3 # Electrum - lightweight Bitcoin client
4 # Copyright (C) 2012 thomasv@ecdsa.org
6 # This program is free software: you can redistribute it and/or modify
7 # it under the terms of the GNU General Public License as published by
8 # the Free Software Foundation, either version 3 of the License, or
9 # (at your option) any later version.
11 # This program is distributed in the hope that it will be useful,
12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 # GNU General Public License for more details.
16 # You should have received a copy of the GNU General Public License
17 # along with this program. If not, see <http://www.gnu.org/licenses/>.
20 import threading, time, Queue, os, sys, shutil
21 from util import user_dir, appdata_dir, print_error
25 class Blockchain(threading.Thread):
27 def __init__(self, config, network):
28 threading.Thread.__init__(self)
31 self.network = network
32 self.lock = threading.Lock()
35 self.headers_url = 'http://headers.electrum.org/blockchain_headers'
36 self.set_local_height()
37 self.queue = Queue.Queue()
41 return self.local_height
45 with self.lock: self.running = False
49 with self.lock: return self.running
53 self.init_headers_file()
54 self.set_local_height()
55 print_error( "blocks:", self.local_height )
60 while self.is_running():
63 result = self.queue.get()
67 if not result: continue
70 if not header: continue
72 height = header.get('block_height')
74 if height <= self.local_height:
77 if height > self.local_height + 50:
78 if not self.get_and_verify_chunks(i, header, height):
81 if height > self.local_height:
82 # get missing parts from interface (until it connects to my chain)
83 chain = self.get_chain( i, header )
85 # skip that server if the result is not consistent
91 if self.verify_chain( chain ):
92 print_error("height:", height, i.server)
94 self.save_header(header)
96 print_error("error", i.server)
97 # todo: dismiss that server
101 self.network.new_blockchain_height(height, i)
106 def verify_chain(self, chain):
108 first_header = chain[0]
109 prev_header = self.read_header(first_header.get('block_height') -1)
113 height = header.get('block_height')
115 prev_hash = self.hash_header(prev_header)
116 bits, target = self.get_target(height/2016, chain)
117 _hash = self.hash_header(header)
119 assert prev_hash == header.get('prev_block_hash')
120 assert bits == header.get('bits')
121 assert int('0x'+_hash,16) < target
131 def verify_chunk(self, index, hexdata):
132 data = hexdata.decode('hex')
137 previous_hash = ("0"*64)
139 prev_header = self.read_header(index*2016-1)
140 if prev_header is None: raise
141 previous_hash = self.hash_header(prev_header)
143 bits, target = self.get_target(index)
146 height = index*2016 + i
147 raw_header = data[i*80:(i+1)*80]
148 header = self.header_from_string(raw_header)
149 _hash = self.hash_header(header)
150 assert previous_hash == header.get('prev_block_hash')
151 assert bits == header.get('bits')
152 assert int('0x'+_hash,16) < target
154 previous_header = header
155 previous_hash = _hash
157 self.save_chunk(index, data)
158 print_error("validated chunk %d"%height)
162 def header_to_string(self, res):
163 s = int_to_hex(res.get('version'),4) \
164 + rev_hex(res.get('prev_block_hash')) \
165 + rev_hex(res.get('merkle_root')) \
166 + int_to_hex(int(res.get('timestamp')),4) \
167 + int_to_hex(int(res.get('bits')),4) \
168 + int_to_hex(int(res.get('nonce')),4)
172 def header_from_string(self, s):
173 hex_to_int = lambda s: int('0x' + s[::-1].encode('hex'), 16)
175 h['version'] = hex_to_int(s[0:4])
176 h['prev_block_hash'] = hash_encode(s[4:36])
177 h['merkle_root'] = hash_encode(s[36:68])
178 h['timestamp'] = hex_to_int(s[68:72])
179 h['bits'] = hex_to_int(s[72:76])
180 h['nonce'] = hex_to_int(s[76:80])
183 def hash_header(self, header):
184 return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
187 return os.path.join( self.config.path, 'blockchain_headers')
189 def init_headers_file(self):
190 filename = self.path()
191 if os.path.exists(filename):
195 import urllib, socket
196 socket.setdefaulttimeout(30)
197 print_error("downloading ", self.headers_url )
198 urllib.urlretrieve(self.headers_url, filename)
201 print_error( "download failed. creating file", filename )
202 open(filename,'wb+').close()
204 def save_chunk(self, index, chunk):
205 filename = self.path()
206 f = open(filename,'rb+')
207 f.seek(index*2016*80)
210 self.set_local_height()
212 def save_header(self, header):
213 data = self.header_to_string(header).decode('hex')
214 assert len(data) == 80
215 height = header.get('block_height')
216 filename = self.path()
217 f = open(filename,'rb+')
221 self.set_local_height()
224 def set_local_height(self):
226 if os.path.exists(name):
227 h = os.path.getsize(name)/80 - 1
228 if self.local_height != h:
229 self.local_height = h
232 def read_header(self, block_height):
234 if os.path.exists(name):
236 f.seek(block_height*80)
240 h = self.header_from_string(h)
244 def get_target(self, index, chain=None):
246 chain = [] # Do not use mutables as default values!
248 max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
249 if index == 0: return 0x1d00ffff, max_target
251 first = self.read_header((index-1)*2016)
252 last = self.read_header(index*2016-1)
255 if h.get('block_height') == index*2016-1:
258 nActualTimespan = last.get('timestamp') - first.get('timestamp')
259 nTargetTimespan = 14*24*60*60
260 nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
261 nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
263 bits = last.get('bits')
269 target = (a) * pow(2, 8 * (bits/MM - 3))
272 new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
275 c = ("%064X"%new_target)[2:]
281 c = int('0x'+c[0:6],16)
286 new_bits = c + MM * i
287 return new_bits, new_target
290 def request_header(self, i, h, queue):
291 print_error("requesting header %d from %s"%(h, i.server))
292 i.send([ ('blockchain.block.get_header',[h])], lambda i,r: queue.put((i,r)))
294 def retrieve_header(self, i, queue):
297 ir = queue.get(timeout=1)
299 print_error('timeout')
308 print_error('Verifier received an error:', r)
316 if method == 'blockchain.block.get_header':
321 def get_chain(self, interface, final_header):
323 header = final_header
324 chain = [ final_header ]
325 requested_header = False
326 queue = Queue.Queue()
328 while self.is_running():
331 header = self.retrieve_header(interface, queue)
332 if not header: return
333 chain = [ header ] + chain
334 requested_header = False
336 height = header.get('block_height')
337 previous_header = self.read_header(height -1)
338 if not previous_header:
339 self.request_header(interface, height - 1, queue)
340 requested_header = True
343 # verify that it connects to my chain
344 prev_hash = self.hash_header(previous_header)
345 if prev_hash != header.get('prev_block_hash'):
347 self.request_header(interface, height - 1, queue)
348 requested_header = True
352 # the chain is complete
356 def get_and_verify_chunks(self, i, header, height):
358 queue = Queue.Queue()
359 min_index = (self.local_height + 1)/2016
360 max_index = (height + 1)/2016
362 while n < max_index + 1:
363 print_error( "Requesting chunk:", n )
364 r = i.synchronous_get([ ('blockchain.block.get_chunk',[n])])[0]
368 self.verify_chunk(n, r)
371 print_error('Verify chunk failed!')