/*
* Copyright 2009 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.gradle.cache.internal.btree;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class FreeListBlockStore implements BlockStore {
private final BlockStore store;
private final BlockStore freeListStore;
private final int maxBlockEntries;
private FreeListBlock freeListBlock;
public FreeListBlockStore(BlockStore store, int maxBlockEntries) {
this.store = store;
freeListStore = this;
this.maxBlockEntries = maxBlockEntries;
}
public void open(final Runnable initAction, final Factory factory) {
Runnable freeListInitAction = new Runnable() {
public void run() {
freeListBlock = new FreeListBlock();
store.write(freeListBlock);
store.flush();
initAction.run();
}
};
Factory freeListFactory = new Factory() {
public Object create(Class<? extends BlockPayload> type) {
if (type == FreeListBlock.class) {
return new FreeListBlock();
}
return factory.create(type);
}
};
store.open(freeListInitAction, freeListFactory);
freeListBlock = store.readFirst(FreeListBlock.class);
}
public void close() {
freeListBlock = null;
store.close();
}
public void clear() {
store.clear();
}
public void remove(BlockPayload block) {
Block container = block.getBlock();
store.remove(block);
freeListBlock.add(container.getPos(), container.getSize());
}
public <T extends BlockPayload> T readFirst(Class<T> payloadType) {
return store.read(freeListBlock.getNextPos(), payloadType);
}
public <T extends BlockPayload> T read(BlockPointer pos, Class<T> payloadType) {
return store.read(pos, payloadType);
}
public void write(BlockPayload block) {
attach(block);
store.write(block);
}
public void attach(BlockPayload block) {
store.attach(block);
freeListBlock.alloc(block.getBlock());
}
public void flush() {
store.flush();
}
private void verify() {
FreeListBlock block = store.readFirst(FreeListBlock.class);
verify(block, Integer.MAX_VALUE);
}
private void verify(FreeListBlock block, int maxValue) {
if (block.largestInNextBlock > maxValue) {
throw new RuntimeException("corrupt free list");
}
int current = 0;
for (FreeListEntry entry : block.entries) {
if (entry.size > maxValue) {
throw new RuntimeException("corrupt free list");
}
if (entry.size < block.largestInNextBlock) {
throw new RuntimeException("corrupt free list");
}
if (entry.size < current) {
throw new RuntimeException("corrupt free list");
}
current = entry.size;
}
if (!block.nextBlock.isNull()) {
verify(store.read(block.nextBlock, FreeListBlock.class), block.largestInNextBlock);
}
}
public class FreeListBlock extends BlockPayload {
private List<FreeListEntry> entries = new ArrayList<FreeListEntry>();
private int largestInNextBlock;
private BlockPointer nextBlock = BlockPointer.start();
// Transient fields
private FreeListBlock prev;
private FreeListBlock next;
@Override
protected int getSize() {
return Block.LONG_SIZE + Block.INT_SIZE + Block.INT_SIZE + maxBlockEntries * (Block.LONG_SIZE
+ Block.INT_SIZE);
}
@Override
protected byte getType() {
return 0x44;
}
@Override
protected void read(DataInputStream inputStream) throws Exception {
nextBlock = BlockPointer.pos(inputStream.readLong());
largestInNextBlock = inputStream.readInt();
int count = inputStream.readInt();
for (int i = 0; i < count; i++) {
BlockPointer pos = BlockPointer.pos(inputStream.readLong());
int size = inputStream.readInt();
entries.add(new FreeListEntry(pos, size));
}
}
@Override
protected void write(DataOutputStream outputStream) throws Exception {
outputStream.writeLong(nextBlock.getPos());
outputStream.writeInt(largestInNextBlock);
outputStream.writeInt(entries.size());
for (FreeListEntry entry : entries) {
outputStream.writeLong(entry.pos.getPos());
outputStream.writeInt(entry.size);
}
}
public void add(BlockPointer pos, int size) {
assert !pos.isNull() && size >= 0;
if (size == 0) {
return;
}
if (size < largestInNextBlock) {
FreeListBlock next = getNextBlock();
next.add(pos, size);
return;
}
FreeListEntry entry = new FreeListEntry(pos, size);
int index = Collections.binarySearch(entries, entry);
if (index < 0) {
index = -index - 1;
}
entries.add(index, entry);
if (entries.size() > maxBlockEntries) {
FreeListBlock newBlock = new FreeListBlock();
newBlock.largestInNextBlock = largestInNextBlock;
newBlock.nextBlock = nextBlock;
newBlock.prev = this;
newBlock.next = next;
next = newBlock;
List<FreeListEntry> newBlockEntries = entries.subList(0, entries.size() / 2);
newBlock.entries.addAll(newBlockEntries);
newBlockEntries.clear();
largestInNextBlock = newBlock.entries.get(newBlock.entries.size() - 1).size;
freeListStore.write(newBlock);
nextBlock = newBlock.getPos();
}
freeListStore.write(this);
}
private FreeListBlock getNextBlock() {
if (next == null) {
next = freeListStore.read(nextBlock, FreeListBlock.class);
next.prev = this;
}
return next;
}
public void alloc(Block block) {
if (block.hasPos()) {
return;
}
int requiredSize = block.getSize();
if (entries.isEmpty() || requiredSize <= largestInNextBlock) {
if (nextBlock.isNull()) {
return;
}
getNextBlock().alloc(block);
return;
}
int index = Collections.binarySearch(entries, new FreeListEntry(null, requiredSize));
if (index < 0) {
index = -index - 1;
}
if (index == entries.size()) {
// Largest free block is too small
return;
}
FreeListEntry entry = entries.remove(index);
block.setPos(entry.pos);
block.setSize(entry.size);
freeListStore.write(this);
if (entries.size() == 0 && prev != null) {
prev.nextBlock = nextBlock;
prev.largestInNextBlock = largestInNextBlock;
prev.next = next;
if (next != null) {
next.prev = prev;
}
freeListStore.write(prev);
freeListStore.remove(this);
}
}
}
private static class FreeListEntry implements Comparable<FreeListEntry> {
final BlockPointer pos;
final int size;
private FreeListEntry(BlockPointer pos, int size) {
this.pos = pos;
this.size = size;
}
public int compareTo(FreeListEntry o) {
if (size > o.size) {
return 1;
}
if (size < o.size) {
return -1;
}
return 0;
}
}
}