/*
 * 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 java.io.IOException;

import org.apache.lucene.store.IndexInput;
import org.apache.lucene.store.RandomAccessInput;
import org.apache.lucene.util.Accountable;
import org.apache.lucene.util.LongValues;
import org.apache.lucene.util.RamUsageEstimator;

Retrieves an instance previously written by DirectMonotonicWriter.
See Also:
/** * Retrieves an instance previously written by {@link DirectMonotonicWriter}. * @see DirectMonotonicWriter */
public final class DirectMonotonicReader {
An instance that always returns 0.
/** An instance that always returns {@code 0}. */
private static final LongValues EMPTY = new LongValues() { @Override public long get(long index) { return 0; } };
In-memory metadata that needs to be kept around for DirectMonotonicReader to read data from disk.
/** In-memory metadata that needs to be kept around for * {@link DirectMonotonicReader} to read data from disk. */
public static class Meta implements Accountable { private static final long BASE_RAM_BYTES_USED = RamUsageEstimator.shallowSizeOfInstance(Meta.class); final int blockShift; final int numBlocks; final long[] mins; final float[] avgs; final byte[] bpvs; final long[] offsets; Meta(long numValues, int blockShift) { this.blockShift = blockShift; long numBlocks = numValues >>> blockShift; if ((numBlocks << blockShift) < numValues) { numBlocks += 1; } this.numBlocks = (int) numBlocks; this.mins = new long[this.numBlocks]; this.avgs = new float[this.numBlocks]; this.bpvs = new byte[this.numBlocks]; this.offsets = new long[this.numBlocks]; } @Override public long ramBytesUsed() { return BASE_RAM_BYTES_USED + RamUsageEstimator.sizeOf(mins) + RamUsageEstimator.sizeOf(avgs) + RamUsageEstimator.sizeOf(bpvs) + RamUsageEstimator.sizeOf(offsets); } }
Load metadata from the given IndexInput. @see DirectMonotonicReader#getInstance(Meta, RandomAccessInput)
/** Load metadata from the given {@link IndexInput}. * @see DirectMonotonicReader#getInstance(Meta, RandomAccessInput) */
public static Meta loadMeta(IndexInput metaIn, long numValues, int blockShift) throws IOException { Meta meta = new Meta(numValues, blockShift); for (int i = 0; i < meta.numBlocks; ++i) { meta.mins[i] = metaIn.readLong(); meta.avgs[i] = Float.intBitsToFloat(metaIn.readInt()); meta.offsets[i] = metaIn.readLong(); meta.bpvs[i] = metaIn.readByte(); } return meta; }
Retrieves an instance from the specified slice.
/** * Retrieves an instance from the specified slice. */
public static LongValues getInstance(Meta meta, RandomAccessInput data) throws IOException { final LongValues[] readers = new LongValues[meta.numBlocks]; for (int i = 0; i < meta.mins.length; ++i) { if (meta.bpvs[i] == 0) { readers[i] = EMPTY; } else { readers[i] = DirectReader.getInstance(data, meta.bpvs[i], meta.offsets[i]); } } final int blockShift = meta.blockShift; final long[] mins = meta.mins; final float[] avgs = meta.avgs; return new LongValues() { @Override public long get(long index) { final int block = (int) (index >>> blockShift); final long blockIndex = index & ((1 << blockShift) - 1); final long delta = readers[block].get(blockIndex); return mins[block] + (long) (avgs[block] * blockIndex) + delta; } }; } }