gen_ofp_field_decoders

#!/bin/env python

import argparse

import build.extract_ofp_fields as extract_fields


def main():
    parser = argparse.ArgumentParser(
        description="Tool to generate python ofproto field decoders from"
        "meta-flow information"
    )
    parser.add_argument(
        "metaflow",
        metavar="FILE",
        type=str,
        help="Read meta-flow info from file",
    )

    args = parser.parse_args()

    fields = extract_fields.extract_ofp_fields(args.metaflow)

    field_decoders = {}
    aliases = {}
    for field in fields:
        decoder = get_decoder(field)
        field_decoders[field.get("name")] = decoder
        if field.get("extra_name"):
            field_decoders[field.get("extra_name")] = decoder

        for nxm in field.get("OXM", []):
            aliases[nxm[1]] = field.get("name")

    code = """
# This file is auto-generated. Do not edit!

from ovs.flow import decoders

field_decoders = {{
{decoders}
}}

field_aliases = {{
{aliases}
}}""".format(
        decoders="\n".join(
            [
                "    '{name}': {decoder},".format(name=name, decoder=decoder)
                for name, decoder in field_decoders.items()
            ]
        ),
        aliases="\n".join(
            [
                "    '{alias}': '{name}',".format(name=name, alias=alias)
                for alias, name in aliases.items()
            ]
        )
    )

    print(code)


def get_decoder(field):
    formatting = field.get("formatting")
    if formatting in ["decimal", "hexadecimal"]:
        if field.get("mask") == "MFM_NONE":
            return "decoders.decode_int"
        else:
            if field.get("n_bits") in [8, 16, 32, 64, 128, 992]:
                return "decoders.Mask{}".format(field.get("n_bits"))
            return "decoders.decode_mask({})".format(field.get("n_bits"))
    elif formatting in ["IPv4", "IPv6"]:
        return "decoders.IPMask"
    elif formatting == "Ethernet":
        return "decoders.EthMask"
    else:
        return "decoders.decode_default"


if __name__ == "__main__":
    main()