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   /*
    * Copyright 2016 The Netty Project
    *
    * The Netty Project 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:
    *
    * https://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 io.netty.handler.codec.redis;
  
  import io.netty.util.internal.StringUtil;
  import io.netty.util.internal.UnstableApi;
  
  /**
   * Header of Redis Array Message.
   */
  @UnstableApi
  public class ArrayHeaderRedisMessage implements RedisMessage {
  
      private final long length;
  
      /**
       * Creates a {@link ArrayHeaderRedisMessage} for the given {@code length}.
       */
      public ArrayHeaderRedisMessage(long length) {
          if (length < RedisConstants.NULL_VALUE) {
              throw new RedisCodecException("length: " + length + " (expected: >= " + RedisConstants.NULL_VALUE + ")");
          }
          this.length = length;
      }
  
      /**
       * Get length of this array object.
       */
      public final long length() {
          return length;
      }
  
      /**
       * Returns whether the content of this message is {@code null}.
       *
       * @return indicates whether the content of this message is {@code null}.
       */
      public boolean isNull() {
          return length == RedisConstants.NULL_VALUE;
      }
  
      @Override
      public String toString() {
          return new StringBuilder(StringUtil.simpleClassName(this))
                  .append('[')
                  .append("length=")
                  .append(length)
                  .append(']').toString();
      }
  }