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Refactor Cell.hash function to avoid aggressive recursion #12

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Refactor Cell.hash function to avoid aggressive recursion #12

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36 changes: 34 additions & 2 deletions tvm_valuetypes/cell.py
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Original file line number Diff line number Diff line change
Expand Up @@ -172,9 +172,35 @@ def repr(self):
return ret

def hash(self):
return self._recursive_hash()[2]

def _recursive_hash(self):
# retutrns tuple (level, depth, hash) of current cell
if self.is_special():
raise NotImplementedError('Calculating level not implemented for special cells')
hasher = sha256()
hasher.update(self.repr())
return hasher.digest()
if len(self.refs) == 0:
self_data = b'\x00' + self.bits_descriptor() + self.data.top_upped_bytes()
hasher.update(self_data)
# level and depth is zero
return (0, 0, hasher.digest())
else:
children = [ref._recursive_hash() for ref in self.refs]
max_level = 0
max_depth = 0
depth_block = b''
hashes_block = b''
for depth, level, ref_hash in children:
if level > max_level:
max_level = level
if depth > max_depth:
max_depth = depth
depth_block += (depth // 256).to_bytes(1, "big") + (depth % 256).to_bytes(1, "big")
hashes_block += ref_hash

self_data = (len(self.refs) + max_level * 32).to_bytes(1, "big") + self.bits_descriptor() + self.data.top_upped_bytes()
hasher.update(self_data + depth_block + hashes_block)
return (max_depth + 1, max_level, hasher.digest())

def serialize_for_boc(self, cells_index, ref_size):
# This is not serialization of the cell as boc with this cell as root_cell
Expand Down Expand Up @@ -336,6 +362,12 @@ def test_boc_serialization():
"B5EE9C72410102010007000102000100024995C5FE15")
assert res == reference_serialization_2, "Wrong '<b 0 8 u, <b 73 8 u, b> ref, b>' cell boc-serialization"

def test_cell_hash():
cell_data = 'te6ccsEBFwEAYAAEBQQFBQQFBAQEBAQEBAQEBAQFBAQEAwECyQEBBMsXAgECEgMBBMsXBAEEywcF\nAQIUBgEEywcHAQIBCAECJQkBAsgKAQKhCwECAQwBAiENAQIiDgECqA8BAgEQAQIhEQECARIBBIAD\nEwECqBQBAgEVAQIhFgACIX1S8I0='
cell_boc = codecs.decode(codecs.encode(cell_data, 'utf8'), 'base64')
cell = deserialize_boc(cell_boc)
assert 'MIrkspKfhLvHwcH+yryp0gZZR3vjKOYQ5VTAbqF8zB4=\n' == codecs.decode(codecs.encode(cell.hash(), 'base64'), 'utf-8')


def parse_flags(serialization):
header_byte, serialization = serialization[0], serialization[1:]
Expand Down