TypedReplicationFragment.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Iris/ReplicationSystem/ReplicationFragment.h"
 
namespace UE::Net
{
 
/*
* Typed replication fragments are used when we have generated ReplicationStates
* and will call the SetReplicatedState method on the parent class
* $IRIS TODO: Introduce policies based on ReplicationStateTraits, i.e. should we call other functions on Init etc?
*/
template <typename T, typename ReplicationStateT>
class TReplicationFragment : protected FReplicationFragment
{
public:
    // Receive only
    explicit TReplicationFragment(T& OwnerIn) : FReplicationFragment(EReplicationFragmentTraits::CanReceive), Owner(OwnerIn), SrcState(nullptr) {}
 
    // Replicate 
    TReplicationFragment(T& OwnerIn, ReplicationStateT& SrcReplicationState) : FReplicationFragment(EReplicationFragmentTraits::CanReplicate), Owner(OwnerIn), SrcState(&SrcReplicationState) {}
 
    void Register(FFragmentRegistrationContext& Context);
 
protected:
    // FReplicationFragment
    virtual void ApplyReplicatedState(FReplicationStateApplyContext& Context) const override;
 
 
private:
    T& Owner;
    ReplicationStateT* SrcState;
};
 
template <typename T, typename ReplicationStateT>
void TReplicationFragment<T, ReplicationStateT>::ApplyReplicatedState(FReplicationStateApplyContext& Context) const
{
    // Cast to the expected type
    const ReplicationStateT* ReplicationState  = reinterpret_cast<const ReplicationStateT*>(Context.StateBufferData.ExternalStateBuffer);
 
    // $TODO: We need a state management system here so that we can keep states around until update time
    // either we implement this at this level or we make this part of the replication system, maybe a linear allocator during receive that we will free after we have applied the states
    Owner.ApplyReplicationState(*ReplicationState, Context);
}
 
template <typename T, typename ReplicationStateT>
void TReplicationFragment<T, ReplicationStateT>::Register(FFragmentRegistrationContext& Context)
{
    Context.RegisterReplicationFragment(this, ReplicationStateT::GetReplicationStateDescriptor(), SrcState);
}
 
}