/**
* Copyright 2014 National University of Ireland, Galway.
*
* This file is part of the SIREn project. Project and contact information:
*
* https://github.com/rdelbru/SIREn
*
* Licensed 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.sindice.siren.index.codecs.block;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.IntsRef;
/**
* Abstraction over the block compression algorithm.
*/
public abstract class BlockCompressor {
/**
* Return the window size over the {@link IntsRef} input buffer used during
* compression.
* <p>
* This is to avoid {@link ArrayIndexOutOfBoundsException} if the compressor
* is working on a buffer which size does not match a multiple of the window
* size.
* <p>
* For example, {@link AForBlockCompressor} is performing compression using
* a window of 32 integers. In the case of short postings list with
* 5 integers, the instantiated input buffer must be a multiple of window
* size, i.e., 32 in this case. If the postings list would contain 33 integers
* instead, then the instantiated input buffer should be 64.
*/
public abstract int getWindowSize();
/**
* Compress the specified list of integers into a byte array.
*/
public abstract void compress(IntsRef input, BytesRef output);
/**
* The maximum size in bytes of a compressed block of values
*/
public abstract int maxCompressedSize(int blockSize);
}