forked from LBRYCommunity/lbry-sdk
244 lines
8.1 KiB
Python
244 lines
8.1 KiB
Python
import os
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import struct
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from binascii import unhexlify
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from twisted.internet import threads, defer
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import torba
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from torba.stream import StreamController, execute_serially
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from torba.util import int_to_hex, rev_hex, hash_encode
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from torba.hash import double_sha256, pow_hash
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class BaseHeaders:
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header_size = 80
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verify_bits_to_target = True
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def __init__(self, ledger): # type: (baseledger.BaseLedger) -> BaseHeaders
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self.ledger = ledger
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self._size = None
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self._on_change_controller = StreamController()
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self.on_changed = self._on_change_controller.stream
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@property
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def path(self):
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return os.path.join(self.ledger.path, 'headers')
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def touch(self):
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if not os.path.exists(self.path):
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with open(self.path, 'wb'):
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pass
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@property
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def height(self):
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return len(self) - 1
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def sync_read_length(self):
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return os.path.getsize(self.path) // self.header_size
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def sync_read_header(self, height):
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if 0 <= height < len(self):
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with open(self.path, 'rb') as f:
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f.seek(height * self.header_size)
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return f.read(self.header_size)
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def __len__(self):
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if self._size is None:
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self._size = self.sync_read_length()
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return self._size
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def __getitem__(self, height):
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assert not isinstance(height, slice), \
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"Slicing of header chain has not been implemented yet."
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header = self.sync_read_header(height)
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return self._deserialize(height, header)
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@execute_serially
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@defer.inlineCallbacks
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def connect(self, start, headers):
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yield threads.deferToThread(self._sync_connect, start, headers)
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def _sync_connect(self, start, headers):
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previous_header = None
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for header in self._iterate_headers(start, headers):
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height = header['block_height']
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if previous_header is None and height > 0:
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previous_header = self[height-1]
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self._verify_header(height, header, previous_header)
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previous_header = header
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with open(self.path, 'r+b') as f:
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f.seek(start * self.header_size)
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f.write(headers)
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f.truncate()
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_old_size = self._size
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self._size = self.sync_read_length()
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change = self._size - _old_size
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#log.info('saved {} header blocks'.format(change))
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self._on_change_controller.add(change)
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def _iterate_headers(self, height, headers):
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assert len(headers) % self.header_size == 0
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for idx in range(len(headers) // self.header_size):
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start, end = idx * self.header_size, (idx + 1) * self.header_size
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header = headers[start:end]
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yield self._deserialize(height+idx, header)
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def _verify_header(self, height, header, previous_header):
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previous_hash = self._hash_header(previous_header)
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assert previous_hash == header['prev_block_hash'], \
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"prev hash mismatch: {} vs {}".format(previous_hash, header['prev_block_hash'])
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bits, target = self._calculate_next_work_required(height, previous_header, header)
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assert bits == header['bits'], \
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"bits mismatch: {} vs {} (hash: {})".format(
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bits, header['bits'], self._hash_header(header))
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# TODO: FIX ME!!!
