C / C++ / MFC

int String::ToInteger(String string)
{
	size_t index = 0;
	bool leadSpace = true;
	bool isValue = true;
	bool minus = false;
	int value = 0;
	
	try
	{
		// first scanning if the string has non-numbers
		while(leadSpace)
		{
			TCHAR tcRet = string.GetCharAt(index);
			if (((tcRet < TEXT('0')) || (tcRet > TEXT('9')) ) &&
				(tcRet != TEXT('-')) && (tcRet != TEXT('+')))
			{
				index++;
			}
			else
			{
				leadSpace = false;
			}
		}

		// scan whether the first character is equal to '-' (45) or '+' (43)
		TCHAR tcRet = string.GetCharAt(index);
		if (tcRet == TEXT('-'))
		{
			minus = true;
			index++;
		}
		else if (tcRet == TEXT('+'))
		{
			index++;
		}

		// OK, now a number begins, I hope, if no number is found after the minus
		// or plus sign, we immediatly return 0

		while (isValue)
		{
			TCHAR tcRet = string.GetCharAt(index);
			if (tcRet >= TEXT('0') && tcRet <= TEXT('9'))
			{
				int hold = (int)tcRet - (int)TEXT('0');
				value *= 10;
				value += hold;
				index++;
			}
			else
			{
				if (minus)
					return -value;
				else
					return value;
			}
		}

	}
	catch (Exception ex)
	{
		throw (ex);
	}

	return 0;
}