JSON.cs

using System;
using System.Text;
using System.Collections;
using System.Globalization;

public class JSON
{
	public const int TOKEN_NONE = 0;
	public const int TOKEN_CURLY_OPEN = 1;
	public const int TOKEN_CURLY_CLOSE = 2;
	public const int TOKEN_SQUARED_OPEN = 3;
	public const int TOKEN_SQUARED_CLOSE = 4;
	public const int TOKEN_COLON = 5;
	public const int TOKEN_COMMA = 6;
	public const int TOKEN_STRING = 7;
	public const int TOKEN_NUMBER = 8;
	public const int TOKEN_TRUE = 9;
	public const int TOKEN_FALSE = 10;
	public const int TOKEN_NULL = 11;

	private const int BUILDER_CAPACITY = 2000;

	/// <summary>
	/// Parses the string json into a value
	/// </summary>
	/// <param name="json">A JSON string.</param>
	/// <returns>An ArrayList, a Hashtable, a double, a string, null, true, or false</returns>
	public static object Decode(string json)
	{
		bool success = true;

		return Decode(json, ref success);
	}

	/// <summary>
	/// Parses the string json into a value; and fills 'success' with the successfullness of the parse.
	/// </summary>
	/// <param name="json">A JSON string.</param>
	/// <param name="success">Successful parse?</param>
	/// <returns>An ArrayList, a Hashtable, a double, a string, null, true, or false</returns>
	public static object Decode(string json, ref bool success)
	{
		success = true;
		if (json != null) {
			char[] charArray = json.ToCharArray();
			int index = 0;
			object value = ParseValue(charArray, ref index, ref success);
			return value;
		} else {
			return null;
		}
	}

	/// <summary>
	/// Converts a Hashtable / ArrayList object into a JSON string
	/// </summary>
	/// <param name="json">A Hashtable / ArrayList</param>
	/// <returns>A JSON encoded string, or null if object 'json' is not serializable</returns>
	public static string Encode(object json)
	{
		StringBuilder builder = new StringBuilder(BUILDER_CAPACITY);
		bool success = SerializeValue(json, builder);
		return (success ? builder.ToString() : null);
	}

	protected static Hashtable ParseObject(char[] json, ref int index, ref bool success)
	{
		Hashtable table = new Hashtable();
		int token;

		// {
		NextToken(json, ref index);

		bool done = false;
		while (!done) {
			token = LookAhead(json, index);
			if (token == JSON.TOKEN_NONE) {
				success = false;
				return null;
			} else if (token == JSON.TOKEN_COMMA) {
				NextToken(json, ref index);
			} else if (token == JSON.TOKEN_CURLY_CLOSE) {
				NextToken(json, ref index);
				return table;
			} else {

				// name
				string name = ParseString(json, ref index, ref success);
				if (!success) {
					success = false;
					return null;
				}

				// :
				token = NextToken(json, ref index);
				if (token != JSON.TOKEN_COLON) {
					success = false;
					return null;
				}

				// value
				object value = ParseValue(json, ref index, ref success);
				if (!success) {
					success = false;
					return null;
				}

				table[name] = value;
			}
		}

		return table;
	}

	protected static ArrayList ParseArray(char[] json, ref int index, ref bool success)
	{
		ArrayList array = new ArrayList();

		// [
		NextToken(json, ref index);

		bool done = false;
		while (!done) {
			int token = LookAhead(json, index);
			if (token == JSON.TOKEN_NONE) {
				success = false;
				return null;
			} else if (token == JSON.TOKEN_COMMA) {
				NextToken(json, ref index);
			} else if (token == JSON.TOKEN_SQUARED_CLOSE) {
				NextToken(json, ref index);
				break;
			} else {
				object value = ParseValue(json, ref index, ref success);
				if (!success) {
					return null;
				}

				array.Add(value);
			}
		}

		return array;
	}

	protected static object ParseValue(char[] json, ref int index, ref bool success)
	{
		switch (LookAhead(json, index)) {
			case JSON.TOKEN_STRING:
				return ParseString(json, ref index, ref success);
			case JSON.TOKEN_NUMBER:
				return ParseNumber(json, ref index);
			case JSON.TOKEN_CURLY_OPEN:
				return ParseObject(json, ref index, ref success);
			case JSON.TOKEN_SQUARED_OPEN:
				return ParseArray(json, ref index, ref success);
			case JSON.TOKEN_TRUE:
				NextToken(json, ref index);
				return Boolean.Parse("TRUE");
			case JSON.TOKEN_FALSE:
				NextToken(json, ref index);
				return Boolean.Parse("FALSE");
			case JSON.TOKEN_NULL:
				NextToken(json, ref index);
				return null;
			case JSON.TOKEN_NONE:
				break;
		}

		success = false;
		return null;
	}

	protected static string ParseString(char[] json, ref int index, ref bool success)
	{
		StringBuilder s = new StringBuilder(BUILDER_CAPACITY);
		char c;

