1. Python Bindings for the SAF-AIS APIs
Currie Reid
Linux Product Division
Wind River

2. Outline of Presentation
Requirements
What is Python?
Mapping Python to Requirements
Demo setup
How Python bindings are implemented
Demonstration
Future Works

3. Requirements Enable testing in all phases of the software lifecycle.
Simplify development across different architectures.
Simplify presentation to developers and engineers.
Quickly create tools that make it easy to investigate and monitor the system.
Make it easy to create and modify prototypes.

4. What is Python? General purpose, high-level, interpreted language.
Design philosophy emphasizes code readability.
Large, comprehensive standard library.
Supports object-oriented, imperative, and (lesser degree) functional programming paradigms.
Dynamic type system, automatic memory management.
Free, open-source, many 3rd party packages.

5. Enable testing in all phases of software lifecycle
Test coverage more complete if easy to write tests; test-driven development encouraged!
Tests are portable across architectures.
Built-in modules for testing include unittest and doctest.
Modules available for unit testing, mock testing, fuzz testing, web testing, gui testing, etc.
i.e.: nose, py.test, zope.testing.

6. Simplify development across different architectures
Python scripts are portable across different architectures.
Edit-compile-run cycle is greatly reduced.
Python code can be edited on the target system if required.
Huge collection of native and 3rd-party bindings available to aid/speed development.

7. Simplify presentation to developers and engineers
Python syntax reads like pseudo-code.
Most Python programs much smaller than lower-level implementations.
Easier to examine the problem domain when you abstract-away programming details and challenges associated with the machine.

8. Make it easy to create and modify prototypes
Components and applications can be rapidly prototyped in Python.
Designs can then be hardened in another implementation language.
Ideal glue language.
Working code can be developed much faster than lower-level languages.

9. What Will be Demonstrated
Unit tests written for every interface except SMF.
AMF demo component written in Python.
Admin-commands written in Python.
Server implemented in Python: receives NTF notifications, queries IMM and updates web-client.
Alarms resulting from admin-commands.
Logging from AMF demo component.

10. Explanation of Demonstration System
Virtual appliance; 2 system controllers
OpenSAF framework
Amf_demo: saAmf, saLog
Immwebsocket: saImmOm, saNtf
Immwebclient: HTML5 websockets, CSS, Javascript, JSON

11. Ctypes module: Wrap Libraries in Python
Advanced FFI (Foreign Function Interface) for Python 2.3 and higher.
Included in Python 2.5.
Call functions from DLLs (shared libraries).
Create, access and manipulate simple and complicated C data types in Python.
Enables C callbacks to be implemented in Python.

12. Python Implementation
Conversion of SAF types to ctypes
Definition of Const
Definition of Enumeration
Definition of Structs
Definition of Unions
Dynamic Loading of Libraries and CDLL
Definition of Functions
Definition of callbacks and CFUNCTYPE

13. Conversion of SAF types to ctypes
SaInt8T    = c_char 
SaInt16T    = c_short 
SaInt32T    = c_int 
SaInt64T    = c_longlong 
SaUint8T    = c_ubyte 
SaUint16T   = c_ushort 
SaUint32T   = c_uint 
SaUint64T   = c_ulonglong
...
myuint = SaUint64T(12)

14. Definition of Const saAis = Const()
saAis.SA_TIME_END = 0x7FFFFFFFFFFFFFFF
saAis.SA_TIME_BEGIN = 0x0
saAis.SA_TIME_UNKNOWN = 0x
time_start = saAis.SA_TIME_BEGIN
saAis.SA_TIME_BEGIN = 5 #ERROR: EXCEPTION

15. Definition of Enumeration
SaDispatchFlagsT = SaEnumT 
eSaDispatchFlagsT = Enumeration((
('SA_DISPATCH_ONE', 1), 
('SA_DISPATCH_ALL', 2), ('SA_DISPATCH_BLOCKING', 3), ))
flag = eSaDispatchFlagsT.SA_DISPATCH_ALL
flag_str = eSaDispatchFlagsT.whatis(flag)

16. Definition of Structs dn = SaNameT(‘safApp=OpenSAF’)
class SaNameT(Structure):
_fields_ = [('length', SaUint16T),
('value',(SaInt8T*saAis.SA_MAX_NAME_LENGTH))]
def __init__(self, name=''):
super(SaNameT, self).__init__(len(name), name)
dn = SaNameT(‘safApp=OpenSAF’)

17. Definition of Unions class SaLimitValueT(Union):
_fields_ = [('int64Value', SaInt64T),
('uint64Value', SaUint64T),
('timeValue', SaTimeT),
('floatValue', SaFloatT),
('doubleValue', SaDoubleT)]
un = SaLimitValueT()
un.timeValue =

18. Dynamic Loading of Libraries and CDLL
amfdll = CDLL('libSaAmf.so.0')
amfHandle = SaAmfHandleT()
amfCallbacks = None
version = SaVersionT(‘B’, 1, 1)
rc = saAmfInitialize(amfHandle,
amfCallbacks, version)

19. Definition of Functions
def saAmfInitialize(amfHandle,
amfCallbacks, version):
return amfdll.saAmfInitialize( BYREF(amfHandle),
BYREF(amfCallbacks),
BYREF(version))

20. Definition of callbacks and CFUNCTYPE
SaAmfCSISetCallbackT = CFUNCTYPE(None, SaInvocationT, POINTER(SaNameT), SaAmfHAStateT, SaAmfCSIDescriptorT)
def myCSISetCallback(invoc,
comp, hastate, descr): …
callbacks = SaAmfCallbacksT()
callbacks.saAmfCSISetCallbackT(
SaAmfCSISetCallbackT(myCSISetCallback))

21. Concluding Demonstations
Unit tests written for every interface except SMF.
AMF demo component written in Python.
Admin-commands written in Python.
Server implemented in Python: receives NTF notification, queries IMM and updates web-client.
Alarms resulting from admin-commands.
Logging from AMF demo component.

22. Future Work Complete unit tests for all interfaces.
Bind Python admin-commands into CLI.
Complete SMF bindings.
Create more tools to enhance system useability.
Consider Pythonic interfaces, similar as what was done for Java.
Consider code-generation for Python bindings.
Consider compiled Python: Cython, Psyco, etc.

23. Questions?