p2pool/data.py

   1 from __future__ import division
   2
   3 import hashlib
   4 import os
   5 import random
   6 import time
   7
   8 from twisted.python import log
   9
  10 import p2pool
  11 from p2pool.bitcoin import data as bitcoin_data, script, sha256
  12 from p2pool.util import math, forest, pack
  13
  14 # hashlink
  15
  16 hash_link_type = pack.ComposedType([
  17     ('state', pack.FixedStrType(32)),
  18     ('extra_data', pack.FixedStrType(0)), # bit of a hack, but since the donation script is at the end, const_ending is long enough to always make this empty
  19     ('length', pack.VarIntType()),
  20 ])
  21
  22 def prefix_to_hash_link(prefix, const_ending=''):
  23     assert prefix.endswith(const_ending), (prefix, const_ending)
  24     x = sha256.sha256(prefix)
  25     return dict(state=x.state, extra_data=x.buf[:max(0, len(x.buf)-len(const_ending))], length=x.length//8)
  26
  27 def check_hash_link(hash_link, data, const_ending=''):
  28     extra_length = hash_link['length'] % (512//8)
  29     assert len(hash_link['extra_data']) == max(0, extra_length - len(const_ending))
  30     extra = (hash_link['extra_data'] + const_ending)[len(hash_link['extra_data']) + len(const_ending) - extra_length:]
  31     assert len(extra) == extra_length
  32     return pack.IntType(256).unpack(hashlib.sha256(sha256.sha256(data, (hash_link['state'], extra, 8*hash_link['length'])).digest()).digest())
  33
  34 # shares
  35
  36 share_type = pack.ComposedType([
  37     ('type', pack.VarIntType()),
  38     ('contents', pack.VarStrType()),
  39 ])
  40
  41 def load_share(share, net, peer):
  42     if share['type'] in [0, 1, 2, 3]:
  43         from p2pool import p2p
  44         raise p2p.PeerMisbehavingError('sent an obsolete share')
  45     elif share['type'] == 4:
  46         return Share(net, peer, other_txs=None, **Share.share1a_type.unpack(share['contents']))
  47     elif share['type'] == 5:
  48         share1b = Share.share1b_type.unpack(share['contents'])
  49         return Share(net, peer, merkle_link=bitcoin_data.calculate_merkle_link([0] + [bitcoin_data.hash256(bitcoin_data.tx_type.pack(x)) for x in share1b['other_txs']], 0), **share1b)
  50     elif share['type'] == 6:
  51         return NewShare(net, peer, other_txs=None, **NewShare.share1a_type.unpack(share['contents']))
  52     elif share['type'] == 7:
  53         share1b = NewShare.share1b_type.unpack(share['contents'])
  54         return NewShare(net, peer, merkle_link=bitcoin_data.calculate_merkle_link([0] + [bitcoin_data.hash256(bitcoin_data.tx_type.pack(x)) for x in share1b['other_txs']], 0), **share1b)
  55     else:
  56         raise ValueError('unknown share type: %r' % (share['type'],))
  57
  58 DONATION_SCRIPT = '4104ffd03de44a6e11b9917f3a29f9443283d9871c9d743ef30d5eddcd37094b64d1b3d8090496b53256786bf5c82932ec23c3b74d9f05a6f95a8b5529352656664bac'.decode('hex')
  59
  60 class Share(object):
  61     small_block_header_type = pack.ComposedType([
  62         ('version', pack.VarIntType()), # XXX must be constrained to 32 bits
  63         ('previous_block', pack.PossiblyNoneType(0, pack.IntType(256))),
  64         ('timestamp', pack.IntType(32)),
  65         ('bits', bitcoin_data.FloatingIntegerType()),
  66         ('nonce', pack.IntType(32)),
  67     ])
  68
  69     share_data_type = pack.ComposedType([
  70         ('previous_share_hash', pack.PossiblyNoneType(0, pack.IntType(256))),
  71         ('coinbase', pack.VarStrType()),
  72         ('nonce', pack.IntType(32)),
  73         ('pubkey_hash', pack.IntType(160)),
  74         ('subsidy', pack.IntType(64)),
  75         ('donation', pack.IntType(16)),
  76         ('stale_info', pack.EnumType(pack.IntType(8), dict((k, {0: None, 253: 'orphan', 254: 'doa'}.get(k, 'unk%i' % (k,))) for k in xrange(256)))),
  77         ('desired_version', pack.VarIntType()),
  78     ])
  79
  80     share_info_type = pack.ComposedType([
  81         ('share_data', share_data_type),
  82         ('far_share_hash', pack.PossiblyNoneType(0, pack.IntType(256))),
  83         ('max_bits', bitcoin_data.FloatingIntegerType()),
  84         ('bits', bitcoin_data.FloatingIntegerType()),
  85         ('timestamp', pack.IntType(32)),
  86     ])
  87
  88     share_common_type = pack.ComposedType([
  89         ('min_header', small_block_header_type),
  90         ('share_info', share_info_type),
  91         ('ref_merkle_link', pack.ComposedType([
  92             ('branch', pack.ListType(pack.IntType(256))),
  93             ('index', pack.VarIntType()),
  94         ])),
  95         ('hash_link', hash_link_type),
  96     ])
  97     share1a_type = pack.ComposedType([
  98         ('common', share_common_type),
  99         ('merkle_link', pack.ComposedType([
 100             ('branch', pack.ListType(pack.IntType(256))),
 101             ('index', pack.IntType(0)), # it will always be 0
