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.distributedlog.io;
  
  import static com.google.common.base.Preconditions.checkArgument;
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.PooledByteBufAllocator;
  import java.nio.ByteBuffer;
  import net.jpountz.lz4.LZ4Compressor;
  import net.jpountz.lz4.LZ4Factory;
  import net.jpountz.lz4.LZ4FastDecompressor;
  
  /**
   * An {@code lz4} based {@link CompressionCodec} implementation.
   *
   * <p>All functions are thread safe.
   */
  public class LZ4CompressionCodec implements CompressionCodec {
  
      public static LZ4CompressionCodec of() {
          return INSTANCE;
      }
  
      private static final LZ4CompressionCodec INSTANCE = new LZ4CompressionCodec();
  
      private static final LZ4Factory factory = LZ4Factory.fastestJavaInstance();
      // Used for compression
      private static final LZ4Compressor compressor = factory.fastCompressor();
      // Used to decompress when the size of the output is known
      private static final LZ4FastDecompressor decompressor = factory.fastDecompressor();
  
      @Override
      public ByteBuf compress(ByteBuf uncompressed, int headerLen) {
          checkNotNull(uncompressed);
          checkArgument(uncompressed.readableBytes() > 0);
  
          int uncompressedLen = uncompressed.readableBytes();
          int maxLen = compressor.maxCompressedLength(uncompressedLen);
  
          // get the source bytebuffer
          ByteBuffer uncompressedNio = uncompressed.nioBuffer(uncompressed.readerIndex(), uncompressedLen);
          ByteBuf compressed = PooledByteBufAllocator.DEFAULT.buffer(
                  maxLen + headerLen, maxLen + headerLen);
          ByteBuffer compressedNio = compressed.nioBuffer(headerLen, maxLen);
  
          int compressedLen = compressor.compress(
                  uncompressedNio, uncompressedNio.position(), uncompressedLen,
                  compressedNio, compressedNio.position(), maxLen);
          compressed.writerIndex(compressedLen + headerLen);
  
          return compressed;
      }
  
      @Override
      // length parameter is ignored here because of the way the fastDecompressor works.
      public ByteBuf decompress(ByteBuf compressed, int decompressedSize) {
          checkNotNull(compressed);
          checkArgument(compressed.readableBytes() >= 0);
          checkArgument(decompressedSize >= 0);
  
          ByteBuf uncompressed = PooledByteBufAllocator.DEFAULT.buffer(decompressedSize, decompressedSize);
          ByteBuffer uncompressedNio = uncompressed.nioBuffer(0, decompressedSize);
          ByteBuffer compressedNio = compressed.nioBuffer(compressed.readerIndex(), compressed.readableBytes());
  
          decompressor.decompress(
                  compressedNio, compressedNio.position(),
                  uncompressedNio, uncompressedNio.position(), uncompressedNio.remaining());
          uncompressed.writerIndex(decompressedSize);
          return uncompressed;
      }
  }
  