p2pool/util/forest.py

   1 '''
   2 forest data structure
   3 '''
   4
   5 import itertools
   6
   7 from p2pool.util import skiplist, variable
   8
   9
  10 class TrackerSkipList(skiplist.SkipList):
  11     def __init__(self, tracker):
  12         skiplist.SkipList.__init__(self)
  13         self.tracker = tracker
  14
  15         self.tracker.removed.watch_weakref(self, lambda self, item: self.forget_item(item.hash))
  16
  17     def previous(self, element):
  18         return self.tracker._delta_type.from_element(self.tracker.items[element]).tail
  19
  20
  21 class DistanceSkipList(TrackerSkipList):
  22     def get_delta(self, element):
  23         return element, 1, self.previous(element)
  24
  25     def combine_deltas(self, (from_hash1, dist1, to_hash1), (from_hash2, dist2, to_hash2)):
  26         if to_hash1 != from_hash2:
  27             raise AssertionError()
  28         return from_hash1, dist1 + dist2, to_hash2
  29
  30     def initial_solution(self, start, (n,)):
  31         return 0, start
  32
  33     def apply_delta(self, (dist1, to_hash1), (from_hash2, dist2, to_hash2), (n,)):
  34         if to_hash1 != from_hash2:
  35             raise AssertionError()
  36         return dist1 + dist2, to_hash2
  37
  38     def judge(self, (dist, hash), (n,)):
  39         if dist > n:
  40             return 1
  41         elif dist == n:
  42             return 0
  43         else:
  44             return -1
  45
  46     def finalize(self, (dist, hash), (n,)):
  47         assert dist == n
  48         return hash
  49
  50 def get_attributedelta_type(attrs): # attrs: {name: func}
  51     class ProtoAttributeDelta(object):
  52         __slots__ = ['head', 'tail'] + attrs.keys()
  53
  54         @classmethod
  55         def get_none(cls, element_id):
  56             return cls(element_id, element_id, **dict((k, 0) for k in attrs))
  57
  58         @classmethod
  59         def from_element(cls, item):
  60             return cls(item.hash, item.previous_hash, **dict((k, v(item)) for k, v in attrs.iteritems()))
  61
  62         def __init__(self, head, tail, **kwargs):
  63             self.head, self.tail = head, tail
  64             for k, v in kwargs.iteritems():
  65                 setattr(self, k, v)
  66
  67         def __add__(self, other):
  68             assert self.tail == other.head
  69             return self.__class__(self.head, other.tail, **dict((k, getattr(self, k) + getattr(other, k)) for k in attrs))
  70
  71         def __sub__(self, other):
  72             if self.head == other.head:
  73                 return self.__class__(other.tail, self.tail, **dict((k, getattr(self, k) - getattr(other, k)) for k in attrs))
  74             elif self.tail == other.tail:
  75                 return self.__class__(self.head, other.head, **dict((k, getattr(self, k) - getattr(other, k)) for k in attrs))
  76             else:
  77                 raise AssertionError()
  78
  79         def __repr__(self):
  80             return '%s(%r, %r%s)' % (self.__class__, self.head, self.tail, ''.join(', %s=%r' % (k, getattr(self, k)) for k in attrs))
  81     ProtoAttributeDelta.attrs = attrs
  82     return ProtoAttributeDelta
  83
  84 AttributeDelta = get_attributedelta_type(dict(
  85     height=lambda item: 1,
  86 ))
  87
  88 class Tracker(object):
  89     def __init__(self, items=[], delta_type=AttributeDelta):
  90         self.items = {} # hash -> item
  91         self.reverse = {} # delta.tail -> set of item_hashes
  92
  93         self.heads = {} # head hash -> tail_hash
  94         self.tails = {} # tail hash -> set of head hashes
  95
  96         self._deltas = {} # item_hash -> delta, ref
  97         self._reverse_deltas = {} # ref -> set of item_hashes
  98
  99         self._ref_generator = itertools.count()
 100         self._delta_refs = {} # ref -> delta
 101         self._reverse_delta_refs = {} # delta.tail -> ref
 102
 103         self.added = variable.Event()
 104         self.removed = variable.Event()
 105
 106         self.get_nth_parent_hash = DistanceSkipList(self)
 107
 108         self._delta_type = delta_type
 109
 110         for item in items:
 111             self.add(item)
 112
 113     def add(self, item):
