org.eclipse.jgit.storage.pack.CachedPack Maven / Gradle / Ivy
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* 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
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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.
*
* 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 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;
/**
* 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 {@link #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.
*
* @return the number of deltas; 0 if the number is not known or there are
* no deltas.
* @throws 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 {@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 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 ObjectReuseAsIs} instance that
* originally supplied this CachedPack.
* @return true if this pack contains this object.
*/
public abstract boolean hasObject(ObjectToPack obj,
StoredObjectRepresentation rep);
}