EzStruct

Expressive syntax for working with binary data formats and network protocols. Like the :py:mod:`struct` module, but with a more readable syntax, especially if your format has:

• Length-prefixed variable-length byte sequences or strings
• Count-prefixed variable-count repeated fields
• Terminated (null or otherwise) strings
• String encodings
• Numbers which represent enumeration members

Example:

tcp = ezstruct.Struct(
    "NET_ENDIAN",
    ezstruct.Field("UINT16", name="sport"),
    ezstruct.Field("UINT16", name="dport"),
    ezstruct.Field("UINT32", name="seqno"),
    ezstruct.Field("UINT32", name="ackno"),
    ezstruct.Field("UINT16",
                   name="flags",
                   value_transform=ezstruct.FieldTransform(
                       pack_flags_bitfield,
                       unpack_flags_bitfield)),
    ezstruct.Field("UINT16", name="window_size"),
    ezstruct.Field("UINT16", name="checksum"),
    ezstruct.Field("UINT16", name="urg"),
    ezstruct.Field("BYTES",
                   name="options",
                   default_pack_value={},
                   length=lambda data: data["offset"] - 5,
                   value_transform=ezstruct.FieldTransform(
                       pack_and_pad_options,
                       unpack_options)))

header_data = {"sport": 123,
               "dport": 456,
               "seqno": 1,
               "ackno": 0,
               "flags": {"offset": 5,
                         "syn": 1},
               "window_size": 100,
               "checksum": 0,
               "urg": 0}
header_bytes = tcp.pack_bytes(header_data)
assert tcp.unpack_bytes(header_bytes) == header_data