 102         ])),
 103     ])
 104     share1b_type = pack.ComposedType([
 105         ('common', share_common_type),
 106         ('other_txs', pack.ListType(bitcoin_data.tx_type)),
 107     ])
 108
 109     ref_type = pack.ComposedType([
 110         ('identifier', pack.FixedStrType(64//8)),
 111         ('share_info', share_info_type),
 112     ])
 113
 114     gentx_before_refhash = pack.VarStrType().pack(DONATION_SCRIPT) + pack.IntType(64).pack(0) + pack.VarStrType().pack('\x20' + pack.IntType(256).pack(0))[:2]
 115
 116     @classmethod
 117     def generate_transaction(cls, tracker, share_data, block_target, desired_timestamp, desired_target, ref_merkle_link, net):
 118         previous_share = tracker.shares[share_data['previous_share_hash']] if share_data['previous_share_hash'] is not None else None
 119
 120         height, last = tracker.get_height_and_last(share_data['previous_share_hash'])
 121         assert height >= net.REAL_CHAIN_LENGTH or last is None
 122         if height < net.TARGET_LOOKBEHIND:
 123             pre_target3 = net.MAX_TARGET
 124         else:
 125             attempts_per_second = get_pool_attempts_per_second(tracker, share_data['previous_share_hash'], net.TARGET_LOOKBEHIND, min_work=True, integer=True)
 126             pre_target = 2**256//(net.SHARE_PERIOD*attempts_per_second) - 1 if attempts_per_second else 2**256-1
 127             pre_target2 = math.clip(pre_target, (previous_share.max_target*9//10, previous_share.max_target*11//10))
 128             pre_target3 = math.clip(pre_target2, (0, net.MAX_TARGET))
 129         max_bits = bitcoin_data.FloatingInteger.from_target_upper_bound(pre_target3)
 130         bits = bitcoin_data.FloatingInteger.from_target_upper_bound(math.clip(desired_target, (pre_target3//10, pre_target3)))
 131
 132         weights, total_weight, donation_weight = tracker.get_cumulative_weights(share_data['previous_share_hash'],
 133             min(height, net.REAL_CHAIN_LENGTH),
 134             65535*net.SPREAD*bitcoin_data.target_to_average_attempts(block_target),
 135         )
 136         assert total_weight == sum(weights.itervalues()) + donation_weight, (total_weight, sum(weights.itervalues()) + donation_weight)
 137
 138         amounts = dict((script, share_data['subsidy']*(199*weight)//(200*total_weight)) for script, weight in weights.iteritems()) # 99.5% goes according to weights prior to this share
 139         this_script = bitcoin_data.pubkey_hash_to_script2(share_data['pubkey_hash'])
 140         amounts[this_script] = amounts.get(this_script, 0) + share_data['subsidy']//200 # 0.5% goes to block finder
 141         amounts[DONATION_SCRIPT] = amounts.get(DONATION_SCRIPT, 0) + share_data['subsidy'] - sum(amounts.itervalues()) # all that's left over is the donation weight and some extra satoshis due to rounding
 142
 143         if sum(amounts.itervalues()) != share_data['subsidy'] or any(x < 0 for x in amounts.itervalues()):
 144             raise ValueError()
 145
 146         dests = sorted(amounts.iterkeys(), key=lambda script: (script == DONATION_SCRIPT, amounts[script], script))[-4000:] # block length limit, unlikely to ever be hit
 147
 148         share_info = dict(
 149             share_data=share_data,
 150             far_share_hash=None if last is None and height < 99 else tracker.get_nth_parent_hash(share_data['previous_share_hash'], 99),
 151             max_bits=max_bits,
 152             bits=bits,
 153             timestamp=math.clip(desired_timestamp, (
 154                 (previous_share.timestamp + net.SHARE_PERIOD) - (net.SHARE_PERIOD - 1), # = previous_share.timestamp + 1
 155                 (previous_share.timestamp + net.SHARE_PERIOD) + (net.SHARE_PERIOD - 1),
 156             )) if previous_share is not None else desired_timestamp,
 157         )
 158
 159         return share_info, dict(
 160             version=1,
 161             tx_ins=[dict(
 162                 previous_output=None,
 163                 sequence=None,
 164                 script=share_data['coinbase'].ljust(2, '\x00'),
 165             )],
 166             tx_outs=[dict(value=amounts[script], script=script) for script in dests if amounts[script] or script == DONATION_SCRIPT] + [dict(
 167                 value=0,
 168                 script='\x20' + cls.get_ref_hash(net, share_info, ref_merkle_link),
 169             )],
 170             lock_time=0,
 171         )
 172
 173     @classmethod
 174     def get_ref_hash(cls, net, share_info, ref_merkle_link):
 175         return pack.IntType(256).pack(bitcoin_data.check_merkle_link(bitcoin_data.hash256(cls.ref_type.pack(dict(
 176             identifier=net.IDENTIFIER,
 177             share_info=share_info,
 178         ))), ref_merkle_link))
 179
 180     __slots__ = 'net peer common min_header share_info hash_link merkle_link other_txs hash share_data max_target target timestamp previous_hash new_script desired_version gentx_hash header pow_hash header_hash time_seen'.split(' ')
