src/Lucene.Net.Highlighter/Highlight/SimpleHTMLEncoder.cs

using System.Text;

namespace Lucene.Net.Search.Highlight
{
    /*
     * 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>
    /// Simple <see cref="IEncoder"/> implementation to escape text for HTML output
    /// </summary>
    public class SimpleHTMLEncoder : IEncoder
    {
        public SimpleHTMLEncoder()
        {
        }

        public string EncodeText(string originalText)
        {
            return HtmlEncode(originalText);
        }

        /// <summary>
        /// Encode string into HTML
        /// </summary>
        public static string HtmlEncode(string plainText)
        {
            if (string.IsNullOrEmpty(plainText))
            {
                return string.Empty;
            }

            var result = new StringBuilder(plainText.Length);

            for (int index = 0; index < plainText.Length; index++)
            {
                char ch = plainText[index];

                switch (ch)
                {
                    case '"':
                        result.Append("&quot;");
                        break;

                    case '&':
                        result.Append("&amp;");
                        break;

                    case '<':
                        result.Append("&lt;");
                        break;

                    case '>':
                        result.Append("&gt;");
                        break;

                    case '\'':
                        result.Append("&#x27;");
                        break;

                    case '/':
                        result.Append("&#x2F;");
                        break;

                    default:
                        // LUCENENET TODO: This logic appears to be correct, but need to 
                        // verify and create/alter unit tests to accommodate this change
                        if (ch < 128)
                        {
                            result.Append(ch);
                        }
                        else
                        {
                            result.Append("&#").Append((int)ch).Append(";");
                        }
                        break;
                }
            }

            return result.ToString();
        }
    }
}