def _get_canonical_head(cls, db: BaseDB) -> BaseBeaconBlock:
try:
canonical_head_root = db[
SchemaV1.make_canonical_head_root_lookup_key()]
except KeyError:
raise CanonicalHeadNotFound("No canonical head set for this chain")
return cls._get_block_by_root(db, Hash32(canonical_head_root))
def _set_as_canonical_chain_head(
cls, db: BaseDB, block_root: Hash32
) -> Tuple[Tuple[BaseBeaconBlock, ...], Tuple[BaseBeaconBlock, ...]]:
"""
Set the canonical chain HEAD to the block as specified by the
given block root.
:return: a tuple of the blocks that are newly in the canonical chain, and the blocks that
are no longer in the canonical chain
"""
try:
block = cls._get_block_by_root(db, block_root)
except BlockNotFound:
raise ValueError(
"Cannot use unknown block root as canonical head: {}".format(
block_root))
new_canonical_blocks = tuple(
reversed(cls._find_new_ancestors(db, block)))
old_canonical_blocks = []
for block in new_canonical_blocks:
try:
old_canonical_root = cls._get_canonical_block_root(
db, block.slot)
except BlockNotFound:
# no old_canonical block, and no more possible
break
else:
old_canonical_block = cls._get_block_by_root(
db, old_canonical_root)
old_canonical_blocks.append(old_canonical_block)
for block in new_canonical_blocks:
cls._add_block_slot_to_root_lookup(db, block)
db.set(SchemaV1.make_canonical_head_root_lookup_key(), block.root)
return new_canonical_blocks, tuple(old_canonical_blocks)
