Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/mscorlib/system/collections/caseinsensitivehashcodeprovider.cs

@@ -0,0 +1,83 @@
+// ==++==
+// 
+//   Copyright (c) Microsoft Corporation.  All rights reserved.
+// 
+// ==--==
+/*============================================================
+**
+** Class: CaseInsensitiveHashCodeProvider
+** 
+** <OWNER>[....]</OWNER>
+**
+**
+** Purpose: Designed to support hashtables which require 
+** case-insensitive behavior while still maintaining case,
+** this provides an efficient mechanism for getting the 
+** hashcode of the string ignoring case.
+**
+**
+============================================================*/
+namespace System.Collections {
+//This class does not contain members and does not need to be serializable
+    using System;
+    using System.Collections;
+    using System.Globalization;
+    using System.Diagnostics.Contracts;
+
+    [Serializable]  
+    [Obsolete("Please use StringComparer instead.")]    
+    [System.Runtime.InteropServices.ComVisible(true)]
+    public class CaseInsensitiveHashCodeProvider : IHashCodeProvider {
+        private TextInfo m_text;
+        private static volatile CaseInsensitiveHashCodeProvider m_InvariantCaseInsensitiveHashCodeProvider = null;
+
+        public CaseInsensitiveHashCodeProvider() {
+            m_text = CultureInfo.CurrentCulture.TextInfo;
+        }
+
+        public CaseInsensitiveHashCodeProvider(CultureInfo culture) {
+            if (culture==null) {
+                throw new ArgumentNullException("culture");
+            }
+            Contract.EndContractBlock();
+            m_text = culture.TextInfo;
+        }
+
+        public static CaseInsensitiveHashCodeProvider Default
+        {
+            get
+            {
+                Contract.Ensures(Contract.Result<CaseInsensitiveHashCodeProvider>() != null);
+
+                return new CaseInsensitiveHashCodeProvider(CultureInfo.CurrentCulture);
+            }
+        }
+        
+        public static CaseInsensitiveHashCodeProvider DefaultInvariant
+        {
+            get
+            {
+                Contract.Ensures(Contract.Result<CaseInsensitiveHashCodeProvider>() != null);
+
+                if (m_InvariantCaseInsensitiveHashCodeProvider == null) {
+                    m_InvariantCaseInsensitiveHashCodeProvider = new CaseInsensitiveHashCodeProvider(CultureInfo.InvariantCulture);
+                }
+                return m_InvariantCaseInsensitiveHashCodeProvider;
+            }
+        }
+
+        public int GetHashCode(Object obj) {
+            if (obj==null) {
+                throw new ArgumentNullException("obj");
+            }
+            Contract.EndContractBlock();
+
+            String s = obj as String;
+            if (s==null) {
+                return obj.GetHashCode();
+            }
+
+            return m_text.GetCaseInsensitiveHashCode(s);
+        }
+    }
+}