		EatWhitespace(json, ref index);

		// "
		c = json[index++];

		bool complete = false;
		while (!complete) {

			if (index == json.Length) {
				break;
			}

			c = json[index++];
			if (c == '"') {
				complete = true;
				break;
			} else if (c == '\\') {

				if (index == json.Length) {
					break;
				}
				c = json[index++];
				if (c == '"') {
					s.Append('"');
				} else if (c == '\\') {
					s.Append('\\');
				} else if (c == '/') {
					s.Append('/');
				} else if (c == 'b') {
					s.Append('\b');
				} else if (c == 'f') {
					s.Append('\f');
				} else if (c == 'n') {
					s.Append('\n');
				} else if (c == 'r') {
					s.Append('\r');
				} else if (c == 't') {
					s.Append('\t');
				} else if (c == 'u') {
					int remainingLength = json.Length - index;
					if (remainingLength >= 4) {
						// fetch the next 4 chars
						char[] unicodeCharArray = new char[4];
						Array.Copy(json, index, unicodeCharArray, 0, 4);
						// parse the 32 bit hex into an integer codepoint
						uint codePoint = UInt32.Parse(new string(unicodeCharArray), NumberStyles.HexNumber);
						// convert the integer codepoint to a unicode char and add to string
						s.Append(Char.ConvertFromUtf32((int)codePoint));
						// skip 4 chars
						index += 4;
					} else {
						break;
					}
				}

			} else {
				s.Append(c);
			}

		}

		if (!complete) {
			success = false;
			return null;
		}

		return s.ToString();
	}

	protected static double ParseNumber(char[] json, ref int index)
	{
		EatWhitespace(json, ref index);

		int lastIndex = GetLastIndexOfNumber(json, index);
		int charLength = (lastIndex - index) + 1;
		char[] numberCharArray = new char[charLength];

		Array.Copy(json, index, numberCharArray, 0, charLength);
		index = lastIndex + 1;
		return Double.Parse(new string(numberCharArray), CultureInfo.InvariantCulture);
	}

	protected static int GetLastIndexOfNumber(char[] json, int index)
	{
		int lastIndex;

		for (lastIndex = index; lastIndex < json.Length; lastIndex++) {
			if ("0123456789+-.eE".IndexOf(json[lastIndex]) == -1) {
				break;
			}
		}
		return lastIndex - 1;
	}

	protected static void EatWhitespace(char[] json, ref int index)
	{
		for (; index < json.Length; index++) {
			if (" \t\n\r".IndexOf(json[index]) == -1) {
				break;
			}
		}
	}

	protected static int LookAhead(char[] json, int index)
	{
		int saveIndex = index;
		return NextToken(json, ref saveIndex);
	}

	protected static int NextToken(char[] json, ref int index)
	{
		EatWhitespace(json, ref index);

		if (index == json.Length) {
			return JSON.TOKEN_NONE;
		}

		char c = json[index];
		index++;
		switch (c) {
			case '{':
				return JSON.TOKEN_CURLY_OPEN;
			case '}':
				return JSON.TOKEN_CURLY_CLOSE;
			case '[':
				return JSON.TOKEN_SQUARED_OPEN;
			case ']':
				return JSON.TOKEN_SQUARED_CLOSE;
			case ',':
				return JSON.TOKEN_COMMA;
			case '"':
				return JSON.TOKEN_STRING;
			case '0': case '1': case '2': case '3': case '4':
			case '5': case '6': case '7': case '8': case '9':
			case '-':
				return JSON.TOKEN_NUMBER;
			case ':':
				return JSON.TOKEN_COLON;
		}
		index--;

		int remainingLength = json.Length - index;

		// false
		if (remainingLength >= 5) {
			if (json[index] == 'f' &&
				json[index + 1] == 'a' &&
				json[index + 2] == 'l' &&
				json[index + 3] == 's' &&
				json[index + 4] == 'e') {
				index += 5;
				return JSON.TOKEN_FALSE;
			}
		}

		// true
		if (remainingLength >= 4) {
			if (json[index] == 't' &&
				json[index + 1] == 'r' &&
				json[index + 2] == 'u' &&
				json[index + 3] == 'e') {
				index += 4;
				return JSON.TOKEN_TRUE;
			}
		}

		// null
		if (remainingLength >= 4) {
			if (json[index] == 'n' &&
				json[index + 1] == 'u' &&
				json[index + 2] == 'l' &&
				json[index + 3] == 'l') {
				index += 4;
				return JSON.TOKEN_NULL;
			}
		}

		return JSON.TOKEN_NONE;
	}

	protected static bool SerializeObjectOrArray(object objectOrArray, StringBuilder builder)
	{
		if (objectOrArray is Hashtable) {
			return SerializeObject((Hashtable)objectOrArray, builder);
		} else if (objectOrArray is ArrayList) {
			return SerializeArray((ArrayList)objectOrArray, builder);
		} else {
			return false;
		}
	}

	protected static bool SerializeObject(Hashtable anObject, StringBuilder builder)
	{
		builder.Append("{");

