80 lines
2.2 KiB
Cython
80 lines
2.2 KiB
Cython
cdef object _LRU_MARKER = object()
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@cython.final
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cdef class LruCache:
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cdef:
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object _dict
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int _maxsize
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object _dict_move_to_end
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object _dict_get
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# We use an OrderedDict for LRU implementation. Operations:
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#
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# * We use a simple `__setitem__` to push a new entry:
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# `entries[key] = new_entry`
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# That will push `new_entry` to the *end* of the entries dict.
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#
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# * When we have a cache hit, we call
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# `entries.move_to_end(key, last=True)`
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# to move the entry to the *end* of the entries dict.
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#
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# * When we need to remove entries to maintain `max_size`, we call
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# `entries.popitem(last=False)`
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# to remove an entry from the *beginning* of the entries dict.
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#
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# So new entries and hits are always promoted to the end of the
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# entries dict, whereas the unused one will group in the
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# beginning of it.
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def __init__(self, *, maxsize):
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if maxsize <= 0:
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raise ValueError(
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f'maxsize is expected to be greater than 0, got {maxsize}')
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self._dict = col_OrderedDict()
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self._dict_move_to_end = self._dict.move_to_end
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self._dict_get = self._dict.get
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self._maxsize = maxsize
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cdef get(self, key, default):
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o = self._dict_get(key, _LRU_MARKER)
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if o is _LRU_MARKER:
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return default
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self._dict_move_to_end(key) # last=True
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return o
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cdef inline needs_cleanup(self):
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return len(self._dict) > self._maxsize
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cdef inline cleanup_one(self):
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k, _ = self._dict.popitem(last=False)
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return k
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def __getitem__(self, key):
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o = self._dict[key]
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self._dict_move_to_end(key) # last=True
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return o
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def __setitem__(self, key, o):
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if key in self._dict:
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self._dict[key] = o
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self._dict_move_to_end(key) # last=True
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else:
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self._dict[key] = o
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while self.needs_cleanup():
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self.cleanup_one()
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def __delitem__(self, key):
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del self._dict[key]
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def __contains__(self, key):
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return key in self._dict
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def __len__(self):
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return len(self._dict)
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def __iter__(self):
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return iter(self._dict)
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