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    1   /*
    2    * Copyright 2012 The Netty Project
    3    *
    4    * The Netty Project licenses this file to you under the Apache License,
    5    * version 2.0 (the "License"); you may not use this file except in compliance
    6    * with the License. You may obtain a copy of the License at:
    7    *
    8    *   http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
    12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
    13   * License for the specific language governing permissions and limitations
    14   * under the License.
    15   */
    16  package org.jboss.netty.handler.codec.base64;
    17
    18  import org.jboss.netty.buffer.ChannelBuffer;
    19  import org.jboss.netty.buffer.ChannelBuffers;
    20  import org.jboss.netty.channel.Channel;
    21  import org.jboss.netty.channel.ChannelHandler.Sharable;
    22  import org.jboss.netty.channel.ChannelHandlerContext;
    23  import org.jboss.netty.channel.ChannelPipeline;
    24  import org.jboss.netty.handler.codec.frame.DelimiterBasedFrameDecoder;
    25  import org.jboss.netty.handler.codec.frame.Delimiters;
    26  import org.jboss.netty.handler.codec.frame.FrameDecoder;
    27  import org.jboss.netty.handler.codec.oneone.OneToOneDecoder;
    28  import org.jboss.netty.util.CharsetUtil;
    29
    30  /**
    31   * Decodes a Base64-encoded {@link ChannelBuffer} or US-ASCII {@link String}
    32   * into a {@link ChannelBuffer}.  Please note that this decoder must be used
    33   * with a proper {@link FrameDecoder} such as {@link DelimiterBasedFrameDecoder}
    34   * if you are using a stream-based transport such as TCP/IP.  A typical decoder
    35   * setup for TCP/IP would be:
    36   * <pre>
    37   * {@link ChannelPipeline} pipeline = ...;
    38   *
    39   * // Decoders
    40   * pipeline.addLast("frameDecoder", new {@link DelimiterBasedFrameDecoder}(80, {@link Delimiters#nulDelimiter()}));
    41   * pipeline.addLast("base64Decoder", new {@link Base64Decoder}());
    42   *
    43   * // Encoder
    44   * pipeline.addLast("base64Encoder", new {@link Base64Encoder}());
    45   * </pre>
    46   * @apiviz.landmark
    47   * @apiviz.uses org.jboss.netty.handler.codec.base64.Base64
    48   */
    49  @Sharable
    50  public class Base64Decoder extends OneToOneDecoder {
    51
    52      private final Base64Dialect dialect;
    53
    54      public Base64Decoder() {
    55          this(Base64Dialect.STANDARD);
    56      }
    57
    58      public Base64Decoder(Base64Dialect dialect) {
    59          if (dialect == null) {
    60              throw new NullPointerException("dialect");
    61          }
    62          this.dialect = dialect;
    63      }
    64
    65      @Override
    66      protected Object decode(ChannelHandlerContext ctx, Channel channel, Object msg)
    67              throws Exception {
    68          if (msg instanceof String) {
    69              msg = ChannelBuffers.copiedBuffer((String) msg, CharsetUtil.US_ASCII);
    70          } else if (!(msg instanceof ChannelBuffer)) {
    71              return msg;
    72          }
    73
    74          ChannelBuffer src = (ChannelBuffer) msg;
    75          return Base64.decode(
    76                  src, src.readerIndex(), src.readableBytes(), dialect);
    77      }
    78
    79  }