From 1691ab6319cfc6187bacd20c3c2488760ce7c6e7 Mon Sep 17 00:00:00 2001
From: Nguyen Duc Toan <ntoan96@gmail.com>
Date: Thu, 22 Dec 2022 00:37:55 +0700
Subject: [PATCH] Fix control character bug

---
 src/Tomlyn.Tests/ValidatorTests.cs | 15 +++++++++++++++
 src/Tomlyn/Parsing/Lexer.cs        |  2 +-
 src/Tomlyn/Text/CharHelper.cs      |  5 +++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/Tomlyn.Tests/ValidatorTests.cs b/src/Tomlyn.Tests/ValidatorTests.cs
index bc68d63..c23fd87 100644
--- a/src/Tomlyn.Tests/ValidatorTests.cs
+++ b/src/Tomlyn.Tests/ValidatorTests.cs
@@ -89,5 +89,20 @@ public void TestTableArrayAndInvalidTable()
             Assert.True(doc.HasErrors, "The document should have errors");
         }
 
+        [Test]
+        public void TestValidControlCharacters()
+        {
+            var input = "";
+            input += "backspace='\b'\n";
+            input += "tab='\t'\n";
+            input += "form_feed='\f'\n";
+            input += "quote='\"'\n";
+            input += "backslash='\\'\n";
+            input += "heart='\u2665'\n";
+            input += "some_unicode='\U0002B695'\n";
+            var doc = Toml.Parse(input);
+            Assert.False(doc.HasErrors, "The document should not have errors on valid control characters");
+        }
+
     }
 }
\ No newline at end of file
diff --git a/src/Tomlyn/Parsing/Lexer.cs b/src/Tomlyn/Parsing/Lexer.cs
index 5497851..be02c4f 100644
--- a/src/Tomlyn/Parsing/Lexer.cs
+++ b/src/Tomlyn/Parsing/Lexer.cs
@@ -1016,7 +1016,7 @@ private void ReadStringLiteral(TextPosition start, bool allowMultiline)
                 {
                     AddError("Invalid newline in a string", _position, _position);
                 }
-                else if (CharHelper.IsControlCharacter(_c) && (!isMultiLine || !CharHelper.IsNewLine(_c)))
+                else if (CharHelper.IsControlCharacter(_c) && !CharHelper.IsNonNewlineValidControlCharacter(_c) && (!isMultiLine || !CharHelper.IsNewLine(_c)))
                 {
                     AddError($"Invalid control character found {((char)_c).ToPrintableString()}", start, start);
                 }
diff --git a/src/Tomlyn/Text/CharHelper.cs b/src/Tomlyn/Text/CharHelper.cs
index e2405cd..4cbf944 100644
--- a/src/Tomlyn/Text/CharHelper.cs
+++ b/src/Tomlyn/Text/CharHelper.cs
@@ -24,6 +24,11 @@ public static bool IsControlCharacter(char32 c)
             return c <= 0x1F || c == 0x7F;
         }
 
+        public static bool IsNonNewlineValidControlCharacter(char32 c)
+        {
+            return c == '\b' || c == '\t' || c == '\f';
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsKeyStart(char32 c)
         {