| /* |
| * Copyright (C) 2008, Marek Zawirski <marek.zawirski@gmail.com> 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.file; |
| |
| import java.text.MessageFormat; |
| |
| import org.eclipse.jgit.errors.CorruptObjectException; |
| import org.eclipse.jgit.internal.JGitText; |
| import org.eclipse.jgit.internal.storage.file.PackIndex.MutableEntry; |
| import org.eclipse.jgit.lib.ObjectId; |
| |
| /** |
| * <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 Pack |
| */ |
| public class PackReverseIndex { |
| /** Index we were created from, and that has our ObjectId data. */ |
| private final PackIndex index; |
| |
| /** The number of bytes per entry in the offsetIndex. */ |
| private final long bucketSize; |
| |
| /** |
| * An index into the nth mapping, where the value is the position after the |
| * the last index that contains the values of the bucket. For example given |
| * offset o (and bucket = o / bucketSize), the offset will be contained in |
| * the range nth[offsetIndex[bucket - 1]] inclusive to |
| * nth[offsetIndex[bucket]] exclusive. |
| * |
| * See {@link #binarySearch} |
| */ |
| private final int[] offsetIndex; |
| |
| /** Mapping from indices in offset order to indices in SHA-1 order. */ |
| private final int[] nth; |
| |
| /** |
| * Create reverse index from straight/forward pack index, by indexing all |
| * its entries. |
| * |
| * @param packIndex |
| * forward index - entries to (reverse) index. |
| */ |
| public PackReverseIndex(PackIndex packIndex) { |
| index = packIndex; |
| |
| final long cnt = index.getObjectCount(); |
| if (cnt + 1 > Integer.MAX_VALUE) |
| throw new IllegalArgumentException( |
| JGitText.get().hugeIndexesAreNotSupportedByJgitYet); |
| |
| if (cnt == 0) { |
| bucketSize = Long.MAX_VALUE; |
| offsetIndex = new int[1]; |
| nth = new int[0]; |
| return; |
| } |
| |
| final long[] offsetsBySha1 = new long[(int) cnt]; |
| |
| long maxOffset = 0; |
| int ith = 0; |
| for (MutableEntry me : index) { |
| final long o = me.getOffset(); |
| offsetsBySha1[ith++] = o; |
| if (o > maxOffset) |
| maxOffset = o; |
| } |
| |
| bucketSize = maxOffset / cnt + 1; |
| int[] bucketIndex = new int[(int) cnt]; |
| int[] bucketValues = new int[(int) cnt + 1]; |
| for (int oi = 0; oi < offsetsBySha1.length; oi++) { |
| final long o = offsetsBySha1[oi]; |
| final int bucket = (int) (o / bucketSize); |
| final int bucketValuesPos = oi + 1; |
| final int current = bucketIndex[bucket]; |
| bucketIndex[bucket] = bucketValuesPos; |
| bucketValues[bucketValuesPos] = current; |
| } |
| |
| int nthByOffset = 0; |
| nth = new int[offsetsBySha1.length]; |
| offsetIndex = bucketIndex; // Reuse the allocation |
| for (int bi = 0; bi < bucketIndex.length; bi++) { |
| final int start = nthByOffset; |
| // Insertion sort of the values in the bucket. |
| for (int vi = bucketIndex[bi]; vi > 0; vi = bucketValues[vi]) { |
| final int nthBySha1 = vi - 1; |
| final long o = offsetsBySha1[nthBySha1]; |
| int insertion = nthByOffset++; |
| for (; start < insertion; insertion--) { |
| if (o > offsetsBySha1[nth[insertion - 1]]) |
| break; |
| nth[insertion] = nth[insertion - 1]; |
| } |
| nth[insertion] = nthBySha1; |
| } |
| offsetIndex[bi] = nthByOffset; |
| } |
| } |
| |
| /** |
| * 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. |
| */ |
| public ObjectId findObject(long offset) { |
| final int ith = binarySearch(offset); |
| if (ith < 0) |
| return null; |
| return index.getObjectId(nth[ith]); |
| } |
| |
| /** |
| * 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 org.eclipse.jgit.errors.CorruptObjectException |
| * when there is no object with the provided offset. |
| */ |
| public long findNextOffset(long offset, long maxOffset) |
| throws CorruptObjectException { |
| final int ith = binarySearch(offset); |
| if (ith < 0) |
| throw new CorruptObjectException( |
| MessageFormat.format( |
| JGitText.get().cantFindObjectInReversePackIndexForTheSpecifiedOffset, |
| Long.valueOf(offset))); |
| |
| if (ith + 1 == nth.length) |
| return maxOffset; |
| return index.getOffset(nth[ith + 1]); |
| } |
| |
| int findPostion(long offset) { |
| return binarySearch(offset); |
| } |
| |
| private int binarySearch(long offset) { |
| int bucket = (int) (offset / bucketSize); |
| int low = bucket == 0 ? 0 : offsetIndex[bucket - 1]; |
| int high = offsetIndex[bucket]; |
| while (low < high) { |
| final int mid = (low + high) >>> 1; |
| final long o = index.getOffset(nth[mid]); |
| if (offset < o) |
| high = mid; |
| else if (offset == o) |
| return mid; |
| else |
| low = mid + 1; |
| } |
| return -1; |
| } |
| |
| ObjectId findObjectByPosition(int nthPosition) { |
| return index.getObjectId(nth[nthPosition]); |
| } |
| } |