API: Lucene.Net.Support: Added StringBuilderCharSequenceWrapper class…

… and StringBuilder.ToCharSequence() extension method.

src/Lucene.Net/Support/StringBuilderCharSequenceWrapper.cs

@@ -0,0 +1,74 @@
+using System;
+using System.Text;
+
+namespace Lucene.Net.Support
+{
+    /*
+	 * Licensed to the Apache Software Foundation (ASF) under one or more
+	 * contributor license agreements.  See the NOTICE file distributed with
+	 * this work for additional information regarding copyright ownership.
+	 * The ASF licenses this file to You under the Apache License, Version 2.0
+	 * (the "License"); you may not use this file except in compliance with
+	 * the License.  You may obtain a copy of the License at
+	 *
+	 *     http://www.apache.org/licenses/LICENSE-2.0
+	 *
+	 * Unless required by applicable law or agreed to in writing, software
+	 * distributed under the License is distributed on an "AS IS" BASIS,
+	 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+	 * See the License for the specific language governing permissions and
+	 * limitations under the License.
+	 */
+
+    /// <summary>
+    /// An adapter for <see cref="StringBuilder"/> that implements <see cref="ICharSequence"/>
+    /// </summary>
+    public class StringBuilderCharSequenceWrapper : ICharSequence
+    {
+        private readonly StringBuilder value;
+
+        public StringBuilderCharSequenceWrapper(StringBuilder wrappedValue)
+        {
+            if (wrappedValue == null)
+                throw new ArgumentNullException("wrappedValue");
+
+            this.value = wrappedValue;
+        }
+
+        // LUCENENET specific - added to .NETify
+        public char this[int index]
+        {
+            get { return value[index]; }
+        }
+
+        public int Length
+        {
+            get { return value.Length; }
+        }
+
+        public ICharSequence SubSequence(int start, int end)
+        {
+            return new StringCharSequenceWrapper(value.ToString(start, end - start));
+        }
+
+        public override int GetHashCode()
+        {
+            return value.GetHashCode();
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (obj == null)
+                return false;
+            if (!(obj is StringBuilder))
+                return false;
+
+            return value.Equals(obj as StringBuilder);
+        }
+
+        public override string ToString()
+        {
+            return value.ToString();
+        }
+    }
+}

src/Lucene.Net/Support/StringBuilderExtensions.cs

@@ -216,5 +216,14 @@ public static int IndexOf(this StringBuilder text, string value, int startIndex)
 
             return -1;
         }
+
+        /// <summary>
+        /// Convenience method to wrap a string in a <see cref="StringBuilderCharSequenceWrapper"/>
+        /// so a <see cref="StringBuilder"/> can be used as <see cref="ICharSequence"/> in .NET.
+        /// </summary>
+        public static ICharSequence ToCharSequence(this StringBuilder text)
+        {
+            return new StringBuilderCharSequenceWrapper(text);
+        }
     }
 }