http: reduce raw header name allocations

Reuse the values array instead of allocating a second result array.

Signed-off-by: Roberto Bianchi <roberto.bianchi@spendesk.com>
PR-URL: https://github.com/nodejs/node/pull/66488
Reviewed-By: Gürgün Dayıoğlu <hey@gurgun.day>
Reviewed-By: Tim Perry <pimterry@gmail.com>

benchmark/http/get-raw-header-names.js

@@ -0,0 +1,33 @@
+'use strict';
+
+const common = require('../common.js');
+const assert = require('node:assert');
+const { OutgoingMessage } = require('node:http');
+
+const bench = common.createBenchmark(main, {
+  n: [1e6],
+  headers: [0, 1, 4, 16, 64],
+});
+
+function main({ n, headers }) {
+  const message = new OutgoingMessage();
+  const expected = [];
+  for (let index = 0; index < headers; index++) {
+    const name = `X-Header-${index}`;
+    message.setHeader(name, 'value');
+    expected.push(name);
+  }
+
+  for (let index = 0; index < 1e4; index++) {
+    message.getRawHeaderNames();
+  }
+
+  let result;
+  bench.start();
+  for (let index = 0; index < n; index++) {
+    result = message.getRawHeaderNames();
+  }
+  bench.end(n);
+
+  assert.deepStrictEqual(result, expected);
+}

lib/_http_outgoing.js

@@ -22,7 +22,6 @@
 'use strict';
 
 const {
-  Array,
   ArrayIsArray,
   MathFloor,
   ObjectDefineProperty,
@@ -935,12 +934,11 @@ OutgoingMessage.prototype.getRawHeaderNames = function getRawHeaderNames() {
   const headersMap = this[kOutHeaders];
   if (headersMap === null) return [];
 
-  const values = ObjectValues(headersMap);
-  const headers = Array(values.length);
+  const headers = ObjectValues(headersMap);
   // Retain for(;;) loop for performance reasons
   // Refs: https://github.com/nodejs/node/pull/30958
-  for (let i = 0, l = values.length; i < l; i++) {
-    headers[i] = values[i][0];
+  for (let i = 0; i < headers.length; i++) {
+    headers[i] = headers[i][0];
   }
 
   return headers;

test/parallel/test-http-get-raw-header-names.js

@@ -0,0 +1,43 @@
+'use strict';
+
+require('../common');
+const assert = require('node:assert');
+const { OutgoingMessage } = require('node:http');
+
+const message = new OutgoingMessage();
+assert.deepStrictEqual(message.getRawHeaderNames(), []);
+assert.notStrictEqual(message.getRawHeaderNames(), message.getRawHeaderNames());
+
+message.setHeader('X-First', 'first');
+message.setHeader('10', 'ten');
+message.setHeader('2', 'two');
+message.setHeader('__proto__', 'proto');
+message.setHeader('Constructor', 'constructor');
+message.setHeader('X-Last', 'last');
+
+const expected = ['2', '10', 'X-First', '__proto__', 'Constructor', 'X-Last'];
+const names = message.getRawHeaderNames();
+assert.deepStrictEqual(names, expected);
+names[0] = 'changed';
+names.push('extra');
+assert.deepStrictEqual(message.getRawHeaderNames(), expected);
+assert.strictEqual(message.getHeader('2'), 'two');
+
+message.setHeader('x-FIRST', 'updated');
+expected[2] = 'x-FIRST';
+assert.deepStrictEqual(message.getRawHeaderNames(), expected);
+
+message.removeHeader('X-FIRST');
+message.setHeader('X-First', 'reinserted');
+assert.deepStrictEqual(message.getRawHeaderNames(), [
+  '2', '10', '__proto__', 'Constructor', 'X-Last', 'X-First',
+]);
+
+for (const name of message.getHeaderNames()) {
+  message.removeHeader(name);
+}
+assert.deepStrictEqual(message.getRawHeaderNames(), []);
+assert.notStrictEqual(message.getRawHeaderNames(), message.getRawHeaderNames());
+
+message.setHeader('X-New', 'new');
+assert.deepStrictEqual(message.getRawHeaderNames(), ['X-New']);