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/*
 * Copyright 2005-2014 Red Hat, Inc.
 * Red Hat 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.hornetq.utils;

import java.io.IOException;
import java.io.InputStream;
import java.util.zip.DataFormatException;
import java.util.zip.Inflater;

/**
 * An InflaterReader
 * It takes an compressed input stream and decompressed it as it is being read.
 * Not for concurrent use.
 *
 * @author Howard Gao
 */
public class InflaterReader extends InputStream
{
   private Inflater inflater = new Inflater();

   private InputStream input;

   private byte[] readBuffer;
   private int pointer;
   private int length;

   public InflaterReader(InputStream input)
   {
      this(input, 1024);
   }

   public InflaterReader(InputStream input, int bufferSize)
   {
      this.input = input;
      this.readBuffer = new byte[bufferSize];
      this.pointer = -1;
   }

   public int read() throws IOException
   {
      if (pointer == -1)
      {
         try
         {
            length = doRead(readBuffer, 0, readBuffer.length);
            if (length == 0)
            {
               return -1;
            }
            pointer = 0;
         }
         catch (DataFormatException e)
         {
            IOException e2 = new IOException(e.getMessage());
            e2.initCause(e);
            throw e2;
         }
      }

      int value = readBuffer[pointer] & 0xFF;
      pointer++;
      if (pointer == length)
      {
         pointer = -1;
      }

      return value;
   }

   /*
    * feed inflater more bytes in order to get some
    * decompressed output.
    * returns number of bytes actually got
    */
   private int doRead(byte[] buf, int offset, int len) throws DataFormatException, IOException
   {
      int read = 0;
      int n = 0;
      byte[] inputBuffer = new byte[len];

      while (len > 0)
      {
         n = inflater.inflate(buf, offset, len);
         if (n == 0)
         {
            if (inflater.finished())
            {
               break;
            }
            else if (inflater.needsInput())
            {
               //feeding
               int m = input.read(inputBuffer);

               if (m == -1)
               {
                  //it shouldn't be here, throw exception
                  throw new DataFormatException("Input is over while inflater still expecting data");
               }
               else
               {
                  //feed the data in
                  inflater.setInput(inputBuffer, 0, m);
                  n = inflater.inflate(buf, offset, len);
                  if (n > 0)
                  {
                     read += n;
                     offset += n;
                     len -= n;
                  }
               }
            }
            else
            {
               //it shouldn't be here, throw
               throw new DataFormatException("Inflater is neither finished nor needing input.");
            }
         }
         else
         {
            read += n;
            offset += n;
            len -= n;
         }
      }
      return read;
   }

}