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|
- from .abc import DefaultMapping
-
-
- class _DefaultSize(object):
- def __getitem__(self, _):
- return 1
-
- def __setitem__(self, _, value):
- assert value == 1
-
- def pop(self, _):
- return 1
-
-
- class Cache(DefaultMapping):
- """Mutable mapping to serve as a simple cache or cache base class."""
-
- __size = _DefaultSize()
-
- def __init__(self, maxsize, getsizeof=None):
- if getsizeof:
- self.getsizeof = getsizeof
- if self.getsizeof is not Cache.getsizeof:
- self.__size = dict()
- self.__data = dict()
- self.__currsize = 0
- self.__maxsize = maxsize
-
- def __repr__(self):
- return '%s(%r, maxsize=%r, currsize=%r)' % (
- self.__class__.__name__,
- list(self.__data.items()),
- self.__maxsize,
- self.__currsize,
- )
-
- def __getitem__(self, key):
- try:
- return self.__data[key]
- except KeyError:
- return self.__missing__(key)
-
- def __setitem__(self, key, value):
- maxsize = self.__maxsize
- size = self.getsizeof(value)
- if size > maxsize:
- raise ValueError('value too large')
- if key not in self.__data or self.__size[key] < size:
- while self.__currsize + size > maxsize:
- self.popitem()
- if key in self.__data:
- diffsize = size - self.__size[key]
- else:
- diffsize = size
- self.__data[key] = value
- self.__size[key] = size
- self.__currsize += diffsize
-
- def __delitem__(self, key):
- size = self.__size.pop(key)
- del self.__data[key]
- self.__currsize -= size
-
- def __contains__(self, key):
- return key in self.__data
-
- def __missing__(self, key):
- raise KeyError(key)
-
- def __iter__(self):
- return iter(self.__data)
-
- def __len__(self):
- return len(self.__data)
-
- @property
- def maxsize(self):
- """The maximum size of the cache."""
- return self.__maxsize
-
- @property
- def currsize(self):
- """The current size of the cache."""
- return self.__currsize
-
- @staticmethod
- def getsizeof(value):
- """Return the size of a cache element's value."""
- return 1
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