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