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blockchain.py
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blockchain.py
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#!/usr/bin/env python
#
# Electrum - lightweight Bitcoin client
# Copyright (C) 2012 thomasv@ecdsa.org
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
from decimal import Decimal
import threading, time, Queue, os, sys, shutil
from math import pow as dec_pow
from util import user_dir, appdata_dir, print_error, print_msg
from bitcoin import *
try:
from vtc_scrypt import getPoWHash
except ImportError:
print_msg("Warning: vtc_scrypt not available, using fallback")
from scrypt import scrypt_N_1_1_80 as getPoWHash
KGW_headers = [{} for x in xrange(4032)]
Kimoto_vals = [1 + (0.7084 * dec_pow((Decimal(x+1)/Decimal(144)), -1.228)) for x in xrange(4032)]
class Blockchain(threading.Thread):
def __init__(self, config, network):
threading.Thread.__init__(self)
self.daemon = True
self.config = config
self.network = network
self.lock = threading.Lock()
self.local_height = 0
self.running = False
#self.headers_url = 'http://electrum-vert.org/blockchain_headers'
self.set_local_height()
self.queue = Queue.Queue()
def height(self):
return self.local_height
def stop(self):
with self.lock: self.running = False
def is_running(self):
with self.lock: return self.running
def run(self):
self.init_headers_file()
self.set_local_height()
print_error( "blocks:", self.local_height )
with self.lock:
self.running = True
while self.is_running():
try:
result = self.queue.get()
except Queue.Empty:
continue
if not result: continue
i, header = result
if not header: continue
height = header.get('block_height')
if height <= self.local_height:
continue
if height > self.local_height + 50:
if not self.get_and_verify_chunks(i, header, height):
continue
if height > self.local_height:
# get missing parts from interface (until it connects to my chain)
chain = self.get_chain( i, header )
# skip that server if the result is not consistent
if not chain:
print_error('e')
continue
# verify the chain
if self.verify_chain( chain ):
print_error("height:", height, i.server)
for header in chain[:-1]:
self.save_header(header)
else:
print_error("error", i.server)
# todo: dismiss that server
continue
self.network.new_blockchain_height(height, i)
def verify_chain(self, chain):
first_header = chain[0]
prev_header = self.read_header(first_header.get('block_height') -1)
for header in chain[:-1]:
height = header.get('block_height')
prev_hash = self.hash_header(prev_header)
bits, target = self.get_target(height, chain)
_hash = self.pow_hash_header(header)
try:
assert prev_hash == header.get('prev_block_hash')
assert bits == header.get('bits')
assert int('0x'+_hash,16) < target
print_error('verified height: ', height)
except Exception, e:
print_error('exception: ', e)
return False
prev_header = header
return True
def verify_chunk(self, index, hexdata):
data = hexdata.decode('hex')
height = index*2016
num = len(data)/80
if index == 0:
previous_hash = ("0"*64)
else:
prev_header = self.read_header(index*2016-1)
if prev_header is None: raise
previous_hash = self.hash_header(prev_header)
if height < 26754:
bits, target = self.get_target(index)
for i in xrange(num):
height = index*2016 + i
raw_header = data[i*80:(i+1)*80]
header = self.header_from_string(raw_header)
_hash = self.pow_hash_header(header)
if height >= 26754:
bits, target = self.get_target(height, data=data)
assert previous_hash == header.get('prev_block_hash')
assert bits == header.get('bits')
assert int('0x'+_hash,16) < target
print_error( 'verified height ', str(height))
previous_header = header
previous_hash = self.hash_header(header)
self.save_chunk(index, data)
print_error("validated chunk %d"%height)
def header_to_string(self, res):
s = int_to_hex(res.get('version'),4) \
+ rev_hex(res.get('prev_block_hash')) \
+ rev_hex(res.get('merkle_root')) \
+ int_to_hex(int(res.get('timestamp')),4) \
+ int_to_hex(int(res.get('bits')),4) \
+ int_to_hex(int(res.get('nonce')),4)
return s
def header_from_string(self, s):
hex_to_int = lambda s: int('0x' + s[::-1].encode('hex'), 16)
h = {}
h['version'] = hex_to_int(s[0:4])
h['prev_block_hash'] = hash_encode(s[4:36])
h['merkle_root'] = hash_encode(s[36:68])
h['timestamp'] = hex_to_int(s[68:72])
h['bits'] = hex_to_int(s[72:76])
h['nonce'] = hex_to_int(s[76:80])
return h
def hash_header(self, header):
return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
def pow_hash_header(self, header):
return rev_hex(getPoWHash(self.header_to_string(header).decode('hex')).encode('hex'))
def path(self):
return os.path.join( self.config.path, 'blockchain_headers')
def init_headers_file(self):
filename = self.path()
if os.path.exists(filename):
return
try:
import urllib, socket
socket.setdefaulttimeout(30)
print_error("downloading ", self.headers_url )
urllib.urlretrieve(self.headers_url, filename)
print_error("done.")
