193 lines
6.8 KiB
Python
193 lines
6.8 KiB
Python
import os
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import logging
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from io import BytesIO
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from typing import Optional, Iterator, Tuple
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from binascii import hexlify
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from twisted.internet import threads, defer
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from torba.util import ArithUint256
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from torba.hash import double_sha256
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log = logging.getLogger(__name__)
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class InvalidHeader(Exception):
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def __init__(self, height, message):
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super().__init__(message)
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self.message = message
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self.height = height
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class BaseHeaders:
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header_size: int
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chunk_size: int
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max_target: int
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genesis_hash: Optional[bytes]
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target_timespan: int
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validate_difficulty: bool = True
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def __init__(self, path) -> None:
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if path == ':memory:':
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self.io = BytesIO()
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self.path = path
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self._size: Optional[int] = None
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self._header_connect_lock = defer.DeferredLock()
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def open(self):
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if self.path != ':memory:':
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self.io = open(self.path, 'a+b')
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return defer.succeed(True)
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def close(self):
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self.io.close()
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return defer.succeed(True)
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@staticmethod
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def serialize(header: dict) -> bytes:
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raise NotImplementedError
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@staticmethod
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def deserialize(height, header):
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raise NotImplementedError
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def get_next_chunk_target(self, chunk: int) -> ArithUint256:
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return ArithUint256(self.max_target)
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@staticmethod
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def get_next_block_target(chunk_target: ArithUint256, previous: Optional[dict],
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current: Optional[dict]) -> ArithUint256:
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return chunk_target
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def __len__(self) -> int:
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if self._size is None:
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self._size = self.io.seek(0, os.SEEK_END) // self.header_size
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return self._size
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def __bool__(self):
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return True
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def __getitem__(self, height) -> dict:
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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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return self.deserialize(height, self.get_raw_header(height))
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def get_raw_header(self, height) -> bytes:
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self.io.seek(height * self.header_size, os.SEEK_SET)
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return self.io.read(self.header_size)
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@property
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def height(self) -> int:
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return len(self)-1
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def hash(self, height=None) -> bytes:
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return self.hash_header(
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self.get_raw_header(height if height is not None else self.height)
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)
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@staticmethod
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def hash_header(header: bytes) -> bytes:
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if header is None:
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return b'0' * 64
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return hexlify(double_sha256(header)[::-1])
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@defer.inlineCallbacks
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def connect(self, start: int, headers: bytes):
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added = 0
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bail = False
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yield self._header_connect_lock.acquire()
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try:
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for height, chunk in self._iterate_chunks(start, headers):
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try:
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# validate_chunk() is CPU bound and reads previous chunks from file system
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yield threads.deferToThread(self.validate_chunk, height, chunk)
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except InvalidHeader as e:
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bail = True
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chunk = chunk[:(height-e.height+1)*self.header_size]
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written = 0
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if chunk:
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self.io.seek(height * self.header_size, os.SEEK_SET)
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written = self.io.write(chunk) // self.header_size
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self.io.truncate()
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# .seek()/.write()/.truncate() might also .flush() when needed
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# the goal here is mainly to ensure we're definitely flush()'ing
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yield threads.deferToThread(self.io.flush)
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self._size = None
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added += written
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if bail:
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break
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finally:
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self._header_connect_lock.release()
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defer.returnValue(added)
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def validate_chunk(self, height, chunk):
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previous_hash, previous_header, previous_previous_header = None, None, None
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if height > 0:
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previous_header = self[height-1]
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previous_hash = self.hash(height-1)
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if height > 1:
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previous_previous_header = self[height-2]
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chunk_target = self.get_next_chunk_target(height // 2016 - 1)
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for current_hash, current_header in self._iterate_headers(height, chunk):
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block_target = self.get_next_block_target(chunk_target, previous_previous_header, previous_header)
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self.validate_header(height, current_hash, current_header, previous_hash, block_target)
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previous_previous_header = previous_header
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previous_header = current_header
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previous_hash = current_hash
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def validate_header(self, height: int, current_hash: bytes,
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header: dict, previous_hash: bytes, target: ArithUint256):
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if previous_hash is None:
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if self.genesis_hash is not None and self.genesis_hash != current_hash:
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raise InvalidHeader(
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height, "genesis header doesn't match: {} vs expected {}".format(
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current_hash.decode(), self.genesis_hash.decode())
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)
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return
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if header['prev_block_hash'] != previous_hash:
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raise InvalidHeader(
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height, "previous hash mismatch: {} vs expected {}".format(
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header['prev_block_hash'].decode(), previous_hash.decode())
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)
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if self.validate_difficulty:
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if header['bits'] != target.compact:
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raise InvalidHeader(
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height, "bits mismatch: {} vs expected {}".format(
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header['bits'], target.compact)
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)
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proof_of_work = self.get_proof_of_work(current_hash)
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if proof_of_work > target:
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raise InvalidHeader(
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height, "insufficient proof of work: {} vs target {}".format(
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proof_of_work.value, target.value)
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)
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@staticmethod
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def get_proof_of_work(header_hash: bytes) -> ArithUint256:
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return ArithUint256(int(b'0x' + header_hash, 16))
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def _iterate_chunks(self, height: int, headers: bytes) -> Iterator[Tuple[int, bytes]]:
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assert len(headers) % self.header_size == 0
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start = 0
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end = (self.chunk_size - height % self.chunk_size) * self.header_size
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while start < end:
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yield height + (start // self.header_size), headers[start:end]
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start = end
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end = min(len(headers), end + self.chunk_size * self.header_size)
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def _iterate_headers(self, height: int, headers: bytes) -> Iterator[Tuple[bytes, dict]]:
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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.hash_header(header), self.deserialize(height+idx, header)
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