Speed up split_ns_and_tag

Author: mischov

native/meeseeks_html5ever_nif/src/flat_dom.rs

@@ -363,11 +363,10 @@ impl NifEncoder for Parent {
 // Node
 
 fn split_ns_and_tag(ns_tag: &str) -> (&str, &str) {
-    let v: Vec<&str> = ns_tag.splitn(2, ":").collect();
-    match v.len() {
-        1 => ("", v[0]),
-        2 => (v[0], v[1]),
-        _ => unreachable!(),
+    let first_colon = ns_tag.find(':').unwrap_or_else(|| ns_tag.len());
+    match ns_tag.split_at(first_colon) {
+        (tag, "") => ("", tag),
+        (ns, tag) => (ns, &tag[1..]),
     }
 }