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

Subject: Re: [Boost-users] [spirit] Qi rule for GPS NMEA
From: Michael Powell (mwpowellhtx_at_[hidden])
Date: 2013-09-05 22:00:09

On Thu, Sep 5, 2013 at 8:54 PM, Michael Caisse <mcaisse-lists_at_[hidden]> 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 <mwpowellhtx_at_[hidden]> 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
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