def add_block(self, block_name, block_type, starting_address, size):
"""Add a new block identified by its name"""
with self._data_lock: # thread-safe
if size <= 0:
raise InvalidArgumentError("size must be a positive number")
if starting_address < 0:
raise InvalidArgumentError(
"starting address must be zero or positive number")
if block_name in self._blocks:
raise DuplicatedKeyError("Block %s already exists. " %
block_name)
if block_type not in self._memory:
raise InvalidModbusBlockError("Invalid block type %d" %
block_type)
# check that the new block doesn't overlap an existing block
# it means that only 1 block per type must correspond to a given address
# for example: it must not have 2 holding registers at address 100
index = 0
for i in xrange(len(self._memory[block_type])):
block = self._memory[block_type][i]
if block.is_in(starting_address, size):
raise OverlapModbusBlockError, "Overlap block at %d size %d" % (
block.starting_address, block.size)
if block.starting_address > starting_address:
index = i
break
# if the block is ok: register it
self._blocks[block_name] = (block_type, starting_address)
# add it in the 'per type' shortcut
self._memory[block_type].insert(
index, ModbusBlockDatabusMediator(block_name,
starting_address))
def build_request(self, pdu, slave):
"""Add the Modbus RTU part to the request"""
self._request_address = slave
if (self._request_address < 0) or (self._request_address > 255):
raise InvalidArgumentError("Invalid address {0}".format(self._request_address))
data = struct.pack(">B", self._request_address) + pdu
crc = struct.pack(">H", utils.calculate_crc(data))
return data + crc
def build_request(self, pdu, slave):
"""Add the Modbus TCP part to the request"""
if (slave < 0) or (slave > 255):
raise InvalidArgumentError("{0} Invalid value for slave id".format(slave))
self._request_mbap.length = len(pdu) + 1
self._request_mbap.transaction_id = self._get_transaction_id()
self._request_mbap.unit_id = slave
mbap = self._request_mbap.pack()
return mbap + pdu