Re: bit level matching on x3

Hi,

you are right. A out-of-box byte_(from, to) rule would be very nice!
Because this rule is not provided by spirit, you can write it yourself:

#include <boost/config/warning_disable.hpp>
#include <boost/spirit/home/x3.hpp>
#include <boost/spirit/home/x3/binary.hpp>

#include <iostream>

namespace x3 = boost::spirit::x3;

const auto byte_rule = [](const std::uint8_t from, const std::uint8_t to)
{
	const auto check = [from, to](auto& ctx)
	{
		const std::uint8_t value = x3::_attr(ctx);
		x3::_val(ctx) = value;
		x3::_pass(ctx) = from <= value && value <= to;
	};

	return x3::byte_ [check];
};

int main() {
    using x3::byte_;

    // input data
    std::string s = { 
        char(0b11110000),
        char(0b11110001),
        char(0b11110011)
    };

    // rule
    //auto match = +byte_(0b11110000);
    auto match = +byte_rule(0b11110000, 0b11111111); // no range version
like char_

    auto it = s.begin();
    auto end = s.end();
    bool r = x3::phrase_parse(
        it, end,
        match, x3::space);

    std::cout << std::boolalpha << r << std::endl;
    std::cout << std::distance(it, end) << " bytes remaining." << std::endl;
}

Best regards,
Mike...



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