Newtonsoft.Json\Converters\RegexConverter.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Text.RegularExpressions;

using Newtonsoft.Json.Bson;

namespace Newtonsoft.Json.Converters

{

  /// <summary>

  /// Converts a <see cref="Regex"/> to and from JSON and BSON.

  /// </summary>

  public class RegexConverter : JsonConverter

  {

    /// <summary>

    /// Writes the JSON representation of the object.

    /// </summary>

    /// <param name="writer">The <see cref="JsonWriter"/> to write to.</param>

    /// <param name="value">The value.</param>

    /// <param name="serializer">The calling serializer.</param>

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

    {

      Regex regex = (Regex) value;

      BsonWriter bsonWriter = writer as BsonWriter;

      if (bsonWriter != null)

        WriteBson(bsonWriter, regex);

      else

        WriteJson(writer, regex);

    }

    private bool HasFlag(RegexOptions options, RegexOptions flag)

    {

      return ((options & flag) == flag);

    }

    private void WriteBson(BsonWriter writer, Regex regex)

    {

      // Regular expression - The first cstring is the regex pattern, the second

      // is the regex options string. Options are identified by characters, which 

      // must be stored in alphabetical order. Valid options are 'i' for case 

      // insensitive matching, 'm' for multiline matching, 'x' for verbose mode, 

      // 'l' to make \w, \W, etc. locale dependent, 's' for dotall mode 

      // ('.' matches everything), and 'u' to make \w, \W, etc. match unicode.

      string options = null;

      if (HasFlag(regex.Options, RegexOptions.IgnoreCase))

        options += "i";

      if (HasFlag(regex.Options, RegexOptions.Multiline))

        options += "m";

      if (HasFlag(regex.Options, RegexOptions.Singleline))

        options += "s";

      options += "u";

      if (HasFlag(regex.Options, RegexOptions.ExplicitCapture))

        options += "x";

      writer.WriteRegex(regex.ToString(), options);

    }

    private void WriteJson(JsonWriter writer, Regex regex)

    {

      writer.WriteStartObject();

      writer.WritePropertyName("Pattern");

      writer.WriteValue(regex.ToString());

      writer.WritePropertyName("Options");

      writer.WriteValue(regex.Options);

      writer.WriteEndObject();

    }

    /// <summary>

    /// Reads the JSON representation of the object.

    /// </summary>

    /// <param name="reader">The <see cref="JsonReader"/> to read from.</param>

    /// <param name="objectType">Type of the object.</param>

    /// <param name="existingValue">The existing value of object being read.</param>

    /// <param name="serializer">The calling serializer.</param>

    /// <returns>The object value.</returns>

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)

    {

      BsonReader bsonReader = reader as BsonReader;

      if (bsonReader != null)

        return ReadBson(bsonReader);

      else

        return ReadJson(reader);

    }

    private object ReadBson(BsonReader reader)

    {

      string regexText = (string)reader.Value;

      int patternOptionDelimiterIndex = regexText.LastIndexOf(@"/");

      string patternText = regexText.Substring(1, patternOptionDelimiterIndex - 1);

      string optionsText = regexText.Substring(patternOptionDelimiterIndex + 1);

      RegexOptions options = RegexOptions.None;

      foreach (char c in optionsText)

      {

        switch (c)

        {

          case 'i':

            options |= RegexOptions.IgnoreCase;

            break;

          case 'm':

            options |= RegexOptions.Multiline;

            break;

          case 's':

            options |= RegexOptions.Singleline;

            break;

          case 'x':

            options |= RegexOptions.ExplicitCapture;

            break;

        }

      }

      return new Regex(patternText, options);

    }

    private Regex ReadJson(JsonReader reader)

    {

      reader.Read();

      reader.Read();

      string pattern = (string) reader.Value;

      reader.Read();

      reader.Read();

      int options = Convert.ToInt32(reader.Value);

      reader.Read();

      return new Regex(pattern, (RegexOptions)options);

    }

    /// <summary>

    /// Determines whether this instance can convert the specified object type.

    /// </summary>

    /// <param name="objectType">Type of the object.</param>

    /// <returns>

    /// 	<c>true</c> if this instance can convert the specified object type; otherwise, <c>false</c>.

    /// </returns>

    public override bool CanConvert(Type objectType)

    {

      return (objectType == typeof (Regex));

    }

  }

}