Issue while decoding

[rkyrahulyadav]

Hi,
i am getting a data-buff from a function that is FAST encoded and using mFAST for decoding the mssg.

`void BroadcastManagerFO::readBroadcast(unsigned char *databuf, int nbytes) {
// Read XML template from file

const mfast::templates_description* descriptions[] = {
MDIFastTemplates::description() // generated from fast_type_gen
};

mfast::fast_decoder decoder;

// In current implementation, decoder.include() can only be called
// exactly once per decoder/encoder
decoder.include(descriptions);

const char* first = reinterpret_cast<const char*>(databuf);
const char* last = reinterpret_cast<const char*>(databuf + nbytes);
std::cout<<"NBYTES:"<<nbytes<<std::endl;

mfast::message_cref msg = decoder.decode(first, last);
// Caveat 1: the variable *first* would be updated to the start of next unread position after decode().
// Caveat 2: msg is only valid before next decoder.decode() is called or decoder object is destroyed.
 std::cout<<"MSGID: "<<msg.id()<<" "<<msg.name()<<std::endl;
 

if (msg.id() == MDIFastTemplates::MDPacketHeader::the_id)
{   
     MDIFastTemplates::MDPacketHeader_cref ref = static_cast<MDIFastTemplates::MDPacketHeader_cref>(msg);
    
     uint32_t sequenceNumber;
     memcpy(&sequenceNumber , ref.get_PacketSeqNum().data() , 4);
     std::cout << ref.get_SenderCompID().name()<<" "<< ref.get_SenderCompID().value()<<" "<<ref.get_SenderCompID().id()<<std::endl;
     std::cout << ref.get_PacketSeqNum().name()<<" "<<sequenceNumber<<" "<<std::endl;
     first = first + 17;
    message_printer printer(std::cout);
    printer.visit(ref, 0);
}



 if(msg.id() == MDIFastTemplates::DepthSnapshot::the_id){
      MDIFastTemplates::DepthSnapshot_cref ref = static_cast<MDIFastTemplates::DepthSnapshot_cref>(msg);
      std::cout<<ref.get_MsgType().name()<<" "<<ref.get_MsgType().value()<<" "<<ref.get_MsgType().id()<<std::endl;
}

std::cout<<"--------------------DONE-----------------------"<<std::endl;

}`

Here databuff containing...Header + some other template
but why i am not able to get other template id apart from header?
is anything i am doing wrong

[ksergey]

@rkyrahulyadav

If I understand right your databuf points to buffer which contains few FAST messages. In this case you can write something like:

while (first != last) { 
  auto msg = decoder.decode(first, last);
  
  // process msg...
}

[rkyrahulyadav]

@ksergey i did that thing earlier. but still it printing only template id of header.
it should decode a header then some other template id.

[rkyrahulyadav]

Do anyone use mFast in production for FAST decoding to data of exchanges.