package java.io;

public class RandomAccessFile {
  private long peer;
  private long length;
  private long position = 0;
  
  public RandomAccessFile(String name, String mode)
    throws FileNotFoundException
  {
    if (! mode.equals("r")) throw new IllegalArgumentException();

    long[] result = new long[2];
    open(name, result);
    peer = result[0];
    length = result[1];
  }

  private static native void open(String name, long[] result)
    throws FileNotFoundException;

  public long length() throws IOException {
    return length;
  }

  public long getFilePointer() throws IOException {
    return position;
  }

  public void seek(long position) throws IOException {
    if (position < 0 || position > length) throw new IOException();

    this.position = position;
  }

  public void readFully(byte[] buffer, int offset, int length)
    throws IOException
  {
    if (peer == 0) throw new IOException();

    if (length == 0) return;

    if (position + length > this.length) throw new EOFException();

    if (offset < 0 || offset + length > buffer.length)
      throw new ArrayIndexOutOfBoundsException();

    copy(peer, position, buffer, offset, length);
  }

  private static native void copy(long peer, long position, byte[] buffer,
                                  int offset, int length);

  public void close() throws IOException {
    if (peer != 0) {
      close(peer);
      peer = 0;
    }
  }

  private static native void close(long peer);
}