/// <summary>
/// Attempt to parse a string into a JSONObject.
/// </summary>
/// <param name="jsonString"></param>
/// <returns>A new JSONObject or null if parsing fails.</returns>
public static JSONObject Parse(string jsonString)
{
if (string.IsNullOrEmpty(jsonString))
{
return(null);
}
JSONValue currentValue = null;
var keyList = new List <string>();
var state = JSONParsingState.Object;
for (var startPosition = 0; startPosition < jsonString.Length; ++startPosition)
{
startPosition = SkipWhitespace(jsonString, startPosition);
switch (state)
{
case JSONParsingState.Object:
if (jsonString[startPosition] != '{')
{
return(Fail('{', startPosition));
}
JSONValue newObj = new JSONObject();
if (currentValue != null)
{
newObj.Parent = currentValue;
}
currentValue = newObj;
state = JSONParsingState.Key;
break;
case JSONParsingState.EndObject:
if (jsonString[startPosition] != '}')
{
return(Fail('}', startPosition));
}
if (currentValue.Parent == null)
{
return(currentValue.Obj);
}
switch (currentValue.Parent.Type)
{
case JSONValueType.Object:
currentValue.Parent.Obj.values[keyList.Pop()] = new JSONValue(currentValue.Obj);
break;
case JSONValueType.Array:
currentValue.Parent.Array.Add(new JSONValue(currentValue.Obj));
break;
default:
return(Fail("valid object", startPosition));
}
currentValue = currentValue.Parent;
state = JSONParsingState.ValueSeparator;
break;
case JSONParsingState.Key:
if (jsonString[startPosition] == '}')
{
--startPosition;
state = JSONParsingState.EndObject;
break;
}
var key = ParseString(jsonString, ref startPosition);
if (key == null)
{
return(Fail("key string", startPosition));
}
keyList.Add(key);
state = JSONParsingState.KeyValueSeparator;
break;
case JSONParsingState.KeyValueSeparator:
if (jsonString[startPosition] != ':')
{
return(Fail(':', startPosition));
}
state = JSONParsingState.Value;
break;
case JSONParsingState.ValueSeparator:
switch (jsonString[startPosition])
{
case ',':
state = currentValue.Type == JSONValueType.Object ? JSONParsingState.Key : JSONParsingState.Value;
break;
case '}':
state = JSONParsingState.EndObject;
--startPosition;
break;
case ']':
state = JSONParsingState.EndArray;
--startPosition;
break;
default:
return(Fail(", } ]", startPosition));
}
break;
case JSONParsingState.Value: {
var c = jsonString[startPosition];
if (c == '"')
{
state = JSONParsingState.String;
}
else if (char.IsDigit(c) || c == '-')
{
state = JSONParsingState.Number;
}
else
{
switch (c)
{
case '{':
state = JSONParsingState.Object;
break;
case '[':
state = JSONParsingState.Array;
break;
case ']':
if (currentValue.Type == JSONValueType.Array)
{
state = JSONParsingState.EndArray;
}
else
{
return(Fail("valid array", startPosition));
}
break;
case 'f':
case 't':
state = JSONParsingState.Boolean;
break;
case 'n':
state = JSONParsingState.Null;
break;
default:
return(Fail("beginning of value", startPosition));
}
}
--startPosition; //To re-evaluate this char in the newly selected state
break;
}
case JSONParsingState.String:
var str = ParseString(jsonString, ref startPosition);
if (str == null)
{
return(Fail("string value", startPosition));
}
switch (currentValue.Type)
{
case JSONValueType.Object:
currentValue.Obj.values[keyList.Pop()] = new JSONValue(str);
break;
case JSONValueType.Array:
currentValue.Array.Add(str);
break;
default:
JSONLogger.Error("Fatal error, current JSON value not valid");
return(null);
}
state = JSONParsingState.ValueSeparator;
