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.kafka.common.requests;
  
  import org.apache.kafka.common.message.ResponseHeaderData;
  import org.apache.kafka.common.protocol.ByteBufferAccessor;
  import org.apache.kafka.common.protocol.ObjectSerializationCache;
  
  import java.nio.ByteBuffer;
  import java.util.Objects;
  
  /**
   * A response header in the kafka protocol.
   */
  public class ResponseHeader implements AbstractRequestResponse {
      private static final int SIZE_NOT_INITIALIZED = -1;
      private final ResponseHeaderData data;
      private final short headerVersion;
      private int size = SIZE_NOT_INITIALIZED;
  
      public ResponseHeader(int correlationId, short headerVersion) {
          this(new ResponseHeaderData().setCorrelationId(correlationId), headerVersion);
      }
  
      public ResponseHeader(ResponseHeaderData data, short headerVersion) {
          this.data = data;
          this.headerVersion = headerVersion;
      }
  
      /**
       * Calculates the size of {@link ResponseHeader} in bytes.
       *
       * This method to calculate size should be only when it is immediately followed by
       * {@link #write(ByteBuffer, ObjectSerializationCache)} method call. In such cases, ObjectSerializationCache
       * helps to avoid the serialization twice. In all other cases, {@link #size()} should be preferred instead.
       *
       * Calls to this method leads to calculation of size every time it is invoked. {@link #size()} should be preferred
       * instead.
       *
       * Visible for testing.
       */
      int size(ObjectSerializationCache serializationCache) {
          return data().size(serializationCache, headerVersion);
      }
  
      /**
       * Returns the size of {@link ResponseHeader} in bytes.
       *
       * Calls to this method are idempotent and inexpensive since it returns the cached value of size after the first
       * invocation.
       */
      public int size() {
          if (this.size == SIZE_NOT_INITIALIZED) {
              this.size = size(new ObjectSerializationCache());
          }
          return size;
      }
  
      public int correlationId() {
          return this.data.correlationId();
      }
  
      public short headerVersion() {
          return headerVersion;
      }
  
      public ResponseHeaderData data() {
          return data;
      }
  
      // visible for testing
      void write(ByteBuffer buffer, ObjectSerializationCache serializationCache) {
          data.write(new ByteBufferAccessor(buffer), serializationCache, headerVersion);
      }
  
      @Override
      public String toString() {
          return "ResponseHeader("
              + "correlationId=" + data.correlationId()
              + ", headerVersion=" + headerVersion
              + ")";
      }
  
      public static ResponseHeader parse(ByteBuffer buffer, short headerVersion) {
          final int bufferStartPositionForHeader = buffer.position();
          final ResponseHeader header = new ResponseHeader(
              new ResponseHeaderData(new ByteBufferAccessor(buffer), headerVersion), headerVersion);
          // Size of header is calculated by the shift in the position of buffer's start position during parsing.
          // Prior to parsing, the buffer's start position points to header data and after the parsing operation
          // the buffer's start position points to api message. For more information on how the buffer is
          // constructed, see RequestUtils#serialize()
          header.size = Math.max(buffer.position() - bufferStartPositionForHeader, 0);
          return header;
      }
  
      @Override
      public boolean equals(Object o) {
          if (this == o) return true;
          if (o == null || getClass() != o.getClass()) return false;
          ResponseHeader that = (ResponseHeader) o;
          return headerVersion == that.headerVersion &&
              Objects.equals(data, that.data);
      }
  
      @Override
      public int hashCode() {
          return Objects.hash(data, headerVersion);
      }
  }
  