/*
 * 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.util.packed;


import static org.apache.lucene.util.BitUtil.zigZagDecode;
import static org.apache.lucene.util.packed.AbstractBlockPackedWriter.BPV_SHIFT;
import static org.apache.lucene.util.packed.AbstractBlockPackedWriter.MAX_BLOCK_SIZE;
import static org.apache.lucene.util.packed.AbstractBlockPackedWriter.MIN_BLOCK_SIZE;
import static org.apache.lucene.util.packed.AbstractBlockPackedWriter.MIN_VALUE_EQUALS_0;
import static org.apache.lucene.util.packed.BlockPackedReaderIterator.readVLong;
import static org.apache.lucene.util.packed.PackedInts.checkBlockSize;
import static org.apache.lucene.util.packed.PackedInts.numBlocks;

import java.io.IOException;

import org.apache.lucene.index.CorruptIndexException;
import org.apache.lucene.store.IndexInput;
import org.apache.lucene.util.Accountable;
import org.apache.lucene.util.LongValues;

Provides random access to a stream written with BlockPackedWriter.
@lucene.internal
/** * Provides random access to a stream written with {@link BlockPackedWriter}. * @lucene.internal */
public final class BlockPackedReader extends LongValues implements Accountable { private final int blockShift, blockMask; private final long valueCount; private final long[] minValues; private final PackedInts.Reader[] subReaders; private final long sumBPV;
Sole constructor.
/** Sole constructor. */
public BlockPackedReader(IndexInput in, int packedIntsVersion, int blockSize, long valueCount, boolean direct) throws IOException { this.valueCount = valueCount; blockShift = checkBlockSize(blockSize, MIN_BLOCK_SIZE, MAX_BLOCK_SIZE); blockMask = blockSize - 1; final int numBlocks = numBlocks(valueCount, blockSize); long[] minValues = null; subReaders = new PackedInts.Reader[numBlocks]; long sumBPV = 0; for (int i = 0; i < numBlocks; ++i) { final int token = in.readByte() & 0xFF; final int bitsPerValue = token >>> BPV_SHIFT; sumBPV += bitsPerValue; if (bitsPerValue > 64) { throw new CorruptIndexException("Corrupted Block#" + i, in); } if ((token & MIN_VALUE_EQUALS_0) == 0) { if (minValues == null) { minValues = new long[numBlocks]; } minValues[i] = zigZagDecode(1L + readVLong(in)); } if (bitsPerValue == 0) { subReaders[i] = new PackedInts.NullReader(blockSize); } else { final int size = (int) Math.min(blockSize, valueCount - (long) i * blockSize); if (direct) { final long pointer = in.getFilePointer(); subReaders[i] = PackedInts.getDirectReaderNoHeader(in, PackedInts.Format.PACKED, packedIntsVersion, size, bitsPerValue); in.seek(pointer + PackedInts.Format.PACKED.byteCount(packedIntsVersion, size, bitsPerValue)); } else { subReaders[i] = PackedInts.getReaderNoHeader(in, PackedInts.Format.PACKED, packedIntsVersion, size, bitsPerValue); } } } this.minValues = minValues; this.sumBPV = sumBPV; } @Override public long get(long index) { assert index >= 0 && index < valueCount; final int block = (int) (index >>> blockShift); final int idx = (int) (index & blockMask); return (minValues == null ? 0 : minValues[block]) + subReaders[block].get(idx); } @Override public long ramBytesUsed() { long size = 0; for (PackedInts.Reader reader : subReaders) { size += reader.ramBytesUsed(); } return size; } @Override public String toString() { long avgBPV = subReaders.length == 0 ? 0 : sumBPV / subReaders.length; return getClass().getSimpleName() + "(blocksize=" + (1<<blockShift) + ",size=" + valueCount + ",avgBPV=" + avgBPV + ")"; } }