Extremely fast Json encoder for c# with no dependancies (except StringBuilder).

Json.cs

/* 
 * Copyright 2017, 2018, 2019 Captive Reality Ltd - All Rights Reserved
 * Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is 
 * hereby granted, provided that the above copyright notice and this permission notice appear in all copies.
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE 
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE
 * FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, 
 * ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 * 
 * Source: https://gist.github.com/markcastle/324cb4fa03048404ee1ecbac5174a7b5
 * 
 * Description: 
 * Extremely fast Json encoder for c# with no dependancies (except StringBuilder).
 * This is not a json parser.
 * We can also automatically do some auto escaping.
 * Written by Mark Castle <mark.castle@captivereality.com>, July 2017
 *
 * Usage: 
 * 
 * Utils.Json json = new Utils.Json();
 * json.Add("App", "AppName");
 * json.Add("Integer1", intVariable1);
 * json.Add("Integer2", intVariable2);
 * json.Add("Integer3", intVariable3);
 * return json.toString();
 * 
 * Changelog:
 * 26/07/2017 - Created by MC
 * 
 * references:
 * 
 */

using System;
using System.Text;

namespace CaptiveReality.Utils
{
    /// <summary>
    /// Very fast Json builder utility.
    /// Builds JSON only (eg, Cannot Parse Json)
    /// </summary>
    public class Json
    {

        StringBuilder _json = new StringBuilder();

        /// <summary>
        /// Constructor
        /// </summary>
        public Json()
        {

        }

        /// <summary>
        /// Add a string value
        /// </summary>
        /// <param name="name"></param>
        /// <param name="value"></param>
        public void AddJson(string name, string value)
        {
            if (_json.Length != 0)
            {
                _json.Append(",");

            }
            _json.Append("\"").Append(name).Append("\":").Append(value);

        }

        public void Append(string jsonToAppend)
        {
            if (_json.Length != 0)
            {
                _json.Append(",");

            }
            _json.Append(jsonToAppend);
        }

        /// <summary>
        /// Merge a json string with our existing json.
        /// </summary>
        /// <param name="jsonToMerge"></param>
        public void Merge(string jsonToMerge)
        {
            if (_json.Length != 0)
            {
                _json.Append(",");
            }

            _json.Append(jsonToMerge.TrimStart('{').TrimEnd('}'));
        }

        /// <summary>
        /// Add a float
        /// Converts floats using zero decimal places.  Possibly not what is wanted for most normal use, but it is what I want for memory bytes.
        /// </summary>
        /// <param name="name"></param>
        /// <param name="value"></param>
        public void Add(string name, float value)
        {
            if (_json.Length != 0)
            {
                _json.Append(",");

            }
            _json.Append("\"").Append(name).Append("\":").Append(value.ToString("{0:0.#######}"));
        }

        /// <summary>
        /// Add an integer value
        /// </summary>
        /// <param name="name"></param>
        /// <param name="value"></param>
        public void Add(string name, int value)
        {
            if (_json.Length != 0)
            {
                _json.Append(",");

            }
            _json.Append("\"").Append(name).Append("\":").Append(value.ToString());

        }

        /// <summary>
        /// Add Json
        /// </summary>
        /// <param name="name"></param>
        /// <param name="value"></param>
        public void Add(string name, Json value)
        {
            if (_json.Length != 0)
            {
                _json.Append(",");

            }
            _json.Append("\"").Append(name).Append("\":").Append(value.toString());

        }

        /// <summary>
        /// Add string with auto escaping
        /// </summary>
        /// <param name="name"></param>
        /// <param name="value"></param>
        /// <param name="cleanForJson"></param>
        public void Add(string name, string value, bool cleanForJson = true)
        {
            if (_json.Length != 0)
            {
                _json.Append(",");

            }
            _json.Append("\"").Append(name).Append("\":").Append("\"").Append((cleanForJson ? escapeForJson(value) : value)).Append("\"");

        }

        /// <summary>
        /// Add a bool
        /// </summary>
        /// <param name="name"></param>
        /// <param name="value"></param>
        public void Add(string name, bool value)
        {
            if (_json.Length != 0)
            {
                _json.Append(",");

            }
            _json.Append("\"").Append(name).Append("\":").Append((value ? "true" : "false"));

        }

        /// <summary>
        /// Clear everything
        /// </summary>
        public void Clear()
        {
            _json = new StringBuilder();
        }

        /// <summary>
        /// Convert to a string
        /// </summary>
        /// <returns></returns>
        public string toString()
        {

            return "{" + _json.ToString() + "}";
        }

        /// <summary>
        /// Return the string builder representation
        /// </summary>
        /// <returns></returns>
        public StringBuilder toStringBuilder()
        {
            return _json;
        }

        /// <summary>
        /// Append
        /// </summary>
        /// <param name="jsonToAppend"></param>
        public void Append(StringBuilder jsonToAppend)
        {
            if (_json.Length != 0)
            {
                _json.Append(",");

            }
            _json.Append(jsonToAppend);
        }


        /// <summary>
        /// Auto string escaping
        /// </summary>
        /// <param name="s"></param>
        /// <returns></returns>
        public static string escapeForJson(string s)
        {
            if (s == null || s.Length == 0)
            {
                return "";
            }

            char c = '\0';
            int i;
            int len = s.Length;
            StringBuilder sb = new StringBuilder(len + 4);
            string t;

            for (i = 0; i < len; i += 1)
            {
                c = s[i];
                switch (c)
                {
                    case '\\':
                    case '"':
                        sb.Append('\\');
                        sb.Append(c);
                        break;
                    case '/':
                        sb.Append('\\');
                        sb.Append(c);
                        break;
                    case '\b':
                        sb.Append("\\b");
                        break;
                    case '\t':
                        sb.Append("\\t");
                        break;
                    case '\n':
                        sb.Append("\\n");
                        break;
                    case '\f':
                        sb.Append("\\f");
                        break;
                    case '\r':
                        sb.Append("\\r");
                        break;
                    default:
                        if (c < ' ')
                        {
                            t = "000" + String.Format("X", c);
                            sb.Append("\\u" + t.Substring(t.Length - 4));
                        }
                        else
                        {
                            sb.Append(c);
                        }
                        break;
                }
            }
            return sb.ToString();
        }
    }

}