content: /*
   * 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.arrow.vector.compression;
  
  import org.apache.arrow.memory.ArrowBuf;
  import org.apache.arrow.memory.BufferAllocator;
  import org.apache.arrow.memory.util.MemoryUtil;
  import org.apache.arrow.util.Preconditions;
  
  /**
   * The base class for concrete compression codecs, providing common logic for all compression
   * codecs.
   */
  public abstract class AbstractCompressionCodec implements CompressionCodec {
  
    @Override
    public ArrowBuf compress(BufferAllocator allocator, ArrowBuf uncompressedBuffer) {
      if (uncompressedBuffer.writerIndex() == 0L) {
        // shortcut for empty buffer
        ArrowBuf compressedBuffer = allocator.buffer(CompressionUtil.SIZE_OF_UNCOMPRESSED_LENGTH);
        compressedBuffer.setLong(0, 0);
        compressedBuffer.writerIndex(CompressionUtil.SIZE_OF_UNCOMPRESSED_LENGTH);
        uncompressedBuffer.close();
        return compressedBuffer;
      }
  
      ArrowBuf compressedBuffer = doCompress(allocator, uncompressedBuffer);
      long compressedLength =
          compressedBuffer.writerIndex() - CompressionUtil.SIZE_OF_UNCOMPRESSED_LENGTH;
      long uncompressedLength = uncompressedBuffer.writerIndex();
  
      if (compressedLength > uncompressedLength) {
        // compressed buffer is larger, send the raw buffer
        compressedBuffer.close();
        // XXX: this makes a copy of uncompressedBuffer
        compressedBuffer = CompressionUtil.packageRawBuffer(allocator, uncompressedBuffer);
      } else {
        writeUncompressedLength(compressedBuffer, uncompressedLength);
      }
  
      uncompressedBuffer.close();
      return compressedBuffer;
    }
  
    @Override
    public ArrowBuf decompress(BufferAllocator allocator, ArrowBuf compressedBuffer) {
      Preconditions.checkArgument(
          compressedBuffer.writerIndex() >= CompressionUtil.SIZE_OF_UNCOMPRESSED_LENGTH,
          "Not enough data to decompress.");
  
      long decompressedLength = readUncompressedLength(compressedBuffer);
  
      if (decompressedLength == 0L) {
        // shortcut for empty buffer
        compressedBuffer.close();
        return allocator.getEmpty();
      }
  
      if (decompressedLength == CompressionUtil.NO_COMPRESSION_LENGTH) {
        // no compression
        return CompressionUtil.extractUncompressedBuffer(compressedBuffer);
      }
  
      ArrowBuf decompressedBuffer = doDecompress(allocator, compressedBuffer);
      compressedBuffer.close();
      return decompressedBuffer;
    }
  
    protected void writeUncompressedLength(ArrowBuf compressedBuffer, long uncompressedLength) {
      if (!MemoryUtil.LITTLE_ENDIAN) {
        uncompressedLength = Long.reverseBytes(uncompressedLength);
      }
      // first 8 bytes reserved for uncompressed length, according to the specification
      compressedBuffer.setLong(0, uncompressedLength);
    }
  
    protected long readUncompressedLength(ArrowBuf compressedBuffer) {
      long decompressedLength = compressedBuffer.getLong(0);
      if (!MemoryUtil.LITTLE_ENDIAN) {
        decompressedLength = Long.reverseBytes(decompressedLength);
      }
      return decompressedLength;
    }
  
    /**
     * The method that actually performs the data compression. The layout of the returned compressed
     * buffer is the compressed data, plus 8 bytes reserved at the beginning of the buffer for the
     * uncompressed data size.
     *
     * <p>Please note that this method is not responsible for releasing the uncompressed buffer.
     */
    protected abstract ArrowBuf doCompress(BufferAllocator allocator, ArrowBuf uncompressedBuffer);
  
    /**
     * The method that actually performs the data decompression. The layout of the compressed buffer
     * is the compressed data, plus 8 bytes at the beginning of the buffer storing the uncompressed
     * data size.
     *
     * <p>Please note that this method is not responsible for releasing the compressed buffer.
     */
    protected abstract ArrowBuf doDecompress(BufferAllocator allocator, ArrowBuf compressedBuffer);
  }
  