 181
 182     def __init__(self, net, peer, common, merkle_link, other_txs):
 183         self.net = net
 184         self.peer = peer
 185         self.common = common
 186         self.min_header = common['min_header']
 187         self.share_info = common['share_info']
 188         self.hash_link = common['hash_link']
 189         self.merkle_link = merkle_link
 190         self.other_txs = other_txs
 191
 192         if len(self.share_info['share_data']['coinbase']) > 100:
 193             raise ValueError('''coinbase too large! %i bytes''' % (len(self.self.share_data['coinbase']),))
 194
 195         if len(merkle_link['branch']) > 16:
 196             raise ValueError('merkle branch too long!')
 197
 198         if p2pool.DEBUG and other_txs is not None and bitcoin_data.calculate_merkle_link([0] + [bitcoin_data.hash256(bitcoin_data.tx_type.pack(x)) for x in other_txs], 0) != merkle_link:
 199             raise ValueError('merkle_link and other_txs do not match')
 200
 201         assert not self.hash_link['extra_data'], repr(self.hash_link['extra_data'])
 202
 203         self.share_data = self.share_info['share_data']
 204         self.max_target = self.share_info['max_bits'].target
 205         self.target = self.share_info['bits'].target
 206         self.timestamp = self.share_info['timestamp']
 207         self.previous_hash = self.share_data['previous_share_hash']
 208         self.new_script = bitcoin_data.pubkey_hash_to_script2(self.share_data['pubkey_hash'])
 209         self.desired_version = self.share_data['desired_version']
 210
 211         self.gentx_hash = check_hash_link(
 212             self.hash_link,
 213             self.get_ref_hash(net, self.share_info, common['ref_merkle_link']) + pack.IntType(32).pack(0),
 214             self.gentx_before_refhash,
 215         )
 216         merkle_root = bitcoin_data.check_merkle_link(self.gentx_hash, merkle_link)
 217         self.header = dict(self.min_header, merkle_root=merkle_root)
 218         self.pow_hash = net.PARENT.POW_FUNC(bitcoin_data.block_header_type.pack(self.header))
 219         self.hash = self.header_hash = bitcoin_data.hash256(bitcoin_data.block_header_type.pack(self.header))
 220
 221         if self.pow_hash > self.target:
 222             from p2pool import p2p
 223             raise p2p.PeerMisbehavingError('share PoW invalid')
 224
 225         if other_txs is not None and not self.pow_hash <= self.header['bits'].target:
 226             raise ValueError('other_txs provided when not a block solution')
 227         if other_txs is None and self.pow_hash <= self.header['bits'].target:
 228             raise ValueError('other_txs not provided when a block solution')
 229
 230         # XXX eww
 231         self.time_seen = time.time()
 232
 233     def __repr__(self):
 234         return '<Share %s>' % (' '.join('%s=%r' % (k, getattr(self, k)) for k in self.__slots__),)
 235
 236     def as_share(self):
 237         if not self.pow_hash <= self.header['bits'].target: # share1a
 238             return dict(type=4, contents=self.share1a_type.pack(dict(common=self.common, merkle_link=self.merkle_link)))
 239         else: # share1b
 240             return dict(type=5, contents=self.share1b_type.pack(dict(common=self.common, other_txs=self.other_txs)))
 241
 242     def check(self, tracker):
 243         if self.share_data['previous_share_hash'] is not None:
 244             previous_share = tracker.shares[self.share_data['previous_share_hash']]
 245             if isinstance(previous_share, NewShare):
 246                 from p2pool import p2p
 247                 raise p2p.PeerMisbehavingError('''Share can't follow NewShare''')
 248         share_info, gentx = self.generate_transaction(tracker, self.share_info['share_data'], self.header['bits'].target, self.share_info['timestamp'], self.share_info['bits'].target, self.common['ref_merkle_link'], self.net)
 249         if share_info != self.share_info:
 250             raise ValueError('share_info invalid')
 251         if bitcoin_data.hash256(bitcoin_data.tx_type.pack(gentx)) != self.gentx_hash:
 252             raise ValueError('''gentx doesn't match hash_link''')
 253         return gentx # only used by as_block
 254
 255     def as_block(self, tracker):
 256         if self.other_txs is None:
 257             raise ValueError('share does not contain all txs')
 258         return dict(header=self.header, txs=[self.check(tracker)] + self.other_txs)
 259
 260 class NewShare(Share):
 261     def __init__(self, *args, **kwargs):
 262         Share.__init__(self, *args, **kwargs)
 263         self.hash = bitcoin_data.hash256(share_type.pack(self.as_share()))
 264
 265     def check(self, tracker):
 266         if self.share_data['previous_share_hash'] is not None:
