/*
* 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.
*/
/**
* Packed integer arrays and streams.
*
* <p>
* The packed package provides
* <ul>
* <li>sequential and random access capable arrays of positive longs,</li>
* <li>routines for efficient serialization and deserialization of streams of packed integers.</li>
* </ul>
*
* The implementations provide different trade-offs between memory usage and
* access speed. The standard usage scenario is replacing large int or long
* arrays in order to reduce the memory footprint.
* <p>
* The main access point is the {@link org.apache.lucene.util.packed.PackedInts} factory.
*
* <h3>In-memory structures</h3>
*
* <ul>
* <li><b>{@link org.apache.lucene.util.packed.PackedInts.Mutable}</b><ul>
* <li>Only supports positive longs.</li>
* <li>Requires the number of bits per value to be known in advance.</li>
* <li>Random-access for both writing and reading.</li>
* </ul></li>
* <li><b>{@link org.apache.lucene.util.packed.GrowableWriter}</b><ul>
* <li>Same as PackedInts.Mutable but grows the number of bits per values when needed.</li>
* <li>Useful to build a PackedInts.Mutable from a read-once stream of longs.</li>
* </ul></li>
* <li><b>{@link org.apache.lucene.util.packed.PagedGrowableWriter}</b><ul>
* <li>Slices data into fixed-size blocks stored in GrowableWriters.</li>
* <li>Supports more than 2B values.</li>
* <li>You should use PackedLongValues instead if you don't need random write access.</li>
* </ul></li>
* <li><b>{@link org.apache.lucene.util.packed.PackedLongValues#deltaPackedBuilder}</b><ul>
* <li>Can store any sequence of longs.</li>
* <li>Compression is good when values are close to each other.</li>
* <li>Supports random reads, but only sequential writes.</li>
* <li>Can address up to 2^42 values.</li>
* </ul></li>
* <li><b>{@link org.apache.lucene.util.packed.PackedLongValues#packedBuilder}</b><ul>
* <li>Same as deltaPackedBuilder but assumes values are 0-based.</li>
* </ul></li>
* <li><b>{@link org.apache.lucene.util.packed.PackedLongValues#monotonicBuilder}</b><ul>
* <li>Same as deltaPackedBuilder except that compression is good when the stream is a succession of affine functions.</li>
* </ul></li>
* </ul>
*
* <h3>Disk-based structures</h3>
*
* <ul>
* <li><b>{@link org.apache.lucene.util.packed.PackedInts.Writer}, {@link org.apache.lucene.util.packed.PackedInts.Reader}, {@link org.apache.lucene.util.packed.PackedInts.ReaderIterator}</b><ul>
* <li>Only supports positive longs.</li>
* <li>Requires the number of bits per value to be known in advance.</li>
* <li>Supports both fast sequential access with low memory footprint with ReaderIterator and random-access by either loading values in memory or leaving them on disk with Reader.</li>
* </ul></li>
* <li><b>{@link org.apache.lucene.util.packed.BlockPackedWriter}, {@link org.apache.lucene.util.packed.BlockPackedReader}, {@link org.apache.lucene.util.packed.BlockPackedReaderIterator}</b><ul>
* <li>Splits the stream into fixed-size blocks.</li>
* <li>Compression is good when values are close to each other.</li>
* <li>Can address up to 2B * blockSize values.</li>
* </ul></li>
* <li><b>{@link org.apache.lucene.util.packed.MonotonicBlockPackedWriter}, {@link org.apache.lucene.util.packed.MonotonicBlockPackedReader}</b><ul>
* <li>Same as the non-monotonic variants except that compression is good when the stream is a succession of affine functions.</li>
* <li>The reason why there is no sequential access is that if you need sequential access, you should rather delta-encode and use BlockPackedWriter.</li>
* </ul></li>
* <li><b>{@link org.apache.lucene.util.packed.PackedDataOutput}, {@link org.apache.lucene.util.packed.PackedDataInput}</b><ul>
* <li>Writes sequences of longs where each long can use any number of bits.</li>
* </ul></li>
* </ul>
*/
package org.apache.lucene.util.packed;