RAMInputStream(RAMFile f) throws IOException 
{
      
    file = f;
    length = file.length;
    if (length/BUFFER_SIZE  >= Integer.MAX_VALUE) {
      throw new IOException("Too large RAMFile! "+length); 
    }
    // make sure that we switch to the
    // first needed buffer lazily
    currentBufferIndex = -1;
    currentBuffer = null;
}

 public  void close() 
{
    // nothing to do here
}

 public long getFilePointer() 
{
    return currentBufferIndex <  0 ? 0 : bufferStart + bufferPosition;
}

 public long length() 
{
    return length;
}

 public byte readByte() throws IOException 
{
    if (bufferPosition  >= bufferLength) {
      currentBufferIndex++;
      switchCurrentBuffer(true);
    }
    return currentBuffer[bufferPosition++];
}

 public  void readBytes(byte[] b,
    int offset,
    int len) throws IOException 
{
    while (len  > 0) {
      if (bufferPosition  >= bufferLength) {
        currentBufferIndex++;
        switchCurrentBuffer(true);
      }
      int remainInBuffer = bufferLength - bufferPosition;
      int bytesToCopy = len <  remainInBuffer ? len : remainInBuffer;
      System.arraycopy(currentBuffer, bufferPosition, b, offset, bytesToCopy);
      offset += bytesToCopy;
      len -= bytesToCopy;
      bufferPosition += bytesToCopy;
    }
}

 public  void seek(long pos) throws IOException 
{
    if (currentBuffer==null || pos <  bufferStart || pos  >= bufferStart + BUFFER_SIZE) {
      currentBufferIndex = (int) (pos / BUFFER_SIZE);
      switchCurrentBuffer(false);
    }
    bufferPosition = (int) (pos % BUFFER_SIZE);
}