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persistent_dict.py
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persistent_dict.py
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class PersistentDict(object):
def __init__(self):
super(PersistentDict, self).__init__()
self._root = None
self._count = 0
self._has_none = False
self._none_val = None
@classmethod
def _new(cls, count, root, has_none, none_val):
self = cls.__new__(cls)
self._count = count
self._root = root
self._has_none = has_none
self._none_val = none_val
return self
def __len__(self):
return self._count
def __iter__(self):
return self.iterkeys()
def __contains__(self, key):
try:
self.getitem(key)
except KeyError:
return False
else:
return True
def getitem(self, key):
if key is None:
if self._has_none:
return self._none_val
else:
raise KeyError(key)
if self._root is not None:
return self._root.getitem(0, key, hash(key))
raise KeyError(key)
def setitem(self, key, val):
if key is None:
if self._has_none and val == self._none_val:
return self
return self._new(self._count if self._has_none else self._count + 1, self._root, True, val)
root = (BitmapIndexedNode.EMPTY if self._root is None else self._root)
new_root, added = root.setitem(0, key, hash(key), val)
if new_root is root:
return self
return self._new(self._count + 1 if added else self._count, new_root, self._has_none, self._none_val)
def delitem(self, key):
if key is None:
if self._has_none:
return self._new(self._count - 1, self._root, False, None)
else:
raise KeyError(key)
if self._root is None:
raise KeyError(key)
new_root = self._root.delitem(0, key, hash(key))
return self._new(self._count - 1, new_root, self._has_none, self._none_val)
def get(self, key, default=None):
try:
return self.getitem(key)
except KeyError:
return default
def iterkeys(self):
for k, v in self.iteritems():
yield k
def itervalues(self):
for k, v in self.iteritems():
yield v
def iteritems(self):
if self._root is None:
return iter([])
return self._root.iteritems()
def keys(self):
return [k for k, v in self.iteritems()]
def values(self):
return [v for k, v in self.iteritems()]
def items(self):
return list(self.iteritems())
class Node(object):
pass
class BitmapIndexedNode(Node):
def __init__(self, bitmap, data):
super(BitmapIndexedNode, self).__init__()
self.bitmap = bitmap
self.data = data
def index(self, bit):
return bitcount(self.bitmap & (bit - 1))
def getitem(self, shift, key, hash_val):
bit = bitpos(hash_val, shift)
if (self.bitmap & bit) == 0:
raise KeyError(key)
idx = self.index(bit)
key_or_none = self.data[2 * idx]
val_or_node = self.data[2 * idx + 1]
if key_or_none is None:
return val_or_node.getitem(shift + 5, key, hash_val)
if key == key_or_none:
return val_or_node
raise KeyError(key)
def setitem(self, shift, key, hash_val, val):
bit = bitpos(hash_val, shift)
idx = self.index(bit)
if (self.bitmap & bit) != 0:
key_or_none = self.data[2 * idx]
val_or_node = self.data[2 * idx + 1]
if key_or_none is None:
n, added = val_or_node.setitem(shift + 5, key, hash_val, val)
if n is val_or_node:
return self, False
data = self.data[:]
data[2 * idx + 1] = n
return BitmapIndexedNode(self.bitmap, data), added
if key == key_or_none:
if val == val_or_node:
return self, False
data = self.data[:]
data[2 * idx + 1] = val
return BitmapIndexedNode(self.bitmap, data), False
data = self.data[:]
data[2 * idx] = None
data[2 * idx + 1] = create_node(shift + 5, key_or_none, val_or_node, key, hash_val, val)
return BitmapIndexedNode(self.bitmap, data), True
else:
n = bitcount(self.bitmap)
if n >= 16:
nodes = [None] * 32
jdx = mask(hash_val, shift)
nodes[jdx], added = BitmapIndexedNode.EMPTY.setitem(shift + 5, key, hash_val, val)
j = 0
for i in range(32):
if (self.bitmap >> i) & 1 != 0:
if self.data[j] is None:
nodes[i] = self.data[j + 1]
else:
nodes[i], _ = BitmapIndexedNode.EMPTY.setitem(shift + 5, self.data[j], hash(self.data[j]), self.data[j + 1])
added = True
j += 2
return ArrayNode(n + 1, nodes), added
else:
new_data = [None] * (2 * (n + 1))
