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

On Thu, Sep 5, 2013 at 8:54 PM, Michael Caisse wrote:

On 09/05/2013 06:42 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.

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?

Hi Michael -

Parsing NMEA is about as easy as you have described in english.

rule = lit('$') >> ~char_('*') >> lit('$') >> hex >> lit("\r\n");

Pretty straightforward. How about the wrinkle of enforcing the NMEA 2-hex-digit checksum?

That should parse into the fusion adapted sequence you have described.

hth - michael

-- Michael Caisse ciere consulting ciere.com _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users