93 lines
2.2 KiB
Python
93 lines
2.2 KiB
Python
SENTINEL = object()
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class TreeCache(object):
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"""
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Tree-based backing store for LruCache. Allows subtrees of data to be deleted
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efficiently.
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Keys must be tuples.
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"""
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def __init__(self):
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self.size = 0
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self.root = {}
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def __setitem__(self, key, value):
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return self.set(key, value)
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def __contains__(self, key):
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return self.get(key, SENTINEL) is not SENTINEL
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def set(self, key, value):
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node = self.root
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for k in key[:-1]:
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node = node.setdefault(k, {})
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node[key[-1]] = _Entry(value)
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self.size += 1
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def get(self, key, default=None):
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node = self.root
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for k in key[:-1]:
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node = node.get(k, None)
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if node is None:
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return default
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return node.get(key[-1], _Entry(default)).value
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def clear(self):
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self.size = 0
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self.root = {}
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def pop(self, key, default=None):
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nodes = []
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node = self.root
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for k in key[:-1]:
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node = node.get(k, None)
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nodes.append(node) # don't add the root node
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if node is None:
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return default
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popped = node.pop(key[-1], SENTINEL)
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if popped is SENTINEL:
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return default
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node_and_keys = zip(nodes, key)
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node_and_keys.reverse()
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node_and_keys.append((self.root, None))
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for i in range(len(node_and_keys) - 1):
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n, k = node_and_keys[i]
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if n:
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break
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node_and_keys[i + 1][0].pop(k)
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popped, cnt = _strip_and_count_entires(popped)
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self.size -= cnt
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return popped
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def __len__(self):
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return self.size
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class _Entry(object):
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__slots__ = ["value"]
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def __init__(self, value):
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self.value = value
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def _strip_and_count_entires(d):
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"""Takes an _Entry or dict with leaves of _Entry's, and either returns the
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value or a dictionary with _Entry's replaced by their values.
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Also returns the count of _Entry's
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"""
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if isinstance(d, dict):
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cnt = 0
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for key, value in d.items():
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v, n = _strip_and_count_entires(value)
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d[key] = v
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cnt += n
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return d, cnt
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else:
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return d.value, 1
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