p2pool/util/forest.py

   1 '''
   2 forest data structure
   3 '''
   4
   5 import itertools
   6 import weakref
   7
   8 from p2pool.util import skiplist, variable
   9
  10
  11 class TrackerSkipList(skiplist.SkipList):
  12     def __init__(self, tracker):
  13         skiplist.SkipList.__init__(self)
  14         self.tracker = tracker
  15
  16         self_ref = weakref.ref(self, lambda _: tracker.removed.unwatch(watch_id))
  17         watch_id = self.tracker.removed.watch(lambda item: self_ref().forget_item(item.hash))
  18
  19     def previous(self, element):
  20         return self.tracker._delta_type.from_element(self.tracker.items[element]).tail
  21
  22
  23 class DistanceSkipList(TrackerSkipList):
  24     def get_delta(self, element):
  25         return element, 1, self.previous(element)
  26
  27     def combine_deltas(self, (from_hash1, dist1, to_hash1), (from_hash2, dist2, to_hash2)):
  28         if to_hash1 != from_hash2:
  29             raise AssertionError()
  30         return from_hash1, dist1 + dist2, to_hash2
  31
  32     def initial_solution(self, start, (n,)):
  33         return 0, start
  34
  35     def apply_delta(self, (dist1, to_hash1), (from_hash2, dist2, to_hash2), (n,)):
  36         if to_hash1 != from_hash2:
  37             raise AssertionError()
  38         return dist1 + dist2, to_hash2
  39
  40     def judge(self, (dist, hash), (n,)):
  41         if dist > n:
  42             return 1
  43         elif dist == n:
  44             return 0
  45         else:
  46             return -1
  47
  48     def finalize(self, (dist, hash), (n,)):
  49         assert dist == n
  50         return hash
  51
  52 def get_attributedelta_type(attrs): # attrs: {name: func}
  53     class ProtoAttributeDelta(object):
  54         __slots__ = ['head', 'tail'] + attrs.keys()
  55
  56         @classmethod
  57         def get_none(cls, element_id):
  58             return cls(element_id, element_id, **dict((k, 0) for k in attrs))
  59
  60         @classmethod
  61         def from_element(cls, item):
  62             return cls(item.hash, item.previous_hash, **dict((k, v(item)) for k, v in attrs.iteritems()))
  63
  64         def __init__(self, head, tail, **kwargs):
  65             self.head, self.tail = head, tail
  66             for k, v in kwargs.iteritems():
  67                 setattr(self, k, v)
  68
  69         def __add__(self, other):
  70             assert self.tail == other.head
  71             return self.__class__(self.head, other.tail, **dict((k, getattr(self, k) + getattr(other, k)) for k in attrs))
  72
  73         def __sub__(self, other):
  74             if self.head == other.head:
  75                 return self.__class__(other.tail, self.tail, **dict((k, getattr(self, k) - getattr(other, k)) for k in attrs))
  76             elif self.tail == other.tail:
  77                 return self.__class__(self.head, other.head, **dict((k, getattr(self, k) - getattr(other, k)) for k in attrs))
  78             else:
  79                 raise AssertionError()
  80
  81         def __repr__(self):
  82             return '%s(%r, %r%s)' % (self.__class__, self.head, self.tail, ''.join(', %s=%r' % (k, getattr(self, k)) for k in attrs))
  83     ProtoAttributeDelta.attrs = attrs
  84     return ProtoAttributeDelta
  85
  86 AttributeDelta = get_attributedelta_type(dict(
  87     height=lambda item: 1,
  88 ))
  89
  90 class Tracker(object):
  91     def __init__(self, items=[], delta_type=AttributeDelta, subset_of=None):
  92         self.items = {} # hash -> item
  93         self.reverse = {} # delta.tail -> set of item_hashes
  94
  95         self.heads = {} # head hash -> tail_hash
  96         self.tails = {} # tail hash -> set of head hashes
  97
  98         self._deltas = {} # item_hash -> delta, ref
  99         self._reverse_deltas = {} # ref -> set of item_hashes
 100
 101         self._ref_generator = itertools.count()
 102         self._delta_refs = {} # ref -> delta
 103         self._reverse_delta_refs = {} # delta.tail -> ref
 104
 105         self.added = variable.Event()
 106         self.removed = variable.Event()
 107
