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290 lines
11 KiB
290 lines
11 KiB
#!/usr/bin/env python
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#
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# Electrum - lightweight Bitcoin client
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# Copyright (C) 2012 thomasv@ecdsa.org
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#
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# Permission is hereby granted, free of charge, to any person
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# obtaining a copy of this software and associated documentation files
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# (the "Software"), to deal in the Software without restriction,
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# including without limitation the rights to use, copy, modify, merge,
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# publish, distribute, sublicense, and/or sell copies of the Software,
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# and to permit persons to whom the Software is furnished to do so,
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# subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be
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# included in all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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import os
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import util
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import bitcoin
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from bitcoin import *
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MAX_TARGET = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
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class Blockchain(util.PrintError):
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'''Manages blockchain headers and their verification'''
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def __init__(self, config, network):
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self.config = config
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self.network = network
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self.checkpoint_height, self.checkpoint_hash = self.get_checkpoint()
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self.check_truncate_headers()
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self.set_local_height()
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def height(self):
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return self.local_height
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def init(self):
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import threading
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if os.path.exists(self.path()):
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self.downloading_headers = False
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return
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self.downloading_headers = True
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t = threading.Thread(target = self.init_headers_file)
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t.daemon = True
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t.start()
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def pass_checkpoint(self, header):
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if type(header) is not dict:
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return False
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if header.get('block_height') != self.checkpoint_height:
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return True
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if header.get('prev_block_hash') is None:
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header['prev_block_hash'] = '00'*32
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try:
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_hash = self.hash_header(header)
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except:
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return False
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return _hash == self.checkpoint_hash
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def verify_header(self, header, prev_header, bits, target):
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prev_hash = self.hash_header(prev_header)
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_hash = self.hash_header(header)
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if prev_hash != header.get('prev_block_hash'):
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raise BaseException("prev hash mismatch: %s vs %s" % (prev_hash, header.get('prev_block_hash')))
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if not self.pass_checkpoint(header):
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raise BaseException('failed checkpoint')
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if self.checkpoint_height == header.get('block_height'):
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self.print_error("validated checkpoint", self.checkpoint_height)
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if bitcoin.TESTNET:
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return
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if bits != header.get('bits'):
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raise BaseException("bits mismatch: %s vs %s" % (bits, header.get('bits')))
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if int('0x' + _hash, 16) > target:
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raise BaseException("insufficient proof of work: %s vs target %s" % (int('0x' + _hash, 16), target))
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def verify_chain(self, chain):
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first_header = chain[0]
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prev_header = self.read_header(first_header.get('block_height') - 1)
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for header in chain:
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height = header.get('block_height')
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bits, target = self.get_target(height / 2016, chain)
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self.verify_header(header, prev_header, bits, target)
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prev_header = header
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def verify_chunk(self, index, data):
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num = len(data) / 80
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prev_header = None
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if index != 0:
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prev_header = self.read_header(index*2016 - 1)
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bits, target = self.get_target(index)
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for i in range(num):
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raw_header = data[i*80:(i+1) * 80]
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header = self.deserialize_header(raw_header, index*2016 + i)
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self.verify_header(header, prev_header, bits, target)
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prev_header = header
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def serialize_header(self, res):
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s = int_to_hex(res.get('version'), 4) \
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+ rev_hex(res.get('prev_block_hash')) \
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+ rev_hex(res.get('merkle_root')) \
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+ int_to_hex(int(res.get('timestamp')), 4) \
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+ int_to_hex(int(res.get('bits')), 4) \
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+ int_to_hex(int(res.get('nonce')), 4)
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return s
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def deserialize_header(self, s, height):
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hex_to_int = lambda s: int('0x' + s[::-1].encode('hex'), 16)
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h = {}
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h['version'] = hex_to_int(s[0:4])
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h['prev_block_hash'] = hash_encode(s[4:36])
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h['merkle_root'] = hash_encode(s[36:68])
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h['timestamp'] = hex_to_int(s[68:72])
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h['bits'] = hex_to_int(s[72:76])
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h['nonce'] = hex_to_int(s[76:80])
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h['block_height'] = height
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return h
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def hash_header(self, header):
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if header is None:
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return '0' * 64
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return hash_encode(Hash(self.serialize_header(header).decode('hex')))
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def path(self):
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return util.get_headers_path(self.config)
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def init_headers_file(self):
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filename = self.path()
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try:
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import urllib, socket
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socket.setdefaulttimeout(30)
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self.print_error("downloading ", bitcoin.HEADERS_URL)
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urllib.urlretrieve(bitcoin.HEADERS_URL, filename + '.tmp')
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os.rename(filename + '.tmp', filename)
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self.print_error("done.")
