the only way to determine delta counts is to
	 * scan the pack file's contents one object at a time, implementors should
	 * return 0 and avoid the high cost of the scan.
	 *
	 * @return the number of deltas; 0 if the number is not known or there are
	 *         no deltas.
	 * @throws java.io.IOException
	 *             if the delta count cannot be read.
	 */
	public long getDeltaCount() throws IOException {
		return 0;
	}

	
Determine if this pack contains the object representation given.

PackWriter uses this method during the finding sources phase to prune
away any objects from the leading thin-pack that already appear within
this pack and should not be sent twice.
 Implementors are strongly encouraged to rely on looking at rep only and using its internal state to decide if this object is within this pack. Implementors should ensure a representation from this cached pack is tested as part of ObjectReuseAsIs.selectObjectRepresentation(PackWriter, ProgressMonitor, Iterable<ObjectToPack>) , ensuring this method would eventually return true if the object would be included by this cached pack. 
Params:
obj – 
           the object being packed. Can be used as an ObjectId.
rep –  representation from the ObjectReuseAsIs instance that originally supplied this CachedPack.
Returns:
true if this pack contains this object./**
	 * Determine if this pack contains the object representation given.
	 * <p>
	 * PackWriter uses this method during the finding sources phase to prune
	 * away any objects from the leading thin-pack that already appear within
	 * this pack and should not be sent twice.
	 * <p>
	 * Implementors are strongly encouraged to rely on looking at {@code rep}
	 * only and using its internal state to decide if this object is within this
	 * pack. Implementors should ensure a representation from this cached pack
	 * is tested as part of
	 * {@link org.eclipse.jgit.internal.storage.pack.ObjectReuseAsIs#selectObjectRepresentation(PackWriter, org.eclipse.jgit.lib.ProgressMonitor, Iterable)}
	 * , ensuring this method would eventually return true if the object would
	 * be included by this cached pack.
	 *
	 * @param obj
	 *            the object being packed. Can be used as an ObjectId.
	 * @param rep
	 *            representation from the
	 *            {@link org.eclipse.jgit.internal.storage.pack.ObjectReuseAsIs}
	 *            instance that originally supplied this CachedPack.
	 * @return true if this pack contains this object.
	 */
	public abstract boolean hasObject(ObjectToPack obj,
			StoredObjectRepresentation rep);
}