 267             previous_share = tracker.shares[self.share_data['previous_share_hash']]
 268             if isinstance(previous_share, Share):
 269                 if tracker.get_height(previous_share.hash) < self.net.CHAIN_LENGTH:
 270                     from p2pool import p2p
 271                     raise p2p.PeerMisbehavingError('NewShare without enough history')
 272                 else:
 273                     # Share -> NewShare only valid if 85% of hashes in [self.net.CHAIN_LENGTH*9//10, self.net.CHAIN_LENGTH] for new version
 274                     counts = get_desired_version_counts(tracker,
 275                         tracker.get_nth_parent_hash(previous_share.hash, self.net.CHAIN_LENGTH*9//10), self.net.CHAIN_LENGTH//10)
 276                     if counts.get(2, 0) < sum(counts.itervalues())*85//100:
 277                         from p2pool import p2p
 278                         raise p2p.PeerMisbehavingError('NewShare without enough hash power upgraded')
 279         share_info, gentx = self.generate_transaction(tracker, self.share_info['share_data'], self.header['bits'].target, self.share_info['timestamp'], self.share_info['bits'].target, self.common['ref_merkle_link'], self.net)
 280         if share_info != self.share_info:
 281             raise ValueError('share_info invalid')
 282         if bitcoin_data.hash256(bitcoin_data.tx_type.pack(gentx)) != self.gentx_hash:
 283             raise ValueError('''gentx doesn't match hash_link''')
 284         return gentx # only used by as_block
 285
 286     def as_share(self):
 287         if not self.pow_hash <= self.header['bits'].target: # share1a
 288             return dict(type=6, contents=self.share1a_type.pack(dict(common=self.common, merkle_link=self.merkle_link)))
 289         else: # share1b
 290             return dict(type=7, contents=self.share1b_type.pack(dict(common=self.common, other_txs=self.other_txs)))
 291
 292
 293 class WeightsSkipList(forest.TrackerSkipList):
 294     # share_count, weights, total_weight
 295
 296     def get_delta(self, element):
 297         from p2pool.bitcoin import data as bitcoin_data
 298         share = self.tracker.shares[element]
 299         att = bitcoin_data.target_to_average_attempts(share.target)
 300         return 1, {share.new_script: att*(65535-share.share_data['donation'])}, att*65535, att*share.share_data['donation']
 301
 302     def combine_deltas(self, (share_count1, weights1, total_weight1, total_donation_weight1), (share_count2, weights2, total_weight2, total_donation_weight2)):
 303         return share_count1 + share_count2, math.add_dicts(weights1, weights2), total_weight1 + total_weight2, total_donation_weight1 + total_donation_weight2
 304
 305     def initial_solution(self, start, (max_shares, desired_weight)):
 306         assert desired_weight % 65535 == 0, divmod(desired_weight, 65535)
 307         return 0, None, 0, 0
 308
 309     def apply_delta(self, (share_count1, weights_list, total_weight1, total_donation_weight1), (share_count2, weights2, total_weight2, total_donation_weight2), (max_shares, desired_weight)):
 310         if total_weight1 + total_weight2 > desired_weight and share_count2 == 1:
 311             assert (desired_weight - total_weight1) % 65535 == 0
 312             script, = weights2.iterkeys()
 313             new_weights = {script: (desired_weight - total_weight1)//65535*weights2[script]//(total_weight2//65535)}
 314             return share_count1 + share_count2, (weights_list, new_weights), desired_weight, total_donation_weight1 + (desired_weight - total_weight1)//65535*total_donation_weight2//(total_weight2//65535)
 315         return share_count1 + share_count2, (weights_list, weights2), total_weight1 + total_weight2, total_donation_weight1 + total_donation_weight2
 316
 317     def judge(self, (share_count, weights_list, total_weight, total_donation_weight), (max_shares, desired_weight)):
 318         if share_count > max_shares or total_weight > desired_weight:
 319             return 1
 320         elif share_count == max_shares or total_weight == desired_weight:
 321             return 0
 322         else:
 323             return -1
 324
 325     def finalize(self, (share_count, weights_list, total_weight, total_donation_weight), (max_shares, desired_weight)):
 326         assert share_count <= max_shares and total_weight <= desired_weight
 327         assert share_count == max_shares or total_weight == desired_weight
 328         return math.add_dicts(*math.flatten_linked_list(weights_list)), total_weight, total_donation_weight
 329
 330 class OkayTracker(forest.Tracker):
 331     def __init__(self, net, my_share_hashes, my_doa_share_hashes):
 332         forest.Tracker.__init__(self, delta_type=forest.get_attributedelta_type(dict(forest.AttributeDelta.attrs,
 333             work=lambda share: bitcoin_data.target_to_average_attempts(share.target),
