From 98571ab496cbf4d8a5e0df091d19d3206b9ed1eb Mon Sep 17 00:00:00 2001
From: Evan You <yyx990803@gmail.com>
Date: Thu, 19 Sep 2019 21:18:18 -0400
Subject: [PATCH] perf(compiler): further improve advanceBy perf

---
 packages/compiler-core/src/utils.ts | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/packages/compiler-core/src/utils.ts b/packages/compiler-core/src/utils.ts
index ccea3ce80a..354b8ec1b2 100644
--- a/packages/compiler-core/src/utils.ts
+++ b/packages/compiler-core/src/utils.ts
@@ -36,15 +36,21 @@ export function advancePositionWithMutation(
 ): Position {
   __DEV__ && assert(numberOfCharacters <= source.length)
 
-  const str = source.slice(0, numberOfCharacters)
-  const lines = str.split(/\r?\n/)
+  let linesCount = 0
+  let lastNewLinePos = -1
+  for (let i = 0; i < numberOfCharacters; i++) {
+    if (source.charCodeAt(i) === 10 /* newline char code */) {
+      linesCount++
+      lastNewLinePos = i
+    }
+  }
 
   pos.offset += numberOfCharacters
-  pos.line += lines.length - 1
+  pos.line += linesCount
   pos.column =
-    lines.length === 1
+    lastNewLinePos === -1
       ? pos.column + numberOfCharacters
-      : Math.max(1, lines.pop()!.length)
+      : Math.max(1, numberOfCharacters - lastNewLinePos - 1)
 
   return pos
 }
-- 
2.47.3