AaronFiore/electrum
1
0
Fork 0
Code Activity

blockchain: chain hierarchy based on most work, not length

Browse Source
This commit is contained in:
SomberNight
2018-11-22 17:13:43 +01:00
parent 141ff99580
commit 65ce3deeaa
1 changed files with 41 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

43
electrum/blockchain.py
View File

@@ -141,6 +141,11 @@ def read_blockchains(config: 'SimpleConfig'):
def get_best_chain() -> 'Blockchain':
return blockchains[constants.net.GENESIS]
# block hash -> chain work; up to and including that block
_CHAINWORK_CACHE = {
"0000000000000000000000000000000000000000000000000000000000000000": 0, # virtual block at height -1
} # type: Dict[str, int]
class Blockchain(util.PrintError):
"""
@@ -319,10 +324,10 @@ class Blockchain(util.PrintError):
they will be stored in different files."""
if self.parent is None:
return False
parent_branch_size = self.parent.height() - self.forkpoint + 1
if parent_branch_size >= self.size(): # FIXME most work, not length
if self.parent.get_chainwork() >= self.get_chainwork():
return False
self.print_error("swap", self.forkpoint, self.parent.forkpoint)
parent_branch_size = self.parent.height() - self.forkpoint + 1
forkpoint = self.forkpoint # type: Optional[int]
parent = self.parent # type: Optional[Blockchain]
child_old_id = self.get_id()
@@ -481,6 +486,40 @@ class Blockchain(util.PrintError):
bitsBase >>= 8
return bitsN << 24 | bitsBase
def chainwork_of_header_at_height(self, height: int) -> int:
"""work done by single header at given height"""
chunk_idx = height // 2016 - 1
target = self.get_target(chunk_idx)
work = ((2 ** 256 - target - 1) // (target + 1)) + 1
return work
@with_lock
def get_chainwork(self, height=None) -> int:
if height is None:
height = max(0, self.height())
if constants.net.TESTNET:
# On testnet/regtest, difficulty works somewhat different.
# It's out of scope to properly implement that.
return height
last_retarget = height // 2016 * 2016 - 1
cached_height = last_retarget
while _CHAINWORK_CACHE.get(self.get_hash(cached_height)) is None:
if cached_height <= -1:
break
cached_height -= 2016
assert cached_height >= -1, cached_height
running_total = _CHAINWORK_CACHE[self.get_hash(cached_height)]
while cached_height < last_retarget:
cached_height += 2016
work_in_single_header = self.chainwork_of_header_at_height(cached_height)
work_in_chunk = 2016 * work_in_single_header
running_total += work_in_chunk
_CHAINWORK_CACHE[self.get_hash(cached_height)] = running_total
cached_height += 2016
work_in_single_header = self.chainwork_of_header_at_height(cached_height)
work_in_last_partial_chunk = (height % 2016 + 1) * work_in_single_header
return running_total + work_in_last_partial_chunk
def can_connect(self, header: dict, check_height: bool=True) -> bool:
if header is None:
return False