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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.elasticsearch.index.translog;
import org.elasticsearch.ElasticsearchException;
import org.elasticsearch.common.io.stream.ByteBufferStreamInput;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
/**
* A base class for all classes that allows reading ops from translog files
*/
public abstract class BaseTranslogReader implements Comparable<BaseTranslogReader> {
protected final long generation;
protected final FileChannel channel;
protected final Path path;
protected final long firstOperationOffset;
public BaseTranslogReader(long generation, FileChannel channel, Path path, long firstOperationOffset) {
assert Translog.parseIdFromFileName(path) == generation : "generation mismatch. Path: " + Translog.parseIdFromFileName(path) + " but generation: " + generation;
this.generation = generation;
this.path = path;
this.channel = channel;
this.firstOperationOffset = firstOperationOffset;
}
public long getGeneration() {
return this.generation;
}
public abstract long sizeInBytes();
abstract public int totalOperations();
public final long getFirstOperationOffset() {
return firstOperationOffset;
}
public Translog.Operation read(Translog.Location location) throws IOException {
assert location.generation == generation : "read location's translog generation [" + location.generation + "] is not [" + generation + "]";
ByteBuffer buffer = ByteBuffer.allocate(location.size);
try (BufferedChecksumStreamInput checksumStreamInput = checksummedStream(buffer, location.translogLocation, location.size, null)) {
return read(checksumStreamInput);
}
}
/** read the size of the op (i.e., number of bytes, including the op size) written at the given position */
protected final int readSize(ByteBuffer reusableBuffer, long position) {
// read op size from disk
assert reusableBuffer.capacity() >= 4 : "reusable buffer must have capacity >=4 when reading opSize. got [" + reusableBuffer.capacity() + "]";
try {
reusableBuffer.clear();
reusableBuffer.limit(4);
readBytes(reusableBuffer, position);
reusableBuffer.flip();
// Add an extra 4 to account for the operation size integer itself
final int size = reusableBuffer.getInt() + 4;
final long maxSize = sizeInBytes() - position;
if (size < 0 || size > maxSize) {
throw new TranslogCorruptedException("operation size is corrupted must be [0.." + maxSize + "] but was: " + size);
}
return size;
} catch (IOException e) {
throw new ElasticsearchException("unexpected exception reading from translog snapshot of " + this.path, e);
}
}
public Translog.Snapshot newSnapshot() {
return new TranslogSnapshot(generation, channel, path, firstOperationOffset, sizeInBytes(), totalOperations());
}
/**
* reads an operation at the given position and returns it. The buffer length is equal to the number
* of bytes reads.
*/
protected final BufferedChecksumStreamInput checksummedStream(ByteBuffer reusableBuffer, long position, int opSize, BufferedChecksumStreamInput reuse) throws IOException {
final ByteBuffer buffer;
if (reusableBuffer.capacity() >= opSize) {
buffer = reusableBuffer;
} else {
buffer = ByteBuffer.allocate(opSize);
}
buffer.clear();
buffer.limit(opSize);
readBytes(buffer, position);
buffer.flip();
return new BufferedChecksumStreamInput(new ByteBufferStreamInput(buffer), reuse);
}
protected Translog.Operation read(BufferedChecksumStreamInput inStream) throws IOException {
return Translog.readOperation(inStream);
}
/**
* reads bytes at position into the given buffer, filling it.
*/
abstract protected void readBytes(ByteBuffer buffer, long position) throws IOException;
@Override
public String toString() {
return "translog [" + generation + "][" + path + "]";
}
@Override
public int compareTo(BaseTranslogReader o) {
return Long.compare(getGeneration(), o.getGeneration());
}
public Path path() {
return path;
}
}
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