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Neo4j kernel is a lightweight, embedded Java database designed to
store data structured as graphs rather than tables. For more
information, see http://neo4j.org.
/*
* Copyright (c) "Neo4j"
* Neo4j Sweden AB [https://neo4j.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see element type
*/
public class EagerBuffer extends DefaultCloseListenable {
public static final IntUnaryOperator KEEP_CONSTANT_CHUNK_SIZE = size -> size;
public static final IntUnaryOperator GROW_NEW_CHUNKS_BY_50_PCT = size -> size + (size >> 1);
public static final IntUnaryOperator GROW_NEW_CHUNKS_BY_100_PCT = size -> size << 1;
private static final long SHALLOW_SIZE = shallowSizeOfInstance(EagerBuffer.class);
private final MemoryTracker scopedMemoryTracker;
private final IntUnaryOperator growthStrategy;
private final ChunkMemoryEstimator memoryEstimator;
private EagerBuffer.Chunk first;
private EagerBuffer.Chunk current;
private long size;
private final int maxChunkSize;
public static EagerBuffer createEagerBuffer(MemoryTracker memoryTracker) {
return createEagerBuffer(
memoryTracker, 1024, ArrayUtil.MAX_ARRAY_SIZE, GROW_NEW_CHUNKS_BY_50_PCT); // Grow by 50%
}
public static EagerBuffer createEagerBuffer(
MemoryTracker memoryTracker, int initialChunkSize) {
return createEagerBuffer(
memoryTracker, initialChunkSize, ArrayUtil.MAX_ARRAY_SIZE, GROW_NEW_CHUNKS_BY_50_PCT); // Grow by 50%
}
public static EagerBuffer createEagerBuffer(
MemoryTracker memoryTracker, int initialChunkSize, int maxChunkSize, IntUnaryOperator growthStrategy) {
return createEagerBuffer(
memoryTracker, initialChunkSize, maxChunkSize, growthStrategy, ChunkMemoryEstimator.createDefault());
}
public static EagerBuffer createEagerBuffer(
MemoryTracker memoryTracker,
int initialChunkSize,
int maxChunkSize,
IntUnaryOperator growthStrategy,
ChunkMemoryEstimator memoryEstimator) {
MemoryTracker scopedMemoryTracker = memoryTracker.getScopedMemoryTracker();
scopedMemoryTracker.allocateHeap(SHALLOW_SIZE
+ SCOPED_MEMORY_TRACKER_SHALLOW_SIZE
+ shallowSizeOfInstance(IntUnaryOperator.class)
+ shallowSizeOfInstance(ChunkMemoryEstimator.class));
return new EagerBuffer<>(scopedMemoryTracker, initialChunkSize, maxChunkSize, growthStrategy, memoryEstimator);
}
private EagerBuffer(
MemoryTracker scopedMemoryTracker,
int initialChunkSize,
int maxChunkSize,
IntUnaryOperator growthStrategy,
ChunkMemoryEstimator memoryEstimator) {
this.scopedMemoryTracker = scopedMemoryTracker;
this.maxChunkSize = maxChunkSize;
this.growthStrategy = growthStrategy;
this.memoryEstimator = memoryEstimator;
first = new EagerBuffer.Chunk<>(
initialChunkSize, scopedMemoryTracker.getScopedMemoryTracker(), memoryEstimator);
current = first;
}
public void add(T element) {
if (!current.add(element)) {
int newChunkSize = grow(current.elements.length);
EagerBuffer.Chunk newChunk = new EagerBuffer.Chunk<>(
newChunkSize, scopedMemoryTracker.getScopedMemoryTracker(), memoryEstimator);
current.next = newChunk;
current = newChunk;
current.add(element);
}
size++;
}
public long size() {
return size;
}
/**
* Non-closing iterator.
*/
public Iterator iterator() {
return new EagerBufferIterator(false);
}
public Iterator autoClosingIterator() {
return new EagerBufferIterator(true);
}
@Override
public void closeInternal() {
first = null;
current = null;
scopedMemoryTracker.close();
}
@Override
public boolean isClosed() {
return false;
}
@VisibleForTesting
public int numberOfChunks() {
int i = 0;
var chunk = first;
while (chunk != null) {
chunk = chunk.next;
i++;
}
return i;
}
private int grow(int size) {
if (size == maxChunkSize) {
return size;
}
int newSize = growthStrategy.applyAsInt(size);
if (newSize <= 0 || newSize > maxChunkSize) // Check overflow
{
return maxChunkSize;
}
return newSize;
}
private class EagerBufferIterator implements Iterator {
private final boolean autoClosing;
private EagerBuffer.Chunk chunk;
private int index;
EagerBufferIterator(boolean autoClosing) {
this.autoClosing = autoClosing;
chunk = first;
if (autoClosing) {
EagerBuffer.this.first = null;
EagerBuffer.this.current = null;
}
}
@Override
public boolean hasNext() {
if (chunk == null || index >= chunk.cursor) {
if (autoClosing) {
EagerBuffer.this.close();
}
return false;
}
return true;
}
@SuppressWarnings("unchecked")
@Override
public T next() {
Object element = chunk.elements[index++];
if (index >= chunk.cursor) {
var chunkToRelease = chunk;
chunk = chunk.next;
index = 0;
if (autoClosing) {
chunkToRelease.close();
}
}
return (T) element;
}
}
public interface ChunkMemoryEstimator {
long estimateHeapUsage(T element, T previous);
static ChunkMemoryEstimator createDefault() {
return (element, previous) -> element.estimatedHeapUsage();
}
}
private static class Chunk {
private static final long SHALLOW_SIZE = shallowSizeOfInstance(EagerBuffer.Chunk.class);
private final Object[] elements;
private final ChunkMemoryEstimator memoryEstimator;
private final MemoryTracker memoryTracker;
private EagerBuffer.Chunk next;
private int cursor;
Chunk(int size, MemoryTracker memoryTracker, ChunkMemoryEstimator memoryEstimator) {
memoryTracker.allocateHeap(
SHALLOW_SIZE + SCOPED_MEMORY_TRACKER_SHALLOW_SIZE + shallowSizeOfObjectArray(size));
elements = new Object[size];
this.memoryTracker = memoryTracker;
this.memoryEstimator = memoryEstimator;
}
boolean add(T element) {
if (cursor < elements.length) {
@SuppressWarnings("unchecked")
final var previous = cursor == 0 ? null : (T) elements[cursor - 1];
memoryTracker.allocateHeap(memoryEstimator.estimateHeapUsage(element, previous));
elements[cursor++] = element;
return true;
}
return false;
}
void close() {
memoryTracker.close();
}
}
}