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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.lucene50;
import java.io.IOException;
import java.util.Arrays;
import org.apache.lucene.store.DataInput;
import org.apache.lucene.store.DataOutput;
import org.apache.lucene.store.IndexInput;
import org.apache.lucene.store.IndexOutput;
import org.apache.lucene.util.packed.PackedInts.Decoder;
import org.apache.lucene.util.packed.PackedInts.FormatAndBits;
import org.apache.lucene.util.packed.PackedInts;
import static org.apache.lucene.codecs.lucene50.Lucene50PostingsFormat.BLOCK_SIZE;
/**
* Encode all values in normal area with fixed bit width,
* which is determined by the max value in this block.
*/
final class ForUtil {
/**
* Special number of bits per value used whenever all values to encode are equal.
*/
private static final int ALL_VALUES_EQUAL = 0;
/**
* Upper limit of the number of bytes that might be required to stored
* BLOCK_SIZE encoded values.
*/
static final int MAX_ENCODED_SIZE = BLOCK_SIZE * 4;
/**
* Upper limit of the number of values that might be decoded in a single call to
* {@link #readBlock(IndexInput, byte[], int[])}. Although values after
* BLOCK_SIZE are garbage, it is necessary to allocate value buffers
* whose size is {@code >= MAX_DATA_SIZE} to avoid {@link ArrayIndexOutOfBoundsException}s.
*/
static final int MAX_DATA_SIZE;
static {
int maxDataSize = 0;
for(int version=PackedInts.VERSION_START;version<=PackedInts.VERSION_CURRENT;version++) {
for (PackedInts.Format format : PackedInts.Format.values()) {
for (int bpv = 1; bpv <= 32; ++bpv) {
if (!format.isSupported(bpv)) {
continue;
}
final PackedInts.Decoder decoder = PackedInts.getDecoder(format, version, bpv);
final int iterations = computeIterations(decoder);
maxDataSize = Math.max(maxDataSize, iterations * decoder.byteValueCount());
}
}
}
MAX_DATA_SIZE = maxDataSize;
}
/**
* Compute the number of iterations required to decode BLOCK_SIZE
* values with the provided {@link Decoder}.
*/
private static int computeIterations(PackedInts.Decoder decoder) {
return (int) Math.ceil((float) BLOCK_SIZE / decoder.byteValueCount());
}
/**
* Compute the number of bytes required to encode a block of values that require
* bitsPerValue bits per value with format format.
*/
private static int encodedSize(PackedInts.Format format, int packedIntsVersion, int bitsPerValue) {
final long byteCount = format.byteCount(packedIntsVersion, BLOCK_SIZE, bitsPerValue);
assert byteCount >= 0 && byteCount <= Integer.MAX_VALUE : byteCount;
return (int) byteCount;
}
private final int[] encodedSizes;
private final PackedInts.Encoder[] encoders;
private final PackedInts.Decoder[] decoders;
private final int[] iterations;
/**
* Create a new {@link ForUtil} instance and save state into out.
*/
ForUtil(float acceptableOverheadRatio, DataOutput out) throws IOException {
out.writeVInt(PackedInts.VERSION_CURRENT);
encodedSizes = new int[33];
encoders = new PackedInts.Encoder[33];
decoders = new PackedInts.Decoder[33];
iterations = new int[33];
for (int bpv = 1; bpv <= 32; ++bpv) {
final FormatAndBits formatAndBits = PackedInts.fastestFormatAndBits(
BLOCK_SIZE, bpv, acceptableOverheadRatio);
assert formatAndBits.format.isSupported(formatAndBits.bitsPerValue);
assert formatAndBits.bitsPerValue <= 32;
encodedSizes[bpv] = encodedSize(formatAndBits.format, PackedInts.VERSION_CURRENT, formatAndBits.bitsPerValue);
encoders[bpv] = PackedInts.getEncoder(
formatAndBits.format, PackedInts.VERSION_CURRENT, formatAndBits.bitsPerValue);
decoders[bpv] = PackedInts.getDecoder(
formatAndBits.format, PackedInts.VERSION_CURRENT, formatAndBits.bitsPerValue);
iterations[bpv] = computeIterations(decoders[bpv]);
out.writeVInt(formatAndBits.format.getId() << 5 | (formatAndBits.bitsPerValue - 1));
}
}
/**
* Restore a {@link ForUtil} from a {@link DataInput}.
