cnroutes.js

// https://ftp.apnic.net/apnic/stats/apnic/delegated-apnic-latest

const http = require('http');
const https = require('https');
const url = require('url')
const fs = require('fs');
const readline = require('readline');

function parse(input) {
    const writeStream = fs.createWriteStream("output");

    const rl = readline.createInterface({
        input: input
    });

    let counter = 0;

    rl.on('error', error => {
        console.log("error: " + error);
    });

    rl.on('line', line => {
        if (line.startsWith('#')) return;

        let columns = line.split('|');
        if (columns.length != 7) {
            console.error("unexpected line: " + line);
        } else {
            if (columns[2] != 'ipv4' || columns[1] != 'CN') {
                return;
            }
            if (columns[6] != 'allocated' && columns[6] != 'assigned') {
                console.warn("unexpected line: " + line);
                return;
            }
            let ip = columns[3];
            let mask = columns[4];
            let cidrmask = 32;
            while ((mask & 1) == 0) {
                mask >>= 1;
                cidrmask--;
                if (mask === 0) {
                    console.warn("unexpected mask: " + columns[4]);
                }
            }
            writeStream.write(ip + "/" + cidrmask + "\n");
            counter++;
        }
    });

    rl.on('close', () => {
        console.log("totally " + counter + " line(s)");
        writeStream.close();
    });
}

function fromHttp(_url) {
    let parsed;
    try {
        parsed = url.parse(_url);
    } catch (err) {
        console.error("invalid url: " + err);
        return;
    }

    if (parsed.protocol == 'https:') {
        https.get(parsed.href, res => parse(res));
    } else if (parsed.protocol == 'http:') {
        http.get(parsed.href, res => parse(res));
    } else {
        console.error("unsupported protocol: " + parsed.protocol);
    }
}

function fromFile(filename) {
    parse(fs.createReadStream(filename));
}

// fromFile('delegated-apnic-latest.txt');

fromHttp('https://ftp.apnic.net/apnic/stats/apnic/delegated-apnic-latest');