overflows: does a number string overflow a type

Functions
template<class T >
auto	c4::overflows (csubstr str) noexcept -> typename std::enable_if< std::is_unsigned< T >::value, bool >::type
	Test if the following string would overflow when converted to associated integral types; this function is dispatched with SFINAE to handle differently signed and unsigned types. More...

Detailed Description

Function Documentation

overflows()

template<class T >

auto c4::overflows ( csubstr  str ) -> typename std::enable_if<std::is_unsigned<T>::value, bool>::type

noexcept

Test if the following string would overflow when converted to associated integral types; this function is dispatched with SFINAE to handle differently signed and unsigned types.

Returns

true if number will overflow, false if it fits (or doesn't parse)

See also

Check read for overflow for format specifiers to enforce no-overflow reads

Definition at line 1640 of file charconv.hpp.

{
    C4_STATIC_ASSERT(std::is_integral<T>::value);
 
    if(C4_UNLIKELY(str.len == 0))
    {
        return false;
    }
    else if(str.str[0] == '0')
    {
        if (str.len == 1)
            return false;
        switch (str.str[1])
        {
            case 'x':
            case 'X':
            {
                size_t fno = str.first_not_of('0', 2);
                if (fno == csubstr::npos)
                    return false;
                return !(str.len <= fno + (sizeof(T) * 2));
            }
            case 'b':
            case 'B':
            {
                size_t fno = str.first_not_of('0', 2);
                if (fno == csubstr::npos)
                    return false;
                return !(str.len <= fno +(sizeof(T) * 8));
            }
            case 'o':
            case 'O':
            {
                size_t fno = str.first_not_of('0', 2);
                if(fno == csubstr::npos)
                    return false;
                return detail::charconv_digits<T>::is_oct_overflow(str.sub(fno));
            }
            default:
            {
                size_t fno = str.first_not_of('0', 1);
                if(fno == csubstr::npos)
                    return false;
                return detail::check_overflow(str.sub(fno), detail::charconv_digits<T>::max_value_dec());
            }
        }
    }
    else if(C4_UNLIKELY(str[0] == '-'))
    {
        return true;
    }
    else
    {
        return detail::check_overflow(str, detail::charconv_digits<T>::max_value_dec());
    }
}