nmea0183.cpp

GPS的协议为NMEA0183

#include "nmea0183.h"
#pragma hdrstop

/*
** Author: Samuel R. Blackburn
** CI$: 76300,326
** Internet: [e-mail]
**
** You can use it any way you like.
*/

IMPLEMENT_DYNAMIC( NMEA0183, CObject )

NMEA0183::NMEA0183()
{
   initialize();

   response_table.Add( (RESPONSE *) &Aam );
   response_table.Add( (RESPONSE *) &Alm );
   response_table.Add( (RESPONSE *) &Apb );
   response_table.Add( (RESPONSE *) &Asd );
   response_table.Add( (RESPONSE *) &Bec );
   response_table.Add( (RESPONSE *) &Bod );
   response_table.Add( (RESPONSE *) &Bwc );
   response_table.Add( (RESPONSE *) &Bwr );
   response_table.Add( (RESPONSE *) &Bww );
   response_table.Add( (RESPONSE *) &Dbt );
   response_table.Add( (RESPONSE *) &Dcn );
   response_table.Add( (RESPONSE *) &Dpt );
   response_table.Add( (RESPONSE *) &Fsi );
   response_table.Add( (RESPONSE *) &Gga );
   response_table.Add( (RESPONSE *) &Glc );
   response_table.Add( (RESPONSE *) &Gll );
   response_table.Add( (RESPONSE *) &Gxa );
   response_table.Add( (RESPONSE *) &Hdg );
   response_table.Add( (RESPONSE *) &Hdt );
   response_table.Add( (RESPONSE *) &Hsc );
   response_table.Add( (RESPONSE *) &Lcd );
   response_table.Add( (RESPONSE *) &Mtw );
   response_table.Add( (RESPONSE *) &Mwv );
   response_table.Add( (RESPONSE *) &Oln );
   response_table.Add( (RESPONSE *) &Osd );
   response_table.Add( (RESPONSE *) &Proprietary );
   response_table.Add( (RESPONSE *) &Rma );
   response_table.Add( (RESPONSE *) &Rmb );
   response_table.Add( (RESPONSE *) &Rmc );
   response_table.Add( (RESPONSE *) &Rot );
   response_table.Add( (RESPONSE *) &Rpm );
   response_table.Add( (RESPONSE *) &Rsa );
   response_table.Add( (RESPONSE *) &Rsd );
   response_table.Add( (RESPONSE *) &Rte );
   response_table.Add( (RESPONSE *) &Sfi );
   response_table.Add( (RESPONSE *) &Stn );
   response_table.Add( (RESPONSE *) &Trf );
   response_table.Add( (RESPONSE *) &Ttm );
   response_table.Add( (RESPONSE *) &Vbw );
   response_table.Add( (RESPONSE *) &Vhw );
   response_table.Add( (RESPONSE *) &Vdr );
   response_table.Add( (RESPONSE *) &Vlw );
   response_table.Add( (RESPONSE *) &Vpw );
   response_table.Add( (RESPONSE *) &Vtg );
   response_table.Add( (RESPONSE *) &Wcv );
   response_table.Add( (RESPONSE *) &Wnc );
   response_table.Add( (RESPONSE *) &Wpl );
   response_table.Add( (RESPONSE *) &Xdr );
   response_table.Add( (RESPONSE *) &Xte );
   response_table.Add( (RESPONSE *) &Xtr );
   response_table.Add( (RESPONSE *) &Zda );
   response_table.Add( (RESPONSE *) &Zfo );
   response_table.Add( (RESPONSE *) &Ztg );

   sort_response_table();
   set_container_pointers();
}

NMEA0183::~NMEA0183()
{
   initialize();
}

void NMEA0183::initialize( void )
{
   ASSERT_VALID( this );

   ErrorMessage.Empty();
}

void NMEA0183::set_container_pointers( void )
{
   ASSERT_VALID( this );

   int index = 0;
   int number_of_entries_in_table = response_table.GetSize();

   RESPONSE *this_response = (RESPONSE *) NULL;

   index = 0;

   while( index < number_of_entries_in_table )
   {
      this_response = (RESPONSE *) response_table[ index ];

      this_response->SetContainer( this );

      index++;
   }
}

void NMEA0183::sort_response_table( void )
{
   ASSERT_VALID( this );

   int index = 0;
   int number_of_entries_in_table = response_table.GetSize() - 1;

