dns-suite.js/dns.packer.js

(function (exports) {
'use strict';

var dnspack = exports.DNS_PACKER = {
  pack: function (packet) {
    var total = 0;
    var id = packet.header.id;                      // 2 bytes
    var header = dnspack.packHeader(packet.header); // 2 bytes
    total = 12;                                     // 2+2+2+2 bytes ({qd,an,ns,ar}count)

    var ab = new ArrayBuffer(total);
    var dv = new DataView(ab);
    dv.setUint16(0, id, false);
    dv.setUint16(2, header, false);
    dv.setUint16(4, packet.question.length, false);
    dv.setUint16(6, packet.answer.length, false);
    dv.setUint16(8, packet.authority.length, false);
    // EDNS is added as an additional with TYPE 41 (OPT, 0x29)
    dv.setUint16(10, packet.additional.length + (packet.payload ? 1 : 0), false);

    return ab;
  }
, packHeader: function(h) {
    var val = 0;

    val += (h.qr     << 15) & 0x8000;
    val += (h.opcode << 11) & 0x7800;
    val += (h.aa     << 10) &  0x400;
    val += (h.tc     <<  9) &  0x200;
    val += (h.rd     <<  8) &  0x100;
    val += (h.ra     <<  7) &   0x80;
    val += (h.res1   <<  6) &   0x40;
    val += (h.res2   <<  5) &   0x20;
    val += (h.res3   <<  4) &   0x10;
    val += h.rcode          &    0xF;

    return val;
  }
};

}('undefined' !== typeof window ? window : exports));