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 TrackerView(object):
  89     def __init__(self, tracker, delta_type):
  90         self._tracker = tracker
  91         self._delta_type = delta_type
  92
  93         self._deltas = {} # item_hash -> delta, ref
  94         self._reverse_deltas = {} # ref -> set of item_hashes
  95
  96         self._ref_generator = itertools.count()
  97         self._delta_refs = {} # ref -> delta
  98         self._reverse_delta_refs = {} # delta.tail -> ref
  99
 100         self._tracker.remove_special.watch_weakref(self, lambda self, item: self._handle_remove_special(item))
 101         self._tracker.removed.watch_weakref(self, lambda self, item: self._handle_removed(item))
 102
 103     def _handle_remove_special(self, item):
 104         delta = self._delta_type.from_element(item)
 105
 106         if delta.tail not in self._reverse_delta_refs:
 107             return
 108
 109         # move delta refs referencing children down to this, so they can be moved up in one step
 110         for x in list(self._reverse_deltas.get(self._reverse_delta_refs.get(delta.head, object()), set())):
 111             self.get_last(x)
 112
 113         assert delta.head not in self._reverse_delta_refs, list(self._reverse_deltas.get(self._reverse_delta_refs.get(delta.head, object()), set()))
 114
 115         if delta.tail not in self._reverse_delta_refs:
 116             return
 117
 118         # move ref pointing to this up
 119
 120         ref = self._reverse_delta_refs[delta.tail]
 121         cur_delta = self._delta_refs[ref]
 122         assert cur_delta.tail == delta.tail
 123         self._delta_refs[ref] = cur_delta - self._delta_type.from_element(item)
 124         assert self._delta_refs[ref].tail == delta.head
 125         del self._reverse_delta_refs[delta.tail]
 126         self._reverse_delta_refs[delta.head] = ref
 127
 128     def _handle_removed(self, item):
 129         delta = self._delta_type.from_element(item)
 130
 131         # delete delta entry and ref if it is empty
 132         if delta.head in self._deltas:
 133             delta1, ref = self._deltas.pop(delta.head)
 134             self._reverse_deltas[ref].remove(delta.head)
 135             if not self._reverse_deltas[ref]:
 136                 del self._reverse_deltas[ref]
 137                 delta2 = self._delta_refs.pop(ref)
 138                 del self._reverse_delta_refs[delta2.tail]
 139
 140
 141     def get_height(self, item_hash):
 142         return self.get_delta_to_last(item_hash).height
 143
 144     def get_work(self, item_hash):
 145         return self.get_delta_to_last(item_hash).work
 146
 147     def get_last(self, item_hash):
 148         return self.get_delta_to_last(item_hash).tail
 149
 150     def get_height_and_last(self, item_hash):
 151         delta = self.get_delta_to_last(item_hash)
 152         return delta.height, delta.tail
 153
 154     def _get_delta(self, item_hash):
 155         if item_hash in self._deltas:
 156             delta1, ref = self._deltas[item_hash]
 157             delta2 = self._delta_refs[ref]
 158             res = delta1 + delta2
 159         else:
 160             res = self._delta_type.from_element(self._tracker.items[item_hash])
 161         assert res.head == item_hash
 162         return res
 163
 164     def _set_delta(self, item_hash, delta):
 165         other_item_hash = delta.tail
 166         if other_item_hash not in self._reverse_delta_refs:
 167             ref = self._ref_generator.next()
 168             assert ref not in self._delta_refs
 169             self._delta_refs[ref] = self._delta_type.get_none(other_item_hash)
 170             self._reverse_delta_refs[other_item_hash] = ref
 171             del ref
 172
 173         ref = self._reverse_delta_refs[other_item_hash]
 174         ref_delta = self._delta_refs[ref]
 175         assert ref_delta.tail == other_item_hash
 176
 177         if item_hash in self._deltas:
 178             prev_ref = self._deltas[item_hash][1]
 179             self._reverse_deltas[prev_ref].remove(item_hash)
 180             if not self._reverse_deltas[prev_ref] and prev_ref != ref:
 181                 self._reverse_deltas.pop(prev_ref)
 182                 x = self._delta_refs.pop(prev_ref)
 183                 self._reverse_delta_refs.pop(x.tail)
 184         self._deltas[item_hash] = delta - ref_delta, ref
 185         self._reverse_deltas.setdefault(ref, set()).add(item_hash)
 186
 187     def get_delta_to_last(self, item_hash):
 188         assert isinstance(item_hash, (int, long, type(None)))
 189         delta = self._delta_type.get_none(item_hash)
 190         updates = []
 191         while delta.tail in self._tracker.items:
 192             updates.append((delta.tail, delta))
 193             this_delta = self._get_delta(delta.tail)
 194             delta += this_delta
 195         for update_hash, delta_then in updates:
 196             self._set_delta(update_hash, delta - delta_then)
 197         return delta
 198
 199     def get_delta(self, item, ancestor):
 200         assert self._tracker.is_child_of(ancestor, item)