except Exception:
print_error( "download failed. creating file", filename )
open(filename,'wb+').close()
def save_chunk(self, index, chunk):
filename = self.path()
f = open(filename,'rb+')
f.seek(index*2016*80)
h = f.write(chunk)
f.close()
self.set_local_height()
def save_header(self, header):
data = self.header_to_string(header).decode('hex')
assert len(data) == 80
height = header.get('block_height')
filename = self.path()
f = open(filename,'rb+')
f.seek(height*80)
h = f.write(data)
f.close()
self.set_local_height()
def set_local_height(self):
name = self.path()
if os.path.exists(name):
h = os.path.getsize(name)/80 - 1
if self.local_height != h:
self.local_height = h
def read_header(self, block_height):
name = self.path()
if os.path.exists(name):
f = open(name,'rb')
f.seek(block_height*80)
h = f.read(80)
f.close()
if len(h) == 80:
h = self.header_from_string(h)
return h
def convbignum(self, bits):
# convert to bignum
return (bits & 0xffffff) *(1<<( 8 * ((bits>>24) - 3)))
def convbits(self, target):
# convert it to bits
MM = 256*256*256
c = ("%064X"%target)[2:]
i = 31
while c[0:2]=="00":
c = c[2:]
i -= 1
c = int('0x'+c[0:6],16)
if c >= 0x800000:
c /= 256
i += 1
return c + MM * i
def get_target(self, index, chain=[],data=None):
max_target = 0x00000FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
if index == 0: return 0x1e0ffff0, 0x00000FFFF0000000000000000000000000000000000000000000000000000000
global Kimoto_vals
k_vals = Kimoto_vals
KGW = False
global KGW_headers
if index >= 26754:
KGW = True
minKGWblocks = 144
maxKGWblocks = 4032
if KGW and data or chain:
m= index % 2016
if chain:
m = 0
try:
if m > 0:
raw_l_header = data[(m-1)*80:(m)*80]
last = self.header_from_string(raw_l_header)
ts = last.get('timestamp')
t = self.convbignum(last.get('bits'))
KGW_headers[(index-1)%4032] = {'header':last,'t':t, 'ts':ts}
else:
last = self.read_header(index-1)
t = self.convbignum(last.get('bits'))
ts = last.get('timestamp')
KGW_headers[(index-1)%4032] = {'header':last,'t':t, 'ts':ts}
except Exception:
for h in chain:
if h.get('block_height') == index-1:
last = h
ts = last.get('timestamp')
t = self.convbignum(last.get('bits'))
KGW_headers[(index-1)%4032] = {'header':last,'t':t,'ts':ts}
for i in xrange(1,maxKGWblocks+1):
blockMass = i
KGW_i = index%4032 - i
if KGW_i < 0:
KGW_i = 4032 + KGW_i
if 'header' not in KGW_headers[KGW_i] and blockMass != 1:
if (m-i) >= 0:
raw_f_header = data[(m-i)*80:(m-i+1)*80]
first = self.header_from_string(raw_f_header)
else:
first = self.read_header(index-i)
t = self.convbignum(first.get('bits'))
ts = first.get('timestamp')
KGW_headers[KGW_i] = {'header':first,'t':t, 'ts':ts}
first = KGW_headers[KGW_i]
if blockMass == 1:
pastDiffAvg = first['t']
else:
pastDiffAvg = (first['t'] - pastDiffAvgPrev)/Decimal(blockMass) + pastDiffAvgPrev
pastDiffAvgPrev = pastDiffAvg
if blockMass >= minKGWblocks:
pastTimeActual = KGW_headers[(index-1)%4032]['ts'] - first['ts']
pastTimeTarget = 150*blockMass
if pastTimeActual < 0:
pastTimeActual = 0
pastRateAdjRatio = 1.0
if pastTimeActual != 0 and pastTimeTarget != 0:
