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   /*
    * Copyright 2012 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.http;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.Unpooled;
  import io.netty.util.internal.StringUtil;
  
  import java.util.Map.Entry;
  
  import static io.netty.handler.codec.http.DefaultHttpHeadersFactory.trailersFactory;
  import static io.netty.util.internal.ObjectUtil.checkNotNull;
  
  /**
   * The default {@link LastHttpContent} implementation.
   */
  public class DefaultLastHttpContent extends DefaultHttpContent implements LastHttpContent {
      private final HttpHeaders trailingHeaders;
  
      /**
       * Create a new empty, last HTTP content message.
       */
      public DefaultLastHttpContent() {
          this(Unpooled.buffer(0));
      }
  
      /**
       * Create a new last HTTP content message with the given contents.
       */
      public DefaultLastHttpContent(ByteBuf content) {
          this(content, trailersFactory());
      }
  
      /**
       * Create a new last HTTP content message with the given contents, and optional trailing header validation.
       * <p>
       * <b>Warning!</b> Setting {@code validateHeaders} to {@code false} will mean that Netty won't
       * validate & protect against user-supplied header values that are malicious.
       * This can leave your server implementation vulnerable to
       * <a href="https://cwe.mitre.org/data/definitions/113.html">
       *     CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting')
       * </a>.
       * When disabling this validation, it is the responsibility of the caller to ensure that the values supplied
       * do not contain a non-url-escaped carriage return (CR) and/or line feed (LF) characters.
       *
       * @deprecated Prefer the {@link #DefaultLastHttpContent(ByteBuf)} constructor instead, to always have header
       * validation enabled.
       */
      @Deprecated
      public DefaultLastHttpContent(ByteBuf content, boolean validateHeaders) {
          this(content, trailersFactory().withValidation(validateHeaders));
      }
  
      /**
       * Create a new last HTTP content message with the given contents, and trailing headers from the given factory.
       */
      public DefaultLastHttpContent(ByteBuf content, HttpHeadersFactory trailersFactory) {
          super(content);
          trailingHeaders = trailersFactory.newHeaders();
      }
  
      /**
       * Create a new last HTTP content message with the given contents, and trailing headers.
       */
      public DefaultLastHttpContent(ByteBuf content, HttpHeaders trailingHeaders) {
          super(content);
          this.trailingHeaders = checkNotNull(trailingHeaders, "trailingHeaders");
      }
  
      @Override
      public LastHttpContent copy() {
          return replace(content().copy());
      }
  
      @Override
      public LastHttpContent duplicate() {
          return replace(content().duplicate());
      }
  
      @Override
      public LastHttpContent retainedDuplicate() {
          return replace(content().retainedDuplicate());
      }
  
      @Override
      public LastHttpContent replace(ByteBuf content) {
         return new DefaultLastHttpContent(content, trailingHeaders().copy());
     }
 
     @Override
     public LastHttpContent retain(int increment) {
         super.retain(increment);
         return this;
     }
 
     @Override
     public LastHttpContent retain() {
         super.retain();
         return this;
     }
 
     @Override
     public LastHttpContent touch() {
         super.touch();
         return this;
     }
 
     @Override
     public LastHttpContent touch(Object hint) {
         super.touch(hint);
         return this;
     }
 
     @Override
     public HttpHeaders trailingHeaders() {
         return trailingHeaders;
     }
 
     @Override
     public String toString() {
         StringBuilder buf = new StringBuilder(super.toString());
         buf.append(StringUtil.NEWLINE);
         appendHeaders(buf);
 
         // Remove the last newline.
         buf.setLength(buf.length() - StringUtil.NEWLINE.length());
         return buf.toString();
     }
 
     private void appendHeaders(StringBuilder buf) {
         for (Entry<String, String> e : trailingHeaders()) {
             buf.append(e.getKey());
             buf.append(": ");
             buf.append(e.getValue());
             buf.append(StringUtil.NEWLINE);
         }
     }
 }