extract_packet/extract_packet.cpp

/*
    This example extracts the packet described by the define_packet example.  If
    that example hasn't run, you will need to do that now.  The file that is
    created must be located where this program can find it.
 
    The table below shows what is defined in the packet:
 
    Name        Data Type           Size    Notes
    Version     unsigned integer    4       Should always be zero
    PktId       unsigned integer    12      For this packet, the value is 54
    PktLen      unsigned integer    16      Length of packet after this point
    PktCnt      unsigned integer    8       Packet counter
    Time        system time         32      A.k.a. DT_UNIX_TIME
    IntParam    signed integer      16      First data parameter
    UintParam   unsigned integer    32      Three consecutive values
    FloatParam  double              64      Little-endian floating point
    StrParam    string              800     Varible length string
    Checksum    unsigned integer    32      CRC-32 checksum
 */
 
#include "packet.h"
#include "parameter_collection.h"
#include "parameter.h"
#include <iostream>
#include <stdio.h>
 
using namespace trek;
using namespace std;
 
int main()
{
    //
    //  NOTE: There is only minimal error checking shown in the code below in
    //  order to simplify the example.  In general, only the first time a 
    //  method is used will the error handling be in this example.  You should
    //  always check the returned value when one is available to ensure proper
    //  operation of the code.  Error handling for this example is to exit on
    //  error.
    //
 
    Packet pkt;
    Parameter *param_ptr;
    std::string param_name;
    int32_t ret_value;
 
    //
    //  Read in the packet file.
    //
 
    ret_value = pkt.LoadFile( "my_file.xml" );
 
    if( ret_value )
    {
        // Most likely the file doesn't exist.  Check that the file is there or
        // use a full path name.
        cout << "Could not open file\n";
        return 1;
    }
 
    //
    //  After loading a packet, you must create the 'map' that allows parameter lookup.
    //
 
    pkt.CreateGlobalPacketMap();
 
    //
    //  Normally you would extract a packet that came in from the network or
    //  some other interface.  Since this is a simple example a buffer is shown
    //  below already popluated with data that is valid (including the
    //  checksum).
    //
 
    uint8_t buf[100];
    uint32_t buf_size;
    uint32_t last_bit;
 
    buf[0] = 0x00;      // Version = 0
    buf[1] = 0x36;      // PktId = 54
    buf[2] = 0x00;      // PktLen = 36 (40 - 4 byte offset)
    buf[3] = 0x24;
    buf[4] = 0xfe;      // PktCnt = 254
    buf[5] = 0x53;      // Time = 2014-02-28 21:57:47
    buf[6] = 0x11;
    buf[7] = 0x06;
    buf[8] = 0x5b;
    buf[9] = 0xff;      // IntParam = -1
    buf[10] = 0xff;
    buf[11] = 0x00;     // UintParam(1) = 255
    buf[12] = 0x00;
    buf[13] = 0x00;
    buf[14] = 0xff;
    buf[15] = 0x00;     // UintParam(2) = 256
    buf[16] = 0x00;
    buf[17] = 0x01;
    buf[18] = 0x00;
    buf[19] = 0x00;     // UintParam(3) = 65,536
    buf[20] = 0x01;
    buf[21] = 0x00;
    buf[22] = 0x00;
    buf[23] = 0x00;     // FloatParam = -10000.125
    buf[24] = 0x00;
    buf[25] = 0x00;
    buf[26] = 0x00;
    buf[27] = 0x10;
    buf[28] = 0x88;
    buf[29] = 0xc3;
    buf[30] = 0xc0;
    buf[31] = 0x48;     // StrParam = "Help!"
    buf[32] = 0x65;
    buf[33] = 0x6c;
    buf[34] = 0x70;
    buf[35] = 0x21;
    buf[36] = 0x00;
    buf[37] = 0x20;     // Checksum
    buf[38] = 0x96;
    buf[39] = 0x54;
    buf[40] = 0x1c;
 
    buf_size = 41;
    ret_value = pkt.Extract( buf, buf_size, last_bit );
 
    if( ret_value )
    {
        cout << "Error extracting data\n";
        return 1;
    }
 
    //
    //  Get a list of the parameters in the packet sorted by their start
    //  location.  Get the values of all samples of each parameter as a string.
    //
 
    StringArray all_params;
    pkt.GetSortedParameterList( all_params );
 
    for( uint32_t ii = 0; ii < all_params.Size(); ii++ )
    {
        pkt.FindParameter( all_params.GetAt(ii), &param_ptr );
        
        //
        //  See how many samples a parameter has and get each one.
        //
 
        for( uint32_t jj = 1; jj <= param_ptr->GetNumberOfSamples(); jj++ )
            printf("%s (sample %u): %s\n", all_params.GetAt(ii),
                                           jj,
                                           param_ptr->GetValueAsString(jj) );
    }
 
    //  THE END
    return 0;
}