Java tutorial
/** * 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.hadoop.hdfs.server.namenode; import java.util.Arrays; import java.util.LinkedList; import java.util.List; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor; import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor.CachedBlocksList; import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor.CachedBlocksList.Type; import org.apache.hadoop.util.IntrusiveCollection; import org.apache.hadoop.util.LightWeightGSet; import org.apache.hadoop.util.IntrusiveCollection.Element; import org.apache.hadoop.util.LightWeightGSet.LinkedElement; /** * Represents a cached block. */ @InterfaceAudience.LimitedPrivate({ "HDFS" }) public final class CachedBlock implements Element, LightWeightGSet.LinkedElement { private static final Object[] EMPTY_ARRAY = new Object[0]; /** * Block id. */ private final long blockId; /** * Used to implement #{LightWeightGSet.LinkedElement} */ private LinkedElement nextElement; /** * Bit 15: Mark * Bit 0-14: cache replication factor. */ private short replicationAndMark; /** * Used to implement the CachedBlocksList. * * Since this CachedBlock can be in multiple CachedBlocksList objects, * we need to be able to store multiple 'prev' and 'next' pointers. * The triplets array does this. * * Each triplet contains a CachedBlockList object followed by a * prev pointer, followed by a next pointer. */ private Object[] triplets; public CachedBlock(long blockId, short replication, boolean mark) { this.blockId = blockId; this.triplets = EMPTY_ARRAY; setReplicationAndMark(replication, mark); } public long getBlockId() { return blockId; } @Override public int hashCode() { return (int) (blockId ^ (blockId >>> 32)); } @Override public boolean equals(Object o) { if (o == null) { return false; } if (o == this) { return true; } if (o.getClass() != this.getClass()) { return false; } CachedBlock other = (CachedBlock) o; return other.blockId == blockId; } public void setReplicationAndMark(short replication, boolean mark) { assert replication >= 0; replicationAndMark = (short) ((replication << 1) | (mark ? 0x1 : 0x0)); } public boolean getMark() { return ((replicationAndMark & 0x1) != 0); } public short getReplication() { return (short) (replicationAndMark >>> 1); } /** * Return true if this CachedBlock is present on the given list. */ public boolean isPresent(CachedBlocksList cachedBlocksList) { for (int i = 0; i < triplets.length; i += 3) { CachedBlocksList list = (CachedBlocksList) triplets[i]; if (list == cachedBlocksList) { return true; } } return false; } /** * Get a list of the datanodes which this block is cached, * planned to be cached, or planned to be uncached on. * * @param type If null, this parameter is ignored. * If it is non-null, we match only datanodes which * have it on this list. * See {@link DatanodeDescriptor.CachedBlocksList.Type} * for a description of all the lists. * * @return The list of datanodes. Modifying this list does not * alter the state of the CachedBlock. */ public List<DatanodeDescriptor> getDatanodes(Type type) { List<DatanodeDescriptor> nodes = new LinkedList<DatanodeDescriptor>(); for (int i = 0; i < triplets.length; i += 3) { CachedBlocksList list = (CachedBlocksList) triplets[i]; if ((type == null) || (list.getType() == type)) { nodes.add(list.getDatanode()); } } return nodes; } @Override public void insertInternal(IntrusiveCollection<? extends Element> list, Element prev, Element next) { for (int i = 0; i < triplets.length; i += 3) { if (triplets[i] == list) { throw new RuntimeException("Trying to re-insert an element that " + "is already in the list."); } } Object newTriplets[] = Arrays.copyOf(triplets, triplets.length + 3); newTriplets[triplets.length] = list; newTriplets[triplets.length + 1] = prev; newTriplets[triplets.length + 2] = next; triplets = newTriplets; } @Override public void setPrev(IntrusiveCollection<? extends Element> list, Element prev) { for (int i = 0; i < triplets.length; i += 3) { if (triplets[i] == list) { triplets[i + 1] = prev; return; } } throw new RuntimeException("Called setPrev on an element that wasn't " + "in the list."); } @Override public void setNext(IntrusiveCollection<? extends Element> list, Element next) { for (int i = 0; i < triplets.length; i += 3) { if (triplets[i] == list) { triplets[i + 2] = next; return; } } throw new RuntimeException("Called setNext on an element that wasn't " + "in the list."); } @Override public void removeInternal(IntrusiveCollection<? extends Element> list) { for (int i = 0; i < triplets.length; i += 3) { if (triplets[i] == list) { Object[] newTriplets = new Object[triplets.length - 3]; System.arraycopy(triplets, 0, newTriplets, 0, i); System.arraycopy(triplets, i + 3, newTriplets, i, triplets.length - (i + 3)); triplets = newTriplets; return; } } throw new RuntimeException("Called remove on an element that wasn't " + "in the list."); } @Override public Element getPrev(IntrusiveCollection<? extends Element> list) { for (int i = 0; i < triplets.length; i += 3) { if (triplets[i] == list) { return (Element) triplets[i + 1]; } } throw new RuntimeException("Called getPrev on an element that wasn't " + "in the list."); } @Override public Element getNext(IntrusiveCollection<? extends Element> list) { for (int i = 0; i < triplets.length; i += 3) { if (triplets[i] == list) { return (Element) triplets[i + 2]; } } throw new RuntimeException("Called getNext on an element that wasn't " + "in the list."); } @Override public boolean isInList(IntrusiveCollection<? extends Element> list) { for (int i = 0; i < triplets.length; i += 3) { if (triplets[i] == list) { return true; } } return false; } @Override public String toString() { return new StringBuilder().append("{").append("blockId=").append(blockId).append(", ") .append("replication=").append(getReplication()).append(", ").append("mark=").append(getMark()) .append("}").toString(); } @Override // LightWeightGSet.LinkedElement public void setNext(LinkedElement next) { this.nextElement = next; } @Override // LightWeightGSet.LinkedElement public LinkedElement getNext() { return nextElement; } }