def get_broadcast_message_preview(
self, input_buffer: InputBuffer) -> BroadcastMessagePreview:
"""
Peeks the hash and network number from hashed messages.
Currently, only Broadcast messages are supported here.
:param input_buffer
:return: is full header, message hash, network number, source id, payload length
"""
# -1 for control flag length
broadcast_header_length = self.base_message_type.HEADER_LENGTH + AbstractBroadcastMessage.PAYLOAD_LENGTH - \
constants.CONTROL_FLAGS_LEN
is_full_header = input_buffer.length >= broadcast_header_length
if not is_full_header:
return BroadcastMessagePreview(False, None, None, None, None, None,
None)
else:
_is_full_message, _command, payload_length = self.get_message_header_preview_from_input_buffer(
input_buffer)
broadcast_header = input_buffer.peek_message(
broadcast_header_length)
offset = self.base_message_type.HEADER_LENGTH
block_hash = broadcast_header[offset:offset +
crypto.SHA256_HASH_LEN]
block_hash_with_network_num = broadcast_header[
offset:offset + crypto.SHA256_HASH_LEN +
constants.NETWORK_NUM_LEN]
offset += crypto.SHA256_HASH_LEN
network_num, = struct.unpack_from(
"<L",
broadcast_header[offset:offset + constants.NETWORK_NUM_LEN])
offset += constants.NETWORK_NUM_LEN
source_id = uuid_pack.from_bytes(
struct.unpack_from(
"<16s",
broadcast_header[offset:offset +
constants.NODE_ID_SIZE_IN_BYTES])[0])
offset += constants.NODE_ID_SIZE_IN_BYTES
broadcast_type_bytearray = broadcast_header[offset:offset +
constants.
BROADCAST_TYPE_LEN]
broadcast_type_in_str = struct.unpack_from(
"<4s", broadcast_type_bytearray)[0].decode(
constants.DEFAULT_TEXT_ENCODING)
broadcast_type = BroadcastMessageType(broadcast_type_in_str)
message_id = ConcatHash(
bytearray(block_hash_with_network_num) +
broadcast_type_bytearray, 0)
return BroadcastMessagePreview(is_full_header,
Sha256Hash(block_hash),
broadcast_type, message_id,
network_num, source_id,
payload_length)
def broadcast_type(self) -> BroadcastMessageType:
if self._broadcast_type is None:
off = self.HEADER_LENGTH + AbstractBroadcastMessage.PAYLOAD_LENGTH - constants.CONTROL_FLAGS_LEN
broadcast_type_in_str = struct.unpack_from(
"<4s", self.buf,
off)[0].decode(constants.DEFAULT_TEXT_ENCODING)
self._broadcast_type = BroadcastMessageType(broadcast_type_in_str)
broadcast_type = self._broadcast_type
assert broadcast_type is not None
return broadcast_type