Modify framebuffer and NGA framebuffer to read screen size from board model dtb file. Optimise memory usuage of frame buffer
Add example minigui application with hooks to profiler (which writes results to S:\). Modified NGA framebuffer to run its own dfc queue at high priority
"""Support Eiffel-style preconditions and postconditions.
For example,
class C:
def m1(self, arg):
require arg > 0
return whatever
ensure Result > arg
can be written (clumsily, I agree) as:
class C(Eiffel):
def m1(self, arg):
return whatever
def m1_pre(self, arg):
assert arg > 0
def m1_post(self, Result, arg):
assert Result > arg
Pre- and post-conditions for a method, being implemented as methods
themselves, are inherited independently from the method. This gives
much of the same effect of Eiffel, where pre- and post-conditions are
inherited when a method is overridden by a derived class. However,
when a derived class in Python needs to extend a pre- or
post-condition, it must manually merge the base class' pre- or
post-condition with that defined in the derived class', for example:
class D(C):
def m1(self, arg):
return arg**2
def m1_post(self, Result, arg):
C.m1_post(self, Result, arg)
assert Result < 100
This gives derived classes more freedom but also more responsibility
than in Eiffel, where the compiler automatically takes care of this.
In Eiffel, pre-conditions combine using contravariance, meaning a
derived class can only make a pre-condition weaker; in Python, this is
up to the derived class. For example, a derived class that takes away
the requirement that arg > 0 could write:
def m1_pre(self, arg):
pass
but one could equally write a derived class that makes a stronger
requirement:
def m1_pre(self, arg):
require arg > 50
It would be easy to modify the classes shown here so that pre- and
post-conditions can be disabled (separately, on a per-class basis).
A different design would have the pre- or post-condition testing
functions return true for success and false for failure. This would
make it possible to implement automatic combination of inherited
and new pre-/post-conditions. All this is left as an exercise to the
reader.
"""
from Meta import MetaClass, MetaHelper, MetaMethodWrapper
class EiffelMethodWrapper(MetaMethodWrapper):
def __init__(self, func, inst):
MetaMethodWrapper.__init__(self, func, inst)
# Note that the following causes recursive wrappers around
# the pre-/post-condition testing methods. These are harmless
# but inefficient; to avoid them, the lookup must be done
# using the class.
try:
self.pre = getattr(inst, self.__name__ + "_pre")
except AttributeError:
self.pre = None
try:
self.post = getattr(inst, self.__name__ + "_post")
except AttributeError:
self.post = None
def __call__(self, *args, **kw):
if self.pre:
apply(self.pre, args, kw)
Result = apply(self.func, (self.inst,) + args, kw)
if self.post:
apply(self.post, (Result,) + args, kw)
return Result
class EiffelHelper(MetaHelper):
__methodwrapper__ = EiffelMethodWrapper
class EiffelMetaClass(MetaClass):
__helper__ = EiffelHelper
Eiffel = EiffelMetaClass('Eiffel', (), {})
def _test():
class C(Eiffel):
def m1(self, arg):
return arg+1
def m1_pre(self, arg):
assert arg > 0, "precondition for m1 failed"
def m1_post(self, Result, arg):
assert Result > arg
x = C()
x.m1(12)
## x.m1(-1)
if __name__ == '__main__':
_test()