| /* |
| * Copyright (C) 2011, Google Inc. 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.dfs; |
| |
| |
| /** |
| * Caches recently used objects for {@link DfsReader}. |
| * <p> |
| * This cache is not thread-safe. Each reader should have its own cache. |
| */ |
| final class DeltaBaseCache { |
| private static final int TABLE_BITS = 10; |
| |
| private static final int MASK_BITS = 32 - TABLE_BITS; |
| |
| private static int hash(long position) { |
| return (((int) position) << MASK_BITS) >>> MASK_BITS; |
| } |
| |
| private int maxByteCount; |
| private int curByteCount; |
| |
| private final Entry[] table; |
| |
| private Entry lruHead; |
| private Entry lruTail; |
| |
| DeltaBaseCache(DfsReader reader) { |
| this(reader.getOptions().getDeltaBaseCacheLimit()); |
| } |
| |
| DeltaBaseCache(int maxBytes) { |
| maxByteCount = maxBytes; |
| table = new Entry[1 << TABLE_BITS]; |
| } |
| |
| Entry get(DfsStreamKey key, long position) { |
| Entry e = table[hash(position)]; |
| for (; e != null; e = e.tableNext) { |
| if (e.offset == position && key.equals(e.pack)) { |
| moveToHead(e); |
| return e; |
| } |
| } |
| return null; |
| } |
| |
| void put(DfsStreamKey key, long offset, int objectType, byte[] data) { |
| if (data.length > maxByteCount) |
| return; // Too large to cache. |
| |
| curByteCount += data.length; |
| releaseMemory(); |
| |
| int tableIdx = hash(offset); |
| Entry e = new Entry(key, offset, objectType, data); |
| e.tableNext = table[tableIdx]; |
| table[tableIdx] = e; |
| lruPushHead(e); |
| } |
| |
| private void releaseMemory() { |
| while (curByteCount > maxByteCount && lruTail != null) { |
| Entry e = lruTail; |
| curByteCount -= e.data.length; |
| lruRemove(e); |
| removeFromTable(e); |
| } |
| } |
| |
| private void removeFromTable(Entry e) { |
| int tableIdx = hash(e.offset); |
| Entry 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; |
| } |
| } |
| |
| throw new IllegalStateException(String.format( |
| "entry for %s:%d not in table", //$NON-NLS-1$ |
| e.pack, Long.valueOf(e.offset))); |
| } |
| |
| private void moveToHead(Entry e) { |
| if (e != lruHead) { |
| lruRemove(e); |
| lruPushHead(e); |
| } |
| } |
| |
| private void lruRemove(Entry e) { |
| Entry p = e.lruPrev; |
| Entry n = e.lruNext; |
| |
| if (p != null) { |
| p.lruNext = n; |
| } else { |
| lruHead = n; |
| } |
| |
| if (n != null) { |
| n.lruPrev = p; |
| } else { |
| lruTail = p; |
| } |
| } |
| |
| private void lruPushHead(Entry e) { |
| Entry n = lruHead; |
| e.lruNext = n; |
| if (n != null) |
| n.lruPrev = e; |
| else |
| lruTail = e; |
| |
| e.lruPrev = null; |
| lruHead = e; |
| } |
| |
| int getMemoryUsed() { |
| return curByteCount; |
| } |
| |
| int getMemoryUsedByLruChainForTest() { |
| int r = 0; |
| for (Entry e = lruHead; e != null; e = e.lruNext) { |
| r += e.data.length; |
| } |
| return r; |
| } |
| |
| int getMemoryUsedByTableForTest() { |
| int r = 0; |
| for (Entry t : table) { |
| for (Entry e = t; e != null; e = e.tableNext) { |
| r += e.data.length; |
| } |
| } |
| return r; |
| } |
| |
| static class Entry { |
| final DfsStreamKey pack; |
| final long offset; |
| final int type; |
| final byte[] data; |
| |
| Entry tableNext; |
| Entry lruPrev; |
| Entry lruNext; |
| |
| Entry(DfsStreamKey key, long offset, int type, byte[] data) { |
| this.pack = key; |
| this.offset = offset; |
| this.type = type; |
| this.data = data; |
| } |
| } |
| } |