 114         assert not isinstance(item, (int, long, type(None)))
 115         delta = self._delta_type.from_element(item)
 116
 117         if delta.head in self.items:
 118             raise ValueError('item already present')
 119
 120         if delta.head in self.tails:
 121             heads = self.tails.pop(delta.head)
 122         else:
 123             heads = set([delta.head])
 124
 125         if delta.tail in self.heads:
 126             tail = self.heads.pop(delta.tail)
 127         else:
 128             tail = self.get_last(delta.tail)
 129
 130         self.items[delta.head] = item
 131         self.reverse.setdefault(delta.tail, set()).add(delta.head)
 132
 133         self.tails.setdefault(tail, set()).update(heads)
 134         if delta.tail in self.tails[tail]:
 135             self.tails[tail].remove(delta.tail)
 136
 137         for head in heads:
 138             self.heads[head] = tail
 139
 140         self.added.happened(item)
 141
 142     def remove(self, item_hash):
 143         assert isinstance(item_hash, (int, long, type(None)))
 144         if item_hash not in self.items:
 145             raise KeyError()
 146
 147         item = self.items[item_hash]
 148         del item_hash
 149
 150         delta = self._delta_type.from_element(item)
 151
 152         children = self.reverse.get(delta.head, set())
 153
 154         if delta.head in self.heads and delta.tail in self.tails:
 155             tail = self.heads.pop(delta.head)
 156             self.tails[tail].remove(delta.head)
 157             if not self.tails[delta.tail]:
 158                 self.tails.pop(delta.tail)
 159         elif delta.head in self.heads:
 160             tail = self.heads.pop(delta.head)
 161             self.tails[tail].remove(delta.head)
 162             if self.reverse[delta.tail] != set([delta.head]):
 163                 pass # has sibling
 164             else:
 165                 self.tails[tail].add(delta.tail)
 166                 self.heads[delta.tail] = tail
 167         elif delta.tail in self.tails and len(self.reverse[delta.tail]) <= 1:
 168             # move delta refs referencing children down to this, so they can be moved up in one step
 169             if delta.tail in self._reverse_delta_refs:
 170                 for x in list(self._reverse_deltas.get(self._reverse_delta_refs.get(delta.head, object()), set())):
 171                     self.get_last(x)
 172                 assert delta.head not in self._reverse_delta_refs, list(self._reverse_deltas.get(self._reverse_delta_refs.get(delta.head, None), set()))
 173
 174             heads = self.tails.pop(delta.tail)
 175             for head in heads:
 176                 self.heads[head] = delta.head
 177             self.tails[delta.head] = set(heads)
 178
 179             # move ref pointing to this up
 180             if delta.tail in self._reverse_delta_refs:
 181                 assert delta.head not in self._reverse_delta_refs, list(self._reverse_deltas.get(self._reverse_delta_refs.get(delta.head, object()), set()))
 182
 183                 ref = self._reverse_delta_refs[delta.tail]
 184                 cur_delta = self._delta_refs[ref]
 185                 assert cur_delta.tail == delta.tail
 186                 self._delta_refs[ref] = cur_delta - self._delta_type.from_element(item)
 187                 assert self._delta_refs[ref].tail == delta.head
 188                 del self._reverse_delta_refs[delta.tail]
 189                 self._reverse_delta_refs[delta.head] = ref
 190         else:
 191             raise NotImplementedError()
 192
 193         # delete delta entry and ref if it is empty
 194         if delta.head in self._deltas:
 195             delta1, ref = self._deltas.pop(delta.head)
 196             self._reverse_deltas[ref].remove(delta.head)
 197             if not self._reverse_deltas[ref]:
 198                 del self._reverse_deltas[ref]
 199                 delta2 = self._delta_refs.pop(ref)
 200                 del self._reverse_delta_refs[delta2.tail]
 201
 202         self.items.pop(delta.head)
 203         self.reverse[delta.tail].remove(delta.head)
 204         if not self.reverse[delta.tail]:
 205             self.reverse.pop(delta.tail)
 206
