parse backticks without regex exec

lib/rules_inline/backticks.js

@@ -1,9 +1,7 @@
 // Parse backticks
 
-var END_RE = /`+/g;
-
 module.exports = function backticks(state) {
-  var start, code, max, marker, match,
+  var start, max, marker, matchStart, matchEnd,
       pos = state.pos,
       ch = state.src.charCodeAt(pos);
 
@@ -17,22 +15,23 @@ module.exports = function backticks(state) {
 
   marker = state.src.slice(start, pos);
 
-  END_RE = /`+/g;
-  END_RE.lastIndex = pos;
+  matchStart = matchEnd = pos;
+
+  while ((matchStart = state.src.indexOf('`', matchEnd)) !== -1) {
+    matchEnd = matchStart + 1;
 
-  while ((match = END_RE.exec(state.src)) !== null) {
-    if (match[0].length === marker.length) {
-      code = state.src.slice(pos, END_RE.lastIndex - marker.length);
+    while (matchEnd < max && state.src.charCodeAt(matchEnd) === 0x60/* ` */) { matchEnd++; }
+
+    if (matchEnd - matchStart === marker.length) {
       state.push({
         type: 'code',
-        content: code
-                  .replace(/[ \n]+/g,' ')
-                  .trim(),
+        content: state.src.slice(pos, matchStart)
+                            .replace(/[ \n]+/g,' ')
+                            .trim(),
         block: false,
         level: state.level
       });
-
-      state.pos += marker.length * 2 + code.length;
+      state.pos = matchEnd;
       return true;
     }
   }