 108         if subset_of is None:
 109             self.get_nth_parent_hash = DistanceSkipList(self)
 110         else:
 111             self.get_nth_parent_hash = subset_of.get_nth_parent_hash
 112
 113         self._delta_type = delta_type
 114         self._subset_of = subset_of
 115
 116         for item in items:
 117             self.add(item)
 118
 119     def add(self, item):
 120         assert not isinstance(item, (int, long, type(None)))
 121         delta = self._delta_type.from_element(item)
 122         if self._subset_of is not None:
 123             assert delta.head in self._subset_of.items
 124
 125         if delta.head in self.items:
 126             raise ValueError('item already present')
 127
 128         if delta.head in self.tails:
 129             heads = self.tails.pop(delta.head)
 130         else:
 131             heads = set([delta.head])
 132
 133         if delta.tail in self.heads:
 134             tail = self.heads.pop(delta.tail)
 135         else:
 136             tail = self.get_last(delta.tail)
 137
 138         self.items[delta.head] = item
 139         self.reverse.setdefault(delta.tail, set()).add(delta.head)
 140
 141         self.tails.setdefault(tail, set()).update(heads)
 142         if delta.tail in self.tails[tail]:
 143             self.tails[tail].remove(delta.tail)
 144
 145         for head in heads:
 146             self.heads[head] = tail
 147
 148         self.added.happened(item)
 149
 150     def remove(self, item_hash):
 151         assert isinstance(item_hash, (int, long, type(None)))
 152         if item_hash not in self.items:
 153             raise KeyError()
 154         if self._subset_of is not None:
 155             assert item_hash in self._subset_of.items
 156
 157         item = self.items[item_hash]
 158         del item_hash
 159
 160         delta = self._delta_type.from_element(item)
 161
 162         children = self.reverse.get(delta.head, set())
 163
 164         if delta.head in self.heads and delta.tail in self.tails:
 165             tail = self.heads.pop(delta.head)
 166             self.tails[tail].remove(delta.head)
 167             if not self.tails[delta.tail]:
 168                 self.tails.pop(delta.tail)
 169         elif delta.head in self.heads:
 170             tail = self.heads.pop(delta.head)
 171             self.tails[tail].remove(delta.head)
 172             if self.reverse[delta.tail] != set([delta.head]):
 173                 pass # has sibling
 174             else:
 175                 self.tails[tail].add(delta.tail)
 176                 self.heads[delta.tail] = tail
 177         elif delta.tail in self.tails and len(self.reverse[delta.tail]) <= 1:
 178             # move delta refs referencing children down to this, so they can be moved up in one step
 179             if delta.tail in self._reverse_delta_refs:
 180                 for x in list(self._reverse_deltas.get(self._reverse_delta_refs.get(delta.head, object()), set())):
 181                     self.get_last(x)
 182                 assert delta.head not in self._reverse_delta_refs, list(self._reverse_deltas.get(self._reverse_delta_refs.get(delta.head, None), set()))
 183
 184             heads = self.tails.pop(delta.tail)
 185             for head in heads:
 186                 self.heads[head] = delta.head
 187             self.tails[delta.head] = set(heads)
 188
 189             # move ref pointing to this up
 190             if delta.tail in self._reverse_delta_refs:
 191                 assert delta.head not in self._reverse_delta_refs, list(self._reverse_deltas.get(self._reverse_delta_refs.get(delta.head, object()), set()))
 192
 193                 ref = self._reverse_delta_refs[delta.tail]
 194                 cur_delta = self._delta_refs[ref]
 195                 assert cur_delta.tail == delta.tail
 196                 self._delta_refs[ref] = cur_delta - self._delta_type.from_element(item)
 197                 assert self._delta_refs[ref].tail == delta.head
 198                 del self._reverse_delta_refs[delta.tail]
 199                 self._reverse_delta_refs[delta.head] = ref
 200         else:
 201             raise NotImplementedError()
 202
