void FHotReloadClassReinstancer::UpdateDefaultProperties()
{
struct FPropertyToUpdate
{
UProperty* Property;
FName SubobjectName;
uint8* OldSerializedValuePtr;
uint8* NewValuePtr;
int64 OldSerializedSize;
};
/** Memory writer archive that supports UObject values the same way as FCDOWriter. */
class FPropertyValueMemoryWriter : public FMemoryWriter
{
public:
FPropertyValueMemoryWriter(TArray<uint8>& OutData)
: FMemoryWriter(OutData)
{}
virtual FArchive& operator<<(class UObject*& InObj) override
{
FArchive& Ar = *this;
if (InObj)
{
FName ClassName = InObj->GetClass()->GetFName();
FName ObjectName = InObj->GetFName();
Ar << ClassName;
Ar << ObjectName;
}
else
{
FName UnusedName = NAME_None;
Ar << UnusedName;
Ar << UnusedName;
}
return *this;
}
virtual FArchive& operator<<(FName& InName) override
{
FArchive& Ar = *this;
NAME_INDEX ComparisonIndex = InName.GetComparisonIndex();
NAME_INDEX DisplayIndex = InName.GetDisplayIndex();
int32 Number = InName.GetNumber();
Ar << ComparisonIndex;
Ar << DisplayIndex;
Ar << Number;
return Ar;
}
virtual FArchive& operator<<(FLazyObjectPtr& LazyObjectPtr) override
{
FArchive& Ar = *this;
auto UniqueID = LazyObjectPtr.GetUniqueID();
Ar << UniqueID;
return *this;
}
virtual FArchive& operator<<(FAssetPtr& AssetPtr) override
{
FArchive& Ar = *this;
auto UniqueID = AssetPtr.GetUniqueID();
Ar << UniqueID;
return Ar;
}
virtual FArchive& operator<<(FStringAssetReference& Value) override
{
FArchive& Ar = *this;
Ar << Value.AssetLongPathname;
return Ar;
}
};
// Collect default subobjects to update their properties too
const int32 DefaultSubobjectArrayCapacity = 16;
TArray<UObject*> DefaultSubobjectArray;
DefaultSubobjectArray.Empty(DefaultSubobjectArrayCapacity);
NewClass->GetDefaultObject()->CollectDefaultSubobjects(DefaultSubobjectArray);
TArray<FPropertyToUpdate> PropertiesToUpdate;
// Collect all properties that have actually changed
for (auto& Pair : ReconstructedCDOProperties.Properties)
{
auto OldPropertyInfo = OriginalCDOProperties.Properties.Find(Pair.Key);
if (OldPropertyInfo)
{
auto& NewPropertyInfo = Pair.Value;
uint8* OldSerializedValuePtr = OriginalCDOProperties.Bytes.GetData() + OldPropertyInfo->SerializedValueOffset;
uint8* NewSerializedValuePtr = ReconstructedCDOProperties.Bytes.GetData() + NewPropertyInfo.SerializedValueOffset;
if (OldPropertyInfo->SerializedValueSize != NewPropertyInfo.SerializedValueSize ||
FMemory::Memcmp(OldSerializedValuePtr, NewSerializedValuePtr, OldPropertyInfo->SerializedValueSize) != 0)
{
// Property value has changed so add it to the list of properties that need updating on instances
FPropertyToUpdate PropertyToUpdate;
PropertyToUpdate.Property = NewPropertyInfo.Property;
PropertyToUpdate.NewValuePtr = nullptr;
PropertyToUpdate.SubobjectName = NewPropertyInfo.SubobjectName;
if (NewPropertyInfo.Property->GetOuter() == NewClass)
{
PropertyToUpdate.NewValuePtr = PropertyToUpdate.Property->ContainerPtrToValuePtr<uint8>(NewClass->GetDefaultObject());
}
else if (NewPropertyInfo.SubobjectName != NAME_None)
{
UObject* DefaultSubobjectPtr = FindDefaultSubobject(DefaultSubobjectArray, NewPropertyInfo.SubobjectName);
if (DefaultSubobjectPtr && NewPropertyInfo.Property->GetOuter() == DefaultSubobjectPtr->GetClass())
{
PropertyToUpdate.NewValuePtr = PropertyToUpdate.Property->ContainerPtrToValuePtr<uint8>(DefaultSubobjectPtr);
}
}
if (PropertyToUpdate.NewValuePtr)
{
PropertyToUpdate.OldSerializedValuePtr = OldSerializedValuePtr;
PropertyToUpdate.OldSerializedSize = OldPropertyInfo->SerializedValueSize;
PropertiesToUpdate.Add(PropertyToUpdate);
}
}
}
}
if (PropertiesToUpdate.Num())
{
TArray<uint8> CurrentValueSerializedData;
// Update properties on all existing instances of the class
for (FObjectIterator It(NewClass); It; ++It)
{
UObject* ObjectPtr = *It;
DefaultSubobjectArray.Empty(DefaultSubobjectArrayCapacity);
ObjectPtr->CollectDefaultSubobjects(DefaultSubobjectArray);
for (auto& PropertyToUpdate : PropertiesToUpdate)
{
uint8* InstanceValuePtr = nullptr;
if (PropertyToUpdate.SubobjectName == NAME_None)
{
InstanceValuePtr = PropertyToUpdate.Property->ContainerPtrToValuePtr<uint8>(ObjectPtr);
}
else
{
UObject* DefaultSubobjectPtr = FindDefaultSubobject(DefaultSubobjectArray, PropertyToUpdate.SubobjectName);
if (DefaultSubobjectPtr && PropertyToUpdate.Property->GetOuter() == DefaultSubobjectPtr->GetClass())
{
InstanceValuePtr = PropertyToUpdate.Property->ContainerPtrToValuePtr<uint8>(DefaultSubobjectPtr);
}
}
if (InstanceValuePtr)
{
// Serialize current value to a byte array as we don't have the previous CDO to compare against, we only have its serialized property data
CurrentValueSerializedData.Empty(CurrentValueSerializedData.Num() + CurrentValueSerializedData.GetSlack());
FPropertyValueMemoryWriter CurrentValueWriter(CurrentValueSerializedData);
PropertyToUpdate.Property->SerializeItem(CurrentValueWriter, InstanceValuePtr);
// Update only when the current value on the instance is identical to the original CDO
if (CurrentValueSerializedData.Num() == PropertyToUpdate.OldSerializedSize &&
FMemory::Memcmp(CurrentValueSerializedData.GetData(), PropertyToUpdate.OldSerializedValuePtr, CurrentValueSerializedData.Num()) == 0)
{
// Update with the new value
PropertyToUpdate.Property->CopyCompleteValue(InstanceValuePtr, PropertyToUpdate.NewValuePtr);
}
}
}
}
}
}
