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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
- *
- * 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.storage.dht;
-
- import java.lang.ref.SoftReference;
-
- /**
- * Caches recently used objects for {@link DhtReader}.
- * <p>
- * This cache is not thread-safe. Each reader should have its own cache.
- */
- final class DeltaBaseCache {
- private final DhtReader.Statistics stats;
-
- private int maxByteCount;
-
- private final Slot[] table;
-
- private Slot lruHead;
-
- private Slot lruTail;
-
- private int curByteCount;
-
- DeltaBaseCache(DhtReader reader) {
- stats = reader.getStatistics();
-
- DhtReaderOptions options = reader.getOptions();
- maxByteCount = options.getDeltaBaseCacheLimit();
- table = new Slot[options.getDeltaBaseCacheSize()];
- }
-
- Entry get(ChunkKey key, int position) {
- Slot e = table[hash(key, position)];
- for (; e != null; e = e.tableNext) {
- if (e.offset == position && key.equals(e.chunkKey)) {
- Entry buf = e.data.get();
- if (buf != null) {
- moveToHead(e);
- stats.deltaBaseCache_Hits++;
- return buf;
- }
- }
- }
- stats.deltaBaseCache_Miss++;
- return null;
- }
-
- void put(ChunkKey key, int offset, int objectType, byte[] data) {
- if (data.length > maxByteCount)
- return; // Too large to cache.
-
- curByteCount += data.length;
- releaseMemory();
-
- int tableIdx = hash(key, offset);
- Slot e = new Slot(key, offset, data.length);
- e.data = new SoftReference<Entry>(new Entry(data, objectType));
- e.tableNext = table[tableIdx];
- table[tableIdx] = e;
- moveToHead(e);
- }
-
- private void releaseMemory() {
- while (curByteCount > maxByteCount && lruTail != null) {
- Slot currOldest = lruTail;
- Slot nextOldest = currOldest.lruPrev;
-
- curByteCount -= currOldest.size;
- unlink(currOldest);
- removeFromTable(currOldest);
-
- if (nextOldest == null)
- lruHead = null;
- else
- nextOldest.lruNext = null;
- lruTail = nextOldest;
- }
- }
-
- private void removeFromTable(Slot e) {
- int tableIdx = hash(e.chunkKey, e.offset);
- Slot p = table[tableIdx];
-
- if (p == e) {
- table[tableIdx] = e.tableNext;
- return;
- }
-
- for (; p != null; p = p.tableNext) {
- if (p.tableNext == e) {
- p.tableNext = e.tableNext;
- return;
- }
- }
- }
-
- private void moveToHead(final Slot e) {
- unlink(e);
- e.lruPrev = null;
- e.lruNext = lruHead;
- if (lruHead != null)
- lruHead.lruPrev = e;
- else
- lruTail = e;
- lruHead = e;
- }
-
- private void unlink(final Slot e) {
- Slot prev = e.lruPrev;
- Slot next = e.lruNext;
-
- if (prev != null)
- prev.lruNext = next;
- if (next != null)
- next.lruPrev = prev;
- }
-
- private int hash(ChunkKey key, int position) {
- return (((key.hashCode() & 0xfffff000) + position) >>> 1) % table.length;
- }
-
- static class Entry {
- final byte[] data;
-
- final int type;
-
- Entry(final byte[] aData, final int aType) {
- data = aData;
- type = aType;
- }
- }
-
- private static class Slot {
- final ChunkKey chunkKey;
-
- final int offset;
-
- final int size;
-
- Slot tableNext;
-
- Slot lruPrev;
-
- Slot lruNext;
-
- SoftReference<Entry> data;
-
- Slot(ChunkKey key, int offset, int size) {
- this.chunkKey = key;
- this.offset = offset;
- this.size = size;
- }
- }
- }
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