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Hadoop is the distributed computing framework of Apache; hadoop-core contains
the filesystem, job tracker and map/reduce modules
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/**
* 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.fs;
import org.apache.hadoop.io.*;
import java.io.*;
/*
* A BlockLocation lists hosts, offset and length
* of block.
*
*/
public class BlockLocation implements Writable {
static { // register a ctor
WritableFactories.setFactory
(BlockLocation.class,
new WritableFactory() {
public Writable newInstance() { return new BlockLocation(); }
});
}
private String[] hosts; //hostnames of datanodes
private String[] names; //hostname:portNumber of datanodes
private String[] topologyPaths; // full path name in network topology
private long offset; //offset of the of the block in the file
private long length;
/**
* Default Constructor
*/
public BlockLocation() {
this(new String[0], new String[0], 0L, 0L);
}
/**
* Constructor with host, name, offset and length
*/
public BlockLocation(String[] names, String[] hosts, long offset,
long length) {
if (names == null) {
this.names = new String[0];
} else {
this.names = names;
}
if (hosts == null) {
this.hosts = new String[0];
} else {
this.hosts = hosts;
}
this.offset = offset;
this.length = length;
this.topologyPaths = new String[0];
}
/**
* Constructor with host, name, network topology, offset and length
*/
public BlockLocation(String[] names, String[] hosts, String[] topologyPaths,
long offset, long length) {
this(names, hosts, offset, length);
if (topologyPaths == null) {
this.topologyPaths = new String[0];
} else {
this.topologyPaths = topologyPaths;
}
}
/**
* Get the list of hosts (hostname) hosting this block
*/
public String[] getHosts() throws IOException {
if ((hosts == null) || (hosts.length == 0)) {
return new String[0];
} else {
return hosts;
}
}
/**
* Get the list of names (hostname:port) hosting this block
*/
public String[] getNames() throws IOException {
if ((names == null) || (names.length == 0)) {
return new String[0];
} else {
return this.names;
}
}
/**
* Get the list of network topology paths for each of the hosts.
* The last component of the path is the host.
*/
public String[] getTopologyPaths() throws IOException {
if ((topologyPaths == null) || (topologyPaths.length == 0)) {
return new String[0];
} else {
return this.topologyPaths;
}
}
/**
* Get the start offset of file associated with this block
*/
public long getOffset() {
return offset;
}
/**
* Get the length of the block
*/
public long getLength() {
return length;
}
/**
* Set the start offset of file associated with this block
*/
public void setOffset(long offset) {
this.offset = offset;
}
/**
* Set the length of block
*/
public void setLength(long length) {
this.length = length;
}
/**
* Set the hosts hosting this block
*/
public void setHosts(String[] hosts) throws IOException {
if (hosts == null) {
this.hosts = new String[0];
} else {
this.hosts = hosts;
}
}
/**
* Set the names (host:port) hosting this block
*/
public void setNames(String[] names) throws IOException {
if (names == null) {
this.names = new String[0];
} else {
this.names = names;
}
}
/**
* Set the network topology paths of the hosts
*/
public void setTopologyPaths(String[] topologyPaths) throws IOException {
if (topologyPaths == null) {
this.topologyPaths = new String[0];
} else {
this.topologyPaths = topologyPaths;
}
}
/**
* Implement write of Writable
*/
public void write(DataOutput out) throws IOException {
out.writeLong(offset);
out.writeLong(length);
out.writeInt(names.length);
for (int i=0; i < names.length; i++) {
Text name = new Text(names[i]);
name.write(out);
}
out.writeInt(hosts.length);
for (int i=0; i < hosts.length; i++) {
Text host = new Text(hosts[i]);
host.write(out);
}
out.writeInt(topologyPaths.length);
for (int i=0; i < topologyPaths.length; i++) {
Text host = new Text(topologyPaths[i]);
host.write(out);
}
}
/**
* Implement readFields of Writable
*/
public void readFields(DataInput in) throws IOException {
this.offset = in.readLong();
this.length = in.readLong();
int numNames = in.readInt();
this.names = new String[numNames];
for (int i = 0; i < numNames; i++) {
Text name = new Text();
name.readFields(in);
names[i] = name.toString();
}
int numHosts = in.readInt();
for (int i = 0; i < numHosts; i++) {
Text host = new Text();
host.readFields(in);
hosts[i] = host.toString();
}
int numTops = in.readInt();
Text path = new Text();
for (int i = 0; i < numTops; i++) {
path.readFields(in);
topologyPaths[i] = path.toString();
}
}
public String toString() {
StringBuilder result = new StringBuilder();
result.append(offset);
result.append(',');
result.append(length);
for(String h: hosts) {
result.append(',');
result.append(h);
}
return result.toString();
}
}