break;
case JSONParsingState.Number:
var number = ParseNumber(jsonString, ref startPosition);
if (double.IsNaN(number))
{
return(Fail("valid number", startPosition));
}
switch (currentValue.Type)
{
case JSONValueType.Object:
currentValue.Obj.values[keyList.Pop()] = new JSONValue(number);
break;
case JSONValueType.Array:
currentValue.Array.Add(number);
break;
default:
JSONLogger.Error("Fatal error, current JSON value not valid");
return(null);
}
state = JSONParsingState.ValueSeparator;
break;
case JSONParsingState.Boolean:
if (jsonString[startPosition] == 't')
{
if (jsonString.Length < startPosition + 4 ||
jsonString[startPosition + 1] != 'r' ||
jsonString[startPosition + 2] != 'u' ||
jsonString[startPosition + 3] != 'e')
{
return(Fail("true", startPosition));
}
switch (currentValue.Type)
{
case JSONValueType.Object:
currentValue.Obj.values[keyList.Pop()] = new JSONValue(true);
break;
case JSONValueType.Array:
currentValue.Array.Add(new JSONValue(true));
break;
default:
JSONLogger.Error("Fatal error, current JSON value not valid");
return(null);
}
startPosition += 3;
}
else
{
if (jsonString.Length < startPosition + 5 ||
jsonString[startPosition + 1] != 'a' ||
jsonString[startPosition + 2] != 'l' ||
jsonString[startPosition + 3] != 's' ||
jsonString[startPosition + 4] != 'e')
{
return(Fail("false", startPosition));
}
switch (currentValue.Type)
{
case JSONValueType.Object:
currentValue.Obj.values[keyList.Pop()] = new JSONValue(false);
break;
case JSONValueType.Array:
currentValue.Array.Add(new JSONValue(false));
break;
default:
JSONLogger.Error("Fatal error, current JSON value not valid");
return(null);
}
startPosition += 4;
}
state = JSONParsingState.ValueSeparator;
break;
case JSONParsingState.Array:
if (jsonString[startPosition] != '[')
{
return(Fail('[', startPosition));
}
JSONValue newArray = new JSONArray();
if (currentValue != null)
{
newArray.Parent = currentValue;
}
currentValue = newArray;
state = JSONParsingState.Value;
break;
case JSONParsingState.EndArray:
if (jsonString[startPosition] != ']')
{
return(Fail(']', startPosition));
}
if (currentValue.Parent == null)
{
return(currentValue.Obj);
}
switch (currentValue.Parent.Type)
{
case JSONValueType.Object:
currentValue.Parent.Obj.values[keyList.Pop()] = new JSONValue(currentValue.Array);
break;
case JSONValueType.Array:
currentValue.Parent.Array.Add(new JSONValue(currentValue.Array));
break;
default:
return(Fail("valid object", startPosition));
}
currentValue = currentValue.Parent;
state = JSONParsingState.ValueSeparator;
break;
case JSONParsingState.Null:
if (jsonString[startPosition] == 'n')
{
if (jsonString.Length < startPosition + 4 ||
jsonString[startPosition + 1] != 'u' ||
jsonString[startPosition + 2] != 'l' ||
jsonString[startPosition + 3] != 'l')
{
return(Fail("null", startPosition));
}
switch (currentValue.Type)
{
case JSONValueType.Object:
currentValue.Obj.values[keyList.Pop()] = new JSONValue(JSONValueType.Null);
break;
case JSONValueType.Array:
currentValue.Array.Add(new JSONValue(JSONValueType.Null));
break;
default:
JSONLogger.Error("Fatal error, current JSON value not valid");
return(null);
}
startPosition += 3;
}
state = JSONParsingState.ValueSeparator;
break;
}
}
JSONLogger.Error("Unexpected end of string");
return(null);
}
static JSONObject Fail(string expected, int position)
{
JSONLogger.Error("Invalid json string, expecting " + expected + " at " + position);
return(null);
}