hadoop BlockData 源码
haddop BlockData 代码
文件路径:/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/prefetch/BlockData.java
/*
* 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.impl.prefetch;
import static org.apache.hadoop.fs.impl.prefetch.Validate.checkNotNegative;
import static org.apache.hadoop.fs.impl.prefetch.Validate.checkPositiveInteger;
import static org.apache.hadoop.fs.impl.prefetch.Validate.checkWithinRange;
/**
* Holds information about blocks of data in a file.
*/
public final class BlockData {
// State of each block of data.
enum State {
/** Data is not yet ready to be read from this block (still being prefetched). */
NOT_READY,
/** A read of this block has been enqueued in the prefetch queue. */
QUEUED,
/** A read of this block has been enqueued in the prefetch queue. */
READY,
/** This block has been cached in the local disk cache. */
CACHED
}
/**
* State of all blocks in a file.
*/
private State[] state;
/**
* The size of a file.
*/
private final long fileSize;
/**
* The file is divided into blocks of this size.
*/
private final int blockSize;
/**
* The file has these many blocks.
*/
private final int numBlocks;
/**
* Constructs an instance of {@link BlockData}.
* @param fileSize the size of a file.
* @param blockSize the file is divided into blocks of this size.
* @throws IllegalArgumentException if fileSize is negative.
* @throws IllegalArgumentException if blockSize is negative.
* @throws IllegalArgumentException if blockSize is zero or negative.
*/
public BlockData(long fileSize, int blockSize) {
checkNotNegative(fileSize, "fileSize");
if (fileSize == 0) {
checkNotNegative(blockSize, "blockSize");
} else {
checkPositiveInteger(blockSize, "blockSize");
}
this.fileSize = fileSize;
this.blockSize = blockSize;
this.numBlocks =
(fileSize == 0)
? 0
: ((int) (fileSize / blockSize)) + (fileSize % blockSize > 0
? 1
: 0);
this.state = new State[this.numBlocks];
for (int b = 0; b < this.numBlocks; b++) {
setState(b, State.NOT_READY);
}
}
/**
* Gets the size of each block.
* @return the size of each block.
*/
public int getBlockSize() {
return blockSize;
}
/**
* Gets the size of the associated file.
* @return the size of the associated file.
*/
public long getFileSize() {
return fileSize;
}
/**
* Gets the number of blocks in the associated file.
* @return the number of blocks in the associated file.
*/
public int getNumBlocks() {
return numBlocks;
}
/**
* Indicates whether the given block is the last block in the associated file.
* @param blockNumber the id of the desired block.
* @return true if the given block is the last block in the associated file, false otherwise.
* @throws IllegalArgumentException if blockNumber is invalid.
*/
public boolean isLastBlock(int blockNumber) {
if (fileSize == 0) {
return false;
}
throwIfInvalidBlockNumber(blockNumber);
return blockNumber == (numBlocks - 1);
}
/**
* Gets the id of the block that contains the given absolute offset.
* @param offset the absolute offset to check.
* @return the id of the block that contains the given absolute offset.
* @throws IllegalArgumentException if offset is invalid.
*/
public int getBlockNumber(long offset) {
throwIfInvalidOffset(offset);
return (int) (offset / blockSize);
}
/**
* Gets the size of the given block.
* @param blockNumber the id of the desired block.
* @return the size of the given block.
*/
public int getSize(int blockNumber) {
if (fileSize == 0) {
return 0;
}
if (isLastBlock(blockNumber)) {
return (int) (fileSize - (((long) blockSize) * (numBlocks - 1)));
} else {
return blockSize;
}
}
/**
* Indicates whether the given absolute offset is valid.
* @param offset absolute offset in the file..
* @return true if the given absolute offset is valid, false otherwise.
*/
public boolean isValidOffset(long offset) {
return (offset >= 0) && (offset < fileSize);
}
/**
* Gets the start offset of the given block.
* @param blockNumber the id of the given block.
* @return the start offset of the given block.
* @throws IllegalArgumentException if blockNumber is invalid.
*/
public long getStartOffset(int blockNumber) {
throwIfInvalidBlockNumber(blockNumber);
return blockNumber * (long) blockSize;
}
/**
* Gets the relative offset corresponding to the given block and the absolute offset.
* @param blockNumber the id of the given block.
* @param offset absolute offset in the file.
* @return the relative offset corresponding to the given block and the absolute offset.
* @throws IllegalArgumentException if either blockNumber or offset is invalid.
*/
public int getRelativeOffset(int blockNumber, long offset) {
throwIfInvalidOffset(offset);
return (int) (offset - getStartOffset(blockNumber));
}
/**
* Gets the state of the given block.
* @param blockNumber the id of the given block.
* @return the state of the given block.
* @throws IllegalArgumentException if blockNumber is invalid.
*/
public State getState(int blockNumber) {
throwIfInvalidBlockNumber(blockNumber);
return state[blockNumber];
}
/**
* Sets the state of the given block to the given value.
* @param blockNumber the id of the given block.
* @param blockState the target state.
* @throws IllegalArgumentException if blockNumber is invalid.
*/
public void setState(int blockNumber, State blockState) {
throwIfInvalidBlockNumber(blockNumber);
state[blockNumber] = blockState;
}
// Debug helper.
public String getStateString() {
StringBuilder sb = new StringBuilder();
int blockNumber = 0;
while (blockNumber < numBlocks) {
State tstate = getState(blockNumber);
int endBlockNumber = blockNumber;
while ((endBlockNumber < numBlocks) && (getState(endBlockNumber)
== tstate)) {
endBlockNumber++;
}
sb.append(
String.format("[%03d ~ %03d] %s%n", blockNumber, endBlockNumber - 1,
tstate));
blockNumber = endBlockNumber;
}
return sb.toString();
}
private void throwIfInvalidBlockNumber(int blockNumber) {
checkWithinRange(blockNumber, "blockNumber", 0, numBlocks - 1);
}
private void throwIfInvalidOffset(long offset) {
checkWithinRange(offset, "offset", 0, fileSize - 1);
}
}
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