 203         # delete delta entry and ref if it is empty
 204         if delta.head in self._deltas:
 205             delta1, ref = self._deltas.pop(delta.head)
 206             self._reverse_deltas[ref].remove(delta.head)
 207             if not self._reverse_deltas[ref]:
 208                 del self._reverse_deltas[ref]
 209                 delta2 = self._delta_refs.pop(ref)
 210                 del self._reverse_delta_refs[delta2.tail]
 211
 212         self.items.pop(delta.head)
 213         self.reverse[delta.tail].remove(delta.head)
 214         if not self.reverse[delta.tail]:
 215             self.reverse.pop(delta.tail)
 216
 217         self.removed.happened(item)
 218
 219     def get_height(self, item_hash):
 220         return self.get_delta_to_last(item_hash).height
 221
 222     def get_work(self, item_hash):
 223         return self.get_delta_to_last(item_hash).work
 224
 225     def get_last(self, item_hash):
 226         return self.get_delta_to_last(item_hash).tail
 227
 228     def get_height_and_last(self, item_hash):
 229         delta = self.get_delta_to_last(item_hash)
 230         return delta.height, delta.tail
 231
 232     def _get_delta(self, item_hash):
 233         if item_hash in self._deltas:
 234             delta1, ref = self._deltas[item_hash]
 235             delta2 = self._delta_refs[ref]
 236             res = delta1 + delta2
 237         else:
 238             res = self._delta_type.from_element(self.items[item_hash])
 239         assert res.head == item_hash
 240         return res
 241
 242     def _set_delta(self, item_hash, delta):
 243         other_item_hash = delta.tail
 244         if other_item_hash not in self._reverse_delta_refs:
 245             ref = self._ref_generator.next()
 246             assert ref not in self._delta_refs
 247             self._delta_refs[ref] = self._delta_type.get_none(other_item_hash)
 248             self._reverse_delta_refs[other_item_hash] = ref
 249             del ref
 250
 251         ref = self._reverse_delta_refs[other_item_hash]
 252         ref_delta = self._delta_refs[ref]
 253         assert ref_delta.tail == other_item_hash
 254
 255         if item_hash in self._deltas:
 256             prev_ref = self._deltas[item_hash][1]
 257             self._reverse_deltas[prev_ref].remove(item_hash)
 258             if not self._reverse_deltas[prev_ref] and prev_ref != ref:
 259                 self._reverse_deltas.pop(prev_ref)
 260                 x = self._delta_refs.pop(prev_ref)
 261                 self._reverse_delta_refs.pop(x.tail)
 262         self._deltas[item_hash] = delta - ref_delta, ref
 263         self._reverse_deltas.setdefault(ref, set()).add(item_hash)
 264
 265     def get_delta_to_last(self, item_hash):
 266         assert isinstance(item_hash, (int, long, type(None)))
 267         delta = self._delta_type.get_none(item_hash)
 268         updates = []
 269         while delta.tail in self.items:
 270             updates.append((delta.tail, delta))
 271             this_delta = self._get_delta(delta.tail)
 272             delta += this_delta
 273         for update_hash, delta_then in updates:
 274             self._set_delta(update_hash, delta - delta_then)
 275         return delta
 276
 277     def get_delta(self, item, ancestor):
 278         assert self.is_child_of(ancestor, item)
 279         return self.get_delta_to_last(item) - self.get_delta_to_last(ancestor)
 280
 281     def get_chain(self, start_hash, length):
 282         assert length <= self.get_height(start_hash)
 283         for i in xrange(length):
 284             yield self.items[start_hash]
 285             start_hash = self._delta_type.from_element(self.items[start_hash]).tail
 286
 287     def is_child_of(self, item_hash, possible_child_hash):
 288         height, last = self.get_height_and_last(item_hash)
 289         child_height, child_last = self.get_height_and_last(possible_child_hash)
 290         if child_last != last:
 291             return None # not connected, so can't be determined
 292         height_up = child_height - height
 293         return height_up >= 0 and self.get_nth_parent_hash(possible_child_hash, height_up) == item_hash