   RESPONSE *this_response = (RESPONSE *) NULL;
   RESPONSE *that_response = (RESPONSE *) NULL;

   BOOL sorted = FALSE;

   while( sorted == FALSE )
   {
      sorted = TRUE;

      index = 0;

      while( index < number_of_entries_in_table )
      {
         this_response = (RESPONSE *) response_table[ index     ];
         that_response = (RESPONSE *) response_table[ index + 1 ];

         if ( this_response->Mnemonic.Compare( that_response->Mnemonic ) > 0 )
         {
            response_table[ index     ] = that_response;
            response_table[ index + 1 ] = this_response;

            sorted = FALSE;
         }

         index++;
      }
   }
}

/*
** Public Interface
*/

BOOL NMEA0183::IsGood( void ) const
{
   ASSERT_VALID( this );

   /*
   ** NMEA 0183 sentences begin with $ and and with CR LF
   */

   if ( sentence.Sentence[ 0 ] != '$' )
   {
      return( FALSE );
   }

   /*
   ** Next to last character must be a CR
   */

   if ( sentence.Sentence.Mid( sentence.Sentence.GetLength() - 2, 1 ) != CARRIAGE_RETURN )
   {
      return( FALSE );
   }

   if ( sentence.Sentence.Right( 1 ) != LINE_FEED )
   {
      return( FALSE );
   }

   return( TRUE );
}

BOOL NMEA0183::Parse( void )
{
   ASSERT_VALID( this );

   BOOL return_value = FALSE;

   if ( IsGood() )
   {
      int index       = 0;
      int comparison  = 0;
      int drop_dead   = 0;
      int exit_loop   = 0;
      int lower_limit = 0;
      int upper_limit = 0;

      CString mnemonic;

      RESPONSE *response_p = (RESPONSE *) NULL;

      mnemonic = sentence.Field( 0 );

      /*
      ** See if this is a proprietary field
      */

      if ( mnemonic.Left( 1 ) == 'P' )
      {
         mnemonic = "P";
      }
      else
      {
         mnemonic = mnemonic.Right( 3 );
      }

      /*
      ** Set up our default error message
      */

      ErrorMessage = mnemonic;
      ErrorMessage += " is an unknown type of sentence";

      LastSentenceIDReceived = mnemonic;

      /*
      ** Do a Binary Search to call the appropriate function
      */

      lower_limit = 0;
      upper_limit = response_table.GetSize();
      index       = upper_limit / 2;
      drop_dead   = ( index < 10 ) ? 10 : index + 2;

      /*
      ** The drop_dead is here as an insurance policy that we will never get stuck in an endless loop.
      ** I have encountered situations where the inaccuracy of the division leaves the loop stuck when
      ** it can't find something.
      */

      while( exit_loop == 0 )
      {
         response_p = (RESPONSE *) response_table[ index ];

         comparison = mnemonic.Compare( response_p->Mnemonic );

         if ( comparison == 0 )
         {
            return_value = response_p->Parse( sentence );

            /*
            ** Set your ErrorMessage
            */

            if ( return_value == TRUE )
            {
               ErrorMessage = "No Error";
               LastSentenceIDParsed = response_p->Mnemonic;
               TalkerID = talker_id( sentence );
               ExpandedTalkerID = expand_talker_id( TalkerID );
            }
            else
            {
               ErrorMessage = response_p->ErrorMessage;
            }

            exit_loop = 1;
         }
         else
         {
            if ( comparison < 0 )
            {
               upper_limit = index;
            }
            else
            {
               lower_limit = index;
            }

            if ( lower_limit == upper_limit )
            {
               exit_loop = 1;
               return_value = FALSE;
            }
            else
            {
               index = ( lower_limit + upper_limit ) / 2;
            }
         }

         drop_dead--;

         if ( drop_dead < 0 )
         {
            exit_loop = 1;
            return_value = FALSE;
         }
      }
   }
   else
   {
      return_value = FALSE;
   }

   return( return_value );
}

NMEA0183& NMEA0183::operator << ( const char *source )
{
   ASSERT_VALID( this );

   sentence = source;

   return( *this );
}

NMEA0183& NMEA0183::operator >> ( CString& destination )
{
   ASSERT_VALID( this );

   destination = sentence;

   return( *this );
}