| /* |
| * 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; |
| } |
| } |
| } |