@spalger/kibana/src/ui/public/utils/CidrMask.js

Kibana is an open source (Apache Licensed), browser based analytics and search dashboard for Elasticsearch. Kibana is a snap to setup and start using. Kibana strives to be easy to get started with, while also being flexible and powerful, just like Elastic

define(function (require) {
  var Ipv4Address = require('ui/utils/Ipv4Address');
  var NUM_BITS = 32;

  function throwError(mask) {
    throw Error('Invalid CIDR mask: ' + mask);
  }

  function CidrMask(mask) {
    var splits = mask.split('\/');
    if (splits.length !== 2) throwError(mask);
    this.initialAddress = new Ipv4Address(splits[0]);
    this.prefixLength = Number(splits[1]);
    if (this.prefixLength < 1 || this.prefixLength > NUM_BITS) throwError(mask);
  }

  CidrMask.prototype.getRange = function () {
    var variableBits = NUM_BITS - this.prefixLength;
    var fromAddress = this.initialAddress.valueOf() >> variableBits << variableBits >>> 0; // >>> 0 coerces to unsigned
    var numAddresses = Math.pow(2, variableBits);
    return {
      from: new Ipv4Address(fromAddress).toString(),
      to: new Ipv4Address(fromAddress + numAddresses - 1).toString()
    };
  };

  CidrMask.prototype.toString = function () {
    return this.initialAddress.toString() + '/' + this.prefixLength;
  };

  return CidrMask;
});