dns: minor refactor of dns module

Move to the more efficient module.exports = {} pattern. PR-URL: #11597 Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Claudio Rodriguez <cjrodr@yahoo.com> Reviewed-By: Michaël Zasso <targos@protonmail.com>

Author: jasnell

lib/dns.js

@@ -99,7 +99,7 @@ function onlookupall(err, addresses) {
 
 // Easy DNS A/AAAA look up
 // lookup(hostname, [options,] callback)
-exports.lookup = function lookup(hostname, options, callback) {
+function lookup(hostname, options, callback) {
  var hints = 0;
  var family = -1;
  var all = false;
@@ -119,9 +119,9 @@ exports.lookup = function lookup(hostname, options, callback) {
  all = options.all === true;
 
  if (hints !== 0 &&
- hints !== exports.ADDRCONFIG &&
- hints !== exports.V4MAPPED &&
- hints !== (exports.ADDRCONFIG | exports.V4MAPPED)) {
+ hints !== cares.AI_ADDRCONFIG &&
+ hints !== cares.AI_V4MAPPED &&
+ hints !== (cares.AI_ADDRCONFIG | cares.AI_V4MAPPED)) {
  throw new TypeError('Invalid argument: hints must use valid flags');
  }
  } else {
@@ -166,7 +166,7 @@ exports.lookup = function lookup(hostname, options, callback) {
 
  callback.immediately = true;
  return req;
-};
+}
 
 
 function onlookupservice(err, host, service) {
@@ -178,7 +178,7 @@ function onlookupservice(err, host, service) {
 
 
 // lookupService(address, port, callback)
-exports.lookupService = function lookupService(host, port, callback) {
+function lookupService(host, port, callback) {
  if (arguments.length !== 3)
  throw new Error('Invalid arguments');
 
@@ -205,7 +205,7 @@ exports.lookupService = function lookupService(host, port, callback) {
 
  callback.immediately = true;
  return req;
-};
+}
 
 
 function onresolve(err, result, ttls) {
@@ -251,26 +251,25 @@ function resolver(bindingName) {
 
 
 var resolveMap = Object.create(null);
-exports.resolve4 = resolveMap.A = resolver('queryA');
-exports.resolve6 = resolveMap.AAAA = resolver('queryAaaa');
-exports.resolveCname = resolveMap.CNAME = resolver('queryCname');
-exports.resolveMx = resolveMap.MX = resolver('queryMx');
-exports.resolveNs = resolveMap.NS = resolver('queryNs');
-exports.resolveTxt = resolveMap.TXT = resolver('queryTxt');
-exports.resolveSrv = resolveMap.SRV = resolver('querySrv');
-exports.resolvePtr = resolveMap.PTR = resolver('queryPtr');
-exports.resolveNaptr = resolveMap.NAPTR = resolver('queryNaptr');
-exports.resolveSoa = resolveMap.SOA = resolver('querySoa');
-exports.reverse = resolver('getHostByAddr');
-
-
-exports.resolve = function resolve(hostname, type_, callback_) {
+resolveMap.A = resolver('queryA');
+resolveMap.AAAA = resolver('queryAaaa');
+resolveMap.CNAME = resolver('queryCname');
+resolveMap.MX = resolver('queryMx');
+resolveMap.NS = resolver('queryNs');
+resolveMap.TXT = resolver('queryTxt');
+resolveMap.SRV = resolver('querySrv');
+resolveMap.PTR = resolver('queryPtr');
+resolveMap.NAPTR = resolver('queryNaptr');
+resolveMap.SOA = resolver('querySoa');
+
+
+function resolve(hostname, type_, callback_) {
  var resolver, callback;
  if (typeof type_ === 'string') {
  resolver = resolveMap[type_];
  callback = callback_;
  } else if (typeof type_ === 'function') {
- resolver = exports.resolve4;
+ resolver = resolveMap.A;
  callback = type_;
  } else {
  throw new Error('"type" argument must be a string');
@@ -281,15 +280,15 @@ exports.resolve = function resolve(hostname, type_, callback_) {
  } else {
  throw new Error(`Unknown type "${type_}"`);
  }
-};
+}
 
 
-exports.getServers = function getServers() {
+function getServers() {
  return cares.getServers();
-};
+}
 
