Python bindings for SAF-AIS APIs offer many advantages to middleware developers, application developers, tool developers and testers. The bindings help to speed up the software development lifecycle and enable rapid deployment of architecture-independent components and services. This session will describe main principles guiding Python bindings implementation, and will have extensive in-depth application Python code examples using SAF-AIS services.

1. Python Bindings for SA Forum AIS APIs
Hans Feldt
Ericsson
Currie Reid
Linux Product Division
Wind River

2. Outline of Presentation
• Objectives
• What is Python?
• Mapping Python to Objectives
• How Python bindings are implemented
• (Demonstration)
• Future Works

3. Objectives
• 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.
• Designed to be extensible
• 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. Popularity and Usage
• Twice awarded as “Programming language of the
Year” by TIOBE (2007 & 2010)
• Ranked number 8 in the TIOBE popularity index
• Used as a scripting language for web applications
(Django, Pylons, …)
• Used as an embedded scripting language in other
programs (GIMP, GDB, ..)
• OpenSAF related: Mercurial, Buildbot, Trac, Yum
• Standard component in Linux distributions

6. 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.

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

8. 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.
• Do more with less

9. 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.
• Identify “hot spots” in application and possibly
optimize by extending with C/C++

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

11. Python Bindings Implementation
• Conversion of SAF types to ctypes
• Definition of Const
• Definition of Enumeration
• Definition of Struct
• Definition of Union
• Dynamic Loading of Libraries and CDLL
• Definition of Functions
• Definition of callbacks and CFUNCTYPE

12. 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)

13. Definition of Const
saAis = Const()
saAis.SA_TIME_END = 0x7FFFFFFFFFFFFFFF
saAis.SA_TIME_BEGIN = 0x0
saAis.SA_TIME_UNKNOWN = 0x8000000000000000
time_start = saAis.SA_TIME_BEGIN
saAis.SA_TIME_BEGIN = 5 #ERROR: EXCEPTION

14. 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)

15. Definition of Structs
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’)

16. Definition of Unions
class SaLimitValueT(Union):
_fields_ = [('int64Value', SaInt64T),
('uint64Value', SaUint64T),
('timeValue', SaTimeT),
('floatValue', SaFloatT),
('doubleValue', SaDoubleT)]
un = SaLimitValueT()
un.timeValue = 5000000000

17. Dynamic Loading of Libraries using CDLL
amfdll = CDLL('libSaAmf.so.0')
Functions in the library accessible as
attributes of the amfdll object.

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

19. Example usage
amfHandle = SaAmfHandleT()
amfCallbacks = None
version = SaVersionT(‘B’, 1, 1)
rc = saAmfInitialize(amfHandle,
amfCallbacks, 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. Bindings in 4.2
• A 1:1 mapping primarily aimed for OpenSAF
services testing
• Samples using the bindings

22. Future Work
• Pythonic interfaces (inspired by Java bindings?)
• OpenSAF test framework using Python bindings
• Simple GUI for management
• Bindings for IMM A.02.11 – OpenSAF
extensions
• Complete SMF bindings

23. Example of Pythonic Interface
def foo(parent, values, mods, dn1, dn2):
owner = SaImmOmOwner(‘Hans’)
owner.set(parent)
ccb = SaImmOmCcb(owner)
ccb.objectCreate(‘TestClass’, parent, values)
ccb.objectModify(dn1, mods)
ccb.objectDelete(dn2)
ccb.apply()

24. Questions?