[CSharp] Add a new CharStream that converts the symbols to upper or lower case.

contributors.txt

@@ -175,4 +175,6 @@ YYYY/MM/DD, github id, Full name, email
 2017/11/05, ajaypanyala, Ajay Panyala, ajay.panyala@gmail.com
 2017/11/24, zqlu.cn, Zhiqiang Lu, zqlu.cn@gmail.com
 2017/11/28, niccroad, Nicolas Croad, nic.croad@gmail.com
-2017/12/03, oranoran, Oran Epelbaum, oran / epelbaum me
+2017/12/01, DavidMoraisFerreira, David Morais Ferreira, david.moraisferreira@gmail.com
+2017/12/01, SebastianLng, Sebastian Lang, sebastian.lang@outlook.com
+2017/12/03, oranoran, Oran Epelbaum, oran / epelbaum me

runtime/CSharp/runtime/CSharp/Antlr4.Runtime/Antlr4.Runtime.vs2013.csproj

@@ -54,6 +54,7 @@
     <Compile Include="Atn\ATNDeserializationOptions.cs" />
     <Compile Include="Atn\ATNDeserializer.cs" />
     <Compile Include="Atn\ConflictInfo.cs" />
+    <Compile Include="CaseChangingCharStream.cs" />
     <Compile Include="CharStreams.cs" />
     <Compile Include="Dfa\AbstractEdgeMap.cs" />
     <Compile Include="Dfa\AcceptStateInfo.cs" />

runtime/CSharp/runtime/CSharp/Antlr4.Runtime/CaseChangingCharStream.cs

@@ -0,0 +1,105 @@
+/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
+ * Use of this file is governed by the BSD 3-clause license that
+ * can be found in the LICENSE.txt file in the project root.
+ */
+using System;
+using Antlr4.Runtime.Misc;
+
+namespace Antlr4.Runtime
+{
+    /// <summary>
+    /// This class supports case-insensitive lexing by wrapping an existing
+    /// <see cref="ICharStream"/> and forcing the lexer to see either upper or
+    /// lowercase characters. Grammar literals should then be either upper or
+    /// lower case such as 'BEGIN' or 'begin'. The text of the character
+    /// stream is unaffected. Example: input 'BeGiN' would match lexer rule
+    /// 'BEGIN' if constructor parameter upper=true but getText() would return
+    /// 'BeGiN'.
+    /// </summary>
+    public class CaseChangingCharStream : ICharStream
+    {
+        private ICharStream stream;
+        private bool upper;
+
+        /// <summary>
+        /// Constructs a new CaseChangingCharStream wrapping the given <paramref name="stream"/> forcing
+        /// all characters to upper case or lower case.
+        /// </summary>
+        /// <param name="stream">The stream to wrap.</param>
+        /// <param name="upper">If true force each symbol to upper case, otherwise force to lower.</param>
+        public CaseChangingCharStream(ICharStream stream, bool upper)
+        {
+            this.stream = stream;
+            this.upper = upper;
+        }
+
+        public int Index
+        {
+            get
+            {
+                return stream.Index;
+            }
+        }
+
+        public int Size
+        {
+            get
+            {
+                return stream.Size;
+            }
+        }
+
+        public string SourceName
+        {
+            get
+            {
+                return stream.SourceName;
+            }
+        }
+
+        public void Consume()
+        {
+            stream.Consume();
+        }
+
+        [return: NotNull]
+        public string GetText(Interval interval)
+        {
+            return stream.GetText(interval);
+        }
+
+        public int LA(int i)
+        {
+            int c = stream.LA(i);
+
+            if (c <= 0)
+            {
+                return c;
+            }
+
+            char o = (char)c;
+
+            if (upper)
+            {
+                return (int)char.ToUpperInvariant(o);
+            }
+
+            return (int)char.ToLowerInvariant(o);
+        }
+
+        public int Mark()
+        {
+            return stream.Mark();
+        }
+
+        public void Release(int marker)
+        {
+            stream.Release(marker);
+        }
+
+        public void Seek(int index)
+        {
+            stream.Seek(index);
+        }
+    }
+}

runtime/CSharp/runtime/CSharp/Antlr4.Runtime/CharStreams.cs

@@ -89,5 +89,27 @@ public static ICharStream fromstring(string s)
         {
             return new CodePointCharStream(s);
         }
+
+        /// <summary>
+        /// Takes the stream and forces all symbols to uppercase for lexing purposes 
+        /// but leaves the original text as-is.
+        /// </summary>
+        /// <param name="inStream"></param>
+        /// <returns></returns>
+        public static ICharStream toUpper(ICharStream inStream)
+        {
+            return new CaseChangingCharStream(inStream, true);
+        }
+
+        /// <summary>
+        /// Takes the stream and forces all symbols to lowercase for lexing purposes 
+        /// but leaves the original text as-is.
+        /// </summary>
+        /// <param name="inStream"></param>
+        /// <returns></returns>
+        public static ICharStream toLower(ICharStream inStream)
+        {
+            return new CaseChangingCharStream(inStream, false);
+        }
     }
 }