skip at mojam.com
Mon Aug 30 21:06:12 CEST 1999
Archer> I'm writing some extensions to set up a general SCSI oriented
Archer> test platform in Python. Obviously there's a certain amount of
Archer> C work that has to be done, but I would like to do one of the
Archer> A. access bit fields from a C struct that is returned to Python
Archer> as a string
This is quite doable. Python supports the bitwise operators you're familiar
with in C and the struct module lets you pack and unpack C struct info into
and out of Python strings.
Archer> B. encapsulate the structs as classes with all of the methods
Archer> implemented in C (this would appear to be possible but the
Archer> doc is mute).
Also easily doable. The simplest way I know of is to write an extension
module in C that implements the various methods you are interested in and
then just delegate to them from the actual Python methods, e.g.:
import scsiop # the extension module containing bit ops
def __init__(self, ...):
def get_SCSI_id(self, packed):
"""extract SCSI id from packed string"""
SCSI_id = scsiop.get_SCSI_id(packed)
In scsiop.c you'd implement interesting functions. This technique shouldn't
be necessary just to extract bitfields from structs packed into strings, but
may come in handy in other places.
Skip Montanaro | http://www.mojam.com/
skip at mojam.com | http://www.musi-cal.com/~skip/
847-971-7098 | Python: Programming the way Guido indented...
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