PackBitmapIndex.java
/*
* Copyright (C) 2012, 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.internal.storage.file;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.text.MessageFormat;
import org.eclipse.jgit.errors.CorruptObjectException;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.util.io.SilentFileInputStream;
import com.googlecode.javaewah.EWAHCompressedBitmap;
/**
* Logical representation of the bitmap data stored in the pack index.
* {@link org.eclipse.jgit.lib.ObjectId}s are encoded as a single integer in the
* range [0, {@link #getObjectCount()}). Compressed bitmaps are available at
* certain {@code ObjectId}s, which represent all of the objects reachable from
* that {@code ObjectId} (include the {@code ObjectId} itself). The meaning of
* the positions in the bitmaps can be decoded using {@link #getObject(int)} and
* {@link #ofObjectType(EWAHCompressedBitmap, int)}. Furthermore,
* {@link #findPosition(AnyObjectId)} can be used to build other bitmaps that a
* compatible with the encoded bitmaps available from the index.
*/
public abstract class PackBitmapIndex {
/** Flag bit denoting the bitmap should be reused during index creation. */
public static final int FLAG_REUSE = 1;
/**
* Read an existing pack bitmap index file from a buffered stream.
* <p>
* The format of the file will be automatically detected and a proper access
* implementation for that format will be constructed and returned to the
* caller. The file may or may not be held open by the returned instance.
*
* @param idxFile
* existing pack .bitmap to read.
* @param packIndex
* the pack index for the corresponding pack file.
* @param reverseIndex
* the pack reverse index for the corresponding pack file.
* @return a copy of the index in-memory.
* @throws java.io.IOException
* the stream cannot be read.
* @throws CorruptObjectException
* the stream does not contain a valid pack bitmap index.
*/
public static PackBitmapIndex open(
File idxFile, PackIndex packIndex, PackReverseIndex reverseIndex)
throws IOException {
try (SilentFileInputStream fd = new SilentFileInputStream(
idxFile)) {
try {
return read(fd, packIndex, reverseIndex);
} catch (IOException ioe) {
throw new IOException(
MessageFormat.format(JGitText.get().unreadablePackIndex,
idxFile.getAbsolutePath()),
ioe);
}
}
}
/**
* Read an existing pack bitmap index file from a buffered stream.
* <p>
* The format of the file will be automatically detected and a proper access
* implementation for that format will be constructed and returned to the
* caller. The file may or may not be held open by the returned instance.
*
* @param fd
* stream to read the bitmap index file from. The stream must be
* buffered as some small IOs are performed against the stream.
* The caller is responsible for closing the stream.
* @param packIndex
* the pack index for the corresponding pack file.
* @param reverseIndex
* the pack reverse index for the corresponding pack file.
* @return a copy of the index in-memory.
* @throws java.io.IOException
* the stream cannot be read.
* @throws CorruptObjectException
* the stream does not contain a valid pack bitmap index.
*/
public static PackBitmapIndex read(
InputStream fd, PackIndex packIndex, PackReverseIndex reverseIndex)
throws IOException {
return new PackBitmapIndexV1(fd, packIndex, reverseIndex);
}
/** Footer checksum applied on the bottom of the pack file. */
byte[] packChecksum;
/**
* Finds the position in the bitmap of the object.
*
* @param objectId
* the id for which the bitmap position will be found.
* @return the bitmap id or -1 if the object was not found.
*/
public abstract int findPosition(AnyObjectId objectId);
/**
* Get the object at the bitmap position.
*
* @param position
* the id for which the object will be found.
* @return the ObjectId.
* @throws java.lang.IllegalArgumentException
* when the item is not found.
*/
public abstract ObjectId getObject(int position) throws IllegalArgumentException;
/**
* Returns a bitmap containing positions for objects that have the given Git
* type.
*
* @param bitmap
* the object bitmap.
* @param type
* the Git type.
* @return the object bitmap with only objects of the Git type.
*/
public abstract EWAHCompressedBitmap ofObjectType(
EWAHCompressedBitmap bitmap, int type);
/**
* Returns the previously constructed bitmap for the object.
*
* @param objectId
* the id for which the bitmap will be found.
* @return the bitmap or null if the object was not found.
*/
public abstract EWAHCompressedBitmap getBitmap(AnyObjectId objectId);
/**
* Obtain the total number of objects described by this index.
* {@code getObjectCount() - 1} is the largest bit that will be set in a
* bitmap.
*
* @return number of objects in this index, and likewise in the associated
* pack that this index was generated from.
*/
public abstract int getObjectCount();
/**
* Returns the number of bitmaps in this bitmap index.
*
* @return the number of bitmaps in this bitmap index.
*/
public abstract int getBitmapCount();
}