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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.base64;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandler.Sharable;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelPipeline;
  import io.netty.handler.codec.ByteToMessageDecoder;
  import io.netty.handler.codec.DelimiterBasedFrameDecoder;
  import io.netty.handler.codec.Delimiters;
  import io.netty.handler.codec.MessageToMessageDecoder;
  import io.netty.util.internal.ObjectUtil;
  
  import java.util.List;
  
  /**
   * Decodes a Base64-encoded {@link ByteBuf} or US-ASCII {@link String}
   * into a {@link ByteBuf}.  Please note that this decoder must be used
   * with a proper {@link ByteToMessageDecoder} such as {@link DelimiterBasedFrameDecoder}
   * if you are using a stream-based transport such as TCP/IP.  A typical decoder
   * setup for TCP/IP would be:
   * <pre>
   * {@link ChannelPipeline} pipeline = ...;
   *
   * // Decoders
   * pipeline.addLast("frameDecoder", new {@link DelimiterBasedFrameDecoder}(80, {@link Delimiters#nulDelimiter()}));
   * pipeline.addLast("base64Decoder", new {@link Base64Decoder}());
   *
   * // Encoder
   * pipeline.addLast("base64Encoder", new {@link Base64Encoder}());
   * </pre>
   */
  @Sharable
  public class Base64Decoder extends MessageToMessageDecoder<ByteBuf> {
  
      private final Base64Dialect dialect;
  
      public Base64Decoder() {
          this(Base64Dialect.STANDARD);
      }
  
      public Base64Decoder(Base64Dialect dialect) {
          this.dialect = ObjectUtil.checkNotNull(dialect, "dialect");
      }
  
      @Override
      protected void decode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out) throws Exception {
          out.add(Base64.decode(msg, msg.readerIndex(), msg.readableBytes(), dialect));
      }
  }