fix: rewrite getLineOffset function

Author: galaxian85

lib/common/utils.js

@@ -293,33 +293,9 @@ function normalizeReference(str) {
 var _g = typeof global !== 'undefined' ? global : window;
 var tokensRef = new _g.WeakMap();
 
-// TODO: performance tweaks for emphasis **_* pattern which has only 1/10 performance after adding line offset
-function getLineOffset(state, tokenIdx) {
-  var blockState = state.env.state_block;
-  var parentToken = state.env.parentToken;
-  var tokensBefore = typeof tokenIdx !== 'undefined' ? state.tokens.slice(0, tokenIdx) : state.tokens;
-
-  var resultsMap = tokensRef.get(state.tokens);
-  if (resultsMap) {
-    var cachedResult = resultsMap.get(tokenIdx);
-    if (typeof cachedResult !== 'undefined') {
-      return cachedResult;
-    }
-  } else {
-    resultsMap = new _g.Map();
-    tokensRef.set(state.tokens, resultsMap);
-  }
-
-  var linesBefore = tokensBefore.filter(function (t) { return t.type === 'softbreak' || t.type === 'hardbreak'; }).length;
-
-  var lineOffset = 0;
-  for (var i = 0; i < linesBefore; i++) {
-    var startLine = i + parentToken.map[0] + 1;
-    lineOffset += blockState.tShift[startLine];
-  }
-
-  resultsMap.set(tokenIdx, lineOffset);
-  return lineOffset;
+function getLineOffset(state) {
+  const blockState = state.env.state_block;
+  return blockState.lineOffsets[state.currentLine] ?? 0;
 }
 
 function trimLeftOffset(str) {