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except Exception:
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self.print_error("download failed. creating file", filename)
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open(filename, 'wb+').close()
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self.downloading_headers = False
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self.set_local_height()
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self.print_error("%d blocks" % self.local_height)
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def save_chunk(self, index, chunk):
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filename = self.path()
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f = open(filename, 'rb+')
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f.seek(index * 2016 * 80)
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h = f.write(chunk)
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f.close()
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self.set_local_height()
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def save_header(self, header):
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data = self.serialize_header(header).decode('hex')
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assert len(data) == 80
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height = header.get('block_height')
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filename = self.path()
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f = open(filename, 'rb+')
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f.seek(height * 80)
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h = f.write(data)
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f.close()
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self.set_local_height()
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def set_local_height(self):
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self.local_height = 0
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name = self.path()
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if os.path.exists(name):
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h = os.path.getsize(name)/80 - 1
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if self.local_height != h:
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self.local_height = h
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def read_header(self, block_height):
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name = self.path()
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if os.path.exists(name):
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f = open(name, 'rb')
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f.seek(block_height * 80)
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h = f.read(80)
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f.close()
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if len(h) == 80:
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h = self.deserialize_header(h, block_height)
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return h
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def BIP9(self, height, flag):
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v = self.read_header(height)['version']
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return ((v & 0xE0000000) == 0x20000000) and ((v & flag) == flag)
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def segwit_support(self, N=144):
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h = self.local_height
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return sum([self.BIP9(h-i, 2) for i in range(N)])*10000/N/100.
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def check_truncate_headers(self):
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checkpoint = self.read_header(self.checkpoint_height)
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if checkpoint is None:
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return
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if self.hash_header(checkpoint) == self.checkpoint_hash:
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return
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self.print_error('checkpoint mismatch:', self.hash_header(checkpoint), self.checkpoint_hash)
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self.truncate_headers(self.checkpoint_height)
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def truncate_headers(self, height):
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self.print_error('Truncating headers file at height %d'%height)
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name = self.path()
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f = open(name, 'rb+')
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f.seek(height * 80)
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f.truncate()
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f.close()
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def get_target(self, index, chain=None):
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if bitcoin.TESTNET:
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return 0, 0
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if index == 0:
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return 0x1d00ffff, MAX_TARGET
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first = self.read_header((index-1) * 2016)
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last = self.read_header(index*2016 - 1)
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if last is None:
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for h in chain:
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if h.get('block_height') == index*2016 - 1:
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last = h
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assert last is not None
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# bits to target
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bits = last.get('bits')
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bitsN = (bits >> 24) & 0xff
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if not (bitsN >= 0x03 and bitsN <= 0x1d):
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raise BaseException("First part of bits should be in [0x03, 0x1d]")
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bitsBase = bits & 0xffffff
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if not (bitsBase >= 0x8000 and bitsBase <= 0x7fffff):
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raise BaseException("Second part of bits should be in [0x8000, 0x7fffff]")
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target = bitsBase << (8 * (bitsN-3))
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# new target
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nActualTimespan = last.get('timestamp') - first.get('timestamp')
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nTargetTimespan = 14 * 24 * 60 * 60
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nActualTimespan = max(nActualTimespan, nTargetTimespan / 4)
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nActualTimespan = min(nActualTimespan, nTargetTimespan * 4)
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new_target = min(MAX_TARGET, (target*nActualTimespan) / nTargetTimespan)
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# convert new target to bits
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c = ("%064x" % new_target)[2:]
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while c[:2] == '00' and len(c) > 6:
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c = c[2:]
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bitsN, bitsBase = len(c) / 2, int('0x' + c[:6], 16)
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if bitsBase >= 0x800000:
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bitsN += 1
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bitsBase >>= 8
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new_bits = bitsN << 24 | bitsBase
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return new_bits, bitsBase << (8 * (bitsN-3))
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def can_connect(self, header):
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previous_height = header['block_height'] - 1
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previous_header = self.read_header(previous_height)
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if not previous_header:
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return False
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prev_hash = self.hash_header(previous_header)
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if prev_hash != header.get('prev_block_hash'):
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return False
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height = header.get('block_height')
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bits, target = self.get_target(height / 2016)
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try:
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self.verify_header(header, previous_header, bits, target)
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except:
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return False
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return True
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def connect_chunk(self, idx, hexdata):
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try:
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data = hexdata.decode('hex')
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self.verify_chunk(idx, data)
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self.print_error("validated chunk %d" % idx)
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self.save_chunk(idx, data)
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return True
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except BaseException as e:
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self.print_error('verify_chunk failed', str(e))
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return False
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def get_checkpoint(self):
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height = self.config.get('checkpoint_height', 0)
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value = self.config.get('checkpoint_value', bitcoin.GENESIS)
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return (height, value)
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def set_checkpoint(self, height, value):
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self.checkpoint_height = height
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self.checkpoint_hash = value
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self.config.set_key('checkpoint_height', height)
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self.config.set_key('checkpoint_value', value)
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self.check_truncate_headers()
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