pastRateAdjRatio = Decimal(pastTimeTarget)/Decimal(pastTimeActual)
eventHorizon = k_vals[(blockMass-1)]
eventHorizonFast = eventHorizon
eventHorizonSlow = 1/Decimal(eventHorizon)
if pastRateAdjRatio <= eventHorizonSlow or pastRateAdjRatio >= eventHorizonFast:
print_error('blockMass: ', blockMass, 'adjratio: ', pastRateAdjRatio, ' eventHorizon: ', eventHorizon)
first = first['header']
break
elif blockMass == maxKGWblocks:
print_error('blockMass: ', blockMass, 'adjratio: ', pastRateAdjRatio, ' eventHorizon: ', eventHorizon)
first = first['header']
else:
# Vertcoin: go back the full period unless it's the first retarget
if index == 1:
first = self.read_header(0)
else:
first = self.read_header((index-1)*2016-1)
last = self.read_header(index*2016-1)
if last is None:
for h in chain:
if h.get('block_height') == index*2016-1:
last = h
nActualTimespan = last.get('timestamp') - first.get('timestamp')
nTargetTimespan = 84*60*60
if index < 26754:
nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
target = self.convbignum(last.get('bits'))
else:
nActualTimespan = pastTimeActual
nTargetTimespan = pastTimeTarget
target = pastDiffAvg
# new target
new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
new_bits = self.convbits(new_target)
return new_bits, new_target
def request_header(self, i, h, queue):
print_error("requesting header %d from %s"%(h, i.server))
i.send([ ('blockchain.block.get_header',[h])], lambda i,r: queue.put((i,r)))
def retrieve_header(self, i, queue):
while True:
try:
ir = queue.get(timeout=1)
except Queue.Empty:
print_error('timeout')
continue
if not ir:
continue
i, r = ir
if r.get('error'):
print_error('Verifier received an error:', r)
continue
# 3. handle response
method = r['method']
params = r['params']
result = r['result']
if method == 'blockchain.block.get_header':
return result
def get_chain(self, interface, final_header):
header = final_header
chain = [ final_header ]
requested_header = False
queue = Queue.Queue()
height = header.get('block_height')
while self.is_running():
if requested_header:
header = self.retrieve_header(interface, queue)
if not header: return
chain = [ header ] + chain
requested_header = False
height = header.get('block_height')
previous_header = self.read_header(height -1)
if not previous_header:
self.request_header(interface, height - 1, queue)
requested_header = True
continue
# verify that it connects to my chain
prev_hash = self.hash_header(previous_header)
if prev_hash != header.get('prev_block_hash'):
print_error("reorg")
self.request_header(interface, height - 1, queue)
requested_header = True
continue
else:
# the chain is complete
return chain
def get_and_verify_chunks(self, i, header, height):
queue = Queue.Queue()
min_index = (self.local_height + 1)/2016
max_index = (height + 1)/2016
n = min_index
while n < max_index + 1:
print_error( "Requesting chunk:", n )
r = i.synchronous_get([ ('blockchain.block.get_chunk',[n])])[0]
if not r:
continue
try:
self.verify_chunk(n, r)
n = n + 1
except Exception, e:
print_error('Verify chunk failed!', e)
break
n = n - 1
if n < 0:
return False
return True