145 lines
4.0 KiB
Python
145 lines
4.0 KiB
Python
"""Tracing metaclass.
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XXX This is very much a work in progress.
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"""
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import types, sys
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class TraceMetaClass:
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"""Metaclass for tracing.
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Classes defined using this metaclass have an automatic tracing
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feature -- by setting the __trace_output__ instance (or class)
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variable to a file object, trace messages about all calls are
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written to the file. The trace formatting can be changed by
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defining a suitable __trace_call__ method.
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"""
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__inited = 0
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def __init__(self, name, bases, dict):
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self.__name__ = name
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self.__bases__ = bases
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self.__dict = dict
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# XXX Can't define __dict__, alas
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self.__inited = 1
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def __getattr__(self, name):
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try:
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return self.__dict[name]
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except KeyError:
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for base in self.__bases__:
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try:
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return base.__getattr__(name)
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except AttributeError:
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pass
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raise AttributeError(name)
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def __setattr__(self, name, value):
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if not self.__inited:
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self.__dict__[name] = value
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else:
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self.__dict[name] = value
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def __call__(self, *args, **kw):
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inst = TracingInstance()
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inst.__meta_init__(self)
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try:
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init = inst.__getattr__('__init__')
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except AttributeError:
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init = lambda: None
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init(*args, **kw)
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return inst
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__trace_output__ = None
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class TracingInstance:
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"""Helper class to represent an instance of a tracing class."""
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def __trace_call__(self, fp, fmt, *args):
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fp.write((fmt+'\n') % args)
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def __meta_init__(self, klass):
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self.__class = klass
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def __getattr__(self, name):
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# Invoked for any attr not in the instance's __dict__
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try:
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raw = self.__class.__getattr__(name)
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except AttributeError:
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raise AttributeError(name)
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if type(raw) != types.FunctionType:
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return raw
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# It's a function
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fullname = self.__class.__name__ + "." + name
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if not self.__trace_output__ or name == '__trace_call__':
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return NotTracingWrapper(fullname, raw, self)
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else:
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return TracingWrapper(fullname, raw, self)
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class NotTracingWrapper:
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def __init__(self, name, func, inst):
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self.__name__ = name
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self.func = func
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self.inst = inst
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def __call__(self, *args, **kw):
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return self.func(self.inst, *args, **kw)
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class TracingWrapper(NotTracingWrapper):
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def __call__(self, *args, **kw):
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self.inst.__trace_call__(self.inst.__trace_output__,
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"calling %s, inst=%s, args=%s, kw=%s",
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self.__name__, self.inst, args, kw)
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try:
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rv = self.func(self.inst, *args, **kw)
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except:
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t, v, tb = sys.exc_info()
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self.inst.__trace_call__(self.inst.__trace_output__,
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"returning from %s with exception %s: %s",
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self.__name__, t, v)
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raise t(v).with_traceback(tb)
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else:
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self.inst.__trace_call__(self.inst.__trace_output__,
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"returning from %s with value %s",
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self.__name__, rv)
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return rv
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Traced = TraceMetaClass('Traced', (), {'__trace_output__': None})
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def _test():
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global C, D
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class C(Traced):
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def __init__(self, x=0): self.x = x
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def m1(self, x): self.x = x
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def m2(self, y): return self.x + y
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__trace_output__ = sys.stdout
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class D(C):
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def m2(self, y): print("D.m2(%r)" % (y,)); return C.m2(self, y)
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__trace_output__ = None
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x = C(4321)
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print(x)
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print(x.x)
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print(x.m1(100))
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print(x.m1(10))
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print(x.m2(33))
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print(x.m1(5))
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print(x.m2(4000))
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print(x.x)
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print(C.__init__)
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print(C.m2)
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print(D.__init__)
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print(D.m2)
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y = D()
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print(y)
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print(y.m1(10))
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print(y.m2(100))
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print(y.x)
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if __name__ == '__main__':
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_test()
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