Re: [Boost-users] [spirit] Qi rule for GPS NMEA

6 Sep 2013

      On Thu, Sep 5, 2013 at 8:42 PM, Michael Powell  wrote:
...
Oh yeah, and then I am adapting it into a struct:
BOOST_FUSION_ADAPT_STRUCT(
    dchem::drivers::nmea::basic_nmea_message_t,
    (std::string, m_message)
    (int, m_checksum)
)
Or at least I'd like to. I've got the general framework understood
from the employee-examples.
Thanks again.
I came up with something like this, but I may be completely off the mark:

    qi::rule r_message;

    qi::rule r_checksum;

    qi::rule r_start;

        using qi::char_;
        using qi::lit;
        using qi::hex;

        r_message %= +(char_);

        r_checksum %= hex >> hex;

        r_start %= lit('$') >> r_message
                >> lit('*') >> r_checksum
                >> lit('\r') >> lit('\n');

The I/O transport itself will handle wrapping/unwrapping when it sees
'$' and the terminus "\r\n" and pass that along to the parser for
handling.

What I am uncertain about is how the rules consume the message and
engage with the adaptation.

Thank ye...
...
On Thu, Sep 5, 2013 at 8:39 PM, Michael Powell  wrote:
...
Hello,
I'm digging into a qi rule for GPS NMEA and want to approach it as a
kind of 2-pass parser. First pass to extract the message and
hex-formatted checksum. Next pass to parse out the actual messages
from the message.
I believe I comprehend how to go about the second pass. For the first
pass, I want to parse $XYZ*HH\r\n.
That's the literal '$', and everything between there and the literal
'*', followed by the two hex characters, as a complete field, followed
by the terminal CR+LF.
How do I express the "all characters excluding '*'" for the NMEA
message? Then the hex field?
Thanks...
Regards,
Michael Powell