		IDictionaryEnumerator e = anObject.GetEnumerator();
		bool first = true;
		while (e.MoveNext()) {
			string key = e.Key.ToString();
			object value = e.Value;

			if (!first) {
				builder.Append(", ");
			}

			SerializeString(key, builder);
			builder.Append(":");
			if (!SerializeValue(value, builder)) {
				return false;
			}

			first = false;
		}

		builder.Append("}");
		return true;
	}

	protected static bool SerializeArray(ArrayList anArray, StringBuilder builder)
	{
		builder.Append("[");

		bool first = true;
		for (int i = 0; i < anArray.Count; i++) {
			object value = anArray[i];

			if (!first) {
				builder.Append(", ");
			}

			if (!SerializeValue(value, builder)) {
				return false;
			}

			first = false;
		}

		builder.Append("]");
		return true;
	}

	protected static bool SerializeValue(object value, StringBuilder builder)
	{
		if (value is string) {
			SerializeString((string)value, builder);
		} else if (value is Hashtable) {
			SerializeObject((Hashtable)value, builder);
		} else if (value is ArrayList) {
			SerializeArray((ArrayList)value, builder);
		} else if (IsNumeric(value)) {
			SerializeNumber(Convert.ToDouble(value), builder);
		} else if ((value is Boolean) && ((Boolean)value == true)) {
			builder.Append("true");
		} else if ((value is Boolean) && ((Boolean)value == false)) {
			builder.Append("false");
		} else if (value == null) {
			builder.Append("null");
		} else {
			return false;
		}
		return true;
	}

	protected static void SerializeString(string aString, StringBuilder builder)
	{
		builder.Append("\"");

		char[] charArray = aString.ToCharArray();
		for (int i = 0; i < charArray.Length; i++) {
			char c = charArray[i];
			if (c == '"') {
				builder.Append("\\\"");
			} else if (c == '\\') {
				builder.Append("\\\\");
			} else if (c == '\b') {
				builder.Append("\\b");
			} else if (c == '\f') {
				builder.Append("\\f");
			} else if (c == '\n') {
				builder.Append("\\n");
			} else if (c == '\r') {
				builder.Append("\\r");
			} else if (c == '\t') {
				builder.Append("\\t");
			} else {
				int codepoint = Convert.ToInt32(c);
				if ((codepoint >= 32) && (codepoint <= 126)) {
					builder.Append(c);
				} else {
					builder.Append("\\u" + Convert.ToString(codepoint, 16).PadLeft(4, '0'));
				}
			}
		}

		builder.Append("\"");
	}

	protected static void SerializeNumber(double number, StringBuilder builder)
	{
		builder.Append(Convert.ToString(number, CultureInfo.InvariantCulture));
	}

	/// <summary>
	/// Determines if a given object is numeric in any way
	/// (can be integer, double, null, etc).
	///
	/// Thanks to mtighe for pointing out Double.TryParse to me.
	/// </summary>
	protected static bool IsNumeric(object o)
	{
		double result;

		return (o == null) ? false : Double.TryParse(o.ToString(), out result);
	}


	/*
	 * Expando extension. Requires C# 4.
	 * Thanks to Andrew Steward Gibson
	 *
	 * Remove the space between * and / on the line below if C# 4 is available, and uncomment the "using" statement at the top of the file:
	 * /

	/// <summary>
	/// Decodes json string and turns it into an Expando object.
	/// </summary>
	/// <param name="json">The JSON string to be hydrated</param>
	/// <returns>ExpandoObject</returns>
	public static dynamic JsonHydrate(string json)
	{
		dynamic ret = new ExpandoObject();
		ret.Parsed = (Hashtable)Decode(json);
		Parse(ret, ret.Parsed);
		return ret;
	}

	/// <summary>
	/// Recursively parses a hashtable of key value pairs into a graph of dynamic objects.
	/// </summary>
	/// <param name="decorationTarget"></param>
	/// <param name="table"></param>
	private static void Parse(dynamic decorationTarget, Hashtable table)
	{
		foreach (string key in table.Keys) {
			IDictionary<string, object> retDict = decorationTarget;
			object propertyValue = table[key];
			if (propertyValue is Hashtable) {
				dynamic nestedObject = new ExpandoObject();
				Parse(nestedObject, (Hashtable)propertyValue);
				propertyValue = nestedObject;
			}
			((IDictionary<string, object>)decorationTarget).Add(key, propertyValue);
		}
	}

	// */
}