new_data[:2 * idx] = self.data[:2 * idx]
new_data[2 * idx] = key
new_data[2 * idx + 1] = val
new_data[2 * (idx + 1):] = self.data[2 * idx:]
return BitmapIndexedNode(self.bitmap | bit, new_data), True
def delitem(self, shift, key, hash_val):
bit = bitpos(hash_val, shift)
if (self.bitmap & bit) == 0:
raise KeyError(key)
idx = self.index(bit)
key_or_none = self.data[2 * idx]
val_or_node = self.data[2 * idx + 1]
if key_or_none is None:
n = val_or_node.delitem(shift + 5, key, hash_val)
if n is not None:
data = self.data[:]
data[2 * idx + 1] = n
return BitmapIndexedNode(self.bitmap, data)
if self.bitmap == bit:
return None
data = self.data[:2 * idx] + self.data[2 * idx + 2:]
return BitmapIndexedNode(self.bitmap ^ bit, data)
if key == key_or_none:
data = self.data[:]
data = self.data[:2 * idx] + self.data[2 * idx + 2:]
return BitmapIndexedNode(self.bitmap ^ bit, data)
raise KeyError(key)
def iteritems(self):
for i in range(0, len(self.data), 2):
if self.data[i] is None:
for item in self.data[i + 1].iteritems():
yield item
else:
yield (self.data[i], self.data[i + 1])
BitmapIndexedNode.EMPTY = BitmapIndexedNode(0, [])
class ArrayNode(Node):
def __init__(self, count, data):
super(ArrayNode, self).__init__()
self.count = count
self.data = data
def getitem(self, shift, key, hash_val):
idx = mask(hash_val, shift)
node = self.data[idx]
if node is None:
raise KeyError(key)
return node.getitem(shift + 5, key, hash_val)
def setitem(self, shift, key, hash_val, val):
idx = mask(hash_val, shift)
node = self.data[idx]
if node is None:
data = self.data[:]
data[idx], _ = BitmapIndexedNode.EMPTY.setitem(shift + 5, key, hash_val, val)
return ArrayNode(self.count + 1, data), True
n, added = node.setitem(shift + 5, key, hash_val, val)
if n is node:
return self, False
data = self.data[:]
data[idx] = n
return ArrayNode(self.count, data), True
def delitem(self, shift, key, hash_val):
idx = mask(hash_val, shift)
node = self.data[idx]
if node is None:
raise KeyError(key)
n = node.delitem(shift + 5, key, hash_val)
if n is None:
if self.count < 8:
raise NotImplementedError
else:
data = self.data[:]
data[idx] = n
return ArrayNode(self.count - 1, data)
else:
data = self.data[:]
data[idx] = n
return ArrayNode(self.count, data)
class HashCollisionNode(Node):
def __init__(self, hash_val, count, data):
super(HashCollisionNode, self).__init__()
self.hash_val = hash_val
self.count = count
self.data = data
def find_index(self, key):
for i in range(0, 2 * self.count, 2):
if key == self.data[i]:
return i
return -1
def getitem(self, shift, key, hash_val):
idx = self.find_index(key)
if idx < 0:
raise KeyError(key)
if key == self.data[idx]:
return self.data[idx + 1]
raise KeyError
def setitem(self, shift, key, hash_val, val):
if hash_val == self.hash_val:
idx = self.find_index(key)
if idx < 0:
return HashCollisionNode(self.hash_val, self.count + 1, self.data + [key, val]), True
elif self.data[idx + 1] == val:
return self, False
else:
data = self.data[:]
data[idx + 1] = val
return HashCollisionNode(self.hash_val, self.count, data), True
return BitmapIndexedNode(bitpos(self.hash_val, shift), [None, self]).setitem(shift, key, hash_val, val)
def delitem(self, shift, key, hash_val):
idx = self.find_index(key)
if idx < 0:
raise KeyError(key)
if self.count == 0:
return None
data = self.data[:idx] + self.data[idx + 2:]
return HashCollisionNode(self.hash_val, self.count - 1, data)
def iteritems(self):
for i in range(0, len(self.data), 2):
yield self.data[i], self.data[i + 1]
def create_node(shift, key1, val1, key2, hash_val2, val2):
hash_val1 = hash(key1)
if hash_val1 == hash_val2:
return HashCollisionNode(hash_val1, 2, [key1, val1, key2, val2])
node, _ = BitmapIndexedNode.EMPTY.setitem(shift, key1, hash_val1, val1)
node, _ = node.setitem(shift, key2, hash_val2, val2)
return node
def bitpos(hash_val, shift):
return 1 << mask(hash_val, shift)
def mask(hash_val, shift):
return (hash_val >> shift) & 0x01F
def bitcount(n):
i = 0
while n:
if n & 1:
i += 1
n >>= 1
return i