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   /*
    * Copyright 2013 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:
    *
    *   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.jboss.netty.handler.codec.spdy;
  
  import org.jboss.netty.buffer.ChannelBuffer;
  import org.jboss.netty.buffer.ChannelBuffers;
  
  import java.nio.ByteOrder;
  import java.util.Set;
  
  import static org.jboss.netty.handler.codec.spdy.SpdyCodecUtil.*;
  
  public class SpdyHeaderBlockRawEncoder extends SpdyHeaderBlockEncoder {
  
      private final int version;
  
      public SpdyHeaderBlockRawEncoder(SpdyVersion spdyVersion) {
          if (spdyVersion == null) {
              throw new NullPointerException("spdyVersion");
          }
          version = spdyVersion.getVersion();
      }
  
      private static void setLengthField(ChannelBuffer buffer, int writerIndex, int length) {
          buffer.setInt(writerIndex, length);
      }
  
      private static void writeLengthField(ChannelBuffer buffer, int length) {
          buffer.writeInt(length);
      }
  
      @Override
      public ChannelBuffer encode(SpdyHeadersFrame headerFrame) throws Exception {
          Set<String> names = headerFrame.headers().names();
          int numHeaders = names.size();
          if (numHeaders == 0) {
              return ChannelBuffers.EMPTY_BUFFER;
          }
          if (numHeaders > SPDY_MAX_NV_LENGTH) {
              throw new IllegalArgumentException(
                      "header block contains too many headers");
          }
          ChannelBuffer headerBlock = ChannelBuffers.dynamicBuffer(
                  ByteOrder.BIG_ENDIAN, 256);
          writeLengthField(headerBlock, numHeaders);
          for (String name: names) {
              byte[] nameBytes = name.getBytes("UTF-8");
              writeLengthField(headerBlock, nameBytes.length);
              headerBlock.writeBytes(nameBytes);
              int savedIndex = headerBlock.writerIndex();
              int valueLength = 0;
              writeLengthField(headerBlock, valueLength);
              for (String value: headerFrame.headers().getAll(name)) {
                  byte[] valueBytes = value.getBytes("UTF-8");
                  if (valueBytes.length > 0) {
                      headerBlock.writeBytes(valueBytes);
                      headerBlock.writeByte(0);
                      valueLength += valueBytes.length + 1;
                  }
              }
              if (valueLength != 0) {
                  valueLength --;
              }
              if (valueLength > SPDY_MAX_NV_LENGTH) {
                  throw new IllegalArgumentException(
                          "header exceeds allowable length: " + name);
              }
              if (valueLength > 0) {
                  setLengthField(headerBlock, savedIndex, valueLength);
                  headerBlock.writerIndex(headerBlock.writerIndex() - 1);
              }
          }
          return headerBlock;
      }
  
      @Override
      void end() {
      }
  }