 334             min_work=lambda share: bitcoin_data.target_to_average_attempts(share.max_target),
 335         )))
 336         self.net = net
 337         self.verified = forest.Tracker(delta_type=forest.get_attributedelta_type(dict(forest.AttributeDelta.attrs,
 338             work=lambda share: bitcoin_data.target_to_average_attempts(share.target),
 339             my_count=lambda share: 1 if share.hash in my_share_hashes else 0,
 340             my_doa_count=lambda share: 1 if share.hash in my_doa_share_hashes else 0,
 341             my_orphan_announce_count=lambda share: 1 if share.hash in my_share_hashes and share.share_data['stale_info'] == 'orphan' else 0,
 342             my_dead_announce_count=lambda share: 1 if share.hash in my_share_hashes and share.share_data['stale_info'] == 'doa' else 0,
 343         )), subset_of=self)
 344         self.get_cumulative_weights = WeightsSkipList(self)
 345
 346     def attempt_verify(self, share):
 347         if share.hash in self.verified.shares:
 348             return True
 349         height, last = self.get_height_and_last(share.hash)
 350         if height < self.net.CHAIN_LENGTH + 1 and last is not None:
 351             raise AssertionError()
 352         try:
 353             share.check(self)
 354         except:
 355             log.err(None, 'Share check failed:')
 356             return False
 357         else:
 358             self.verified.add(share)
 359             return True
 360
 361     def think(self, block_rel_height_func, previous_block, bits):
 362         desired = set()
 363
 364         # O(len(self.heads))
 365         #   make 'unverified heads' set?
 366         # for each overall head, attempt verification
 367         # if it fails, attempt on parent, and repeat
 368         # if no successful verification because of lack of parents, request parent
 369         bads = set()
 370         for head in set(self.heads) - set(self.verified.heads):
 371             head_height, last = self.get_height_and_last(head)
 372
 373             for share in self.get_chain(head, head_height if last is None else min(5, max(0, head_height - self.net.CHAIN_LENGTH))):
 374                 if self.attempt_verify(share):
 375                     break
 376                 if share.hash in self.heads:
 377                     bads.add(share.hash)
 378             else:
 379                 if last is not None:
 380                     desired.add((
 381                         self.shares[random.choice(list(self.reverse_shares[last]))].peer,
 382                         last,
 383                         max(x.timestamp for x in self.get_chain(head, min(head_height, 5))),
 384                         min(x.target for x in self.get_chain(head, min(head_height, 5))),
 385                     ))
 386         for bad in bads:
 387             assert bad not in self.verified.shares
 388             assert bad in self.heads
 389             if p2pool.DEBUG:
 390                 print "BAD", bad
 391             self.remove(bad)
 392
 393         # try to get at least CHAIN_LENGTH height for each verified head, requesting parents if needed
 394         for head in list(self.verified.heads):
 395             head_height, last_hash = self.verified.get_height_and_last(head)
 396             last_height, last_last_hash = self.get_height_and_last(last_hash)
 397             # XXX review boundary conditions
 398             want = max(self.net.CHAIN_LENGTH - head_height, 0)
 399             can = max(last_height - 1 - self.net.CHAIN_LENGTH, 0) if last_last_hash is not None else last_height
 400             get = min(want, can)
 401             #print 'Z', head_height, last_hash is None, last_height, last_last_hash is None, want, can, get
 402             for share in self.get_chain(last_hash, get):
 403                 if not self.attempt_verify(share):
 404                     break
 405             if head_height < self.net.CHAIN_LENGTH and last_last_hash is not None:
 406                 desired.add((
 407                     self.shares[random.choice(list(self.verified.reverse_shares[last_hash]))].peer,
 408                     last_last_hash,
 409                     max(x.timestamp for x in self.get_chain(head, min(head_height, 5))),
 410                     min(x.target for x in self.get_chain(head, min(head_height, 5))),
 411                 ))
 412
 413         # decide best tree
 414         decorated_tails = sorted((self.score(max(self.verified.tails[tail_hash], key=self.verified.get_work), block_rel_height_func), tail_hash) for tail_hash in self.verified.tails)
 415         if p2pool.DEBUG:
 416             print len(decorated_tails), 'tails:'
 417             for score, tail_hash in decorated_tails:
 418                 print format_hash(tail_hash), score
 419         best_tail_score, best_tail = decorated_tails[-1] if decorated_tails else (None, None)
