Imported Upstream version 5.16.0.100

Former-commit-id: 38faa55fb9669e35e7d8448b15c25dc447f25767

mcs/class/corlib/ReferenceSources/TextInfo.cs

@@ -1,4 +1,5 @@
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 
 namespace System.Globalization
 {
@@ -198,7 +199,7 @@ namespace System.Globalization
 			return c;
 		}
 
-		static unsafe int InternalCompareStringOrdinalIgnoreCase (String strA, int indexA, String strB, int indexB, int lenA, int lenB)
+		internal static unsafe int InternalCompareStringOrdinalIgnoreCase (String strA, int indexA, String strB, int indexB, int lenA, int lenB)
 		{
 			if (strA == null) {
 				return strB == null ? 0 : -1;
@@ -229,6 +230,47 @@ namespace System.Globalization
 				return lengthA - lengthB;
 			}
 		}
+
+		internal void ToLowerAsciiInvariant (ReadOnlySpan<char> source, Span<char> destination)
+		{
+			for (int i = 0; i < source.Length; i++)
+			{
+				destination [i] = ToLowerAsciiInvariant (source [i]);
+			}
+		}
+
+		internal void ToUpperAsciiInvariant (ReadOnlySpan<char> source, Span<char> destination)
+		{
+			for (int i = 0; i < source.Length; i++)
+			{
+				destination [i] = ToUpperAsciiInvariant (source[i]);
+			}
+		}
+
+		internal unsafe void ChangeCase (ReadOnlySpan<char> source, Span<char> destination, bool toUpper)
+		{
+			if (source.IsEmpty)
+				return;
+
+			var ti = CultureInfo.CurrentCulture.TextInfo;
+
+			fixed (char* pSource = &MemoryMarshal.GetReference (source))
+			fixed (char* pResult = &MemoryMarshal.GetReference (destination)) {
+				int length = 0;
+				char* a = pSource, b = pResult;
+				if (toUpper) {
+					while (length < source.Length) {
+						*b++ = ti.ToUpper (*a++);
+						length++;
+					}
+				} else {
+					while (length < source.Length) {
+						*b++ = ti.ToLower (*a++);
+						length++;
+					}
+				}
+			}
+		}
 	}
 
 	static class TextInfoToUpperData