forked from LBRYCommunity/lbry-sdk
331 lines
13 KiB
Python
331 lines
13 KiB
Python
import base64
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import os
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import struct
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import asyncio
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import hashlib
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import logging
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import zlib
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from io import BytesIO
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from contextlib import asynccontextmanager
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from typing import Optional, Iterator, Tuple, Callable
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from binascii import hexlify, unhexlify
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from lbry.crypto.hash import sha512, double_sha256, ripemd160
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from lbry.wallet.util import ArithUint256
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from .checkpoints import HASHES
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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 Headers:
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header_size = 112
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chunk_size = 10**16
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max_target = 0x0000ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
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genesis_hash = b'9c89283ba0f3227f6c03b70216b9f665f0118d5e0fa729cedf4fb34d6a34f463'
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target_timespan = 150
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checkpoint = (600_000, b'100b33ca3d0b86a48f0d6d6f30458a130ecb89d5affefe4afccb134d5a40f4c2')
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first_block_timestamp = 1466646588 # block 1, as 0 is off by a lot
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timestamp_average_offset = 160.6855883050695 # calculated at 733447
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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.chunk_getter: Optional[Callable] = None
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async def open(self):
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if self.path != ':memory:':
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if not os.path.exists(self.path):
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self.io = open(self.path, 'w+b')
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else:
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self.io = open(self.path, 'r+b')
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async def close(self):
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self.io.close()
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@staticmethod
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def serialize(header):
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return b''.join([
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struct.pack('<I', header['version']),
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unhexlify(header['prev_block_hash'])[::-1],
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unhexlify(header['merkle_root'])[::-1],
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unhexlify(header['claim_trie_root'])[::-1],
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struct.pack('<III', header['timestamp'], header['bits'], header['nonce'])
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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[100:112])
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return {
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'version': version,
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'prev_block_hash': hexlify(header[4:36][::-1]),
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'merkle_root': hexlify(header[36:68][::-1]),
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'claim_trie_root': hexlify(header[68:100][::-1]),
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'timestamp': timestamp,
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'bits': bits,
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'nonce': nonce,
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'block_height': height,
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}
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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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def get_next_block_target(self, max_target: ArithUint256, previous: Optional[dict],
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current: Optional[dict]) -> ArithUint256:
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# https://github.com/lbryio/lbrycrd/blob/master/src/lbry.cpp
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if previous is None and current is None:
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return max_target
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if previous is None:
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previous = current
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actual_timespan = current['timestamp'] - previous['timestamp']
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modulated_timespan = self.target_timespan + int((actual_timespan - self.target_timespan) / 8)
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minimum_timespan = self.target_timespan - int(self.target_timespan / 8) # 150 - 18 = 132
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maximum_timespan = self.target_timespan + int(self.target_timespan / 2) # 150 + 75 = 225
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clamped_timespan = max(minimum_timespan, min(modulated_timespan, maximum_timespan))
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target = ArithUint256.from_compact(current['bits'])
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new_target = min(max_target, (target * clamped_timespan) / self.target_timespan)
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return new_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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async def get(self, height) -> dict:
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if isinstance(height, slice):
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raise NotImplementedError("Slicing of header chain has not been implemented yet.")
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return self.deserialize(height, await self.get_raw_header(height))
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def estimated_timestamp(self, height):
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return self.first_block_timestamp + (height * self.timestamp_average_offset)
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async def get_raw_header(self, height) -> bytes:
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await self.ensure_chunk_at(height)
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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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async def chunk_hash(self, start, count):
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self.io.seek(start * self.header_size, os.SEEK_SET)
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return self.hash_header(self.io.read(count * self.header_size)).decode()
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async def ensure_tip(self):
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await self.ensure_chunk_at(max(HASHES.keys()))
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async def ensure_chunk_at(self, height):
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if await self.has_header(height):
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log.info("has header %s", height)
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return
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log.info("on-demand fetching height %s", height)
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start = (height // 1000) * 1000
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headers = await self.chunk_getter(start) # pylint: disable=not-callable
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chunk = (
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zlib.decompress(base64.b64decode(headers['base64']), wbits=-15, bufsize=600_000)
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)
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chunk_hash = self.hash_header(chunk).decode()
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if HASHES[start] == chunk_hash:
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return self._write(start, chunk)
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raise Exception(
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f"Checkpoint mismatch at height {start}. Expected {HASHES[start]}, but got {chunk_hash} instead."