 420
 421         # decide best verified head
 422         decorated_heads = sorted(((
 423             self.verified.get_work(self.verified.get_nth_parent_hash(h, min(5, self.verified.get_height(h)))),
 424             #self.shares[h].peer is None,
 425             self.shares[h].pow_hash <= self.shares[h].header['bits'].target, # is block solution
 426             (self.shares[h].header['previous_block'], self.shares[h].header['bits']) == (previous_block, bits) or self.shares[h].peer is None,
 427             -self.shares[h].time_seen,
 428         ), h) for h in self.verified.tails.get(best_tail, []))
 429         if p2pool.DEBUG:
 430             print len(decorated_heads), 'heads. Top 10:'
 431             for score, head_hash in decorated_heads[-10:]:
 432                 print '   ', format_hash(head_hash), format_hash(self.shares[head_hash].previous_hash), score
 433         best_head_score, best = decorated_heads[-1] if decorated_heads else (None, None)
 434
 435         # eat away at heads
 436         if decorated_heads:
 437             for i in xrange(1000):
 438                 to_remove = set()
 439                 for share_hash, tail in self.heads.iteritems():
 440                     if share_hash in [head_hash for score, head_hash in decorated_heads[-5:]]:
 441                         #print 1
 442                         continue
 443                     if self.shares[share_hash].time_seen > time.time() - 300:
 444                         #print 2
 445                         continue
 446                     if share_hash not in self.verified.shares and max(self.shares[after_tail_hash].time_seen for after_tail_hash in self.reverse_shares.get(tail)) > time.time() - 120: # XXX stupid
 447                         #print 3
 448                         continue
 449                     to_remove.add(share_hash)
 450                 if not to_remove:
 451                     break
 452                 for share_hash in to_remove:
 453                     if share_hash in self.verified.shares:
 454                         self.verified.remove(share_hash)
 455                     self.remove(share_hash)
 456                 #print "_________", to_remove
 457
 458         # drop tails
 459         for i in xrange(1000):
 460             to_remove = set()
 461             for tail, heads in self.tails.iteritems():
 462                 if min(self.get_height(head) for head in heads) < 2*self.net.CHAIN_LENGTH + 10:
 463                     continue
 464                 for aftertail in self.reverse_shares.get(tail, set()):
 465                     if len(self.reverse_shares[self.shares[aftertail].previous_hash]) > 1: # XXX
 466                         print "raw"
 467                         continue
 468                     to_remove.add(aftertail)
 469             if not to_remove:
 470                 break
 471             # if removed from this, it must be removed from verified
 472             #start = time.time()
 473             for aftertail in to_remove:
 474                 if self.shares[aftertail].previous_hash not in self.tails:
 475                     print "erk", aftertail, self.shares[aftertail].previous_hash
 476                     continue
 477                 if aftertail in self.verified.shares:
 478                     self.verified.remove(aftertail)
 479                 self.remove(aftertail)
 480             #end = time.time()
 481             #print "removed! %i %f" % (len(to_remove), (end - start)/len(to_remove))
 482
 483         if best is not None:
 484             best_share = self.shares[best]
 485             if (best_share.header['previous_block'], best_share.header['bits']) != (previous_block, bits) and best_share.header_hash != previous_block and best_share.peer is not None:
 486                 if p2pool.DEBUG:
 487                     print 'Stale detected! %x < %x' % (best_share.header['previous_block'], previous_block)
 488                 best = best_share.previous_hash
 489
 490             timestamp_cutoff = min(int(time.time()), best_share.timestamp) - 3600
 491             target_cutoff = 2**256//(self.net.SHARE_PERIOD*best_tail_score[1] + 1) * 2 if best_tail_score[1] is not None else 2**256-1
 492         else:
 493             timestamp_cutoff = int(time.time()) - 24*60*60
 494             target_cutoff = 2**256-1
 495
 496         if p2pool.DEBUG:
 497             print 'Desire %i shares. Cutoff: %s old diff>%.2f' % (len(desired), math.format_dt(time.time() - timestamp_cutoff), bitcoin_data.target_to_difficulty(target_cutoff))
 498             for peer, hash, ts, targ in desired:
 499                 print '   ', '%s:%i' % peer.addr if peer is not None else None, format_hash(hash), math.format_dt(time.time() - ts), bitcoin_data.target_to_difficulty(targ), ts >= timestamp_cutoff, targ <= target_cutoff
 500
