| /* |
| * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org> 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.lang.ref.SoftReference; |
| |
| import org.eclipse.jgit.storage.file.WindowCacheConfig; |
| |
| class DeltaBaseCache { |
| private static final int CACHE_SZ = 1024; |
| |
| static final SoftReference<Entry> DEAD; |
| |
| private static int hash(long position) { |
| return (((int) position) << 22) >>> 22; |
| } |
| |
| private static volatile int defaultMaxByteCount; |
| |
| private final int maxByteCount; |
| |
| private final Slot[] cache; |
| |
| private Slot lruHead; |
| |
| private Slot lruTail; |
| |
| private int openByteCount; |
| |
| static { |
| DEAD = new SoftReference<>(null); |
| reconfigure(new WindowCacheConfig()); |
| } |
| |
| static void reconfigure(WindowCacheConfig cfg) { |
| defaultMaxByteCount = cfg.getDeltaBaseCacheLimit(); |
| } |
| |
| DeltaBaseCache() { |
| maxByteCount = defaultMaxByteCount; |
| cache = new Slot[CACHE_SZ]; |
| } |
| |
| Entry get(PackFile pack, long position) { |
| Slot e = cache[hash(position)]; |
| if (e == null) |
| return null; |
| if (e.provider == pack && e.position == position) { |
| final Entry buf = e.data.get(); |
| if (buf != null) { |
| moveToHead(e); |
| return buf; |
| } |
| } |
| return null; |
| } |
| |
| void store(final PackFile pack, final long position, |
| final byte[] data, final int objectType) { |
| if (data.length > maxByteCount) |
| return; // Too large to cache. |
| |
| Slot e = cache[hash(position)]; |
| if (e == null) { |
| e = new Slot(); |
| cache[hash(position)] = e; |
| } else { |
| clearEntry(e); |
| } |
| |
| openByteCount += data.length; |
| releaseMemory(); |
| |
| e.provider = pack; |
| e.position = position; |
| e.sz = data.length; |
| e.data = new SoftReference<>(new Entry(data, objectType)); |
| moveToHead(e); |
| } |
| |
| private 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; |
| } |
| } |
| |
| private void moveToHead(Slot e) { |
| unlink(e); |
| e.lruPrev = null; |
| e.lruNext = lruHead; |
| if (lruHead != null) |
| lruHead.lruPrev = e; |
| else |
| lruTail = e; |
| lruHead = e; |
| } |
| |
| private void unlink(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 void clearEntry(Slot e) { |
| openByteCount -= e.sz; |
| e.provider = null; |
| e.data = DEAD; |
| e.sz = 0; |
| } |
| |
| static class Entry { |
| final byte[] data; |
| |
| final int type; |
| |
| Entry(byte[] aData, int aType) { |
| data = aData; |
| type = aType; |
| } |
| } |
| |
| private static class Slot { |
| Slot lruPrev; |
| |
| Slot lruNext; |
| |
| PackFile provider; |
| |
| long position; |
| |
| int sz; |
| |
| SoftReference<Entry> data = DEAD; |
| } |
| } |