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.calcite.runtime;
  
  import org.apache.calcite.avatica.util.ByteString;
  
  import org.apache.commons.lang3.StringUtils;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  import java.nio.charset.Charset;
  import java.util.zip.DeflaterOutputStream;
  
  /**
   * A collection of functions used in compression and decompression.
   */
  public class CompressionFunctions {
  
    private CompressionFunctions() {
    }
  
    /**
     * MySql Compression is based on zlib.
     * <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/zip/Deflater.html">Deflater</a>
     * is used to implement compression.
     */
    public static @Nullable ByteString compress(@Nullable String data) {
      try {
        if (data == null) {
          return null;
        }
        if (StringUtils.isEmpty(data)) {
          return new ByteString(new byte[0]);
        }
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        ByteBuffer dataLength = ByteBuffer.allocate(4);
        dataLength.order(ByteOrder.LITTLE_ENDIAN);
        dataLength.putInt(data.length());
        outputStream.write(dataLength.array());
        DeflaterOutputStream inflaterStream = new DeflaterOutputStream(outputStream);
        inflaterStream.write(data.getBytes(Charset.defaultCharset()));
        inflaterStream.close();
        return new ByteString(outputStream.toByteArray());
      } catch (IOException e) {
        return null;
      }
    }
  
  }
  