Fix decoding url-encoded tags containing 32bits Unicode

Author: mlaily

YamlDotNet/Core/Scanner.cs

@@ -1680,7 +1680,7 @@ private Token ScanFlowScalar(bool isSingleQuoted)
 
                         if (codeLength > 0)
                         {
-                            uint character = 0;
+                            int character = 0;
 
                             // Scan the character value.
 
@@ -1690,7 +1690,7 @@ private Token ScanFlowScalar(bool isSingleQuoted)
                                 {
                                     throw new SyntaxErrorException(start, cursor.Mark(), "While parsing a quoted scalar, did not find expected hexdecimal number.");
                                 }
-                                character = (uint)((character << 4) + analyzer.AsHex(k));
+                                character = ((character << 4) + analyzer.AsHex(k));
                             }
 
                             // Check the value and write the character.
@@ -1700,7 +1700,7 @@ private Token ScanFlowScalar(bool isSingleQuoted)
                                 throw new SyntaxErrorException(start, cursor.Mark(), "While parsing a quoted scalar, find invalid Unicode character escape code.");
                             }
 
-                            value.Append((char)character);
+                            value.Append(char.ConvertFromUtf32(character));
 
                             // Advance the pointer.
 
@@ -2170,7 +2170,7 @@ private string ScanTagUri(string head, Mark start)
         /// Decode an URI-escape sequence corresponding to a single UTF-8 character.
         /// </summary>
 
-        private char ScanUriEscapes(Mark start)
+        private string ScanUriEscapes(Mark start)
         {
             // Decode the required number of characters.
 
@@ -2223,14 +2223,14 @@ private char ScanUriEscapes(Mark start)
             }
             while (--width > 0);
 
-            var characters = Encoding.UTF8.GetChars(charBytes.ToArray());
+            var result = Encoding.UTF8.GetString(charBytes.ToArray());
 
-            if (characters.Length != 1)
+            if (result.Length == 0 || result.Length > 2)
             {
                 throw new SyntaxErrorException(start, cursor.Mark(), "While parsing a tag, find an incorrect UTF-8 sequence.");
             }
 
-            return characters[0];
+            return result;
         }
 
         /// <summary>