001/**
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one
004 * or more contributor license agreements.  See the NOTICE file
005 * distributed with this work for additional information
006 * regarding copyright ownership.  The ASF licenses this file
007 * to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance
009 * with the License.  You may obtain a copy of the License at
010 *
011 *     http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 */
019package org.apache.hadoop.hbase.util;
020
021import java.util.AbstractCollection;
022import java.util.ArrayList;
023import java.util.List;
024import java.util.NoSuchElementException;
025
026import org.apache.yetus.audience.InterfaceAudience;
027
028/**
029 * A collection class that contains multiple sub-lists, which allows us to not copy lists.
030 * This class does not support modification. The derived classes that add modifications are
031 * not thread-safe.
032 * NOTE: Doesn't implement list as it is not necessary for current usage, feel free to add.
033 */
034@InterfaceAudience.Private
035public class ConcatenatedLists<T> extends AbstractCollection<T> {
036  protected final ArrayList<List<T>> components = new ArrayList<>();
037  protected int size = 0;
038
039  public void addAllSublists(List<? extends List<T>> items) {
040    for (List<T> list : items) {
041      addSublist(list);
042    }
043  }
044
045  public void addSublist(List<T> items) {
046    if (!items.isEmpty()) {
047      this.components.add(items);
048      this.size += items.size();
049    }
050  }
051
052  @Override
053  public int size() {
054    return this.size;
055  }
056
057  @Override
058  public java.util.Iterator<T> iterator() {
059    return new Iterator();
060  }
061
062  @edu.umd.cs.findbugs.annotations.SuppressWarnings(
063    value="URF_UNREAD_PUBLIC_OR_PROTECTED_FIELD",
064    justification="nextWasCalled is using by StripeStoreFileManager")
065  public class Iterator implements java.util.Iterator<T> {
066    protected int currentComponent = 0;
067    protected int indexWithinComponent = -1;
068    protected boolean nextWasCalled = false;
069
070    @Override
071    public boolean hasNext() {
072      return (currentComponent + 1) < components.size()
073          || ((currentComponent + 1) == components.size()
074              && ((indexWithinComponent + 1) < components.get(currentComponent).size()));
075    }
076
077    @Override
078    public T next() {
079      if (!components.isEmpty()) {
080        this.nextWasCalled = true;
081        List<T> src = components.get(currentComponent);
082        if (++indexWithinComponent < src.size()) return src.get(indexWithinComponent);
083        if (++currentComponent < components.size()) {
084          indexWithinComponent = 0;
085          src = components.get(currentComponent);
086          assert src.size() > 0;
087          return src.get(indexWithinComponent);
088        }
089      }
090      this.nextWasCalled = false;
091      throw new NoSuchElementException();
092    }
093
094    @Override
095    public void remove() {
096      throw new UnsupportedOperationException();
097    }
098  }
099}