From 40c575cc5989870261eec7bdf9bbc293ed38e72b Mon Sep 17 00:00:00 2001
From: Sean McArthur <sean.monstar@gmail.com>
Date: Thu, 25 May 2017 10:31:20 -0700
Subject: [PATCH] perf(header): move a branch out of a loop in
 fmt_comma_delimited

---
 src/header/parsing.rs | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/header/parsing.rs b/src/header/parsing.rs
index 8706b32d..0f65fb2f 100644
--- a/src/header/parsing.rs
+++ b/src/header/parsing.rs
@@ -44,10 +44,12 @@ pub fn from_comma_delimited<T: str::FromStr>(raw: &Raw) -> ::Result<Vec<T>> {
 
 /// Format an array into a comma-delimited string.
 pub fn fmt_comma_delimited<T: Display>(f: &mut fmt::Formatter, parts: &[T]) -> fmt::Result {
-    for (i, part) in parts.iter().enumerate() {
-        if i != 0 {
-            try!(f.write_str(", "));
-        }
+    let mut iter = parts.iter();
+    if let Some(part) = iter.next() {
+        try!(Display::fmt(part, f));
+    }
+    for part in iter {
+        try!(f.write_str(", "));
         try!(Display::fmt(part, f));
     }
     Ok(())