From ad1efeaf2315c1ccd25c1e5bccb21df626c1d12c Mon Sep 17 00:00:00 2001
From: Douglas Christopher Wilson <doug@somethingdoug.com>
Date: Thu, 14 Sep 2017 21:12:36 -0400
Subject: [PATCH] perf: reduce overhead when no X-Forwarded-For header

---
 HISTORY.md |  5 +++++
 index.js   | 25 ++++++++++++++++++++-----
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/HISTORY.md b/HISTORY.md
index afbb768..7d8b47a 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -1,3 +1,8 @@
+unreleased
+==========
+
+  * perf: reduce overhead when no `X-Forwarded-For` header
+
 0.1.1 / 2017-09-10
 ==================
 
diff --git a/index.js b/index.js
index e62605d..5739d36 100644
--- a/index.js
+++ b/index.js
@@ -34,14 +34,29 @@ function forwarded (req) {
   }
 
   // simple header parsing
-  var proxyAddrs = (req.headers['x-forwarded-for'] || '')
-    .trim()
-    .split(TOKEN_LIST_REGEXP)
-    .filter(Boolean)
-    .reverse()
+  var proxyAddrs = parse(req.headers['x-forwarded-for'] || '')
   var socketAddr = req.connection.remoteAddress
   var addrs = [socketAddr].concat(proxyAddrs)
 
   // return all addresses
   return addrs
 }
+
+/**
+ * Parse the X-Forwarded-For header.
+ *
+ * @param {string} header
+ * @private
+ */
+
+function parse (header) {
+  if (!header) {
+    return []
+  }
+
+  return header
+    .trim()
+    .split(TOKEN_LIST_REGEXP)
+    .filter(Boolean)
+    .reverse()
+}