Re: [Jython-users] Serial Port

[Samuele P. <pe...@in...>]

Hi.

[Marc Koch]

> Please help, ... what am I missing?!?
something unrelated to serial port usage in java I think

 
> class MySerialPortEventListener (comm.SerialPortEventListener):
>     def serialEvent (self, Event):
>         print Event
>         try:
>             IBuf = '--------'
This assign a python string to IBuf (note: python string are immutable
 they cannot be used as buffers <wink>) ...
>             ILen = IStream.available()
>             while ILen > 0:
>                 INum = IStream.read(IBuf)
read take a byte[], now python strings are actually automatically
converted to byte[] if they are passed to a method that takes such an 
argument but this conversion is done but making a copy of the string
(to respect immutability), java has no const or in or out modifiers
for arguments so jython in any case here could not detect that something
wrong is possibly going on, he just tries to make its best creating
a byte[] array containing just a copy of the string

>                 print 'Read: OK', ILen, INum, IBuf
the copied byte[] is probably modified in the right way, but IBuf
is still a reference to the old string so ...

>                 ILen = IStream.available()
>         except:
>             raise

Solution: the jython idiom for allocating a mutable array that can be passed
to java methods wanting a writeable buffer is:

import jarray

buf = jarray.zeros(<length>,'b') # 'b' stands for bytes 
                                 # <length> is an expr ...

For further details see the doc:
  http://www.jython.org/docs/jarray.html online
or the same in your jython installation tree.

regards.