123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175 |
- /*
- * 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;
- }
- }
- }
|