code.delx.au - monosys/blob - bin/hexhost

   1 #!/usr/bin/env node
   2
   3 'use strict';
   4
   5 const BLOCKSIZE = 3;
   6 const CHARS1 = [
   7     ' ',
   8     ...'0123456789'.split(''),
   9     ...'abcdefghijklmnopqrstuvwxyz'.split(''),
  10     '_',
  11     '-',
  12 ];
  13 const SHIFT = BigInt(Math.ceil(Math.log2(CHARS1.length ** BLOCKSIZE)));
  14 const MASK = 2n**SHIFT - 1n;
  15
  16 const CHARSN = [...Array(BLOCKSIZE - 1)].reduce((acc) => acc.map((v1) => CHARS1.map((v2) => ''+v1+v2)).flat(), CHARS1);
  17 const FMAP = new Map(CHARSN.map((v, i) => [''+v, BigInt(i)]));
  18 const RMAP = new Map(CHARSN.map((v, i) => [BigInt(i), ''+v]));
  19
  20 function main(arg1, arg2) {
  21     if (!arg1) {
  22         console.error('Usage: hexhost fdxx::4a59954e');
  23         console.error('Usage: hexhost fdxx:: hostname');
  24         process.exit(1);
  25     }
  26
  27     if (arg2) {
  28         const prefix = arg1;
  29         const suffix = encode(arg2).replaceAll(/(.{4})/g, '$1:').replace(/:$/, '');
  30         console.log(prefix + suffix);
  31     } else {
  32         const [, suffix] = arg1.split(/::|:0:/);
  33         console.log(decode(suffix));
  34     }
  35 }
  36
  37 function decode(input) {
  38     input = input && input.replaceAll(':', '');
  39     if (!input) {
  40         throw new Error('No suffix found');
  41     }
  42     input = BigInt('0x' + input);
  43     let output = [];
  44     while (input > 0) {
  45         const encodedBlock = input & MASK;
  46         input >>= SHIFT;
  47         const block = RMAP.get(encodedBlock);
  48         if (block !== undefined) {
  49             output.push(block);
  50         }
  51     }
  52     return output.reverse().join('').trim();
  53 }
  54
  55 function encode(input) {
  56     if (input.length / BLOCKSIZE > (64n / SHIFT)) {
  57         throw new Error('Input is too long to fit in a /64!');
  58     }
  59
  60     input = input.toLowerCase();
  61
  62     let out = BigInt(0);
  63     for (let i = 0; i < input.length; i += BLOCKSIZE) {
  64         const block = input.substring(i, i + BLOCKSIZE).padEnd(BLOCKSIZE);
  65         const encodedBlock = FMAP.get(block);
  66         if (encodedBlock !== undefined) {
  67             out = (out << SHIFT) + encodedBlock;
  68         }
  69     }
  70     return out.toString(16);
  71 }
  72
  73 main(process.argv[2], process.argv[3]);