Improved reference scan efficiency, related to #54

lib/rules_block/reference.js

@@ -24,11 +24,22 @@ module.exports = function reference(state, startLine, _endLine, silent) {
       title,
       lines = 0,
       pos = state.bMarks[startLine] + state.tShift[startLine],
-      max,
+      max = state.eMarks[startLine],
       nextLine = startLine + 1;
 
   if (state.src.charCodeAt(pos) !== 0x5B/* [ */) { return false; }
 
+  // Simple check to quickly interrupt scan on [link](url) at the start of line.
+  // Can be useful on practice: https://github.com/markdown-it/markdown-it/issues/54
+  while (++pos < max) {
+    if (state.src.charCodeAt(pos) === 0x5D /* ] */ &&
+        state.src.charCodeAt(pos - 1) !== 0x5C/* \ */) {
+      if (pos + 1 === max) { return false; }
+      if (state.src.charCodeAt(pos + 1) !== 0x3A/* : */) { return false; }
+      break;
+    }
+  }
+
   endLine = state.lineMax;
 
   // jump line-by-line until empty one or EOF