filedescriptor.java

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    return nativeReadBuf(nativeFd, buf, offset, len);
  }

  /**
   * Returns the number of bytes available for reading
   *
   * @return The number of bytes available for reading
   *
   * @exception IOException If an error occurs
   */
  int available() throws IOException
  {
    if (nativeFd == -1L)
      throw new IOException("Invalid FileDescriptor");
    
    return nativeAvailable(nativeFd);
  }

  /**
   * Method to do a "seek" operation on the file
   * 
   * @param offset The number of bytes to seek
   * @param whence The position to seek from, either
   *    SET (0) for the beginning of the file, CUR (1) for the 
   *    current position or END (2) for the end position.
   * @param stopAtEof <code>true</code> to ensure that there is no
   *    seeking past the end of the file, <code>false</code> otherwise.
   *
   * @return The new file position, or -1 if end of file.
   *
   * @exception IOException If an error occurs
   */
  long seek(long offset, int whence, boolean stopAtEof) throws IOException
  {
    if (nativeFd == -1L)
      throw new IOException("Invalid FileDescriptor");

    if ((whence != SET) && (whence != CUR) && (whence != END))
      throw new IllegalArgumentException("Invalid whence value: " + whence);

    return nativeSeek(nativeFd, offset, whence, stopAtEof);
  }

  /**
   * Returns the current position of the file pointer in the file
   *
   * @param fd The native file descriptor
   *
   * @exception IOException If an error occurs
   */
  long getFilePointer() throws IOException
  { 
    if (nativeFd == -1L)
      throw new IOException("Invalid FileDescriptor");

    return nativeGetFilePointer(nativeFd);
  }

  /**
   * Returns the length of the file in bytes
   *
   * @return The length of the file in bytes
   *
   * @exception IOException If an error occurs
   */
  long getLength() throws IOException
  {
    if (nativeFd == -1L)
      throw new IOException("Invalid FileDescriptor");

    return nativeGetLength(nativeFd);
  }

  /**
   * Sets the length of the file to the specified number of bytes
   * This can result in truncation or extension.
   *
   * @param len The new length of the file
   *
   * @exception IOException If an error occurs
   */
  void setLength(long len) throws IOException
  {
    if (nativeFd == -1L)
      throw new IOException("Invalid FileDescriptor");

    if (len < 0)
      throw new IllegalArgumentException("Length cannot be less than zero " +
                                         len);

    nativeSetLength(nativeFd, len);
  }

  // Don't do anything crazy with this
  long getNativeFd()
  {
    return nativeFd;
  }

  private void setNativeFd(long nativeFd)
  {
    this.nativeFd = nativeFd;
  }

  protected void finalize() throws Throwable
  {
    close();
  }

  /*
   * Native FileDescriptor provider interface
   *
   * Platform implementors must implement these methods.  Note that this
   * class guarantees that valid data will be passed to these methods,
   * so basic error checking on input values can be skipped.
   */

  /**
   * This method is called in the class initializer to do any require
   * native library initialization.  It is also responsible for initializing
   * the in, out, and err variables.
   */
  private static native void nativeInit();

  /**
   * Opens the specified file in the specified mode.  This can be done
   * in one of the specified modes:
   * <ul>
   * <li>r - Read Only
   * <li>rw - Read / Write
   * <li>ra - Read / Write - append to end of file
   * <li>rws - Read / Write - synchronous writes of data/metadata
   * <li>rwd - Read / Write - synchronous writes of data.
   *
   * @param path Name of the file to open
   * @param mode Mode to open
   *
   * @return The resulting file descriptor for the opened file, or -1
   * on failure (exception also signaled).
   *
   * @exception IOException If an error occurs.
   */
  private native long nativeOpen(String path, int mode)
    throws FileNotFoundException;

  /**
   * Closes this specified file descriptor
   * 
   * @param fd The native file descriptor to close
   *
   * @return The return code of the native close command.
   *
   * @exception IOException If an error occurs 
   */    
  private native long nativeClose(long fd) throws IOException;
 
  /**
   * Writes a single byte to the file
   *
   * @param fd The native file descriptor to write to
   * @param b The byte to write, encoded in the low eight bits
   *
   * @return The return code of the native write command
   *
   * @exception IOException If an error occurs
   */
  private native long nativeWriteByte(long fd, int b) throws IOException;

  /**
   * Writes a byte buffer to the file
   *
   * @param fd The native file descriptor to write to
   * @param buf The byte buffer to write from
   * @param int The offset into the buffer to start writing from
   * @param len The number of bytes to write.
   *
   * @return The return code of the native write command
   *
   * @exception IOException If an error occurs
   */
  private native long nativeWriteBuf(long fd, byte[] buf, int offset, int len)
    throws IOException;

  /**
   * Reads a single byte from the file
   *
   * @param fd The native file descriptor to read from
   *
   * @return The byte read, in the low eight bits on a long, or -1
   * if end of file
   *
   * @exception IOException If an error occurs
   */
  private native int nativeReadByte(long fd) throws IOException;

  /**
   * Reads a buffer of  bytes from the file
   *
   * @param fd The native file descriptor to read from
   * @param buf The buffer to read bytes into
   * @param offset The offset into the buffer to start storing bytes
   * @param len The number of bytes to read.
   *
   * @return The number of bytes read, or -1 if end of file.
   *
   * @exception IOException If an error occurs
   */
  private native int nativeReadBuf(long fd, byte[] buf, int offset, int len) 
    throws IOException;

  /**
   * Returns the number of bytes available for reading
   *
   * @param fd The native file descriptor
   *
   * @return The number of bytes available for reading
   *
   * @exception IOException If an error occurs
   */
  private native int nativeAvailable(long fd) throws IOException;

  /**
   * Method to do a "seek" operation on the file
   * 
   * @param fd The native file descriptor 
   * @param offset The number of bytes to seek
   * @param whence The position to seek from, either
   *    SET (0) for the beginning of the file, CUR (1) for the 
   *    current position or END (2) for the end position.
   * @param stopAtEof <code>true</code> to ensure that there is no
   *    seeking past the end of the file, <code>false</code> otherwise.
   *
   * @return The new file position, or -1 if end of file.
   *
   * @exception IOException If an error occurs
   */
  private native long nativeSeek(long fd, long offset, int whence, 
                                 boolean stopAtEof)
    throws IOException;

  /**
   * Returns the current position of the file pointer in the file
   *
   * @param fd The native file descriptor
   *
   * @exception IOException If an error occurs
   */
  private native long nativeGetFilePointer(long fd) throws IOException;

  /**
   * Returns the length of the file in bytes
   *
   * @param fd The native file descriptor
   *
   * @return The length of the file in bytes
   *
   * @exception IOException If an error occurs
   */
  private native long nativeGetLength(long fd) throws IOException;

  /**
   * Sets the length of the file to the specified number of bytes
   * This can result in truncation or extension.
   *
   * @param fd The native file descriptor  
   * @param len The new length of the file
   *
   * @exception IOException If an error occurs
   */
  private native void nativeSetLength(long fd, long len) throws IOException;

  /**
   * Tests a file descriptor for validity
   *
   * @param fd The native file descriptor
   *
   * @return <code>true</code> if the fd is valid, <code>false</code> 
   * otherwise
   */
  private native boolean nativeValid(long fd);

  /**
   * Flushes any buffered contents to disk
   *
   * @param fd The native file descriptor
   *
   * @exception IOException If an error occurs
   */
  private native void nativeSync(long fd) throws SyncFailedException;
}