Use a packet structure to wrap raw data

Signed-off-by: Yohann D'ANELLO <ynerant@crans.org>
This commit is contained in:
Yohann D'ANELLO 2020-12-21 16:03:56 +01:00
parent a882228458
commit acf1cffec1
Signed by: ynerant
GPG Key ID: 3A75C55819C8CF85
1 changed files with 70 additions and 1 deletions

View File

@ -48,10 +48,79 @@ class Squinnondation:
while True:
data, addr = squirrel.receive_raw_data()
print("received message: %s" % data)
pkt = Packet.unmarshal(data)
print("received message: %d %d %d %s" % (pkt.magic, pkt.version, pkt.body_length, pkt.body.raw_data))
print(str(pkt.marshal()))
# squirrel.send_raw_data(hazelnut, b"Hello squirrel!")
class TLV:
"""
The Tag-Length-Value contains the different type of data that can be sent.
TODO: add subclasses for each type of TLV
"""
type: int
raw_data: bytes
def validate_data(self) -> bool:
"""
Ensure that the TLV is well-formed.
Raises a ValueError if it is not the case.
TODO: Make some tests
"""
return True
class Packet:
"""
A Packet is a wrapper around the
"""
magic: int
version: int
body_length: int
body: TLV
def validate_data(self) -> bool:
"""
Ensure that the packet is well-formed.
Raises a ValueError if the packet contains bad data.
"""
if self.magic != 95:
raise ValueError("The magic code of the packet must be 95, found: {:d}".format(self.magic))
if self.version != 0:
raise ValueError("The version of the packet is not supported: {:d}".format(self.version))
if not (0 <= self.body_length <= 120):
raise ValueError("The body length of the packet is negative or too high. It must be between 0 and 1020,"
"found: {:d}".format(self.body_length))
return self.body.validate_data()
@staticmethod
def unmarshal(data: bytes) -> "Packet":
"""
Read raw data and build the packet wrapper.
Raises a ValueError whenever the data is invalid.
"""
pkt = Packet()
pkt.magic = data[0]
pkt.version = data[1]
pkt.body_length = int.from_bytes(data[2:4], byteorder="big")
pkt.body = TLV()
pkt.body.raw_data = data[4:4+pkt.body_length]
pkt.validate_data()
return pkt
def marshal(self) -> bytes:
"""
Compute the byte array data associated to the packet.
"""
data = bytes([self.magic, self.version])
data += self.body_length.to_bytes(2, "big")
data += self.body.raw_data
return data
class Hazelnut:
"""
A hazelnut is a connected client, with its socket.