| /* |
| * 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.IndexOutput; |
| import org.apache.lucene.util.ArrayUtil; |
| |
| /** |
| * Write monotonically-increasing sequences of integers. This writer splits |
| * data into blocks and then for each block, computes the average slope, the |
| * minimum value and only encode the delta from the expected value using a |
| * {@link DirectWriter}. |
| * |
| * @see DirectMonotonicReader |
| * @lucene.internal |
| */ |
| public final class DirectMonotonicWriter { |
| |
| public static final int MIN_BLOCK_SHIFT = 2; |
| public static final int MAX_BLOCK_SHIFT = 22; |
| |
| final IndexOutput meta; |
| final IndexOutput data; |
| final long numValues; |
| final long baseDataPointer; |
| final long[] buffer; |
| int bufferSize; |
| long count; |
| boolean finished; |
| |
| DirectMonotonicWriter(IndexOutput metaOut, IndexOutput dataOut, long numValues, int blockShift) { |
| if (blockShift < MIN_BLOCK_SHIFT || blockShift > MAX_BLOCK_SHIFT) { |
| throw new IllegalArgumentException("blockShift must be in [" + MIN_BLOCK_SHIFT + "-" + MAX_BLOCK_SHIFT + "], got " + blockShift); |
| } |
| if (numValues < 0) { |
| throw new IllegalArgumentException("numValues can't be negative, got " + numValues); |
| } |
| final long numBlocks = numValues == 0 ? 0 : ((numValues - 1) >>> blockShift) + 1; |
| if (numBlocks > ArrayUtil.MAX_ARRAY_LENGTH) { |
| throw new IllegalArgumentException("blockShift is too low for the provided number of values: blockShift=" + blockShift + |
| ", numValues=" + numValues + ", MAX_ARRAY_LENGTH=" + ArrayUtil.MAX_ARRAY_LENGTH); |
| } |
| this.meta = metaOut; |
| this.data = dataOut; |
| this.numValues = numValues; |
| final int blockSize = 1 << blockShift; |
| this.buffer = new long[(int) Math.min(numValues, blockSize)]; |
| this.bufferSize = 0; |
| this.baseDataPointer = dataOut.getFilePointer(); |
| } |
| |
| private void flush() throws IOException { |
| assert bufferSize != 0; |
| |
| final float avgInc = (float) ((double) (buffer[bufferSize-1] - buffer[0]) / Math.max(1, bufferSize - 1)); |
| for (int i = 0; i < bufferSize; ++i) { |
| final long expected = (long) (avgInc * (long) i); |
| buffer[i] -= expected; |
| } |
| |
| long min = buffer[0]; |
| for (int i = 1; i < bufferSize; ++i) { |
| min = Math.min(buffer[i], min); |
| } |
| |
| long maxDelta = 0; |
| for (int i = 0; i < bufferSize; ++i) { |
| buffer[i] -= min; |
| // use | will change nothing when it comes to computing required bits |
| // but has the benefit of working fine with negative values too |
| // (in case of overflow) |
| maxDelta |= buffer[i]; |
| } |
| |
| meta.writeLong(min); |
| meta.writeInt(Float.floatToIntBits(avgInc)); |
| meta.writeLong(data.getFilePointer() - baseDataPointer); |
| if (maxDelta == 0) { |
| meta.writeByte((byte) 0); |
| } else { |
| final int bitsRequired = DirectWriter.unsignedBitsRequired(maxDelta); |
| DirectWriter writer = DirectWriter.getInstance(data, bufferSize, bitsRequired); |
| for (int i = 0; i < bufferSize; ++i) { |
| writer.add(buffer[i]); |
| } |
| writer.finish(); |
| meta.writeByte((byte) bitsRequired); |
| } |
| bufferSize = 0; |
| } |
| |
| long previous = Long.MIN_VALUE; |
| |
| /** Write a new value. Note that data might not make it to storage until |
| * {@link #finish()} is called. |
| * @throws IllegalArgumentException if values don't come in order */ |
| public void add(long v) throws IOException { |
| if (v < previous) { |
| throw new IllegalArgumentException("Values do not come in order: " + previous + ", " + v); |
| } |
| if (bufferSize == buffer.length) { |
| flush(); |
| } |
| buffer[bufferSize++] = v; |
| previous = v; |
| count++; |
| } |
| |
| /** This must be called exactly once after all values have been {@link #add(long) added}. */ |
| public void finish() throws IOException { |
| if (count != numValues) { |
| throw new IllegalStateException("Wrong number of values added, expected: " + numValues + ", got: " + count); |
| } |
| if (finished) { |
| throw new IllegalStateException("#finish has been called already"); |
| } |
| if (bufferSize > 0) { |
| flush(); |
| } |
| finished = true; |
| } |
| |
| /** Returns an instance suitable for encoding {@code numValues} into monotonic |
| * blocks of 2<sup>{@code blockShift}</sup> values. Metadata will be written |
| * to {@code metaOut} and actual data to {@code dataOut}. */ |
| public static DirectMonotonicWriter getInstance(IndexOutput metaOut, IndexOutput dataOut, long numValues, int blockShift) { |
| return new DirectMonotonicWriter(metaOut, dataOut, numValues, blockShift); |
| } |
| |
| } |