http: refactor outgoing headers processing

Use a shared function, for..in instead of Object.keys, do less work in
`setHeader` and instead defer some of it until later, and other minor
changes to improve clarity, as well as a slight boost in performance.

PR-URL: https://github.com/nodejs/node/pull/20250
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/benchmark/http/headers.js b/benchmark/http/headers.js
new file mode 100644
index 0000000000..748865afbf
--- /dev/null
+++ b/benchmark/http/headers.js
@@ -0,0 +1,36 @@
+'use strict';
+
+const common = require('../common.js');
+const http = require('http');
+
+const bench = common.createBenchmark(main, {
+  duplicates: [1, 100],
+  n: [10, 1000],
+});
+
+function main({ duplicates, n }) {
+  const headers = {
+    'Connection': 'keep-alive',
+    'Transfer-Encoding': 'chunked',
+  };
+
+  for (var i = 0; i < n / duplicates; i++) {
+    headers[`foo${i}`] = [];
+    for (var j = 0; j < duplicates; j++) {
+      headers[`foo${i}`].push(`some header value ${i}`);
+    }
+  }
+
+  const server = http.createServer(function(req, res) {
+    res.writeHead(200, headers);
+    res.end();
+  });
+  server.listen(common.PORT, function() {
+    bench.http({
+      path: '/',
+      connections: 10
+    }, function() {
+      server.close();
+    });
+  });
+}