Serialization *

Quick Facts

• Version: 1.3

• Enabled with HFSM_ENABLE_SERIALIZATION

• Test: test_serialization.cpp

Interface

hfsm2::Root::SerialBuffer	Buffer for serialization
hfsm2::Root::save(SerialBuffer&) const	Serialize the structural configuration
hfsm2::Root::load(const SerialBuffer&)	De-serialize the configuration and initialize FSM

Example

// Enable serialization
#define HFSM_ENABLE_SERIALIZATION

#include <hfsm2/machine.hpp>
#include <assert.h>

using M = hfsm2::Machine;

using FSM = M::PeerRoot<
                struct State1,
                struct State2
            >;

struct State1 : FSM::State { /* .. */ };
struct State2 : FSM::State { /* .. */ };

int main() {
    // Buffer for serialization
    //  Members:
    //   bitSize - Number of payload bits used
    //   payload - Serialized data
    FSM::Instance::SerialBuffer buffer;

    {
       FSM::Instance fsm;              // Create a new FSM instance
       fsm.changeTo<State2>();         // Request a transition to 'State2'
       fsm.update();                   // Process transitions
       assert(fsm.isActive<State2>()); // Check if transition completed

       fsm.save(buffer);               // Serialize FSM configuration into 'buffer'
    }
    
    {
       FSM::Instance fsm;              // Create a fresh FSM instance
       assert(fsm.isActive<State1>()); // Initial 'State1' is activated by default

       fsm.load(buffer);               // De-serialize FSM from 'buffer'
       assert(fsm.isActive<State2>()); // Check its configuration is restored
    }
}

Serialization Between Different FSMs

As demonstrated in test_serialization.cpp, it is allowed to exchange the SerialBuffer between different FSMs, so long as their hierarchical structure is exactly the same.

This can be useful for network replication between structurally equivalent server and client FSM instances implementing some specific logic.

SerialBuffer Size and Compression

HFSM2 does not compress SerialBuffer.

However, the configuration data saved to SerialBuffer::payload is tightly packed to use the minimal number of bits.

The number of bits used in the payload is recorded in SerialBuffer::bitSize, which could be used for example in custom network replication logic to minimize network bandwidth usage.

Compressing SerialBuffer can also be used to further reduce the size serialized state.