idk

cidragg.go

// go get "inet.af/netaddr"
// echo '[ "208.80.44.0/22", "208.80.44.0/23", "208.80.44.0/24", "208.80.45.0/24", "208.80.46.0/23", "208.80.46.0/24", "208.80.47.0/24" ]' | go run main.go -json - 
package main

import (
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"net"
	"os"
	"strings"

	"inet.af/netaddr"
)

var (
	invalidIPSet = errors.New("invalid IP set")
)

func Aggregate(ranges []string) ([]netaddr.IPPrefix, error) {
	ipsb := new(netaddr.IPSetBuilder)
	for _, r := range ranges {
		_, network, err := net.ParseCIDR(r)
		if err != nil {
			return nil, err
		}
		prefix, ok := netaddr.FromStdIPNet(network)
		if !ok {
			return nil, fmt.Errorf("%v: %w", r, invalidIPSet)
		}
		ipsb.AddPrefix(prefix)
	}
	return ipsb.IPSet().Prefixes(), nil
}

func Fatalln(v ...interface{}) {
	fmt.Fprintln(os.Stderr, v...)
	os.Exit(1)
}

func main() {
	var useJSON bool
	flag.BoolVar(&useJSON, "json", false, "parse input as json")
	flag.Parse()

	var in io.ReadCloser
	filename := flag.Arg(0)
	switch filename {
	case "-", "":
		in = os.Stdin
	default:
		var err error
		in, err = os.Open(filename)
		if err != nil {
			Fatalln(err)
		}
		defer in.Close()
	}

	data, err := ioutil.ReadAll(in)
	if err != nil {
		Fatalln(err)
	}

	var ranges []string
	if useJSON {
		err = json.Unmarshal(data, &ranges)
		if err != nil {
			Fatalln(err)
		}
	} else {
		ranges = strings.Fields(string(data))
	}

	aggregated, err := Aggregate(ranges)
	if err != nil {
		Fatalln(err)
	}

	if useJSON {
		out := json.NewEncoder(os.Stdout)
		out.Encode(aggregated)
	} else {
		for _, agg := range aggregated {
			fmt.Println(agg)
		}
	}
}