• Specification documentation

L3aP for Python

Legible encoding for addressable packets for python

Installation

pip install leap-protocol

Basic Usage

Encoding a packet:

import leap-protocol as leap

codec = leap.Codec("leap-config.json")
packet = leap.Packet("set", "led/red", True)
encoded = codec.encode(packet)

...

Decoding a packet

import leap-protocol as leap

codec = leap.Codec("leap-config.json")

...

# Note, if there is a remainder it will be stored back in bytes
received, packet = codec.Decode(received)
data = codec.unpack(packet)

for branch, value in data.items():
  ... do stuff ...

...

Usage

Codec Class

codec = Codec(config_file_path)

• config_file_path a string to point to the L3aP config file.
• codec L3aP codec object

Instantiates a L3aP codec object for encoding packets to strings and decoding strings to packets.

Example:

codec = leap.Codec("leap-config.json")

bytes = encode(packets)

• packets either a leap.Packet object or a list of leap.packet objects.
• bytes utf-8 byte string

Encodes one or more packets into a utf-8 byte string.

Example:

packet_red = leap.Packet("set", "led/red", True)
packet_blue = leap.Packet("set", "led/blue", True)

encoded = codec.encode([packet_red, packet_blue])

(remainder, packets) = decode(bytes)

• bytes utf-8 encoded byte-string
• remainder unused bytes (if available)
• packets an array of one or more decoded packets, empty if none

Decodes a utf-8 byte string into one or more packets

Example:

received_bytes += rx.read()
received_bytes, packets = codec.decode(received_bytes)

for packet in packets:
  ...

data = unpack(packet)

• packet a leap.Packet
• data a dictionary with address paths as keys (eg. led/red) mapping to thier respective values.

Extracts a dictionary from a packet to map address paths to thier respective values.

Example:

if packet.category == "set":
  commands = codec.unpack(packet)
  if 'led/red' in commands:
    led_red.set(commands['led/red']
    ...

Packet Class

packet = Packet(category, path, payload)

• category the type of packet
• path (optional) a root path of payload data
• payload (optional) the data to accompany the root path
• packet a L3aP packet object

Constructs a L3aP packet for encoding. Note, payload can be an array and set multiple fields at once when the path is a parent.

Example:

accelerometer_packet = leap.Packet("pub", "imu/accel", [accel_x, accel_y, accel_z])
disable_packet = leap.Packet("set", "control/balance/disable")
...

add(path, payload)

• path a root path of payload data
• payload (optional) the data to accompany the root path

Adds path to the packet and optionally a payload. This can be used to create compound packets which allows sets of data to be processed at the same time.

Example:

sensor_packet = leap.Packet("pub", "imu/accel", [accel_x, accel_y, accel_z])
sensor_packet.add("barometer/pressure", baro_pressure)
...

category

The packet's category string.

Example:

if packet.category == "pub":
  update_model(codec.unpack(packet))
...

Verification

result = verify(config_file)

• config_file a valid L3aP config file
• result false if config_file is invalid, true otherwise

Checks the contents of a config_file for errors. Prints details of the first failure to stdout. Useful for regression testing.

Example:

...
def test_valid_config(self):
  assert(leap.verify("leap-config.json"))
...

Command Line

Generate a default json config file:

python3 -m leap --json filename.toml

Generate a default toml config file:

python3 -m leap --toml filename.toml

Verify the contents of your toml/json config file:

python3 -m leap --validate filename.json

Help:

python3 -m leap --help