banlist.py

#!/usr/bin/env python3
#
# Copyright (c) 2017 John Newbery
# Distributed under the MIT software license, see the accompanying
# file COPYING or http://www.opensource.org/licenses/mit-license.php.
"""Deserialize banlist.dat file."""
from datastructures import Ban
from serialize import open_bs, SerializationError
from util import hash256

class Banlist():
    """Represents contents of banlist.dat file.

        magic: The network start bytes (4 bytes)
        network (not serialized in file, derived from magic): The network (mainnet, testnet or regtest)
        banmap: a dictionary of banned subnets. Key is a Subnet object, value is a BanEntry object."""
    def __init__(self):
        self.magic = b''
        self.network = ''
        self.banmap = {}

    def deserialize(self, f):
        self.magic, self.network = f.deserialize_magic()
        bl_len = f.deser_compact_size()

        for _ in range(bl_len):
            ban = Ban()
            ban.deserialize(f)

            self.banmap[ban.subnet] = ban.ban_entry

        # Verify the checksum
        position = f.tell()
        f.seek(0)
        if hash256(f.read(position)) != f.read(32):
            raise SerializationError("File checksum incorrect")

    def __repr__(self):
        ret = "Network magic: 0x{} ({})\n".format(self.magic.hex(), self.network)
        if self.banmap:
            ret += "ban entries:\n"
        for subnet, ban in self.banmap.items():
            ret += "   [{}]: {}".format(subnet.__repr__(), ban.__repr__())

        return ret

def dump_banlist(banlist_file):
    banlist = Banlist()

    with open_bs(banlist_file, "r") as f:
        banlist.deserialize(f)

    print(banlist)