org.apache.hadoop.hdfs.protocol.Block Maven / Gradle / Ivy
/**
* 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.protocol;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.File;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.annotation.Nonnull;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableFactories;
import org.apache.hadoop.io.WritableFactory;
/**
* A Block is a Hadoop FS primitive, identified by its block ID (a long). A
* block also has an accompanying generation stamp. A generation stamp is a
* monotonically increasing 8-byte number for each block that is maintained
* persistently by the NameNode. However, for the purposes of this class, two
* Blocks are considered equal iff they have the same block ID.
*
* @see Block#equals(Object)
* @see Block#hashCode()
* @see Block#compareTo(Block)
*/
@InterfaceAudience.Private
@InterfaceStability.Evolving
public class Block implements Writable, Comparable {
public static final String BLOCK_FILE_PREFIX = "blk_";
public static final String METADATA_EXTENSION = ".meta";
static { // register a ctor
WritableFactories.setFactory(Block.class, new WritableFactory() {
@Override
public Writable newInstance() { return new Block(); }
});
}
public static final Pattern blockFilePattern = Pattern
.compile(BLOCK_FILE_PREFIX + "(-??\\d++)$");
public static final Pattern metaFilePattern = Pattern
.compile(BLOCK_FILE_PREFIX + "(-??\\d++)_(\\d++)\\" + METADATA_EXTENSION
+ "$");
public static final Pattern metaOrBlockFilePattern = Pattern
.compile(BLOCK_FILE_PREFIX + "(-??\\d++)(_(\\d++)\\" + METADATA_EXTENSION
+ ")?$");
public static boolean isBlockFilename(File f) {
String name = f.getName();
return blockFilePattern.matcher(name).matches();
}
public static long filename2id(String name) {
Matcher m = blockFilePattern.matcher(name);
return m.matches() ? Long.parseLong(m.group(1)) : 0;
}
public static boolean isMetaFilename(String name) {
return metaFilePattern.matcher(name).matches();
}
public static File metaToBlockFile(File metaFile) {
return new File(metaFile.getParent(), metaFile.getName().substring(
0, metaFile.getName().lastIndexOf('_')));
}
/**
* Get generation stamp from the name of the metafile name
*/
public static long getGenerationStamp(String metaFile) {
Matcher m = metaFilePattern.matcher(metaFile);
return m.matches() ? Long.parseLong(m.group(2))
: HdfsConstants.GRANDFATHER_GENERATION_STAMP;
}
/**
* Get the blockId from the name of the meta or block file
*/
public static long getBlockId(String metaOrBlockFile) {
Matcher m = metaOrBlockFilePattern.matcher(metaOrBlockFile);
return m.matches() ? Long.parseLong(m.group(1)) : 0;
}
private long blockId;
private long numBytes;
private long generationStamp;
public Block() {this(0, 0, 0);}
public Block(final long blkid, final long len, final long generationStamp) {
set(blkid, len, generationStamp);
}
public Block(final long blkid) {
this(blkid, 0, HdfsConstants.GRANDFATHER_GENERATION_STAMP);
}
public Block(Block blk) {
this(blk.blockId, blk.numBytes, blk.generationStamp);
}
/**
* Find the blockid from the given filename
*/
public Block(File f, long len, long genstamp) {
this(filename2id(f.getName()), len, genstamp);
}
public void set(long blkid, long len, long genStamp) {
this.blockId = blkid;
this.numBytes = len;
this.generationStamp = genStamp;
}
public long getBlockId() {
return blockId;
}
public void setBlockId(long bid) {
blockId = bid;
}
/**
* Get the block name. The format of the name is in the format:
*
* blk_1, blk_2, blk_3, etc.
*
*
* @return the block name
*/
public String getBlockName() {
return BLOCK_FILE_PREFIX + blockId;
}
public long getNumBytes() {
return numBytes;
}
public void setNumBytes(long len) {
this.numBytes = len;
}
public long getGenerationStamp() {
return generationStamp;
}
public void setGenerationStamp(long stamp) {
generationStamp = stamp;
}
/**
* A helper method to output the string representation of the Block portion of
* a derived class' instance.
*
* @param b the target object
* @return the string representation of the block
*/
public static String toString(final Block b) {
return new StringBuilder(BLOCK_FILE_PREFIX)
.append(b.blockId)
.append('_')
.append(b.generationStamp)
.toString();
}
/**
* Get the block name. The format of the name is in the format:
*
* blk_block-id_generation, blk_1_1, blk_1_2, blk_2_1, etc.
*
*
* @return the full block name
*/
@Override
public String toString() {
return Block.toString(this);
}
public void appendStringTo(StringBuilder sb) {
sb.append(BLOCK_FILE_PREFIX)
.append(blockId)
.append('_')
.append(getGenerationStamp());
}
/////////////////////////////////////
// Writable
/////////////////////////////////////
@Override // Writable
public void write(DataOutput out) throws IOException {
writeHelper(out);
}
@Override // Writable
public void readFields(DataInput in) throws IOException {
readHelper(in);
}
final void writeHelper(DataOutput out) throws IOException {
out.writeLong(blockId);
out.writeLong(numBytes);
out.writeLong(generationStamp);
}
final void readHelper(DataInput in) throws IOException {
this.blockId = in.readLong();
this.numBytes = in.readLong();
this.generationStamp = in.readLong();
if (numBytes < 0) {
throw new IOException("Unexpected block size: " + numBytes);
}
}
// write only the identifier part of the block
public void writeId(DataOutput out) throws IOException {
out.writeLong(blockId);
out.writeLong(generationStamp);
}
// Read only the identifier part of the block
public void readId(DataInput in) throws IOException {
this.blockId = in.readLong();
this.generationStamp = in.readLong();
}
/**
* Compares this Block with the specified Block for order. Returns a negative
* integer, zero, or a positive integer as this Block is less than, equal to,
* or greater than the specified Block. Blocks are ordered based on their
* block ID.
*
* @param b the Block to be compared
* @return a negative integer, zero, or a positive integer as this Block is
* less than, equal to, or greater than the specified Block.
*/
@Override
public int compareTo(@Nonnull Block b) {
return Long.compare(blockId, b.blockId);
}
/**
* Indicates whether some Block is "equal to" this one. Two blocks are
* considered equal if they have the same block ID.
*
* @param obj the reference object with which to compare.
* @return true if this Block is the same as the argument; false otherwise.
*/
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (!(obj instanceof Block)) {
return false;
}
Block other = (Block) obj;
return (blockId == other.blockId);
}
/**
* Returns a hash code value for the Block. The hash code adheres to the
* general contract of hashCode. If two Blocks are equal according to the
* equals(Object) method, then calling the hashCode method on each of the two
* blocks produce the same integer result.
*
* @return a hash code value for this block
* @see Block#equals(Object)
*/
@Override
public int hashCode() {
return Long.hashCode(blockId);
}
/**
* A helper function to determine if two blocks are equal, based on the block
* ID and the generation stamp. This is a different equalities check than the
* default behavior of the Block class. Two blocks are considered equal by
* this function iff the two blocks have the same block ID and the same
* generation stamp, or if both blocks are null.
*
* @param a an object
* @param b an object to be compared with {@code a} for equality
* @return {@code true} if the blocks are deeply equal to each other and
* {@code false} otherwise
* @see Block
*/
public static boolean matchingIdAndGenStamp(Block a, Block b) {
if (a == b) {
return true;
} else if (a == null || b == null) {
return false;
} else {
return a.blockId == b.blockId && a.generationStamp == b.generationStamp;
}
}
}