Method parse_number

include/boost/json/basic_parser_impl.hpp:1980–2756

template<class Handler>
template<bool StackEmpty_, char First_, number_precision Numbers_>
const char*
basic_parser<Handler>::
parse_number(const char* p,
    std::integral_constant<bool, StackEmpty_> stack_empty,
    std::integral_constant<char, First_> first,
    std::integral_constant<number_precision, Numbers_> mode)
{
    constexpr bool precise_parsing = mode == number_precision::precise;
    constexpr bool no_parsing = mode == number_precision::none;

    // only one of these will be true if we are not resuming
    // if negative then !zero_first && !nonzero_first
    // if zero_first then !nonzero_first && !negative
    // if nonzero_first then !zero_first && !negative
    bool const negative = first == '-';
    bool const zero_first = first == '0';
    bool const nonzero_first = first == '+';
    detail::const_stream_wrapper cs(p, end_);
    number num;
    const char* begin = cs.begin();
    if(stack_empty || st_.empty())
    {
        num.bias = 0;
        num.exp = 0;
        num.frac = false;
        num_buf_.clear();

        //----------------------------------
        //
        // '-'
        // leading minus sign
        //
        BOOST_ASSERT(cs);
        if(negative)
            ++cs;

        num.neg = negative;
        num.frac = false;
        num.exp = 0;
        num.bias = 0;

        // fast path
        if( cs.remain() >= 16 + 1 + 16 ) // digits . digits
        {
            int n1;

            if( nonzero_first ||
                (negative && *cs != '0') )
            {
                n1 = detail::count_digits( cs.begin() );
                BOOST_ASSERT(n1 >= 0 && n1 <= 16);

                if( negative && n1 == 0 && opt_.allow_infinity_and_nan )
                {
                    return parse_literal(
                        p - 1,
                        detail::literals_c<detail::literals::neg_infinity>());
                }