| Copyright: | 2013 by Matthew Sachs |
|---|---|
| license: | Apache License v2.0 |
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