1   /*
    2    * Licensed to the Apache Software Foundation (ASF) under one or more
    3    * contributor license agreements.  See the NOTICE file distributed with
    4    * this work for additional information regarding copyright ownership.
    5    * The ASF licenses this file to You under the Apache License, Version 2.0
    6    * (the "License"); you may not use this file except in compliance with
    7    * the License.  You may obtain a copy of the License at
    8    *
    9    *      http://www.apache.org/licenses/LICENSE-2.0
   10    *
   11    * Unless required by applicable law or agreed to in writing, software
   12    * distributed under the License is distributed on an "AS IS" BASIS,
   13    * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   14    * See the License for the specific language governing permissions and
   15    * limitations under the License.
   16    */
   17   package org.apache.pdfbox.io;
   18   
   19   import java.io.IOException;
   20   import java.util.Arrays;
   21   
   22   /**
   23    * An interface to allow PDF files to be stored completely in memory.
   24    *
   25    * @author <a href="mailto:ben@benlitchfield.com">Ben Litchfield</a>
   26    * @version $Revision: 1.2 $
   27    */
   28   public class RandomAccessBuffer implements RandomAccess
   29   {
   30   
   31       private static final int EXTRA_SPACE = 16384; // 16kb
   32       private byte[] buffer;
   33       private long pointer;
   34       private long size;
   35   
   36       /**
   37        * Default constructor.
   38        */
   39       public RandomAccessBuffer()
   40       {
   41           buffer = new byte[EXTRA_SPACE];
   42           pointer = 0;
   43           size = EXTRA_SPACE;
   44       }
   45   
   46       /**
   47        * {@inheritDoc}
   48        */
   49       public void close() throws IOException
   50       {
   51           buffer = null;
   52           pointer = 0;
   53           size = 0;
   54       }
   55   
   56       /**
   57        * {@inheritDoc}
   58        */
   59       public void seek(long position) throws IOException
   60       {
   61           this.pointer = position;
   62       }
   63   
   64       /**
   65        * {@inheritDoc}
   66        */
   67       public int read() throws IOException
   68       {
   69           if (pointer >= this.size)
   70           {
   71               return -1;
   72           }
   73           int result = buffer[(int)pointer];
   74           pointer++;
   75           return result;
   76       }
   77   
   78       /**
   79        * {@inheritDoc}
   80        */
   81       public int read(byte[] b, int offset, int length) throws IOException
   82       {
   83           if (pointer >= this.size)
   84           {
   85               return 0;
   86           }
   87           int maxLength = (int) Math.min(length, this.size-pointer);
   88           System.arraycopy(buffer, (int) pointer, b, offset, maxLength);
   89           pointer += maxLength;
   90           return maxLength;
   91       }
   92   
   93       /**
   94        * {@inheritDoc}
   95        */
   96       public long length() throws IOException
   97       {
   98           return size;
   99       }
  100   
  101       /**
  102        * {@inheritDoc}
  103        */
  104       public void write(int b) throws IOException
  105       {
  106           write(new byte[] {(byte) b}, 0, 1);
  107       }
  108   
  109       /**
  110        * {@inheritDoc}
  111        */
  112       public void write(byte[] b, int offset, int length) throws IOException
  113       {
  114           if (pointer+length >= buffer.length)
  115           {
  116               // expand buffer
  117               byte[] temp = new byte[buffer.length+length+EXTRA_SPACE];
  118               Arrays.fill(temp, (byte)0);
  119               System.arraycopy(buffer, 0, temp, 0, (int) this.size);
  120               buffer = temp;
  121           }
  122           System.arraycopy(b, offset, buffer, (int)pointer, length);
  123           pointer += length;
  124           if (pointer > this.size)
  125           {
  126               this.size = pointer;
  127           }
  128       }
  129   }