node: improve accessor perf of process.env

Set process.env array entries in JS.

PR-URL: nodejs#3780
Reviewed-By: Fedor Indutny <fedor@indutny.com>

benchmark/misc/bench-env.js

@@ -0,0 +1,18 @@
+'use strict';
+
+const common = require('../common');
+
+const bench = common.createBenchmark(main, {
+  n: [1e5],
+});
+
+
+function main(conf) {
+  const n = conf.n >>> 0;
+  bench.start();
+  for (var i = 0; i < n; i++) {
+    // Access every item in object to process values.
+    Object.keys(process.env);
+  }
+  bench.end(n);
+}

src/node.cc

@@ -2560,31 +2560,42 @@ static void EnvDeleter(Local<String> property,
 
 
 static void EnvEnumerator(const PropertyCallbackInfo<Array>& info) {
-  Isolate* isolate = info.GetIsolate();
+  Environment* env = Environment::GetCurrent(info);
+  Isolate* isolate = env->isolate();
+  Local<Context> ctx = env->context();
+  Local<Function> fn = env->push_values_to_array_function();
+  Local<Value> argv[NODE_PUSH_VAL_TO_ARRAY_MAX];
+  size_t idx = 0;
+
 #ifdef __POSIX__
   int size = 0;
   while (environ[size])
     size++;
 
-  Local<Array> envarr = Array::New(isolate, size);
+  Local<Array> envarr = Array::New(isolate);
 
   for (int i = 0; i < size; ++i) {
     const char* var = environ[i];
     const char* s = strchr(var, '=');
     const int length = s ? s - var : strlen(var);
-    Local<String> name = String::NewFromUtf8(isolate,
-                                             var,
-                                             String::kNormalString,
-                                             length);
-    envarr->Set(i, name);
+    argv[idx] = String::NewFromUtf8(isolate,
+                                    var,
+                                    String::kNormalString,
+                                    length);
+    if (++idx >= ARRAY_SIZE(argv)) {
+      fn->Call(ctx, envarr, idx, argv).ToLocalChecked();
+      idx = 0;
+    }
+  }
+  if (idx > 0) {
+    fn->Call(ctx, envarr, idx, argv).ToLocalChecked();
   }
 #else  // _WIN32
   WCHAR* environment = GetEnvironmentStringsW();
   if (environment == nullptr)
     return;  // This should not happen.
   Local<Array> envarr = Array::New(isolate);
   WCHAR* p = environment;
-  int i = 0;
   while (*p) {
     WCHAR *s;
     if (*p == L'=') {
@@ -2599,13 +2610,19 @@ static void EnvEnumerator(const PropertyCallbackInfo<Array>& info) {
     }
     const uint16_t* two_byte_buffer = reinterpret_cast<const uint16_t*>(p);
     const size_t two_byte_buffer_len = s - p;
-    Local<String> value = String::NewFromTwoByte(isolate,
-                                                 two_byte_buffer,
-                                                 String::kNormalString,
-                                                 two_byte_buffer_len);
-    envarr->Set(i++, value);
+    argv[idx] = String::NewFromTwoByte(isolate,
+                                       two_byte_buffer,
+                                       String::kNormalString,
+                                       two_byte_buffer_len);
+    if (++idx >= ARRAY_SIZE(argv)) {
+      fn->Call(ctx, envarr, idx, argv).ToLocalChecked();
+      idx = 0;
+    }
     p = s + wcslen(s) + 1;
   }
+  if (idx > 0) {
+    fn->Call(ctx, envarr, idx, argv).ToLocalChecked();
+  }
   FreeEnvironmentStringsW(environment);
 #endif