LBRYFoundation/LBRY-Vault
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Thomas Zarebczan 2018-11-16 17:18:07 -05:00
parent 90c8e4450e
commit b8aee9940d
1 changed files with 42 additions and 6 deletions
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48
electrum/blockchain.py
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@ -177,7 +177,7 @@ class Blockchain(util.PrintError):
p = self.path()
self._size = os.path.getsize(p)//HEADER_SIZE if os.path.exists(p) else 0
def verify_header(self, header: dict, prev_hash: str, target: int, expected_header_hash: str=None) -> None:
def verify_header(self, header: dict, prev_hash: str, target: int, bits: int, expected_header_hash: str=None) -> None:
_hash = hash_header(header)
if expected_header_hash and expected_header_hash != _hash:
raise Exception("hash mismatches with expected: {} vs {}".format(expected_header_hash, _hash))
@ -185,7 +185,6 @@ class Blockchain(util.PrintError):
raise Exception("prev hash mismatch: %s vs %s" % (prev_hash, header.get('prev_block_hash')))
if constants.net.TESTNET:
return
bits = self.target_to_bits(target)
if bits != header.get('bits'):
raise Exception("bits mismatch: %s vs %s" % (bits, header.get('bits')))
if int('0x' + _hash, 16) > target:
@ -195,7 +194,7 @@ class Blockchain(util.PrintError):
num = len(data) // HEADER_SIZE
start_height = index * 2016
prev_hash = self.get_hash(start_height - 1)
target = self.get_target(index-1)
bits, target = self.get_target2(index-1)
for i in range(num):
height = start_height + i
try:
@ -204,7 +203,7 @@ class Blockchain(util.PrintError):
expected_header_hash = None
raw_header = data[i*HEADER_SIZE : (i+1)*HEADER_SIZE]
header = deserialize_header(raw_header, index*2016 + i)
self.verify_header(header, prev_hash, target, expected_header_hash)
self.verify_header(header, prev_hash, target, bits, expected_header_hash)
prev_hash = hash_header(header)
def path(self):
@ -383,6 +382,43 @@ class Blockchain(util.PrintError):
bnNew = ArithUint256(self.MAX_TARGET)
return bnNew.GetCompact(), bnNew._value
def get_target2(self, index, chain='main'):
"""
this follows the calculations in lbrycrd/src/lbry.cpp
Returns: (bits, target)
"""
if index == 0:
return self.GENESIS_BITS, self.MAX_TARGET
first = self.read_header(index * 2016)
last = self.read_header(index * 2016 + 2015)
assert last is not None, "Last shouldn't be none"
# bits to target
bits = last.get('bits')
# print_error("Last bits: ", bits)
self.check_bits(bits)
# new target
nActualTimespan = last.get('timestamp') - first.get('timestamp')
nTargetTimespan = self.N_TARGET_TIMESPAN
nModulatedTimespan = nTargetTimespan - (nActualTimespan - nTargetTimespan) / 8
nMinTimespan = nTargetTimespan - (nTargetTimespan / 8)
nMaxTimespan = nTargetTimespan + (nTargetTimespan / 2)
if nModulatedTimespan < nMinTimespan:
nModulatedTimespan = nMinTimespan
elif nModulatedTimespan > nMaxTimespan:
nModulatedTimespan = nMaxTimespan
bnOld = ArithUint256.SetCompact(bits)
bnNew = bnOld * nModulatedTimespan
# this doesn't work if it is nTargetTimespan even though that
# is what it looks like it should be based on reading the code
# in lbry.cpp
bnNew /= nModulatedTimespan
if bnNew > self.MAX_TARGET:
bnNew = ArithUint256(self.MAX_TARGET)
return bnNew.GetCompact(), bnNew._value
def bits_to_target(self, bits: int) -> int:
bitsN = (bits >> 24) & 0xff
if not (bitsN >= 0x03 and bitsN <= 0x1f):
@ -422,12 +458,12 @@ class Blockchain(util.PrintError):
return False
self.print_error("4")
try:
target = self.get_target(height // 2016 - 1)
bits, target = self.get_target2(height // 2016 - 1)
except MissingHeader:
return False
self.print_error("5")
try:
self.verify_header(header, prev_hash, target)
self.verify_header(header, prev_hash, target, bits)
except BaseException as e:
self.print_error(e)
return False