 
-exports.setServers = function setServers(servers) {
+function setServers(servers) {
  // cache the original servers because in the event of an error setting the
  // servers cares won't have any servers available for resolution
  const orig = cares.getServers();
@@ -326,34 +325,53 @@ exports.setServers = function setServers(servers) {
  var err = cares.strerror(errorNumber);
  throw new Error(`c-ares failed to set servers: "${err}" [${servers}]`);
  }
-};
+}
 
-// uv_getaddrinfo flags
-exports.ADDRCONFIG = cares.AI_ADDRCONFIG;
-exports.V4MAPPED = cares.AI_V4MAPPED;
-
-// ERROR CODES
-exports.NODATA = 'ENODATA';
-exports.FORMERR = 'EFORMERR';
-exports.SERVFAIL = 'ESERVFAIL';
-exports.NOTFOUND = 'ENOTFOUND';
-exports.NOTIMP = 'ENOTIMP';
-exports.REFUSED = 'EREFUSED';
-exports.BADQUERY = 'EBADQUERY';
-exports.BADNAME = 'EBADNAME';
-exports.BADFAMILY = 'EBADFAMILY';
-exports.BADRESP = 'EBADRESP';
-exports.CONNREFUSED = 'ECONNREFUSED';
-exports.TIMEOUT = 'ETIMEOUT';
-exports.EOF = 'EOF';
-exports.FILE = 'EFILE';
-exports.NOMEM = 'ENOMEM';
-exports.DESTRUCTION = 'EDESTRUCTION';
-exports.BADSTR = 'EBADSTR';
-exports.BADFLAGS = 'EBADFLAGS';
-exports.NONAME = 'ENONAME';
-exports.BADHINTS = 'EBADHINTS';
-exports.NOTINITIALIZED = 'ENOTINITIALIZED';
-exports.LOADIPHLPAPI = 'ELOADIPHLPAPI';
-exports.ADDRGETNETWORKPARAMS = 'EADDRGETNETWORKPARAMS';
-exports.CANCELLED = 'ECANCELLED';
+module.exports = {
+ lookup,
+ lookupService,
+ getServers,
+ setServers,
+ resolve,
+ resolve4: resolveMap.A,
+ resolve6: resolveMap.AAAA,
+ resolveCname: resolveMap.CNAME,
+ resolveMx: resolveMap.MX,
+ resolveNs: resolveMap.NS,
+ resolveTxt: resolveMap.TXT,
+ resolveSrv: resolveMap.SRV,
+ resolvePtr: resolveMap.PTR,
+ resolveNaptr: resolveMap.NAPTR,
+ resolveSoa: resolveMap.SOA,
+ reverse: resolver('getHostByAddr'),
+
+ // uv_getaddrinfo flags
+ ADDRCONFIG: cares.AI_ADDRCONFIG,
+ V4MAPPED: cares.AI_V4MAPPED,
+
+ // ERROR CODES
+ NODATA: 'ENODATA',
+ FORMERR: 'EFORMERR',
+ SERVFAIL: 'ESERVFAIL',
+ NOTFOUND: 'ENOTFOUND',
+ NOTIMP: 'ENOTIMP',
+ REFUSED: 'EREFUSED',
+ BADQUERY: 'EBADQUERY',
+ BADNAME: 'EBADNAME',
+ BADFAMILY: 'EBADFAMILY',
+ BADRESP: 'EBADRESP',
+ CONNREFUSED: 'ECONNREFUSED',
+ TIMEOUT: 'ETIMEOUT',
+ EOF: 'EOF',
+ FILE: 'EFILE',
+ NOMEM: 'ENOMEM',
+ DESTRUCTION: 'EDESTRUCTION',
+ BADSTR: 'EBADSTR',
+ BADFLAGS: 'EBADFLAGS',
+ NONAME: 'ENONAME',
+ BADHINTS: 'EBADHINTS',
+ NOTINITIALIZED: 'ENOTINITIALIZED',
+ LOADIPHLPAPI: 'ELOADIPHLPAPI',
+ ADDRGETNETWORKPARAMS: 'EADDRGETNETWORKPARAMS',
+ CANCELLED: 'ECANCELLED'
+};