| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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.apache.jackrabbit.oak.index.indexer.document.flatfile; |
| |
| import com.google.common.base.Preconditions; |
| import org.apache.jackrabbit.oak.index.indexer.document.NodeStateEntry; |
| import org.jetbrains.annotations.NotNull; |
| |
| import java.util.Iterator; |
| import static org.apache.jackrabbit.oak.index.indexer.document.flatfile.FlatFileBufferLinkedList.NodeIterator.iteratorFor; |
| |
| /** |
| * Linked list implementation which supports multiple iterators. The iterator's state |
| * is backed by an actual node in the list. So, modification in the list show up in |
| * iterator (assuming thread safely/volatility) getting handled outside of the class. |
| */ |
| public class FlatFileBufferLinkedList { |
| |
| private ListNode head = new ListNode(); |
| private ListNode tail = head; |
| |
| private int size = 0; |
| private long memUsage = 0; |
| private final long memLimit; |
| |
| FlatFileBufferLinkedList() { |
| this(Long.MAX_VALUE); |
| } |
| |
| FlatFileBufferLinkedList(long memLimit) { |
| this.memLimit = memLimit; |
| } |
| |
| /** |
| * Add {@code item} at the tail of the list |
| */ |
| public void add(@NotNull NodeStateEntry item) { |
| Preconditions.checkArgument(item != null, "Can't add null to the list"); |
| long incomingSize = item.estimatedMemUsage(); |
| long memUsage = estimatedMemoryUsage(); |
| Preconditions.checkState(memUsage + incomingSize <= memLimit, |
| String.format( |
| "Adding item (%s) estimated with %s bytes would increase mem usage beyond upper limit (%s)." + |
| " Current estimated mem usage is %s bytes", item.getPath(), incomingSize, memLimit, memUsage)); |
| tail.next = new ListNode(item); |
| tail = tail.next; |
| size++; |
| this.memUsage += incomingSize; |
| } |
| |
| /** |
| * Remove the first item from the list |
| * @return {@code NodeStateEntry} data in the removed item |
| */ |
| public NodeStateEntry remove() { |
| Preconditions.checkState(!isEmpty(), "Cannot remove item from empty list"); |
| NodeStateEntry ret = head.next.data; |
| head.next.isValid = false; |
| head.next = head.next.next; |
| size--; |
| memUsage -= ret.estimatedMemUsage(); |
| if (size == 0) { |
| tail = head; |
| } |
| return ret; |
| } |
| |
| /** |
| * @return {@link NodeIterator} object which would iterate the whole list |
| */ |
| public NodeIterator iterator() { |
| return iteratorFor(head); |
| } |
| |
| public int size() { |
| return size; |
| } |
| |
| public boolean isEmpty() { |
| return size == 0; |
| } |
| |
| public long estimatedMemoryUsage() { |
| return memUsage; |
| } |
| |
| /** |
| * Represents an item in the list. |
| */ |
| static class ListNode { |
| private ListNode next; |
| private final NodeStateEntry data; |
| private boolean isValid = true; |
| |
| private ListNode() { |
| this.data = null; |
| this.next = null; |
| } |
| |
| ListNode(@NotNull NodeStateEntry data) { |
| Preconditions.checkNotNull(data); |
| this.data = data; |
| this.next = null; |
| } |
| } |
| |
| static class NodeIterator implements Iterator<NodeStateEntry> { |
| private ListNode current; |
| |
| static NodeIterator iteratorFor(@NotNull ListNode node) { |
| Preconditions.checkNotNull(node); |
| return new NodeIterator(node); |
| } |
| |
| NodeIterator(@NotNull ListNode start) { |
| Preconditions.checkNotNull(start); |
| this.current = start; |
| } |
| |
| @Override |
| public boolean hasNext() { |
| return current.next != null; |
| } |
| |
| @Override |
| public NodeStateEntry next() { |
| Preconditions.checkState(current.isValid, "Can't call next from a removed node"); |
| current = current.next; |
| return current.data; |
| } |
| } |
| } |