forked from LBRYCommunity/lbry-sdk
b0bd0b1fc0
+ converted all comment type annotations to python 3 style syntax annotations + pylint & mypy
255 lines
8.4 KiB
Python
255 lines
8.4 KiB
Python
import os
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import struct
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import logging
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import typing
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from binascii import unhexlify
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from twisted.internet import threads, defer
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from torba.stream import StreamController
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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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if typing.TYPE_CHECKING:
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from torba import baseledger
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log = logging.getLogger(__name__)
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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: 'baseledger.BaseLedger') -> None:
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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 hash(self, height=None):
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if height is None:
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height = self.height
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header = self[height]
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return self._hash_header(header)
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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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@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(
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'%s: added %s header blocks, final height %s',
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self.ledger.get_id(), change, self.height
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)
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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, _ = 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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bits_n = (bits >> 24) & 0xff
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assert 0x03 <= bits_n <= 0x1d, \
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"First part of bits should be in [0x03, 0x1d], but it was {}".format(hex(bits_n))
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bits_base = bits & 0xffffff
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assert 0x8000 <= bits_base <= 0x7fffff, \
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"Second part of bits should be in [0x8000, 0x7fffff] but it was {}".format(bits_base)
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# new target
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retarget_timespan = self.ledger.target_timespan
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n_actual_timespan = last['timestamp'] - first['timestamp']
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n_modulated_timespan = retarget_timespan + (n_actual_timespan - retarget_timespan) // 8
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n_min_timespan = retarget_timespan - (retarget_timespan // 8)
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n_max_timespan = retarget_timespan + (retarget_timespan // 2)
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# Limit adjustment step
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if n_modulated_timespan < n_min_timespan:
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n_modulated_timespan = n_min_timespan
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elif n_modulated_timespan > n_max_timespan:
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n_modulated_timespan = n_max_timespan
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# Retarget
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bn_pow_limit = _ArithUint256(self.ledger.max_target)
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bn_new = _ArithUint256.set_compact(last['bits'])
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bn_new *= n_modulated_timespan
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bn_new //= n_modulated_timespan
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if bn_new > bn_pow_limit:
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bn_new = bn_pow_limit
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return bn_new.get_compact(), bn_new._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 from_compact(n_compact):
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"""Convert a compact representation into its value"""
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n_size = n_compact >> 24
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# the lower 23 bits
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n_word = n_compact & 0x007fffff
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if n_size <= 3:
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return n_word >> 8 * (3 - n_size)
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else:
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return n_word << 8 * (n_size - 3)
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@classmethod
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def set_compact(cls, n_compact):
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return cls(cls.from_compact(n_compact))
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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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bits = bin(self._value)[2:]
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for i, d in enumerate(bits):
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if d:
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return (len(bits) - i) + 1
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return 0
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def get_low64(self):
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return self._value & 0xffffffffffffffff
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def get_compact(self):
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"""Convert a value into its compact representation"""
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n_size = (self.bits() + 7) // 8
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if n_size <= 3:
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n_compact = self.get_low64() << 8 * (3 - n_size)
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else:
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n = _ArithUint256(self._value >> 8 * (n_size - 3))
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n_compact = n.get_low64()
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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 n_compact & 0x00800000:
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n_compact >>= 8
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n_size += 1
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assert (n_compact & ~0x007fffff) == 0
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assert n_size < 256
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n_compact |= n_size << 24
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return n_compact
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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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