 501         return best, [(peer, hash) for peer, hash, ts, targ in desired if ts >= timestamp_cutoff and targ <= target_cutoff]
 502
 503     def score(self, share_hash, block_rel_height_func):
 504         # returns approximate lower bound on chain's hashrate in the last self.net.CHAIN_LENGTH*15//16*self.net.SHARE_PERIOD time
 505
 506         head_height = self.verified.get_height(share_hash)
 507         if head_height < self.net.CHAIN_LENGTH:
 508             return head_height, None
 509
 510         end_point = self.verified.get_nth_parent_hash(share_hash, self.net.CHAIN_LENGTH*15//16)
 511
 512         block_height = max(block_rel_height_func(share.header['previous_block']) for share in
 513             self.verified.get_chain(end_point, self.net.CHAIN_LENGTH//16))
 514
 515         return self.net.CHAIN_LENGTH, (self.verified.get_work(share_hash) - self.verified.get_work(end_point))//((0 - block_height + 1)*self.net.PARENT.BLOCK_PERIOD)
 516
 517 def get_pool_attempts_per_second(tracker, previous_share_hash, dist, min_work=False, integer=False):
 518     assert dist >= 2
 519     near = tracker.shares[previous_share_hash]
 520     far = tracker.shares[tracker.get_nth_parent_hash(previous_share_hash, dist - 1)]
 521     attempts = tracker.get_delta(near.hash, far.hash).work if not min_work else tracker.get_delta(near.hash, far.hash).min_work
 522     time = near.timestamp - far.timestamp
 523     if time <= 0:
 524         time = 1
 525     if integer:
 526         return attempts//time
 527     return attempts/time
 528
 529 def get_average_stale_prop(tracker, share_hash, lookbehind):
 530     stales = sum(1 for share in tracker.get_chain(share_hash, lookbehind) if share.share_data['stale_info'] is not None)
 531     return stales/(lookbehind + stales)
 532
 533 def get_stale_counts(tracker, share_hash, lookbehind, rates=False):
 534     res = {}
 535     for share in tracker.get_chain(share_hash, lookbehind - 1):
 536         res['good'] = res.get('good', 0) + bitcoin_data.target_to_average_attempts(share.target)
 537         s = share.share_data['stale_info']
 538         if s is not None:
 539             res[s] = res.get(s, 0) + bitcoin_data.target_to_average_attempts(share.target)
 540     if rates:
 541         dt = tracker.shares[share_hash].timestamp - tracker.shares[tracker.get_nth_parent_hash(share_hash, lookbehind - 1)].timestamp
 542         res = dict((k, v/dt) for k, v in res.iteritems())
 543     return res
 544
 545 def get_expected_payouts(tracker, best_share_hash, block_target, subsidy, net):
 546     weights, total_weight, donation_weight = tracker.get_cumulative_weights(best_share_hash, min(tracker.get_height(best_share_hash), net.REAL_CHAIN_LENGTH), 65535*net.SPREAD*bitcoin_data.target_to_average_attempts(block_target))
 547     res = dict((script, subsidy*weight//total_weight) for script, weight in weights.iteritems())
 548     res[DONATION_SCRIPT] = res.get(DONATION_SCRIPT, 0) + subsidy - sum(res.itervalues())
 549     return res
 550
 551 def get_desired_version_counts(tracker, best_share_hash, dist):
 552     res = {}
 553     for share in tracker.get_chain(best_share_hash, dist):
 554         res[share.desired_version] = res.get(share.desired_version, 0) + bitcoin_data.target_to_average_attempts(share.target)
 555     return res
 556
 557 def get_warnings(tracker, current_work, net):
 558     res = []
 559
 560     desired_version_counts = get_desired_version_counts(tracker, current_work.value['best_share_hash'],
 561         min(60*60//net.SHARE_PERIOD, tracker.get_height(current_work.value['best_share_hash'])))
 562     majority_desired_version = max(desired_version_counts, key=lambda k: desired_version_counts[k])
 563     if majority_desired_version not in [0, 1, 2] and desired_version_counts[majority_desired_version] > sum(desired_version_counts.itervalues())/2:
 564         res.append('A MAJORITY OF SHARES CONTAIN A VOTE FOR AN UNSUPPORTED SHARE IMPLEMENTATION! (v%i with %i%% support)\n'
 565             'An upgrade is likely necessary. Check http://p2pool.forre.st/ for more information.' % (
 566                 majority_desired_version, 100*desired_version_counts[majority_desired_version]/sum(desired_version_counts.itervalues())))
 567
 568     return res
 569
 570 def format_hash(x):
 571     if x is None:
 572         return 'xxxxxxxx'
 573     return '%08x' % (x % 2**32)
 574
 575 class ShareStore(object):
 576     def __init__(self, prefix, net):
 577         self.filename = prefix
 578         self.dirname = os.path.dirname(os.path.abspath(prefix))
 579         self.filename = os.path.basename(os.path.abspath(prefix))
 580         self.net = net
 581         self.known = None # will be filename -> set of share hashes, set of verified hashes
 582         self.known_desired = None
 583
 584     def get_shares(self):
 585         if self.known is not None:
