http: use switch in matchHeader

Using a switch improves clarity of the code but also performance for
all but a few edge cases which remain on par with the old code.

PR-URL: #20131
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yuta Hiroto <hello@hiroppy.me>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: apapirovski

lib/_http_outgoing.js

@@ -52,8 +52,6 @@ const { utcDate } = internalHttp;
 
 const kIsCorked = Symbol('isCorked');
 
-var RE_FIELDS =
-  /^(?:Connection|Transfer-Encoding|Content-Length|Date|Expect|Trailer|Upgrade)$/i;
 var RE_CONN_VALUES = /(?:^|\W)close|upgrade(?:$|\W)/ig;
 var RE_TE_CHUNKED = common.chunkExpression;
 
@@ -449,28 +447,27 @@ function matchConnValue(self, state, value) {
 }
 
 function matchHeader(self, state, field, value) {
-  var m = RE_FIELDS.exec(field);
-  if (!m)
+  if (field.length < 4 || field.length > 17)
     return;
-  var len = m[0].length;
-  if (len === 10) {
-    state.connection = true;
-    matchConnValue(self, state, value);
-  } else if (len === 17) {
-    state.te = true;
-    if (RE_TE_CHUNKED.test(value)) self.chunkedEncoding = true;
-  } else if (len === 14) {
-    state.contLen = true;
-  } else if (len === 4) {
-    state.date = true;
-  } else if (len === 6) {
-    state.expect = true;
-  } else if (len === 7) {
-    var ch = m[0].charCodeAt(0);
-    if (ch === 85 || ch === 117)
-      state.upgrade = true;
-    else
-      state.trailer = true;
+  field = field.toLowerCase();
+  switch (field) {
+    case 'connection':
+      state.connection = true;
+      matchConnValue(self, state, value);
+      break;
+    case 'transfer-encoding':
+      state.te = true;
+      if (RE_TE_CHUNKED.test(value)) self.chunkedEncoding = true;
+      break;
+    case 'content-length':
+      state.contLen = true;
+      break;
+    case 'date':
+    case 'expect':
+    case 'trailer':
+    case 'upgrade':
+      state[field] = true;
+      break;
   }
 }