Version unpacking problems

[erickvermot]

Wrong unpack version.
Should lead to exception.
::

>>> from pyof.v0x01.common.utils import unpack_message
>>> m = unpack_message(b'\x04\x00\x00\x08\x00\x00\x00\x01') # v0x04 Hello message
>>> m.header.version
UBInt8(1)

[renanrodrigo]

It happens because unpack_message creates the header before unpacking the data to it, and the version is defined in creation.
I think the best way to solve this problem is not a local correction, but refactoring the code to put unpack_message in /foundation/ and changing it's behavior: unpack the whole data (including the protocol version).

[diraol]

Proposal:

Create a "general" unpack method under foundation/utils and a specific unpack under <version>/utils, for each version. The "general" unpack would discover the correct version to be used and then call the specific unpack.

May be the specific unpack methods should raise some exception, but I think that this (validation/exception) may be related to the issue #96 anyway.

[erickvermot]

I agree. But I also think 'version handling' could be implemented in some other way.
The problem with "disovering" the correct version is that a connection that was setup for working with v0x01 or some other version, should reject packets from other versions. [update: sorry, this is not a problem if the 'specific' unpack is used like suggested]
blueprint EP09 talks about this, and in Proposal/Other comments section proposes a way to deal with versions.

[erickvermot]

this will be solved if issue #407 is solved.