From 2a66cd34fad7c0d4ac9ca6e1bb70ae5773ce3012 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 31 Dec 2018 02:01:00 +0100
Subject: [PATCH] module: simpler shebang function

This simplifies the shebang function significantly. Before, it was
optimized for two characters input. Any module actually parsed should
however have more characters than just the shebang.
The performance stays the same as before.

PR-URL: https://github.com/nodejs/node/pull/26266
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
---
 lib/internal/modules/cjs/helpers.js | 43 ++++++++---------------------
 1 file changed, 11 insertions(+), 32 deletions(-)

diff --git a/lib/internal/modules/cjs/helpers.js b/lib/internal/modules/cjs/helpers.js
index 2e5290b4520a27..874805beccd39c 100644
--- a/lib/internal/modules/cjs/helpers.js
+++ b/lib/internal/modules/cjs/helpers.js
@@ -5,13 +5,6 @@ const path = require('path');
 const { pathToFileURL } = require('internal/url');
 const { URL } = require('url');
 
-const {
-  CHAR_LINE_FEED,
-  CHAR_CARRIAGE_RETURN,
-  CHAR_EXCLAMATION_MARK,
-  CHAR_HASH,
-} = require('internal/constants');
-
 // Invoke with makeRequireFunction(module) where |module| is the Module object
 // to use as the context for the require() function.
 function makeRequireFunction(mod) {
@@ -67,31 +60,17 @@ function stripBOM(content) {
  */
 function stripShebang(content) {
   // Remove shebang
-  var contLen = content.length;
-  if (contLen >= 2) {
-    if (content.charCodeAt(0) === CHAR_HASH &&
-        content.charCodeAt(1) === CHAR_EXCLAMATION_MARK) {
-      if (contLen === 2) {
-        // Exact match
-        content = '';
-      } else {
-        // Find end of shebang line and slice it off
-        var i = 2;
-        for (; i < contLen; ++i) {
-          var code = content.charCodeAt(i);
-          if (code === CHAR_LINE_FEED || code === CHAR_CARRIAGE_RETURN)
-            break;
-        }
-        if (i === contLen)
-          content = '';
-        else {
-          // Note that this actually includes the newline character(s) in the
-          // new output. This duplicates the behavior of the regular expression
-          // that was previously used to replace the shebang line
-          content = content.slice(i);
-        }
-      }
-    }
+  if (content.charAt(0) === '#' && content.charAt(1) === '!') {
+    // Find end of shebang line and slice it off
+    let index = content.indexOf('\n', 2);
+    if (index === -1)
+      return '';
+    if (content.charAt(index - 1) === '\r')
+      index--;
+    // Note that this actually includes the newline character(s) in the
+    // new output. This duplicates the behavior of the regular expression
+    // that was previously used to replace the shebang line.
+    content = content.slice(index);
   }
   return content;
 }