Re: [Jython-users] Binary data changed in read

[<bc...@wo...>]

[D-Man]

>On Thu, Mar 08, 2001 at 05:09:42PM -0800, John Mudd wrote:
>| This should be easy.  Reading a binary file in Jython causes changes to
>| the data?  But it works in Python.
>
>You forgot to mention that you are using a kernel/OS that likes to
>mangle your data.  ;-)

I strongly suspect that John is using a *nix for the Jython test.

>Use _binary_ mode for writing _binary_ data.

Correct.

>| $ jython
>| Jython 2.0 on javaVM-1.3.0.01 (JIT: null)
>| Type "copyright", "credits" or "license" for more information.
>| >>> tiffObj = open('john.tif', 'r').read()
>| >>> open('junk.tif', 'w').write(tiffObj)
>                        ^
>This is "text" mode and Windoze likes to replace every \n with \r\n in
>such streams.  This is what causes your data corruption.  Fortunately
>on *nix systems the kernel doesn't mangle your streams under the hood.

Incorrect. It is Jython that does this mangling. The issue basicly is:
should a read from a file into a unicode String read the data as binary
(and always set the top 8 bit to zero) or as text by passing the data
through the default encoding.

Without the 'b' flag, Jython is reading and writing the data as if using
a Reader/Writer class. When you use the 'b' flag it uses a
InputStream/OutputStream. 

This overloading of the 'b' flag (the flag also controls the platform
dependent newline translation) is not a good thing, but it was the best
I could come up with. Normally is works as expected and I think that
also goes for John's case.

regards,
finn