 207         self.removed.happened(item)
 208
 209     def get_height(self, item_hash):
 210         return self.get_delta_to_last(item_hash).height
 211
 212     def get_work(self, item_hash):
 213         return self.get_delta_to_last(item_hash).work
 214
 215     def get_last(self, item_hash):
 216         return self.get_delta_to_last(item_hash).tail
 217
 218     def get_height_and_last(self, item_hash):
 219         delta = self.get_delta_to_last(item_hash)
 220         return delta.height, delta.tail
 221
 222     def _get_delta(self, item_hash):
 223         if item_hash in self._deltas:
 224             delta1, ref = self._deltas[item_hash]
 225             delta2 = self._delta_refs[ref]
 226             res = delta1 + delta2
 227         else:
 228             res = self._delta_type.from_element(self.items[item_hash])
 229         assert res.head == item_hash
 230         return res
 231
 232     def _set_delta(self, item_hash, delta):
 233         other_item_hash = delta.tail
 234         if other_item_hash not in self._reverse_delta_refs:
 235             ref = self._ref_generator.next()
 236             assert ref not in self._delta_refs
 237             self._delta_refs[ref] = self._delta_type.get_none(other_item_hash)
 238             self._reverse_delta_refs[other_item_hash] = ref
 239             del ref
 240
 241         ref = self._reverse_delta_refs[other_item_hash]
 242         ref_delta = self._delta_refs[ref]
 243         assert ref_delta.tail == other_item_hash
 244
 245         if item_hash in self._deltas:
 246             prev_ref = self._deltas[item_hash][1]
 247             self._reverse_deltas[prev_ref].remove(item_hash)
 248             if not self._reverse_deltas[prev_ref] and prev_ref != ref:
 249                 self._reverse_deltas.pop(prev_ref)
 250                 x = self._delta_refs.pop(prev_ref)
 251                 self._reverse_delta_refs.pop(x.tail)
 252         self._deltas[item_hash] = delta - ref_delta, ref
 253         self._reverse_deltas.setdefault(ref, set()).add(item_hash)
 254
 255     def get_delta_to_last(self, item_hash):
 256         assert isinstance(item_hash, (int, long, type(None)))
 257         delta = self._delta_type.get_none(item_hash)
 258         updates = []
 259         while delta.tail in self.items:
 260             updates.append((delta.tail, delta))
 261             this_delta = self._get_delta(delta.tail)
 262             delta += this_delta
 263         for update_hash, delta_then in updates:
 264             self._set_delta(update_hash, delta - delta_then)
 265         return delta
 266
 267     def get_delta(self, item, ancestor):
 268         assert self.is_child_of(ancestor, item)
 269         return self.get_delta_to_last(item) - self.get_delta_to_last(ancestor)
 270
 271     def get_chain(self, start_hash, length):
 272         assert length <= self.get_height(start_hash)
 273         for i in xrange(length):
 274             yield self.items[start_hash]
 275             start_hash = self._delta_type.from_element(self.items[start_hash]).tail
 276
 277     def is_child_of(self, item_hash, possible_child_hash):
 278         height, last = self.get_height_and_last(item_hash)
 279         child_height, child_last = self.get_height_and_last(possible_child_hash)
 280         if child_last != last:
 281             return None # not connected, so can't be determined
 282         height_up = child_height - height
 283         return height_up >= 0 and self.get_nth_parent_hash(possible_child_hash, height_up) == item_hash
 284
 285 class SubsetTracker(Tracker):
 286     def __init__(self, subset_of, **kwargs):
 287         Tracker.__init__(self, **kwargs)
 288         self.get_nth_parent_hash = subset_of.get_nth_parent_hash # overwrites Tracker.__init__'s
 289         self._subset_of = subset_of
 290
 291     def add(self, item):
 292         delta = self._delta_type.from_element(item)
 293         if self._subset_of is not None:
 294             assert delta.head in self._subset_of.items
 295         Tracker.add(self, item)
 296
 297     def remove(self, item_hash):
 298         if self._subset_of is not None:
 299             assert item_hash in self._subset_of.items
 300         Tracker.remove(self, item_hash)