def _read_root(self):
"""Create a root node from the first byte of a block"""
STARTS_CHAIN, MATCHES, NUM_CHILDREN = unpack_metadata(self.block[0])
if MATCHES:
pointer = pack_bytes(self.block[1:1+self.pointer_size])
next_pos = 1 + self.pointer_size
else:
pointer = None
next_pos = 1
new_node = Node((STARTS_CHAIN > 0), None, NUM_CHILDREN, pointer)
if new_node.starts_chain:
next_pos = self.read_chain(new_node, next_pos)
return new_node, next_pos
def _read_labeled_node(self, position):
"""Read a branch or chain head into a new :class:`Node` object"""
in_edge = self.block[position+1]
STARTS_CHAIN, MATCHES, NUM_CHILDREN = unpack_metadata(self.block[position])
if MATCHES:
pointer = pack_bytes(self.block[position+2:position+2+self.pointer_size])
next_pos = position + 2 + self.pointer_size
elif NUM_CHILDREN == 0:
raise Exception("Node doesn't match but has no children!")
else:
pointer = None
next_pos = position + 2
new_node = Node((STARTS_CHAIN > 0), in_edge, NUM_CHILDREN, pointer)
return new_node, next_pos
def test_pack_bytes():
assert util.pack_bytes([1, 1]) == 257
