From 34c2c766cabae9c32ab221ad225250a986db996b Mon Sep 17 00:00:00 2001
From: Alex Dima <alexdima@microsoft.com>
Date: Sun, 29 Mar 2020 17:29:47 +0200
Subject: [PATCH] Fixes #93370: Use TextDecoder to create a reverse string

---
 src/vs/editor/common/core/stringBuilder.ts    |  5 +++--
 .../common/modes/supports/richEditBrackets.ts | 20 ++++++++++++++-----
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/src/vs/editor/common/core/stringBuilder.ts b/src/vs/editor/common/core/stringBuilder.ts
index 1ae6347c00e..8a577ab8de2 100644
--- a/src/vs/editor/common/core/stringBuilder.ts
+++ b/src/vs/editor/common/core/stringBuilder.ts
@@ -24,17 +24,18 @@ export interface IStringBuilder {
 }
 
 let _platformTextDecoder: TextDecoder | null;
-function getPlatformTextDecoder(): TextDecoder {
+export function getPlatformTextDecoder(): TextDecoder {
 	if (!_platformTextDecoder) {
 		_platformTextDecoder = new TextDecoder(platform.isLittleEndian() ? 'UTF-16LE' : 'UTF-16BE');
 	}
 	return _platformTextDecoder;
 }
 
+export const hasTextDecoder = (typeof TextDecoder !== 'undefined');
 export let createStringBuilder: (capacity: number) => IStringBuilder;
 export let decodeUTF16LE: (source: Uint8Array, offset: number, len: number) => string;
 
-if (typeof TextDecoder !== 'undefined') {
+if (hasTextDecoder) {
 	createStringBuilder = (capacity) => new StringBuilder(capacity);
 	decodeUTF16LE = standardDecodeUTF16LE;
 } else {
diff --git a/src/vs/editor/common/modes/supports/richEditBrackets.ts b/src/vs/editor/common/modes/supports/richEditBrackets.ts
index ae10537c82e..03a1d102dc1 100644
--- a/src/vs/editor/common/modes/supports/richEditBrackets.ts
+++ b/src/vs/editor/common/modes/supports/richEditBrackets.ts
@@ -4,6 +4,7 @@
  *--------------------------------------------------------------------------------------------*/
 
 import * as strings from 'vs/base/common/strings';
+import * as stringBuilder from 'vs/editor/common/core/stringBuilder';
 import { Range } from 'vs/editor/common/core/range';
 import { LanguageIdentifier } from 'vs/editor/common/modes';
 import { CharacterPair } from 'vs/editor/common/modes/languageConfiguration';
@@ -264,14 +265,23 @@ function createBracketOrRegExp(pieces: string[]): RegExp {
 	return strings.createRegExp(regexStr, true);
 }
 
-let toReversedString = (function () {
+const toReversedString = (function () {
 
 	function reverse(str: string): string {
-		let reversedStr = '';
-		for (let i = str.length - 1; i >= 0; i--) {
-			reversedStr += str.charAt(i);
+		if (stringBuilder.hasTextDecoder) {
+			// create a Uint16Array and then use a TextDecoder to create a string
+			const arr = new Uint16Array(str.length);
+			for (let i = str.length - 1; i >= 0; i--) {
+				arr[i] = str.charCodeAt(i);
+			}
+			return stringBuilder.getPlatformTextDecoder().decode(arr);
+		} else {
+			let result: string[] = [], resultLen = 0;
+			for (let i = str.length - 1; i >= 0; i--) {
+				result[resultLen++] = str.charAt(i);
+			}
+			return result.join('');
 		}
-		return reversedStr;
 	}
 
 	let lastInput: string | null = null;
-- 
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