public static bool TryParseByte(ReadOnlySpan <byte> text, out byte value, out int bytesConsumed, ParsedFormat format = default, SymbolTable symbolTable = null)
{
symbolTable = symbolTable ?? SymbolTable.InvariantUtf8;
if (!format.IsDefault && format.HasPrecision)
{
throw new NotImplementedException("Format with precision not supported.");
}
if (symbolTable == SymbolTable.InvariantUtf8)
{
if (Parsers.IsHexFormat(format))
{
return(Utf8Parser.Hex.TryParseByte(text, out value, out bytesConsumed));
}
else
{
return(Utf8Parser.TryParseByte(text, out value, out bytesConsumed));
}
}
else if (symbolTable == SymbolTable.InvariantUtf16)
{
ReadOnlySpan <char> utf16Text = text.NonPortableCast <byte, char>();
int charactersConsumed;
bool result;
if (Parsers.IsHexFormat(format))
{
result = Utf16Parser.Hex.TryParseByte(utf16Text, out value, out charactersConsumed);
}
else
{
result = Utf16Parser.TryParseByte(utf16Text, out value, out charactersConsumed);
}
bytesConsumed = charactersConsumed * sizeof(char);
return(result);
}
if (Parsers.IsHexFormat(format))
{
throw new NotImplementedException("The only supported encodings for hexadecimal parsing are InvariantUtf8 and InvariantUtf16.");
}
if (!(format.IsDefault || format.Symbol == 'G' || format.Symbol == 'g'))
{
throw new NotImplementedException(String.Format("Format '{0}' not supported.", format.Symbol));
}
SymbolTable.Symbol nextSymbol;
int thisSymbolConsumed;
if (!symbolTable.TryParse(text, out nextSymbol, out thisSymbolConsumed))
{
value = default;
bytesConsumed = 0;
return(false);
}
if (nextSymbol > SymbolTable.Symbol.D9)
{
value = default;
bytesConsumed = 0;
return(false);
}
uint parsedValue = (uint)nextSymbol;
int index = thisSymbolConsumed;
while (index < text.Length)
{
bool success = symbolTable.TryParse(text.Slice(index), out nextSymbol, out thisSymbolConsumed);
if (!success || nextSymbol > SymbolTable.Symbol.D9)
{
bytesConsumed = index;
value = (byte)parsedValue;
return(true);
}
// If parsedValue > (byte.MaxValue / 10), any more appended digits will cause overflow.
// if parsedValue == (byte.MaxValue / 10), any nextDigit greater than 5 implies overflow.
if (parsedValue > byte.MaxValue / 10 || (parsedValue == byte.MaxValue / 10 && nextSymbol > SymbolTable.Symbol.D5))
{
bytesConsumed = 0;
value = default;
return(false);
}
index += thisSymbolConsumed;
parsedValue = parsedValue * 10 + (uint)nextSymbol;
}
bytesConsumed = text.Length;
value = (byte)parsedValue;
return(true);
}