*/
ForUtil(DataInput in) throws IOException {
int packedIntsVersion = in.readVInt();
PackedInts.checkVersion(packedIntsVersion);
encodedSizes = new int[33];
encoders = new PackedInts.Encoder[33];
decoders = new PackedInts.Decoder[33];
iterations = new int[33];
for (int bpv = 1; bpv <= 32; ++bpv) {
final int code = in.readVInt();
final int formatId = code >>> 5;
final int bitsPerValue = (code & 31) + 1;
final PackedInts.Format format = PackedInts.Format.byId(formatId);
assert format.isSupported(bitsPerValue);
encodedSizes[bpv] = encodedSize(format, packedIntsVersion, bitsPerValue);
encoders[bpv] = PackedInts.getEncoder(
format, packedIntsVersion, bitsPerValue);
decoders[bpv] = PackedInts.getDecoder(
format, packedIntsVersion, bitsPerValue);
iterations[bpv] = computeIterations(decoders[bpv]);
}
}
/**
* Write a block of data (For format).
*
* @param data the data to write
* @param encoded a buffer to use to encode data
* @param out the destination output
* @throws IOException If there is a low-level I/O error
*/
void writeBlock(int[] data, byte[] encoded, IndexOutput out) throws IOException {
if (isAllEqual(data)) {
out.writeByte((byte) ALL_VALUES_EQUAL);
out.writeVInt(data[0]);
return;
}
final int numBits = bitsRequired(data);
assert numBits > 0 && numBits <= 32 : numBits;
final PackedInts.Encoder encoder = encoders[numBits];
final int iters = iterations[numBits];
assert iters * encoder.byteValueCount() >= BLOCK_SIZE;
final int encodedSize = encodedSizes[numBits];
assert iters * encoder.byteBlockCount() >= encodedSize;
out.writeByte((byte) numBits);
encoder.encode(data, 0, encoded, 0, iters);
out.writeBytes(encoded, encodedSize);
}
/**
* Read the next block of data (For format).
*
* @param in the input to use to read data
* @param encoded a buffer that can be used to store encoded data
* @param decoded where to write decoded data
* @throws IOException If there is a low-level I/O error
*/
void readBlock(IndexInput in, byte[] encoded, int[] decoded) throws IOException {
final int numBits = in.readByte();
assert numBits <= 32 : numBits;
if (numBits == ALL_VALUES_EQUAL) {
final int value = in.readVInt();
Arrays.fill(decoded, 0, BLOCK_SIZE, value);
return;
}
final int encodedSize = encodedSizes[numBits];
in.readBytes(encoded, 0, encodedSize);
final PackedInts.Decoder decoder = decoders[numBits];
final int iters = iterations[numBits];
assert iters * decoder.byteValueCount() >= BLOCK_SIZE;
decoder.decode(encoded, 0, decoded, 0, iters);
}
/**
* Skip the next block of data.
*
* @param in the input where to read data
* @throws IOException If there is a low-level I/O error
*/
void skipBlock(IndexInput in) throws IOException {
final int numBits = in.readByte();
if (numBits == ALL_VALUES_EQUAL) {
in.readVInt();
return;
}
assert numBits > 0 && numBits <= 32 : numBits;
final int encodedSize = encodedSizes[numBits];
in.seek(in.getFilePointer() + encodedSize);
}
private static boolean isAllEqual(final int[] data) {
final int v = data[0];
for (int i = 1; i < BLOCK_SIZE; ++i) {
if (data[i] != v) {
return false;
}
}
return true;
}
/**
* Compute the number of bits required to serialize any of the longs in
* data.
*/
private static int bitsRequired(final int[] data) {
long or = 0;
for (int i = 0; i < BLOCK_SIZE; ++i) {
assert data[i] >= 0;
or |= data[i];
}
return PackedInts.bitsRequired(or);
}
}
