UE网络-WithNetSharedSerializer详解

发表于 2024-05-15 分类于 UE ， UE网络， WithNetSharedSerializer详解阅读次数：本文字数： 653 阅读时长 ≈ 2 分钟

WithNetSharedSerialization是什么

在进行属性同步时, 每当一个属性发生变化都要发给关心该属性的所有Connection, 如果这些Connection共享一份, 那就可以节省很多内存, 序列化等时间.

一般与WithNetSerializer组合使用.

自定义结构体指定WithNetSharedSerialization

USTRUCT()
struct FExampleStruct1
{
    GENERATED_USTRUCT_BODY()
public:
    UPROPERTY()
    int32		ExampleIntProperty;

    /**
     * @param Ar			FArchive to read or write from.
     * @param Map			PackageMap used to resolve references to UObject*
     * @param bOutSuccess	return value to signify if the serialization was succesfull (if false, an error will be logged by the calling function)
     *
     * @return return true if the serialization was fully mapped. If false, the property will be considered 'dirty' and will replicate again on the next update.
     *	This is needed for UActor* properties. If an actor's Actorchannel is not fully mapped, properties referencing it must stay dirty.
     *	Note that UPackageMap::SerializeObject returns false if an object is unmapped. Generally, you will want to return false from your ::NetSerialize
     *  if you make any calls to ::SerializeObject that return false.
     *
    */
    bool NetSerialize(FArchive& Ar, class UPackageMap* Map, bool& bOutSuccess);
};

template<>
struct TStructOpsTypeTraits< FExampleStruct1 > : public TStructOpsTypeTraitsBase2< FExampleStruct1 >
{
    enum
    {
        WithNetSerializer = true,
        WithNetSharedSerialization = true,
    };
};

将`WithNetSharedSerialization`映射到`EStructFlags::STRUCT_NetSharedSerialization`

构建UScriptStruct

在PreInit时候,构建UScriptStruct

将`WithNetSharedSerialization`属性映射到`EStructFlags::STRUCT_NetSharedSerialization`

构建UScriptStruct, 通过模板, 指定WithNetSharedSerialization属性.

好了, 到此为止, 已经将我们指定的WithNetSharedSerialization映射到EStructFlags::STRUCT_NetSharedSerialization上了. 即UScriptStruct.StructFlags已经包含EStructFlags::STRUCT_NetSharedSerialization属性.

将EStructFlags::STRUCT_NetSharedSerialization映射到ERepLayoutCmdFlags::IsSharedSerialization

在创建RepLayout时(例如:FRepLayout::InitFromClass), 设置RepStruct信息.

Struct类型为:FStructProperty

检测Struct->StructFlags是否包含STRUCT_NetSharedSerialization属性:

这样, 就将STRUCT_NetSharedSerialization属性映射成IsSharedSerialization, 并存储在Cmd.Flags中.

使用WithNetSharedSerialization

通过1-4,已经将WithNetSharedSerialization->EStructFlags::STRUCT_NetSharedSerialization->ERepLayoutCmdFlags::IsSharedSerialization的转化讲清楚了, 并最终存储在Cmd.Flags中. 这里所说的使用WithNetSharedSerialization其实包括EStructFlags::STRUCT_NetSharedSerialization和ERepLayoutCmdFlags::IsSharedSerialization的使用.

在序列化时候, 优先处理SharedSerialization属性

//序列化流程
--UNetDriver.TickFlush()
 |--UNetDriver.ServerReplicateActors()
 | |--UNetDriver.ServerReplicateActors_ProcessPrioritizedActors()
 | | |--UActorChannel.ReplicateActor()
 | | | |--FObjectReplicator.ReplicateProperties()
 | | | | |--FRepLayout.ReplicateProperties()
            // 优先构建SharedSerialization属性
 | | | | | |--FRepLayout.BuildSharedSerialization()
 | | | | | |--FRepLayout.SendProperties()
 | | | | | | |--FRepLayout.SendProperties_r()
 | | | | | | | |--FStructProperty.NetSerializeItem()
 | | | | | | | | |--FExampleStruct.NetSerialize()
 
 | | | | | |--FRepLayout.SendProperties()
 | | | | | | |--FRepLayout.SendProperties_r()
 | | | | | | | |--FStructProperty.NetSerializeItem()
 | | | | | | | | |--FExampleStruct.NetSerialize()
 
 | | | | |--FObjectReplicator.ReplicateCustomDeltaProperties()
 | | | | | |--FObjectReplicator.SendCustomDeltaProperty()
 | | | | | | |--FNetSerializeCB.SendCustomDeltaProperty()
 | | | | | | | |--FRepLayout.SendCustomDeltaProperty()
 | | | | | | | | |--FExampleArray.NetDeltaSerialize()