[Python-Dev] Parametrized codecs

[M.-A. Lemburg]

Andrew Kuchling wrote:
> 
> >The codec design allows extending the constructors using keyword
> >arguments, however I'd rather not add a generic **kws argument
> >to the base classes since this would hide errors (unknown or
> >unsupported keywords, mispellings, etc.).
> 
> Isn't such an argument required at least for StreamReaderWriter,
> because it actually instantiates two objects?
> 
> class StreamReaderWriter:
>     def __init__(self, stream, Reader, Writer, errors='strict'):
> 
>         """ ...
>             Reader, Writer must be factory functions or classes
>             providing the StreamReader, StreamWriter interface resp.
>         """
>         self.stream = stream
>         self.reader = Reader(stream, errors)
>         self.writer = Writer(stream, errors)
> 
> Hmm... you'd better not need to have two different set of keyword
> arguments for Reader and Writer.  Is that limitation acceptable?  

Should be OK since both work on the same stream backend and
thus will normally use the same encoding parameters.

> If
> it is, then the list of changes becomes 1) add **kw to codecs.open,
> and 2) add **kw to StreamReaderWriter's constructor, and apply it to
> the Reader() and Writer() calls.

Right.
 
> >The encoder and decoder functions must work stateless.
> 
> OK, then they're not suitable for encryption (in general, though
> they'd work fine for ECB mode).

Right; would it be feasable to use ECB ciphers for the stateless
part and also allow other modes for the StreamReader/Writer ?

-- 
Marc-Andre Lemburg
CEO eGenix.com Software GmbH
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