http: optimize header storage and matching

This commit implements two optimizations when working with headers:

* Avoid having to explicitly "render" headers and separately store the
original casing for header names.

* Match special header names using a single regular expression instead
of testing one regular expression per header name.

PR-URL: https://github.com/nodejs/node/pull/10558
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/lib/_http_server.js b/lib/_http_server.js
index fe563977a6..d473fd3281 100644
--- a/lib/_http_server.js
+++ b/lib/_http_server.js
@@ -161,7 +161,6 @@ ServerResponse.prototype._implicitHeader = function _implicitHeader() {
 
 ServerResponse.prototype.writeHead = writeHead;
 function writeHead(statusCode, reason, obj) {
-  var headers;
   statusCode |= 0;
   if (statusCode < 100 || statusCode > 999)
     throw new RangeError(`Invalid status code: ${statusCode}`);
@@ -177,17 +176,25 @@ function writeHead(statusCode, reason, obj) {
   }
   this.statusCode = statusCode;
 
+  var headers;
   if (this._headers) {
     // Slow-case: when progressive API and header fields are passed.
+    var k;
     if (obj) {
       var keys = Object.keys(obj);
       for (var i = 0; i < keys.length; i++) {
-        var k = keys[i];
+        k = keys[i];
         if (k) this.setHeader(k, obj[k]);
       }
     }
+    if (k === undefined) {
+      if (this._header) {
+        throw new Error('Can\'t render headers after they are sent to the ' +
+                        'client');
+      }
+    }
     // only progressive api is used
-    headers = this._renderHeaders();
+    headers = this._headers;
   } else {
     // only writeHead() called
     headers = obj;