Hi Michael,
[snip]
> > My opening paragraph may be ambiguously worded - by
> 'interoperability'
> > I didn't mean the ability to run the same code unchanged on CPython
> > and IronPython (I have to change the code anyway to use a different
> > database
> > adapter) - I meant interoperability between pickles persisted into a
> > database from both IronPython and CPython.
> >
>
> So are you telling the database that it is binary data or text?
Binary - the column is a BLOB, but SQLite is dynamically typed, and indeed
weakly typed, and so seems to store pretty much whatever you give it!
>
> Is the question how do I go from a pickle string in
> IronPython to a byte
> array that I can pass to the database adaptor without going
> through an
> explicit encode (which will transform the data)?
Yes.
>
> (One technique would be to explicitly use pickle protocol 0 which is
> less efficient but only creates ascii characters - this is
> actually the
> default. Another alternative would be to use JSON or YAML instead of
> pickle.)
I'm pickling data in the hundreds of megabytes to multi-gigabyte range, so
the binary pickling format is essential for performance and compactness
reasons. This much we know from our experience with the CPython end of
things.
>
> Here is an example of getting a byte array from a binary pickle in
> IronPython:
>
> >>> import pickle
> >>> class A(object):
> ... b = 'hello'
> ... c = (None, 'fish', 7.2, 7j)
> ... a = {1: 2}
> ...
> >>> p = pickle.dumps(A(), protocol=2)
> >>> p
> u'\x80\x02c__main__\nA\nq\x00)\x81q\x01}q\x02b.'
> >>> from System import Array, Byte
> >>> a = Array[Byte](tuple(Byte(ord(c)) for c in p))
> >>> a
> Array[Byte]((<System.Byte object at 0x0000000000000033 [128]>,
> <System.Byte obje...
>
> I hope this is at least slightly helpful. :-)
Its definitely helpful. The Array[Byte] syntax is new to me, but now I've
looked it up, something along these lines looks to what I need. I'll also be
investigating how the 'bytes' type works in IronPython since it seems to be
a distict type from 'str' and close to what I need. The database is
actually giving me Array[Byte] back in IronPython when I extract data that's
been inserted by CPython. In fact 'bytes' appears to be constructable from
IList[Byte] in IronPython.
Thanks again for you help,
Rob
P.S. I've just ordered IronPython in Action. :-)
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