crypto,tls: perf improvements for crypto and tls getCiphers

Improve performance of crypto.getCiphers, getHashes, getCurves
and tls.getCiphers by consolidating filterDuplicates logic, adding
caching of output, and streamlining filterDuplicates implementation.

Benchmarks:

crypto.getCiphers n=1    v6.2.1 = 2559.3, new = 15890 ...... -83.89%
crypto.getCiphers n=5000 v6.2.1 = 3516.3, new = 24203000 ... -99.99%

tls.getCiphers    n=1    v6.2.1 = 3405.3, new = 14877 ...... -77.11%
tls.getCiphers    n=5000 v6.2.1 = 6074.4, new = 24202000 ... -99.97%

PR-URL: https://github.com/nodejs/node/pull/7225
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>

benchmark/crypto/get-ciphers.js

@@ -0,0 +1,20 @@
+'use strict';
+
+const common = require('../common.js');
+
+const bench = common.createBenchmark(main, {
+  n: [1, 5000],
+  v: ['crypto', 'tls']
+});
+
+function main(conf) {
+  const n = +conf.n;
+  const v = conf.v;
+  const method = require(v).getCiphers;
+  var i = 0;
+
+  common.v8ForceOptimization(method);
+  bench.start();
+  for (; i < n; i++) method();
+  bench.end(n);
+}

lib/crypto.js

@@ -632,41 +632,23 @@ exports.randomBytes = exports.pseudoRandomBytes = randomBytes;
 
 exports.rng = exports.prng = randomBytes;
 
-exports.getCiphers = function() {
-  return filterDuplicates(getCiphers());
-};
-
-
-exports.getHashes = function() {
-  return filterDuplicates(getHashes());
-};
+exports.getCiphers = internalUtil.cachedResult(() => {
+  return internalUtil.filterDuplicateStrings(getCiphers());
+});
 
+exports.getHashes = internalUtil.cachedResult(() => {
+  return internalUtil.filterDuplicateStrings(getHashes());
+});
 
-exports.getCurves = function() {
-  return filterDuplicates(getCurves());
-};
+exports.getCurves = internalUtil.cachedResult(() => {
+  return internalUtil.filterDuplicateStrings(getCurves());
+});
 
 Object.defineProperty(exports, 'fips', {
   get: getFipsCrypto,
   set: setFipsCrypto
 });
 
-function filterDuplicates(names) {
-  // Drop all-caps names in favor of their lowercase aliases,
-  // for example, 'sha1' instead of 'SHA1'.
-  var ctx = {};
-  names.forEach(function(name) {
-    var key = name;
-    if (/^[0-9A-Z\-]+$/.test(key)) key = key.toLowerCase();
-    if (!ctx.hasOwnProperty(key) || ctx[key] < name)
-      ctx[key] = name;
-  });
-
-  return Object.getOwnPropertyNames(ctx).map(function(key) {
-    return ctx[key];
-  }).sort();
-}
-
 // Legacy API
 Object.defineProperty(exports, 'createCredentials', {
   configurable: true,

lib/internal/util.js

@@ -121,3 +121,34 @@ exports.normalizeEncoding = function normalizeEncoding(enc) {
     }
   }
 };
+
+// Filters duplicate strings. Used to support functions in crypto and tls
+// modules. Implemented specifically to maintain existing behaviors in each.
+exports.filterDuplicateStrings = function filterDuplicateStrings(items, low) {
+  if (!Array.isArray(items))
+    return [];
+  const len = items.length;
+  if (len <= 1)
+    return items;
+  const map = new Map();
+  for (var i = 0; i < len; i++) {
+    const item = items[i];
+    const key = item.toLowerCase();
+    if (low) {
+      map.set(key, key);
+    } else {
+      if (!map.has(key) || map.get(key) <= item)
+        map.set(key, item);
+    }
+  }
+  return Array.from(map.values()).sort();
+};
+
+exports.cachedResult = function cachedResult(fn) {
+  var result;
+  return () => {
+    if (result === undefined)
+      result = fn();
+    return result;
+  };
+};

lib/tls.js

@@ -1,6 +1,7 @@
 'use strict';
 
-require('internal/util').assertCrypto(exports);
+const internalUtil = require('internal/util');
+internalUtil.assertCrypto(exports);
 
 const net = require('net');
 const url = require('url');
@@ -21,16 +22,9 @@ exports.DEFAULT_CIPHERS =
 
 exports.DEFAULT_ECDH_CURVE = 'prime256v1';
 
-exports.getCiphers = function() {
-  const names = binding.getSSLCiphers();
-  // Drop all-caps names in favor of their lowercase aliases,
-  var ctx = {};
-  names.forEach(function(name) {
-    if (/^[0-9A-Z\-]+$/.test(name)) name = name.toLowerCase();
-    ctx[name] = true;
+exports.getCiphers = internalUtil.cachedResult(() => {
+  return internalUtil.filterDuplicateStrings(binding.getSSLCiphers(), true);
 });
-  return Object.getOwnPropertyNames(ctx).sort();
-};
 
 // Convert protocols array into valid OpenSSL protocols list
 // ("\x06spdy/2\x08http/1.1\x08http/1.0")