/// <summary>
/// Eats the next four characters, assuming hex digits, and converts
/// into the represented character value.
/// </summary>
/// <returns>The parsed character.</returns>
private static char ParseHex(BufferedCharReader input, char[] hexDigits)
{
Debug.Assert(input != null);
Debug.Assert(hexDigits != null);
Debug.Assert(hexDigits.Length == 4);
hexDigits[0] = input.Next();
hexDigits[1] = input.Next();
hexDigits[2] = input.Next();
hexDigits[3] = input.Next();
return((char)ushort.Parse(new string(hexDigits), NumberStyles.HexNumber));
}
/// <summary>
/// Parses the next token from the input and returns it.
/// </summary>
private JsonToken Parse()
{
char ch = NextClean();
//
// String
//
if (ch == '"' || ch == '\'')
{
return(Yield(JsonToken.String(NextString(ch))));
}
//
// Object
//
if (ch == '{')
{
_reader.Back();
return(ParseObject());
}
//
// Array
//
if (ch == '[')
{
_reader.Back();
return(ParseArray());
}
//
// Handle unquoted text. This could be the values true, false, or
// null, or it can be a number. An implementation (such as this one)
// is allowed to also accept non-standard forms.
//
// Accumulate characters until we reach the end of the text or a
// formatting character.
//
StringBuilder sb = new StringBuilder();
char b = ch;
while (ch >= ' ' && ",:]}/\\\"[{;=#".IndexOf(ch) < 0)
{
sb.Append(ch);
ch = _reader.Next();
}
_reader.Back();
string s = sb.ToString().Trim();
if (s.Length == 0)
{
throw SyntaxError("Missing value.");
}
//
// Boolean
//
if (s == JsonBoolean.TrueText || s == JsonBoolean.FalseText)
{
return(Yield(JsonToken.Boolean(s == JsonBoolean.TrueText)));
}
//
// Null
//
if (s == JsonNull.Text)
{
return(Yield(JsonToken.Null()));
}
//
// Number
//
// Try converting it. We support the 0- and 0x- conventions.
// If a number cannot be produced, then the value will just
// be a string. Note that the 0-, 0x-, plus, and implied
// string conventions are non-standard, but a JSON text parser
// is free to accept non-JSON text forms as long as it accepts
// all correct JSON text forms.
//
if ((b >= '0' && b <= '9') || b == '.' || b == '-' || b == '+')
{
if (b == '0' && s.Length > 1 && s.IndexOfAny(_numNonDigitChars) < 0)
{
if (s.Length > 2 && (s[1] == 'x' || s[1] == 'X'))
{
string parsed = TryParseHex(s);
if (!ReferenceEquals(parsed, s))
{
return(Yield(JsonToken.Number(parsed)));
}
}
else
{
string parsed = TryParseOctal(s);
if (!ReferenceEquals(parsed, s))
{
return(Yield(JsonToken.Number(parsed)));
}
}
}
else
{
if (!JsonNumber.IsValid(s))
{
throw SyntaxError(string.Format("The text '{0}' has the incorrect syntax for a number.", s));
}
return(Yield(JsonToken.Number(s)));
}
}
//
// Treat as String in all other cases, e.g. when unquoted.
//
return(Yield(JsonToken.String(s)));
}
internal static StringBuilder Dequote(BufferedCharReader input, char quote, StringBuilder output)
{
Debug.Assert(input != null);
if (output == null)
{
output = new StringBuilder();
}
char[] hexDigits = null;
while (true)
{
char ch = input.Next();
if ((ch == BufferedCharReader.EOF) || (ch == '\n') || (ch == '\r'))
{
throw new FormatException("Unterminated string.");
}
if (ch == '\\')
{
ch = input.Next();
switch (ch)
{
case 'b': output.Append('\b'); break; // Backspace
case 't': output.Append('\t'); break; // Horizontal tab
case 'n': output.Append('\n'); break; // Newline
case 'f': output.Append('\f'); break; // Form feed
case 'r': output.Append('\r'); break; // Carriage return
case 'u':
{
if (hexDigits == null)
{
hexDigits = new char[4];
}
output.Append(ParseHex(input, hexDigits));
break;
}
default:
output.Append(ch);
break;
}
}
else
{
if (ch == quote)
{
return(output);
}
output.Append(ch);
}
}
}