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)
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async def has_header(self, height):
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empty = '56944c5d3f98413ef45cf54545538103cc9f298e0575820ad3591376e2e0f65d'
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all_zeroes = '789d737d4f448e554b318c94063bbfa63e9ccda6e208f5648ca76ee68896557b'
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return await self.chunk_hash(height, 1) not in (empty, all_zeroes)
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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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@property
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def bytes_size(self):
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return len(self) * self.header_size
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async def hash(self, height=None) -> bytes:
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return self.hash_header(
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await 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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@asynccontextmanager
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async def checkpointed_connector(self):
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buf = BytesIO()
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try:
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yield buf
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finally:
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await asyncio.sleep(0)
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final_height = len(self) + buf.tell() // self.header_size
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verifiable_bytes = (self.checkpoint[0] - len(self)) * self.header_size if self.checkpoint else 0
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if verifiable_bytes > 0 and final_height >= self.checkpoint[0]:
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buf.seek(0)
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self.io.seek(0)
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h = hashlib.sha256()
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h.update(self.io.read())
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h.update(buf.read(verifiable_bytes))
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if h.hexdigest().encode() == self.checkpoint[1]:
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buf.seek(0)
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self._write(len(self), buf.read(verifiable_bytes))
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remaining = buf.read()
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buf.seek(0)
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buf.write(remaining)
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buf.truncate()
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else:
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log.warning("Checkpoint mismatch, connecting headers through slow method.")
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if buf.tell() > 0:
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await self.connect(len(self), buf.getvalue())
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async def connect(self, start: int, headers: bytes) -> int:
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added = 0
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bail = False
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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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await 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)*self.header_size]
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added += self._write(height, chunk) if chunk else 0
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if bail:
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break
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return added
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def _write(self, height, verified_chunk):
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self.io.seek(height * self.header_size, os.SEEK_SET)
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written = self.io.write(verified_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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self.io.flush()
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self._size = self.io.tell() // self.header_size
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return written
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async 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 = await self.get(height-1)
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previous_hash = await self.hash(height-1)
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if height > 1:
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previous_previous_header = await self.get(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, f"genesis header doesn't match: {current_hash.decode()} "
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f"vs expected {self.genesis_hash.decode()}")
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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, f"insufficient proof of work: {proof_of_work.value} vs target {target.value}"
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)
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async def repair(self):
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previous_header_hash = fail = None
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batch_size = 36
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for start_height in range(0, self.height, batch_size):
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self.io.seek(self.header_size * start_height)
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headers = self.io.read(self.header_size*batch_size)
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if len(headers) % self.header_size != 0:
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headers = headers[:(len(headers) // self.header_size) * self.header_size]
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for header_hash, header in self._iterate_headers(start_height, headers):
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height = header['block_height']
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if height:
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if header['prev_block_hash'] != previous_header_hash:
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fail = True
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else:
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if header_hash != self.genesis_hash:
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fail = True
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if fail:
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log.warning("Header file corrupted at height %s, truncating it.", height - 1)
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self.io.seek(max(0, (height - 1)) * self.header_size, os.SEEK_SET)
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self.io.truncate()
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self.io.flush()
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self._size = None
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return
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previous_header_hash = header_hash
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@classmethod
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def get_proof_of_work(cls, header_hash: bytes):
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return ArithUint256(int(b'0x' + cls.header_hash_to_pow_hash(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, f"{len(headers)} {len(headers)%self.header_size}"
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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, len(headers)
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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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@staticmethod
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def header_hash_to_pow_hash(header_hash: bytes):
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header_hash_bytes = unhexlify(header_hash)[::-1]
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h = sha512(header_hash_bytes)
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pow_hash = double_sha256(
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ripemd160(h[:len(h) // 2]) +
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ripemd160(h[len(h) // 2:])
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)
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return hexlify(pow_hash[::-1])
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class UnvalidatedHeaders(Headers):
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validate_difficulty = False
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max_target = 0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
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genesis_hash = b'6e3fcf1299d4ec5d79c3a4c91d624a4acf9e2e173d95a1a0504f677669687556'
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