| /* |
| * Copyright (C) 2010, 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.internal.storage.file; |
| |
| import java.util.concurrent.atomic.AtomicReferenceArray; |
| |
| import org.eclipse.jgit.lib.AnyObjectId; |
| import org.eclipse.jgit.lib.ObjectId; |
| |
| /** Remembers objects that are currently unpacked. */ |
| class UnpackedObjectCache { |
| private static final int INITIAL_BITS = 5; // size = 32 |
| |
| private static final int MAX_BITS = 11; // size = 2048 |
| |
| private volatile Table table; |
| |
| UnpackedObjectCache() { |
| table = new Table(INITIAL_BITS); |
| } |
| |
| boolean isUnpacked(AnyObjectId objectId) { |
| return table.contains(objectId); |
| } |
| |
| void add(AnyObjectId objectId) { |
| Table t = table; |
| if (t.add(objectId)) { |
| // The object either already exists in the table, or was |
| // successfully added. Either way leave the table alone. |
| // |
| } else { |
| // The object won't fit into the table. Implement a crude |
| // cache removal by just dropping the table away, but double |
| // it in size for the next incarnation. |
| // |
| Table n = new Table(Math.min(t.bits + 1, MAX_BITS)); |
| n.add(objectId); |
| table = n; |
| } |
| } |
| |
| void remove(AnyObjectId objectId) { |
| if (isUnpacked(objectId)) |
| clear(); |
| } |
| |
| void clear() { |
| table = new Table(INITIAL_BITS); |
| } |
| |
| private static class Table { |
| private static final int MAX_CHAIN = 8; |
| |
| private final AtomicReferenceArray<ObjectId> ids; |
| |
| private final int shift; |
| |
| final int bits; |
| |
| Table(int bits) { |
| this.ids = new AtomicReferenceArray<>(1 << bits); |
| this.shift = 32 - bits; |
| this.bits = bits; |
| } |
| |
| boolean contains(AnyObjectId toFind) { |
| int i = index(toFind); |
| for (int n = 0; n < MAX_CHAIN; n++) { |
| ObjectId obj = ids.get(i); |
| if (obj == null) |
| break; |
| |
| if (AnyObjectId.equals(obj, toFind)) |
| return true; |
| |
| if (++i == ids.length()) |
| i = 0; |
| } |
| return false; |
| } |
| |
| boolean add(AnyObjectId toAdd) { |
| int i = index(toAdd); |
| for (int n = 0; n < MAX_CHAIN;) { |
| ObjectId obj = ids.get(i); |
| if (obj == null) { |
| if (ids.compareAndSet(i, null, toAdd.copy())) |
| return true; |
| else |
| continue; |
| } |
| |
| if (AnyObjectId.equals(obj, toAdd)) |
| return true; |
| |
| if (++i == ids.length()) |
| i = 0; |
| n++; |
| } |
| return false; |
| } |
| |
| private int index(AnyObjectId id) { |
| return id.hashCode() >>> shift; |
| } |
| } |
| } |