HDFS-14837. Review of Block.java. Contributed by David Mollitor.

This commit is contained in:
Inigo Goiri 2019-09-24 09:54:09 -07:00
parent 43203b466d
commit 816d3cb908

View File

@ -17,21 +17,32 @@
*/
package org.apache.hadoop.hdfs.protocol;
import java.io.*;
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 org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.io.*;
import javax.annotation.Nonnull;
/**************************************************
* A Block is a Hadoop FS primitive, identified by a
* long.
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<Block> {
@ -119,8 +130,7 @@ public void set(long blkid, long len, long genStamp) {
this.numBytes = len;
this.generationStamp = genStamp;
}
/**
*/
public long getBlockId() {
return blockId;
}
@ -130,17 +140,21 @@ public void setBlockId(long bid) {
}
/**
* Get the block name. The format of the name is in the format:
* <p>
* blk_1, blk_2, blk_3, etc.
* </p>
*
* @return the block name
*/
public String getBlockName() {
return new StringBuilder().append(BLOCK_FILE_PREFIX)
.append(blockId).toString();
return BLOCK_FILE_PREFIX + blockId;
}
/**
*/
public long getNumBytes() {
return numBytes;
}
public void setNumBytes(long len) {
this.numBytes = len;
}
@ -161,28 +175,33 @@ public void setGenerationStamp(long stamp) {
* @return the string representation of the block
*/
public static String toString(final Block b) {
StringBuilder sb = new StringBuilder();
sb.append(BLOCK_FILE_PREFIX).
append(b.blockId).append("_").
append(b.generationStamp);
return sb.toString();
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:
* <p>
* blk_block-id_generation, blk_1_1, blk_1_2, blk_2_1, etc.
* </p>
*
* @return the full block name
*/
@Override
public String toString() {
return toString(this);
return Block.toString(this);
}
public void appendStringTo(StringBuilder sb) {
sb.append(BLOCK_FILE_PREFIX)
.append(blockId)
.append("_")
.append('_')
.append(getGenerationStamp());
}
/////////////////////////////////////
// Writable
/////////////////////////////////////
@ -223,32 +242,74 @@ public void readId(DataInput in) throws IOException {
this.generationStamp = in.readLong();
}
@Override // Comparable
/**
* 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 blockId < b.blockId ? -1 :
blockId > b.blockId ? 1 : 0;
}
@Override // Object
public boolean equals(Object o) {
return this == o || o instanceof Block && compareTo((Block) o) == 0;
return Long.compare(blockId, b.blockId);
}
/**
* @return true if the two blocks have the same block ID and the same
* generation stamp, or if both blocks are null.
* 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.
*/
public static boolean matchingIdAndGenStamp(Block a, Block b) {
if (a == b) return true; // same block, or both null
// only one null
return !(a == null || b == null) &&
a.blockId == b.blockId &&
a.generationStamp == b.generationStamp;
@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);
}
@Override // Object
/**
* 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() {
//GenerationStamp is IRRELEVANT and should not be used here
return (int)(blockId^(blockId>>>32));
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;
}
}
}