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/*
* Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
* 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.lang.ref.SoftReference;
class UnpackedObjectCache {
private static final int CACHE_SZ = 1024;
private static final SoftReference<Entry> DEAD;
private static int hash(final long position) {
return (((int) position) << 22) >>> 22;
}
private static int maxByteCount;
private static final Slot[] cache;
private static Slot lruHead;
private static Slot lruTail;
private static int openByteCount;
static {
DEAD = new SoftReference<Entry>(null);
maxByteCount = new WindowCacheConfig().getDeltaBaseCacheLimit();
cache = new Slot[CACHE_SZ];
for (int i = 0; i < CACHE_SZ; i++)
cache[i] = new Slot();
}
static synchronized void reconfigure(final WindowCacheConfig cfg) {
final int dbLimit = cfg.getDeltaBaseCacheLimit();
if (maxByteCount != dbLimit) {
maxByteCount = dbLimit;
releaseMemory();
}
}
static synchronized Entry get(final PackFile pack, final long position) {
final Slot e = cache[hash(position)];
if (e.provider == pack && e.position == position) {
final Entry buf = e.data.get();
if (buf != null) {
moveToHead(e);
return buf;
}
}
return null;
}
static synchronized void store(final PackFile pack, final long position,
final byte[] data, final int objectType) {
if (data.length > maxByteCount)
return; // Too large to cache.
final Slot e = cache[hash(position)];
clearEntry(e);
openByteCount += data.length;
releaseMemory();
e.provider = pack;
e.position = position;
e.sz = data.length;
e.data = new SoftReference<Entry>(new Entry(data, objectType));
moveToHead(e);
}
private static void releaseMemory() {
while (openByteCount > maxByteCount && lruTail != null) {
final Slot currOldest = lruTail;
final Slot nextOldest = currOldest.lruPrev;
clearEntry(currOldest);
currOldest.lruPrev = null;
currOldest.lruNext = null;
if (nextOldest == null)
lruHead = null;
else
nextOldest.lruNext = null;
lruTail = nextOldest;
}
}
static synchronized void purge(final PackFile file) {
for (final Slot e : cache) {
if (e.provider == file) {
clearEntry(e);
unlink(e);
}
}
}
private static 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 static void unlink(final Slot e) {
final Slot prev = e.lruPrev;
final Slot next = e.lruNext;
if (prev != null)
prev.lruNext = next;
if (next != null)
next.lruPrev = prev;
}
private static void clearEntry(final Slot e) {
openByteCount -= e.sz;
e.provider = null;
e.data = DEAD;
e.sz = 0;
}
private UnpackedObjectCache() {
throw new UnsupportedOperationException();
}
static class Entry {
final byte[] data;
final int type;
Entry(final byte[] aData, final int aType) {
data = aData;
type = aType;
}
}
private static class Slot {
Slot lruPrev;
Slot lruNext;
PackFile provider;
long position;
int sz;
SoftReference<Entry> data = DEAD;
}
}
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