Re: [Libguestfs] [PATCH nbdkit v2 03/10] python: Implement nbdkit API version 2.

On Fri, Nov 22, 2019 at 02:55:31PM -0600, Eric Blake wrote: > On 11/22/19 1:53 PM, Richard W.M. Jones wrote: > >To avoid breaking existing plugins, Python plugins wishing to use > >version 2 of the API must opt in by declaring: > > > > def api_version(): > > return 2 > > > >(Plugins which do not do this are assumed to want API version 1). > > Could we also permit the python code to declare a global variable > instead of a function? But a function is just fine (and easier to > integrate the way we do all our other callbacks). I couldn't work out how to do this, plus we have the callback_defined function which makes this easy, so yes, I did the easy thing :-) > >@@ -54,20 +61,20 @@ def get_size(h): > > return len(disk) > >-def pread(h, count, offset): > >+def pread(h, count, offset, flags): > > global disk > > return disk[offset:offset+count] > > Do we really want to be passing 'flags' as an integer that the > python script must decode? While I'm no Python programmer, it does look as if existing Python core APIs are happy to use bitmasks, eg: https://docs.python.org/3/library/os.html#os.open and this is also easy to implement and keeps it similar to the C API.