command.py 文件源码

def func(self, args):
        """Evaluate an expression of adding and subtracting networks."""

        expr = args.expression
        accum = [_network_address(expr.pop(0))]

        while len(expr) >= 2:
            operator = expr.pop(0)
            # right-hand side of the expression
            rhs = _network_address(expr.pop(0))

            if operator in ("+", "add", "merge"):
                # add (merge) in a new network
                accum = netaddr.cidr_merge(accum + [rhs])
            elif operator in ("-", "sub", "remove"):
                # subtract (remove) a network

                # for each network in accum, remove the RHS from it, then
                # chain everything into a single flat generator sequence
                # (RHS may be partially contained in more than one accum
                # network)
                minus_rhs = itertools.chain.from_iterable(
                                netaddr.cidr_exclude(network, rhs)
                                for network in accum
                            )
                accum = netaddr.cidr_merge(minus_rhs)
            else:
                raise CommandParseError("invalid operator '%s'" % operator)

        if expr:
            self.warn("ignoring extra argument '%s'" % ' '.join(expr))

        for i in accum:
            print(i)