IP CIDR Complement

ip_complement.py

#!/usr/bin/env python3
"""
ip_complement.py – 计算一组 IPv4 / IPv6 CIDR 的互补网段

用法示例：
    # 直接在命令行给出网段
    python ip_complement.py 10.0.0.0/8 192.168.0.0/16 2001:db8::/32

    # 从文件或管道读取，再输出 JSON
    cat cidr.txt | python ip_complement.py -j
"""

import argparse
import ipaddress
import json
import sys
from typing import Iterable, List


# ---------- 核心算法 ---------- #
def _complement_one_family(nets: List[ipaddress._BaseNetwork]) -> List[ipaddress._BaseNetwork]:
    """求同一地址族(net.version相同)的互补集。"""
    if not nets:
        return []

    version = nets[0].version
    if any(net.version != version for net in nets):
        raise ValueError("所有网段必须属于同一地址族（IPv4 或 IPv6）")

    # 对全集的定义
    full = ipaddress.IPv4Network("0.0.0.0/0") if version == 4 else ipaddress.IPv6Network("::/0")

    # 先合并、排序，确保无重叠且有序
    merged = sorted(ipaddress.collapse_addresses(nets), key=lambda n: int(n.network_address))

    complement: List[ipaddress._BaseNetwork] = []
    cursor = full.network_address

    for net in merged:
        if cursor < net.network_address:
            gap_end = net.network_address - 1
            complement.extend(ipaddress.summarize_address_range(cursor, gap_end))
        next_int = int(net.broadcast_address) + 1
        if next_int > int(full.broadcast_address):
            cursor = None  # 已经到头
            break
        cursor = ipaddress.ip_address(next_int)

    if cursor is not None and int(cursor) <= int(full.broadcast_address):
        complement.extend(
            ipaddress.summarize_address_range(cursor, full.broadcast_address)
        )

    return complement


def complement_cidrs(cidrs: Iterable[str]) -> List[str]:
    """
    传入一串 CIDR 字符串，返回 *字符串* 形式的补集列表。
    为方便起见，这里不区分输入次序，可同时混合 IPv4 / IPv6。
    """
    ipv4_nets, ipv6_nets = [], []

    for s in cidrs:
        net = ipaddress.ip_network(s, strict=False)
        (ipv4_nets if net.version == 4 else ipv6_nets).append(net)

    result = (
        _complement_one_family(ipv4_nets)
        + _complement_one_family(ipv6_nets)
    )
    # 再按地址排序输出（IPv4 在前，随后 IPv6）
    result.sort(key=lambda n: (n.version, int(n.network_address)))
    return [str(n) for n in result]


# ---------- CLI 包装 ---------- #
def main() -> None:
    p = argparse.ArgumentParser(description="IPv4 / IPv6 互补网段计算器")
    p.add_argument("cidrs", nargs="*", help="要排除的 CIDR（留空或指定 - 以从 stdin 读取）")
    p.add_argument(
        "-j", "--json", action="store_true", help="以 JSON 数组形式输出（默认按行输出）"
    )
    args = p.parse_args()

    cidr_inputs: List[str]
    if args.cidrs and args.cidrs != ["-"]:
        cidr_inputs = args.cidrs
    else:
        cidr_inputs = [line.strip() for line in sys.stdin if line.strip()]

    if not cidr_inputs:
        p.error("至少提供一个 CIDR")

    complements = complement_cidrs(cidr_inputs)

    if args.json:
        print(json.dumps(complements, indent=2, ensure_ascii=False))
    else:
        for n in complements:
            print(n)


if __name__ == "__main__":
    main()