ProtocolDataUnits.jl

Encoders and decoders for Protocol Data Units (PDUs)

PDUs encode information as byte streams that can be transmitted across a network or stored. ProtocolDataUnits.jl simplifies the process of encoding and decoding information as PDUs in a declarative way.

Illustrative Example

The usage of the package is best illustrated with a simple example:

using ProtocolDataUnits

# define PDU format
Base.@kwdef struct EthernetFrame <: AbstractPDU
  dstaddr::NTuple{6,UInt8}    # fixed length
  srcaddr::NTuple{6,UInt8}    # fixed length
  ethtype::UInt16             # fixed length
  payload::Vector{UInt8}      # variable length
  crc::UInt32 = 0             # fixed length
end

# declare that the variable length of the payload can be computed
Base.length(::Type{EthernetFrame}, ::Val{:payload}, info) = info.length - 18

# create an Ethernet frame
frame = EthernetFrame(
  dstaddr = (0x01, 0x02, 0x03, 0x04, 0x05, 0x06),
  srcaddr = (0x11, 0x12, 0x13, 0x14, 0x15, 0x16),
  ethtype = 0x0800,
  payload = [0x01, 0x02, 0x03, 0x04, 0x11, 0x12, 0x13, 0x14]
)

# convert to a byte array
bytes = PDU.encode(frame)

# convert back to Ethernet frame
decoded = PDU.decode(bytes, EthernetFrame)

# check that they are the same
@assert frame == decoded

The package can do much more, including nested PDUs, wire-encoding, CRC computation, etc. For more information, read the documentation.

Relationship with Other Packages

ProtoBuf.jl implements the Protocol Buffers specification for encoding/decoding data structures into byte streams. While the functionality sounds similar with ProtocolDataUnits.jl, both serve very different needs. Protocol Buffers provide a great way to encode information in a well-defined way but do not provide the flexibility to declare the format of the encoded information. On the other hand, ProtocolDataUnits.jl allows the developer to declare the byte stream format (typically based on networking specifications), and encode/decode the byte streams into structures.