atod: chars to float64

Functions
bool	c4::atod (csubstr str, double *v) noexcept
	Convert a string to a double precision real number. More...
size_t	c4::atod_first (csubstr str, double *v) noexcept
	Convert a string to a double precision real number. More...

Detailed Description

Function Documentation

bool c4::atod ( csubstr  str, double *  v  )

inlinenoexcept

Convert a string to a double precision real number.

The input string must be trimmed to the value, ie no leading or trailing whitespace can be present.

Returns

true iff the conversion succeeded

See also

atod_first() if the string is not trimmed

Definition at line 2182 of file charconv.hpp.

Referenced by c4::atod_first(), c4::atox(), and c4::from_chars().

{
    C4_ASSERT(str.len > 0);
    C4_ASSERT(str.triml(" \r\t\n").len == str.len);
#if C4CORE_HAVE_FAST_FLOAT
    // fastfloat cannot parse hexadecimal floats
    bool isneg = (str.str[0] == '-');
    csubstr rem = str.sub(isneg || str.str[0] == '+');
    if( ! (rem.len >= 2 && (rem.str[0] == '0' && (rem.str[1] == 'x' || rem.str[1] == 'X'))))
    {
        fast_float::from_chars_result result;
        #ifndef CLANG_TIDY   // suppress a false-positive error (cannot be done with NOLINT: https://stackoverflow.com/questions/62838193/ )
        result = fast_float::from_chars(str.str, str.str + str.len, *v);
        #else
        result = {};
        #endif
        return result.ec == std::errc();
    }
    else if(detail::scan_rhex(rem.sub(2), v))
    {
        *v *= isneg ? -1. : 1.;
        return true;
    }
    return false;
#elif C4CORE_HAVE_STD_FROMCHARS
    std::from_chars_result result;
    result = std::from_chars(str.str, str.str + str.len, *v);
    return result.ec == std::errc();
#else
    csubstr rem = str.sub(str.str[0] == '-' || str.str[0] == '+');
    if(!(rem.len >= 2 && (rem.str[0] == '0' && (rem.str[1] == 'x' || rem.str[1] == 'X'))))
        return detail::scan_one(str, "lf", v) != csubstr::npos;
    else
        return detail::scan_one(str, "la", v) != csubstr::npos;
#endif
}

size_t c4::atod_first ( csubstr  str, double *  v  )

inlinenoexcept

Convert a string to a double precision real number.

Leading whitespace is skipped until valid characters are found.

Returns

the number of characters read from the string, or npos if conversion was not successful or if the string was empty

Definition at line 2224 of file charconv.hpp.

Referenced by c4::from_chars_first().

{
    csubstr trimmed = str.first_real_span();
    if(trimmed.len == 0)
        return csubstr::npos;
    if(atod(trimmed, v))
        return static_cast<size_t>(trimmed.end() - str.begin());
    return csubstr::npos;
}