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/*
* 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.lucene.codecs.uniformsplit;
import java.io.IOException;
import org.apache.lucene.index.CorruptIndexException;
import org.apache.lucene.store.DataInput;
import org.apache.lucene.store.DataOutput;
import org.apache.lucene.util.Accountable;
import org.apache.lucene.util.RamUsageEstimator;
/**
* Block header containing block metadata.
*
* Holds the number of lines in the block.
*
* Holds the base file pointers to apply delta base encoding to all the file
* pointers in the block with {@link DeltaBaseTermStateSerializer}.
*
* Holds the offset to the details region of the block (the term states).
*
* Holds the offset to the middle term of the block to divide the number
* of terms to scan by 2.
*
* @lucene.experimental
*/
public class BlockHeader implements Accountable {
private static final long RAM_USAGE = RamUsageEstimator.shallowSizeOfInstance(BlockHeader.class);
protected int linesCount;
protected long baseDocsFP;
protected long basePositionsFP;
protected long basePayloadsFP;
protected int termStatesBaseOffset;
protected int middleLineIndex;
protected int middleLineOffset;
/**
* @param linesCount Number of lines in the block.
* @param baseDocsFP File pointer to the docs of the first term with docs in the block.
* @param basePositionsFP File pointer to the positions of the first term with positions in the block.
* @param basePayloadsFP File pointer to the payloads of the first term with payloads in the block.
* @param termStatesBaseOffset Offset to the details region of the block (the term states), relative to the block start.
* @param middleLineOffset Offset to the middle term of the block, relative to the block start.
*/
protected BlockHeader(int linesCount, long baseDocsFP, long basePositionsFP, long basePayloadsFP,
int termStatesBaseOffset, int middleLineOffset) {
reset(linesCount, baseDocsFP, basePositionsFP, basePayloadsFP, termStatesBaseOffset, middleLineOffset);
}
/**
* Empty constructor. {@link #reset} must be called before writing.
*/
protected BlockHeader() {
}
protected BlockHeader reset(int linesCount, long baseDocsFP, long basePositionsFP,
long basePayloadsFP, int termStatesBaseOffset, int middleTermOffset) {
this.baseDocsFP = baseDocsFP;
this.basePositionsFP = basePositionsFP;
this.basePayloadsFP = basePayloadsFP;
this.linesCount = linesCount;
this.middleLineIndex = linesCount >> 1;
this.termStatesBaseOffset = termStatesBaseOffset;
this.middleLineOffset = middleTermOffset;
return this;
}
/**
* @return The number of lines in the block.
*/
public int getLinesCount() {
return linesCount;
}
/**
* @return The index of the middle line of the block.
*/
public int getMiddleLineIndex() {
return middleLineIndex;
}
/**
* @return The offset to the middle line of the block, relative to the block start.
*/
public int getMiddleLineOffset() {
return middleLineOffset;
}
/**
* @return The offset to the details region of the block (the term states), relative to the block start.
*/
public int getTermStatesBaseOffset() {
return termStatesBaseOffset;
}
/**
* @return The file pointer to the docs of the first term with docs in the block.
*/
public long getBaseDocsFP() {
return baseDocsFP;
}
/**
* @return The file pointer to the positions of the first term with positions in the block.
*/
public long getBasePositionsFP() {
return basePositionsFP;
}
/**
* @return The file pointer to the payloads of the first term with payloads in the block.
*/
public long getBasePayloadsFP() {
return basePayloadsFP;
}
@Override
public long ramBytesUsed() {
return RAM_USAGE;
}
/**
* Reads/writes block header.
*/
public static class Serializer {
public void write(DataOutput output, BlockHeader blockHeader) throws IOException {
assert blockHeader.linesCount > 0 : "Block header is not initialized";
output.writeVInt(blockHeader.linesCount);
output.writeVLong(blockHeader.baseDocsFP);
output.writeVLong(blockHeader.basePositionsFP);
output.writeVLong(blockHeader.basePayloadsFP);
output.writeVInt(blockHeader.termStatesBaseOffset);
output.writeVInt(blockHeader.middleLineOffset);
}
public BlockHeader read(DataInput input, BlockHeader reuse) throws IOException {
int linesCount = input.readVInt();
if (linesCount <= 0 || linesCount > UniformSplitTermsWriter.MAX_NUM_BLOCK_LINES) {
throw new CorruptIndexException("Illegal number of lines in a block: " + linesCount, input);
}
long baseDocsFP = input.readVLong();
long basePositionsFP = input.readVLong();
long basePayloadsFP = input.readVLong();
int termStatesBaseOffset = input.readVInt();
if (termStatesBaseOffset < 0) {
throw new CorruptIndexException("Illegal termStatesBaseOffset= " + termStatesBaseOffset, input);
}
int middleTermOffset = input.readVInt();
if (middleTermOffset < 0) {
throw new CorruptIndexException("Illegal middleTermOffset= " + middleTermOffset, input);
}
BlockHeader blockHeader = reuse == null ? new BlockHeader() : reuse;
return blockHeader.reset(linesCount, baseDocsFP, basePositionsFP, basePayloadsFP, termStatesBaseOffset, middleTermOffset);
}
}
}