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/*
* Copyright (C) 2008, Marek Zawirski <marek.zawirski@gmail.com>
* 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.
*
* - 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
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.eclipse.jgit.lib;
import java.util.Arrays;
import org.eclipse.jgit.errors.CorruptObjectException;
import org.eclipse.jgit.lib.PackIndex.MutableEntry;
/**
* <p>
* Reverse index for forward pack index. Provides operations based on offset
* instead of object id. Such offset-based reverse lookups are performed in
* O(log n) time.
* </p>
*
* @see PackIndex
* @see PackFile
*/
class PackReverseIndex {
/** Index we were created from, and that has our ObjectId data. */
private final PackIndex index;
/**
* (offset31, truly) Offsets accommodating in 31 bits.
*/
private final int offsets32[];
/**
* Offsets not accommodating in 31 bits.
*/
private final long offsets64[];
/** Position of the corresponding {@link #offsets32} in {@link #index}. */
private final int nth32[];
/** Position of the corresponding {@link #offsets64} in {@link #index}. */
private final int nth64[];
/**
* Create reverse index from straight/forward pack index, by indexing all
* its entries.
*
* @param packIndex
* forward index - entries to (reverse) index.
*/
PackReverseIndex(final PackIndex packIndex) {
index = packIndex;
final long cnt = index.getObjectCount();
final long n64 = index.getOffset64Count();
final long n32 = cnt - n64;
if (n32 > Integer.MAX_VALUE || n64 > Integer.MAX_VALUE
|| cnt > 0xffffffffL)
throw new IllegalArgumentException(
"Huge indexes are not supported by jgit, yet");
offsets32 = new int[(int) n32];
offsets64 = new long[(int) n64];
nth32 = new int[offsets32.length];
nth64 = new int[offsets64.length];
int i32 = 0;
int i64 = 0;
for (final MutableEntry me : index) {
final long o = me.getOffset();
if (o < Integer.MAX_VALUE)
offsets32[i32++] = (int) o;
else
offsets64[i64++] = o;
}
Arrays.sort(offsets32);
Arrays.sort(offsets64);
int nth = 0;
for (final MutableEntry me : index) {
final long o = me.getOffset();
if (o < Integer.MAX_VALUE)
nth32[Arrays.binarySearch(offsets32, (int) o)] = nth++;
else
nth64[Arrays.binarySearch(offsets64, o)] = nth++;
}
}
/**
* Search for object id with the specified start offset in this pack
* (reverse) index.
*
* @param offset
* start offset of object to find.
* @return object id for this offset, or null if no object was found.
*/
ObjectId findObject(final long offset) {
if (offset <= Integer.MAX_VALUE) {
final int i32 = Arrays.binarySearch(offsets32, (int) offset);
if (i32 < 0)
return null;
return index.getObjectId(nth32[i32]);
} else {
final int i64 = Arrays.binarySearch(offsets64, offset);
if (i64 < 0)
return null;
return index.getObjectId(nth64[i64]);
}
}
/**
* Search for the next offset to the specified offset in this pack (reverse)
* index.
*
* @param offset
* start offset of previous object (must be valid-existing
* offset).
* @param maxOffset
* maximum offset in a pack (returned when there is no next
* offset).
* @return offset of the next object in a pack or maxOffset if provided
* offset was the last one.
* @throws CorruptObjectException
* when there is no object with the provided offset.
*/
long findNextOffset(final long offset, final long maxOffset)
throws CorruptObjectException {
if (offset <= Integer.MAX_VALUE) {
final int i32 = Arrays.binarySearch(offsets32, (int) offset);
if (i32 < 0)
throw new CorruptObjectException(
"Can't find object in (reverse) pack index for the specified offset "
+ offset);
if (i32 + 1 == offsets32.length) {
if (offsets64.length > 0)
return offsets64[0];
return maxOffset;
}
return offsets32[i32 + 1];
} else {
final int i64 = Arrays.binarySearch(offsets64, offset);
if (i64 < 0)
throw new CorruptObjectException(
"Can't find object in (reverse) pack index for the specified offset "
+ offset);
if (i64 + 1 == offsets64.length)
return maxOffset;
return offsets64[i64 + 1];
}
}
}
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