Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.Runtime.Serialization/System/Text/SurrogateChar.cs

@@ -0,0 +1,56 @@
+//-----------------------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+//-----------------------------------------------------------------------------
+namespace System.Text
+{
+    using System.Globalization;
+    using System.Runtime.Serialization; // Just for SR
+
+    struct SurrogateChar
+    {
+        char lowChar;
+        char highChar;
+
+        public const int MinValue = 0x10000;
+        public const int MaxValue = MinValue + (1 << 20) - 1;
+
+        const char surHighMin = (char)0xd800;
+        const char surHighMax = (char)0xdbff;
+        const char surLowMin = (char)0xdc00;
+        const char surLowMax = (char)0xdfff;
+
+        public SurrogateChar(int ch)
+        {
+            if (ch < MinValue || ch > MaxValue)
+                throw System.Runtime.Serialization.DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentException(SR.GetString(SR.XmlInvalidSurrogate, ch.ToString("X", CultureInfo.InvariantCulture)), "ch"));
+
+            const int mask = ((1 << 10) - 1);
+
+            this.lowChar = (char)(((ch - MinValue) & mask) + surLowMin);
+            this.highChar = (char)((((ch - MinValue) >> 10) & mask) + surHighMin);
+        }
+
+        public SurrogateChar(char lowChar, char highChar)
+        {
+            if (lowChar < surLowMin || lowChar > surLowMax)
+                throw System.Runtime.Serialization.DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentException(SR.GetString(SR.XmlInvalidLowSurrogate, ((int)lowChar).ToString("X", CultureInfo.InvariantCulture)), "lowChar"));
+
+            if (highChar < surHighMin || highChar > surHighMax)
+                throw System.Runtime.Serialization.DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentException(SR.GetString(SR.XmlInvalidHighSurrogate, ((int)highChar).ToString("X", CultureInfo.InvariantCulture)), "highChar"));
+
+            this.lowChar = lowChar;
+            this.highChar = highChar;
+        }
+
+        public char LowChar { get { return lowChar; } }
+        public char HighChar { get { return highChar; } }
+
+        public int Char
+        {
+            get
+            {
+                return (lowChar - surLowMin) | ((highChar - surHighMin) << 10) + MinValue;
+            }
+        }
+    }
+}