61 lines
1.5 KiB
Python
61 lines
1.5 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.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]] = value
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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], default)
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def clear(self):
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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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return popped
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