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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:
    *
    *   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.buffer;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  import java.nio.channels.GatheringByteChannel;
  import java.nio.channels.ScatteringByteChannel;
  
  
  /**
   * A derived buffer which exposes its parent's sub-region only.  It is
   * recommended to use {@link ChannelBuffer#slice()} and
   * {@link ChannelBuffer#slice(int, int)} instead of calling the constructor
   * explicitly.
   */
  public class SlicedChannelBuffer extends AbstractChannelBuffer implements WrappedChannelBuffer {
  
      private final ChannelBuffer buffer;
      private final int adjustment;
      private final int length;
  
      public SlicedChannelBuffer(ChannelBuffer buffer, int index, int length) {
          if (index < 0 || index > buffer.capacity()) {
              throw new IndexOutOfBoundsException("Invalid index of " + index
                      + ", maximum is " + buffer.capacity());
          }
  
          if (index + length > buffer.capacity()) {
              throw new IndexOutOfBoundsException("Invalid combined index of "
                      + (index + length) + ", maximum is " + buffer.capacity());
          }
  
          this.buffer = buffer;
          adjustment = index;
          this.length = length;
          writerIndex(length);
      }
  
      public ChannelBuffer unwrap() {
          return buffer;
      }
  
      public ChannelBufferFactory factory() {
          return buffer.factory();
      }
  
      public ByteOrder order() {
          return buffer.order();
      }
  
      public boolean isDirect() {
          return buffer.isDirect();
      }
  
      public int capacity() {
          return length;
      }
  
      public boolean hasArray() {
          return buffer.hasArray();
      }
  
      public byte[] array() {
          return buffer.array();
      }
  
      public int arrayOffset() {
          return buffer.arrayOffset() + adjustment;
      }
  
      public byte getByte(int index) {
          checkIndex(index);
          return buffer.getByte(index + adjustment);
      }
  
      public short getShort(int index) {
          checkIndex(index, 2);
          return buffer.getShort(index + adjustment);
      }
  
      public int getUnsignedMedium(int index) {
          checkIndex(index, 3);
         return buffer.getUnsignedMedium(index + adjustment);
     }
 
     public int getInt(int index) {
         checkIndex(index, 4);
         return buffer.getInt(index + adjustment);
     }
 
     public long getLong(int index) {
         checkIndex(index, 8);
         return buffer.getLong(index + adjustment);
     }
 
     public ChannelBuffer duplicate() {
         ChannelBuffer duplicate = new SlicedChannelBuffer(buffer, adjustment, length);
         duplicate.setIndex(readerIndex(), writerIndex());
         return duplicate;
     }
 
     public ChannelBuffer copy(int index, int length) {
         checkIndex(index, length);
         return buffer.copy(index + adjustment, length);
     }
 
     public ChannelBuffer slice(int index, int length) {
         checkIndex(index, length);
         if (length == 0) {
             return ChannelBuffers.EMPTY_BUFFER;
         }
         return new SlicedChannelBuffer(buffer, index + adjustment, length);
     }
 
     public void getBytes(int index, ChannelBuffer dst, int dstIndex, int length) {
         checkIndex(index, length);
         buffer.getBytes(index + adjustment, dst, dstIndex, length);
     }
 
     public void getBytes(int index, byte[] dst, int dstIndex, int length) {
         checkIndex(index, length);
         buffer.getBytes(index + adjustment, dst, dstIndex, length);
     }
 
     public void getBytes(int index, ByteBuffer dst) {
         checkIndex(index, dst.remaining());
         buffer.getBytes(index + adjustment, dst);
     }
 
     public void setByte(int index, int value) {
         checkIndex(index);
         buffer.setByte(index + adjustment, value);
     }
 
     public void setShort(int index, int value) {
         checkIndex(index, 2);
         buffer.setShort(index + adjustment, value);
     }
 
     public void setMedium(int index, int value) {
         checkIndex(index, 3);
         buffer.setMedium(index + adjustment, value);
     }
 
     public void setInt(int index, int value) {
         checkIndex(index, 4);
         buffer.setInt(index + adjustment, value);
     }
 
     public void setLong(int index, long value) {
         checkIndex(index, 8);
         buffer.setLong(index + adjustment, value);
     }
 
     public void setBytes(int index, byte[] src, int srcIndex, int length) {
         checkIndex(index, length);
         buffer.setBytes(index + adjustment, src, srcIndex, length);
     }
 
     public void setBytes(int index, ChannelBuffer src, int srcIndex, int length) {
         checkIndex(index, length);
         buffer.setBytes(index + adjustment, src, srcIndex, length);
     }
 
     public void setBytes(int index, ByteBuffer src) {
         checkIndex(index, src.remaining());
         buffer.setBytes(index + adjustment, src);
     }
 
     public void getBytes(int index, OutputStream out, int length)
             throws IOException {
         checkIndex(index, length);
         buffer.getBytes(index + adjustment, out, length);
     }
 
     public int getBytes(int index, GatheringByteChannel out, int length)
             throws IOException {
         checkIndex(index, length);
         return buffer.getBytes(index + adjustment, out, length);
     }
 
     public int setBytes(int index, InputStream in, int length)
             throws IOException {
         checkIndex(index, length);
         return buffer.setBytes(index + adjustment, in, length);
     }
 
     public int setBytes(int index, ScatteringByteChannel in, int length)
             throws IOException {
         checkIndex(index, length);
         return buffer.setBytes(index + adjustment, in, length);
     }
 
     public ByteBuffer toByteBuffer(int index, int length) {
         checkIndex(index, length);
         return buffer.toByteBuffer(index + adjustment, length);
     }
 
     private void checkIndex(int index) {
         if (index < 0 || index >= capacity()) {
             throw new IndexOutOfBoundsException("Invalid index: " + index
                     + ", maximum is " + capacity());
         }
     }
 
     private void checkIndex(int startIndex, int length) {
         if (length < 0) {
             throw new IllegalArgumentException(
                     "length is negative: " + length);
         }
         if (startIndex < 0) {
             throw new IndexOutOfBoundsException("startIndex cannot be negative");
         }
         if (startIndex + length > capacity()) {
             throw new IndexOutOfBoundsException("Index too big - Bytes needed: "
                     + (startIndex + length) + ", maximum is " + capacity());
         }
     }
 }