53 lines
1.4 KiB
Python
53 lines
1.4 KiB
Python
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"""Key functions for memoizing decorators."""
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__all__ = ('hashkey', 'typedkey')
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class _HashedTuple(tuple):
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"""A tuple that ensures that hash() will be called no more than once
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per element, since cache decorators will hash the key multiple
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times on a cache miss. See also _HashedSeq in the standard
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library functools implementation.
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"""
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__hashvalue = None
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def __hash__(self, hash=tuple.__hash__):
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hashvalue = self.__hashvalue
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if hashvalue is None:
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self.__hashvalue = hashvalue = hash(self)
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return hashvalue
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def __add__(self, other, add=tuple.__add__):
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return _HashedTuple(add(self, other))
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def __radd__(self, other, add=tuple.__add__):
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return _HashedTuple(add(other, self))
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def __getstate__(self):
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return {}
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# used for separating keyword arguments; we do not use an object
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# instance here so identity is preserved when pickling/unpickling
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_kwmark = (_HashedTuple,)
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def hashkey(*args, **kwargs):
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"""Return a cache key for the specified hashable arguments."""
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if kwargs:
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return _HashedTuple(args + sum(sorted(kwargs.items()), _kwmark))
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else:
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return _HashedTuple(args)
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def typedkey(*args, **kwargs):
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"""Return a typed cache key for the specified hashable arguments."""
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key = hashkey(*args, **kwargs)
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key += tuple(type(v) for v in args)
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key += tuple(type(v) for _, v in sorted(kwargs.items()))
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return key
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