HDFS-14837. Review of Block.java. Contributed by David Mollitor.
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@ -17,21 +17,32 @@
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*/
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package org.apache.hadoop.hdfs.protocol;
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import java.io.*;
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import java.io.DataInput;
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import java.io.DataOutput;
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import java.io.File;
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import java.io.IOException;
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import java.util.regex.Matcher;
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import java.util.regex.Pattern;
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import org.apache.hadoop.classification.InterfaceAudience;
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import org.apache.hadoop.classification.InterfaceStability;
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import org.apache.hadoop.io.*;
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import javax.annotation.Nonnull;
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/**************************************************
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* A Block is a Hadoop FS primitive, identified by a
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* long.
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import org.apache.hadoop.classification.InterfaceAudience;
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import org.apache.hadoop.classification.InterfaceStability;
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import org.apache.hadoop.io.Writable;
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import org.apache.hadoop.io.WritableFactories;
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import org.apache.hadoop.io.WritableFactory;
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/**
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* A Block is a Hadoop FS primitive, identified by its block ID (a long). A
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* block also has an accompanying generation stamp. A generation stamp is a
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* monotonically increasing 8-byte number for each block that is maintained
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* persistently by the NameNode. However, for the purposes of this class, two
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* Blocks are considered equal iff they have the same block ID.
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*
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**************************************************/
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* @see Block#equals(Object)
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* @see Block#hashCode()
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* @see Block#compareTo(Block)
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*/
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@InterfaceAudience.Private
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@InterfaceStability.Evolving
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public class Block implements Writable, Comparable<Block> {
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@ -119,8 +130,7 @@ public void set(long blkid, long len, long genStamp) {
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this.numBytes = len;
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this.generationStamp = genStamp;
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}
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/**
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*/
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public long getBlockId() {
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return blockId;
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}
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@ -130,17 +140,21 @@ public void setBlockId(long bid) {
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}
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/**
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* Get the block name. The format of the name is in the format:
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* <p>
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* blk_1, blk_2, blk_3, etc.
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* </p>
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*
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* @return the block name
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*/
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public String getBlockName() {
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return new StringBuilder().append(BLOCK_FILE_PREFIX)
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.append(blockId).toString();
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return BLOCK_FILE_PREFIX + blockId;
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}
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/**
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*/
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public long getNumBytes() {
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return numBytes;
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}
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public void setNumBytes(long len) {
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this.numBytes = len;
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}
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@ -161,28 +175,33 @@ public void setGenerationStamp(long stamp) {
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* @return the string representation of the block
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*/
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public static String toString(final Block b) {
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StringBuilder sb = new StringBuilder();
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sb.append(BLOCK_FILE_PREFIX).
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append(b.blockId).append("_").
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append(b.generationStamp);
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return sb.toString();
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return new StringBuilder(BLOCK_FILE_PREFIX)
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.append(b.blockId)
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.append('_')
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.append(b.generationStamp)
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.toString();
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}
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/**
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* Get the block name. The format of the name is in the format:
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* <p>
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* blk_block-id_generation, blk_1_1, blk_1_2, blk_2_1, etc.
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* </p>
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*
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* @return the full block name
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*/
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@Override
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public String toString() {
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return toString(this);
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return Block.toString(this);
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}
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public void appendStringTo(StringBuilder sb) {
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sb.append(BLOCK_FILE_PREFIX)
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.append(blockId)
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.append("_")
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.append('_')
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.append(getGenerationStamp());
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}
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/////////////////////////////////////
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// Writable
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/////////////////////////////////////
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@ -223,32 +242,74 @@ public void readId(DataInput in) throws IOException {
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this.generationStamp = in.readLong();
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}
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@Override // Comparable
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/**
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* Compares this Block with the specified Block for order. Returns a negative
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* integer, zero, or a positive integer as this Block is less than, equal to,
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* or greater than the specified Block. Blocks are ordered based on their
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* block ID.
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*
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* @param b the Block to be compared
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* @return a negative integer, zero, or a positive integer as this Block is
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* less than, equal to, or greater than the specified Block.
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*/
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@Override
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public int compareTo(@Nonnull Block b) {
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return blockId < b.blockId ? -1 :
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blockId > b.blockId ? 1 : 0;
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}
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@Override // Object
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public boolean equals(Object o) {
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return this == o || o instanceof Block && compareTo((Block) o) == 0;
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return Long.compare(blockId, b.blockId);
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}
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/**
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* @return true if the two blocks have the same block ID and the same
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* generation stamp, or if both blocks are null.
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* Indicates whether some Block is "equal to" this one. Two blocks are
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* considered equal if they have the same block ID.
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*
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* @param obj the reference object with which to compare.
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* @return true if this Block is the same as the argument; false otherwise.
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*/
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public static boolean matchingIdAndGenStamp(Block a, Block b) {
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if (a == b) return true; // same block, or both null
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// only one null
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return !(a == null || b == null) &&
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a.blockId == b.blockId &&
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a.generationStamp == b.generationStamp;
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@Override
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public boolean equals(Object obj) {
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if (this == obj) {
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return true;
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}
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if (!(obj instanceof Block)) {
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return false;
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}
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Block other = (Block) obj;
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return (blockId == other.blockId);
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}
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@Override // Object
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/**
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* Returns a hash code value for the Block. The hash code adheres to the
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* general contract of hashCode. If two Blocks are equal according to the
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* equals(Object) method, then calling the hashCode method on each of the two
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* blocks produce the same integer result.
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*
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* @return a hash code value for this block
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* @see Block#equals(Object)
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*/
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@Override
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public int hashCode() {
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//GenerationStamp is IRRELEVANT and should not be used here
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return (int)(blockId^(blockId>>>32));
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return Long.hashCode(blockId);
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}
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/**
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* A helper function to determine if two blocks are equal, based on the block
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* ID and the generation stamp. This is a different equalities check than the
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* default behavior of the Block class. Two blocks are considered equal by
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* this function iff the two blocks have the same block ID and the same
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* generation stamp, or if both blocks are null.
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*
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* @param a an object
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* @param b an object to be compared with {@code a} for equality
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* @return {@code true} if the blocks are deeply equal to each other and
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* {@code false} otherwise
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* @see Block
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*/
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public static boolean matchingIdAndGenStamp(Block a, Block b) {
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if (a == b) {
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return true;
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} else if (a == null || b == null) {
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return false;
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} else {
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return a.blockId == b.blockId && a.generationStamp == b.generationStamp;
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}
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}
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}
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