 201         return self.get_delta_to_last(item) - self.get_delta_to_last(ancestor)
 202
 203 class Tracker(object):
 204     def __init__(self, items=[], delta_type=AttributeDelta):
 205         self.items = {} # hash -> item
 206         self.reverse = {} # delta.tail -> set of item_hashes
 207
 208         self.heads = {} # head hash -> tail_hash
 209         self.tails = {} # tail hash -> set of head hashes
 210
 211         self.added = variable.Event()
 212         self.remove_special = variable.Event()
 213         self.removed = variable.Event()
 214
 215         self.get_nth_parent_hash = DistanceSkipList(self)
 216
 217         self._delta_type = delta_type
 218         self._default_view = TrackerView(self, delta_type)
 219
 220         for item in items:
 221             self.add(item)
 222
 223     def __getattr__(self, name):
 224         attr = getattr(self._default_view, name)
 225         setattr(self, name, attr)
 226         return attr
 227
 228     def add(self, item):
 229         assert not isinstance(item, (int, long, type(None)))
 230         delta = self._delta_type.from_element(item)
 231
 232         if delta.head in self.items:
 233             raise ValueError('item already present')
 234
 235         if delta.head in self.tails:
 236             heads = self.tails.pop(delta.head)
 237         else:
 238             heads = set([delta.head])
 239
 240         if delta.tail in self.heads:
 241             tail = self.heads.pop(delta.tail)
 242         else:
 243             tail = self.get_last(delta.tail)
 244
 245         self.items[delta.head] = item
 246         self.reverse.setdefault(delta.tail, set()).add(delta.head)
 247
 248         self.tails.setdefault(tail, set()).update(heads)
 249         if delta.tail in self.tails[tail]:
 250             self.tails[tail].remove(delta.tail)
 251
 252         for head in heads:
 253             self.heads[head] = tail
 254
 255         self.added.happened(item)
 256
 257     def remove(self, item_hash):
 258         assert isinstance(item_hash, (int, long, type(None)))
 259         if item_hash not in self.items:
 260             raise KeyError()
 261
 262         item = self.items[item_hash]
 263         del item_hash
 264
 265         delta = self._delta_type.from_element(item)
 266
 267         children = self.reverse.get(delta.head, set())
 268
 269         if delta.head in self.heads and delta.tail in self.tails:
 270             tail = self.heads.pop(delta.head)
 271             self.tails[tail].remove(delta.head)
 272             if not self.tails[delta.tail]:
 273                 self.tails.pop(delta.tail)
 274         elif delta.head in self.heads:
 275             tail = self.heads.pop(delta.head)
 276             self.tails[tail].remove(delta.head)
 277             if self.reverse[delta.tail] != set([delta.head]):
 278                 pass # has sibling
 279             else:
 280                 self.tails[tail].add(delta.tail)
 281                 self.heads[delta.tail] = tail
 282         elif delta.tail in self.tails and len(self.reverse[delta.tail]) <= 1:
 283             heads = self.tails.pop(delta.tail)
 284             for head in heads:
 285                 self.heads[head] = delta.head
 286             self.tails[delta.head] = set(heads)
 287
 288             self.remove_special.happened(item)
 289         else:
 290             raise NotImplementedError()
 291
 292         self.items.pop(delta.head)
 293         self.reverse[delta.tail].remove(delta.head)
 294         if not self.reverse[delta.tail]:
 295             self.reverse.pop(delta.tail)
 296
 297         self.removed.happened(item)
 298
 299     def get_chain(self, start_hash, length):
 300         assert length <= self.get_height(start_hash)
 301         for i in xrange(length):
 302             yield self.items[start_hash]
 303             start_hash = self._delta_type.from_element(self.items[start_hash]).tail
 304
 305     def is_child_of(self, item_hash, possible_child_hash):
 306         height, last = self.get_height_and_last(item_hash)
 307         child_height, child_last = self.get_height_and_last(possible_child_hash)
 308         if child_last != last:
 309             return None # not connected, so can't be determined
 310         height_up = child_height - height
 311         return height_up >= 0 and self.get_nth_parent_hash(possible_child_hash, height_up) == item_hash
 312
 313 class SubsetTracker(Tracker):
 314     def __init__(self, subset_of, **kwargs):
 315         Tracker.__init__(self, **kwargs)
 316         self.get_nth_parent_hash = subset_of.get_nth_parent_hash # overwrites Tracker.__init__'s
 317         self._subset_of = subset_of
 318
 319     def add(self, item):
 320         delta = self._delta_type.from_element(item)
 321         if self._subset_of is not None:
 322             assert delta.head in self._subset_of.items
 323         Tracker.add(self, item)
 324
 325     def remove(self, item_hash):
 326         if self._subset_of is not None:
 327             assert item_hash in self._subset_of.items
 328         Tracker.remove(self, item_hash)