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#_pow_hash = self._pow_hash_header(header)
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#assert int(b'0x' + _pow_hash, 16) <= target, \
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# "insufficient proof of work: {} vs target {}".format(
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# int(b'0x' + _pow_hash, 16), target)
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@staticmethod
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def _serialize(header):
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return b''.join([
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int_to_hex(header['version'], 4),
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rev_hex(header['prev_block_hash']),
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rev_hex(header['merkle_root']),
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int_to_hex(int(header['timestamp']), 4),
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int_to_hex(int(header['bits']), 4),
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int_to_hex(int(header['nonce']), 4)
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])
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@staticmethod
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def _deserialize(height, header):
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version, = struct.unpack('<I', header[:4])
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timestamp, bits, nonce = struct.unpack('<III', header[68:80])
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return {
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'block_height': height,
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'version': version,
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'prev_block_hash': hash_encode(header[4:36]),
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'merkle_root': hash_encode(header[36:68]),
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'timestamp': timestamp,
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'bits': bits,
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'nonce': nonce,
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}
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def _hash_header(self, header):
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if header is None:
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return b'0' * 64
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return hash_encode(double_sha256(unhexlify(self._serialize(header))))
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def _pow_hash_header(self, header):
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if header is None:
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return b'0' * 64
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return hash_encode(pow_hash(unhexlify(self._serialize(header))))
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def _calculate_next_work_required(self, height, first, last):
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if height == 0:
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return self.ledger.genesis_bits, self.ledger.max_target
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if self.verify_bits_to_target:
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bits = last['bits']
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bitsN = (bits >> 24) & 0xff
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assert 0x03 <= bitsN <= 0x1d, \
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"First part of bits should be in [0x03, 0x1d], but it was {}".format(hex(bitsN))
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bitsBase = bits & 0xffffff
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assert 0x8000 <= bitsBase <= 0x7fffff, \
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"Second part of bits should be in [0x8000, 0x7fffff] but it was {}".format(bitsBase)
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# new target
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retargetTimespan = self.ledger.target_timespan
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nActualTimespan = last['timestamp'] - first['timestamp']
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nModulatedTimespan = retargetTimespan + (nActualTimespan - retargetTimespan) // 8
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nMinTimespan = retargetTimespan - (retargetTimespan // 8)
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nMaxTimespan = retargetTimespan + (retargetTimespan // 2)
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# Limit adjustment step
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if nModulatedTimespan < nMinTimespan:
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nModulatedTimespan = nMinTimespan
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elif nModulatedTimespan > nMaxTimespan:
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nModulatedTimespan = nMaxTimespan
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# Retarget
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bnPowLimit = _ArithUint256(self.ledger.max_target)
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bnNew = _ArithUint256.SetCompact(last['bits'])
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bnNew *= nModulatedTimespan
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bnNew //= nModulatedTimespan
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if bnNew > bnPowLimit:
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bnNew = bnPowLimit
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return bnNew.GetCompact(), bnNew._value
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class _ArithUint256:
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""" See: lbrycrd/src/arith_uint256.cpp """
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def __init__(self, value):
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self._value = value
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def __str__(self):
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return hex(self._value)
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@staticmethod
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def fromCompact(nCompact):
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"""Convert a compact representation into its value"""
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nSize = nCompact >> 24
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# the lower 23 bits
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nWord = nCompact & 0x007fffff
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if nSize <= 3:
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return nWord >> 8 * (3 - nSize)
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else:
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return nWord << 8 * (nSize - 3)
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@classmethod
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def SetCompact(cls, nCompact):
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return cls(cls.fromCompact(nCompact))
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def bits(self):
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"""Returns the position of the highest bit set plus one."""
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bn = bin(self._value)[2:]
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for i, d in enumerate(bn):
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if d:
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return (len(bn) - i) + 1
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return 0
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def GetLow64(self):
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return self._value & 0xffffffffffffffff
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def GetCompact(self):
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"""Convert a value into its compact representation"""
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nSize = (self.bits() + 7) // 8
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nCompact = 0
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if nSize <= 3:
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nCompact = self.GetLow64() << 8 * (3 - nSize)
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else:
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bn = _ArithUint256(self._value >> 8 * (nSize - 3))
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nCompact = bn.GetLow64()
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# The 0x00800000 bit denotes the sign.
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# Thus, if it is already set, divide the mantissa by 256 and increase the exponent.
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if nCompact & 0x00800000:
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nCompact >>= 8
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nSize += 1
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assert (nCompact & ~0x007fffff) == 0
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assert nSize < 256
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nCompact |= nSize << 24
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return nCompact
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def __mul__(self, x):
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# Take the mod because we are limited to an unsigned 256 bit number
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return _ArithUint256((self._value * x) % 2 ** 256)
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def __ifloordiv__(self, x):
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self._value = (self._value // x)
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return self
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def __gt__(self, x):
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return self._value > x._value
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