From 5e944abe55945cab53b045453e835a610aa8d1d4 Mon Sep 17 00:00:00 2001
From: Lukas Renggli <renggli@gmail.com>
Date: Tue, 31 Dec 2024 17:35:54 +0100
Subject: [PATCH] For character predicates use `String.fromCharCode` instead of
 extracting the matched range from the source; it brings a small performance
 benefit.

---
 lib/src/parser/predicate/single_character.dart  | 8 +++++---
 lib/src/parser/predicate/unicode_character.dart | 3 +--
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/src/parser/predicate/single_character.dart b/lib/src/parser/predicate/single_character.dart
index 0bb68cce..9c4fac90 100644
--- a/lib/src/parser/predicate/single_character.dart
+++ b/lib/src/parser/predicate/single_character.dart
@@ -18,9 +18,11 @@ class SingleCharacterParser extends CharacterParser {
   Result<String> parseOn(Context context) {
     final buffer = context.buffer;
     final position = context.position;
-    if (position < buffer.length &&
-        predicate.test(buffer.codeUnitAt(position))) {
-      return context.success(buffer[position], position + 1);
+    if (position < buffer.length) {
+      final codeUnit = buffer.codeUnitAt(position);
+      if (predicate.test(codeUnit)) {
+        return context.success(String.fromCharCode(codeUnit), position + 1);
+      }
     }
     return context.failure(message);
   }
diff --git a/lib/src/parser/predicate/unicode_character.dart b/lib/src/parser/predicate/unicode_character.dart
index 31d76db7..0aa335e8 100644
--- a/lib/src/parser/predicate/unicode_character.dart
+++ b/lib/src/parser/predicate/unicode_character.dart
@@ -28,8 +28,7 @@ class UnicodeCharacterParser extends CharacterParser {
         }
       }
       if (predicate.test(codeUnit)) {
-        return context.success(
-            buffer.substring(position, nextPosition), nextPosition);
+        return context.success(String.fromCharCode(codeUnit), nextPosition);
       }
     }
     return context.failure(message);