public static bool TryParseInt32(ReadOnlySpan <byte> text, out int value, out int bytesConsumed, StandardFormat format = default, SymbolTable symbolTable = null)
{
bool isDefault = format.IsDefault;
symbolTable = symbolTable ?? SymbolTable.InvariantUtf8;
if (!isDefault && format.HasPrecision)
{
throw new NotImplementedException("Format with precision not supported.");
}
bool isHex = Parsers.IsHexFormat(format);
if (symbolTable == SymbolTable.InvariantUtf8)
{
return(isHex ? Utf8Parser.TryParse(text, out value, out bytesConsumed, 'X') :
Utf8Parser.TryParse(text, out value, out bytesConsumed));
}
else if (symbolTable == SymbolTable.InvariantUtf16)
{
/*return isHex ? InvariantUtf16.Hex.TryParseInt32(text, out value, out bytesConsumed) :
* InvariantUtf16.TryParseInt32(text, out value, out bytesConsumed);*/
ReadOnlySpan <char> utf16Text = MemoryMarshal.Cast <byte, char>(text);
bool result = isHex ? Utf16Parser.Hex.TryParseInt32(utf16Text, out value, out int charactersConsumed) :
Utf16Parser.TryParseInt32(utf16Text, out value, out charactersConsumed);
bytesConsumed = charactersConsumed * sizeof(char);
return(result);
}
if (isHex)
{
throw new NotImplementedException("The only supported encodings for hexadecimal parsing are InvariantUtf8 and InvariantUtf16.");
}
if (!(isDefault || format.Symbol == 'G' || format.Symbol == 'g'))
{
throw new NotImplementedException(String.Format("Format '{0}' not supported.", format.Symbol));
}
int textLength = text.Length;
if (textLength < 1)
{
goto FalseExit;
}
if (!symbolTable.TryParse(text, out SymbolTable.Symbol symbol, out int consumed))
{
goto FalseExit;
}
sbyte sign = 1;
int index = 0;
if (symbol == SymbolTable.Symbol.MinusSign)
{
sign = -1;
index += consumed;
if (index >= textLength)
{
goto FalseExit;
}
if (!symbolTable.TryParse(text.Slice(index), out symbol, out consumed))
{
goto FalseExit;
}
}
else if (symbol == SymbolTable.Symbol.PlusSign)
{
index += consumed;
if (index >= textLength)
{
goto FalseExit;
}
if (!symbolTable.TryParse(text.Slice(index), out symbol, out consumed))
{
goto FalseExit;
}
}
int answer = 0;
if (Parsers.IsValid(symbol))
{
int numBytes = consumed;
if (symbol == SymbolTable.Symbol.D0)
{
do
{
index += consumed;
if (index >= textLength)
{
goto Done;
}
if (!symbolTable.TryParse(text.Slice(index), out symbol, out consumed))
{
goto Done;
}
} while (symbol == SymbolTable.Symbol.D0);
if (!Parsers.IsValid(symbol))
{
goto Done;
}
}
int firstNonZeroDigitIndex = index;
if (textLength - firstNonZeroDigitIndex < Parsers.Int32OverflowLength * numBytes)
{
do
{
answer = answer * 10 + (int)symbol;
index += consumed;
if (index >= textLength)
{
goto Done;
}
if (!symbolTable.TryParse(text.Slice(index), out symbol, out consumed))
{
goto Done;
}
} while (Parsers.IsValid(symbol));
}
else
{
do
{
answer = answer * 10 + (int)symbol;
index += consumed;
if (index - firstNonZeroDigitIndex == (Parsers.Int32OverflowLength - 1) * numBytes)
{
if (!symbolTable.TryParse(text.Slice(index), out symbol, out consumed))
{
goto Done;
}
if (Parsers.IsValid(symbol))
{
if (Parsers.WillOverFlow(answer, (int)symbol, sign))
{
goto FalseExit;
}
answer = answer * 10 + (int)symbol;
index += consumed;
}
goto Done;
}
if (!symbolTable.TryParse(text.Slice(index), out symbol, out consumed))
{
goto Done;
}
} while (Parsers.IsValid(symbol));
}
goto Done;
}
FalseExit:
bytesConsumed = 0;
value = 0;
return(false);
Done:
bytesConsumed = index;
value = answer * sign;
return(true);
}