 586             raise AssertionError()
 587         known = {}
 588         filenames, next = self.get_filenames_and_next()
 589         for filename in filenames:
 590             share_hashes, verified_hashes = known.setdefault(filename, (set(), set()))
 591             with open(filename, 'rb') as f:
 592                 for line in f:
 593                     try:
 594                         type_id_str, data_hex = line.strip().split(' ')
 595                         type_id = int(type_id_str)
 596                         if type_id == 0:
 597                             pass
 598                         elif type_id == 1:
 599                             pass
 600                         elif type_id == 2:
 601                             verified_hash = int(data_hex, 16)
 602                             yield 'verified_hash', verified_hash
 603                             verified_hashes.add(verified_hash)
 604                         elif type_id == 5:
 605                             raw_share = share_type.unpack(data_hex.decode('hex'))
 606                             if raw_share['type'] in [0, 1, 2, 3]:
 607                                 continue
 608                             share = load_share(raw_share, self.net, None)
 609                             yield 'share', share
 610                             share_hashes.add(share.hash)
 611                         else:
 612                             raise NotImplementedError("share type %i" % (type_id,))
 613                     except Exception:
 614                         log.err(None, "Error while reading saved shares, continuing where left off:")
 615         self.known = known
 616         self.known_desired = dict((k, (set(a), set(b))) for k, (a, b) in known.iteritems())
 617
 618     def _add_line(self, line):
 619         filenames, next = self.get_filenames_and_next()
 620         if filenames and os.path.getsize(filenames[-1]) < 10e6:
 621             filename = filenames[-1]
 622         else:
 623             filename = next
 624
 625         with open(filename, 'ab') as f:
 626             f.write(line + '\n')
 627
 628         return filename
 629
 630     def add_share(self, share):
 631         for filename, (share_hashes, verified_hashes) in self.known.iteritems():
 632             if share.hash in share_hashes:
 633                 break
 634         else:
 635             filename = self._add_line("%i %s" % (5, share_type.pack(share.as_share()).encode('hex')))
 636             share_hashes, verified_hashes = self.known.setdefault(filename, (set(), set()))
 637             share_hashes.add(share.hash)
 638         share_hashes, verified_hashes = self.known_desired.setdefault(filename, (set(), set()))
 639         share_hashes.add(share.hash)
 640
 641     def add_verified_hash(self, share_hash):
 642         for filename, (share_hashes, verified_hashes) in self.known.iteritems():
 643             if share_hash in verified_hashes:
 644                 break
 645         else:
 646             filename = self._add_line("%i %x" % (2, share_hash))
 647             share_hashes, verified_hashes = self.known.setdefault(filename, (set(), set()))
 648             verified_hashes.add(share_hash)
 649         share_hashes, verified_hashes = self.known_desired.setdefault(filename, (set(), set()))
 650         verified_hashes.add(share_hash)
 651
 652     def get_filenames_and_next(self):
 653         suffixes = sorted(int(x[len(self.filename):]) for x in os.listdir(self.dirname) if x.startswith(self.filename) and x[len(self.filename):].isdigit())
 654         return [os.path.join(self.dirname, self.filename + str(suffix)) for suffix in suffixes], os.path.join(self.dirname, self.filename + (str(suffixes[-1] + 1) if suffixes else str(0)))
 655
 656     def forget_share(self, share_hash):
 657         for filename, (share_hashes, verified_hashes) in self.known_desired.iteritems():
 658             if share_hash in share_hashes:
 659                 share_hashes.remove(share_hash)
 660         self.check_remove()
 661
 662     def forget_verified_share(self, share_hash):
 663         for filename, (share_hashes, verified_hashes) in self.known_desired.iteritems():
 664             if share_hash in verified_hashes:
 665                 verified_hashes.remove(share_hash)
 666         self.check_remove()
 667
 668     def check_remove(self):
 669         to_remove = set()
 670         for filename, (share_hashes, verified_hashes) in self.known_desired.iteritems():
 671             #print filename, len(share_hashes) + len(verified_hashes)
 672             if not share_hashes and not verified_hashes:
 673                 to_remove.add(filename)
 674         for filename in to_remove:
 675             self.known.pop(filename)
 676             self.known_desired.pop(filename)
 677             os.remove(filename)
 678             print "REMOVED", filename