Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web.Extensions/Script/Serialization/JavaScriptString.cs

@@ -0,0 +1,92 @@
+//------------------------------------------------------------------------------
+// <copyright file="JavaScriptString.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//------------------------------------------------------------------------------
+ 
+namespace System.Web.Script.Serialization {
+    using System;
+    using System.Diagnostics.CodeAnalysis;
+    using System.Globalization;
+    using System.Text;
+
+    internal class JavaScriptString {
+        private string _s;
+        private int _index;
+
+        internal JavaScriptString(string s) {
+            _s = s;
+        }
+
+        internal Nullable<char> GetNextNonEmptyChar() {
+            while (_s.Length > _index) {
+                char c = _s[_index++];
+                if (!Char.IsWhiteSpace(c)) {
+                    return c;
+                }
+            }
+
+            return null;
+        }
+
+        internal Nullable<char> MoveNext() {
+            if (_s.Length > _index) {
+                return _s[_index++];
+            }
+
+            return null;
+        }
+
+        internal string MoveNext(int count) {
+            if (_s.Length >= _index + count) {
+                string result = _s.Substring(_index, count);
+                _index += count;
+
+                return result;
+            }
+
+            return null;
+        }
+
+        internal void MovePrev() {
+            if (_index > 0) {
+                _index--;
+            }
+        }
+
+        internal void MovePrev(int count) {
+            while (_index > 0 && count > 0) {
+                _index--;
+                count--;
+            }
+        }
+
+        public override string ToString() {
+            if (_s.Length > _index) {
+                return _s.Substring(_index);
+            }
+
+            return String.Empty;
+        }
+
+        internal string GetDebugString(string message) {
+            return message + " (" + _index + "): " + _s;
+        }
+
+        internal int IndexOf(string substr) {
+            if (_s.Length > _index) {
+                return _s.IndexOf(substr, _index, StringComparison.CurrentCulture) - _index;
+            }
+
+            return -1;
+        }
+
+        internal string Substring(int length) {
+            if (_s.Length > _index + length) {
+                return _s.Substring(_index, length);
+            }
+
+            return ToString();
+        }
+    }
+}