This is the adapter library of cereal for UE4 types.

• cereal: https://uscilab.github.io/cereal/; C++ Serialization library, header-only
• UE4: http://www.unrealengine.com/; 3D Game, Architecture, Visualization Engine( Framework, Middle-ware )

• Many common UE4 types are supported! // main feature of this library!
  • See also §Supported types in below.
• Header-only library! // Easy for use your UE4 project.
• No problems for use USTRUCT types. // UE4 built-in serializer is not supported
• Ofcourse, common C++ types are supported. // UE4 build-in serializer is not supported
  • int8, uint8, int16, uint16, int32, uint32 int64, uint64
  • float, double, long double
  • std::string, std::vector, std::map, ... // See also cereal: Standard Library Support
• You can use a similar methods in archiving of JSON, XML and Portable-binary.

• TArray, TMap, TSet
• TInterval ( with FFloatInterval, FInt32Interval )
• TBigInt
• FString, FName
• FDateTime, FTimespan
• FVector, FVector2D
• FBox, FBox2D
• FSphere
• FCapsuleShape
• FLinearColor, FColor
• FIntVector, FIntPoint, FIntVector4, FUintVector4
• FIntRect
• FMatrix, FMatrix2x2
• FScale, FScale2D, FShear2D
• FOrientedBox
• FPlane
• FShpere
• FQuat, FQuat2D
• FTwoVectors

• JSON serializer of UE4 is ...
  • Not supported many common UE4 types; FVector, FTimespan, FVector2D, FBox, FBox2D, FColor, FLinearColor, FIntPoint, FMatrix, FPlane, FScale, FShpere, FBigInt, int8, uint8, int16, uint16, int64, uint64, ...
  • Implemented by inheritance model only ( using virtual functions )
    • If we use it then it will break POD ( standard layout ) of our data structure. vtable increase a data size and break packing of a data array.
    • It cannot use for USTRUCT types.
  • Very complicated and messy to use low-level APIs for a full-manually serialization. ( see FJsonSerializable, UE4/JSON/DOM )

Then, I decided to use cereal and I wrote this adapter library.

1. Prepare a thirdparty library directory:
   1. cd <your-project>
   2. mkdir Thirdparty; or anywhere else as you like
   3. cd Thirdparty
2. Deploy cereal library.
   • git clone [email protected]:USCiLab/cereal.git; <- It's serialization base library
3. Deploy cereal-UE4 library.
   • git clone [email protected]:usagi/cereal-UE4.git; <- It's this library!
4. Add PublicIncludePaths settings to <your-project>.Build.cs; See also below (†1)
5. Write your serialization code in your UE4 project; See also below (†2)
   • And get your serialization results! (†3)

(†1): Step-4's <your-project>.Build.cs

// 1. Add the `using`
using System.IO;

public class YourProject
  : ModuleRules
{
  public YourProject(ReadOnlyTargetRules Target)
    : base( Target )
  {
    // 2. Add below code into your setting
    {
      var base_path = Path.GetDirectoryName( RulesCompiler.GetFileNameFromType( GetType() ) );
      string third_party_path = Path.Combine( base_path, "..", "..", "Thirdparty");
      PublicIncludePaths.Add( Path.Combine( third_party_path, "cereal", "include") );
      PublicIncludePaths.Add( Path.Combine( third_party_path, "cereal-UE4", "include") );
    }
  }
}

(†2): Step-5's e.g.; Now, you can serialize FString, FDateTime, FVector and etc. with cereal!

your-something.h:

// cereal-UE4 serializable class(struct)
USTRUCT( BlueprintType ) struct FMySomething
{ GENERATED_BODY()
  UPROPERTY( BlueprintReadWrite ) FString String;
  UPROPERTY( BlueprintReadWrite ) FDateTime DateTime;
  UPROPERTY( BlueprintReadWrite ) FVector Vector;
  UPROPERTY( BlueprintReadWrite ) TArray< int32 > ArrayI32;
};

// cereal-UE4 external serializer definition for FMySomething type
template < typename A >
void serialize( A& a, FMySomething& in )
{
  a
  ( cereal::make_nvp( "String", in.String )
  , cereal::make_nvp( "DateTime", in.DateTime )
  , cereal::make_nvp( "Vector", in.Vector )
  , cereal::make_nvp( "ArrayI32", in.ArrayI32 )
  );
}

your-something.cpp:

/* ... ( abbreviation ) ...  */

// cereal
#include "cereal/cereal.hpp"
#include "cereal/archives/json.hpp"
// cereal-UE4
#include "cereal-UE4.hxx"
// std::stringstream
#include <sstream>

/* ... ( abbreviation ) ...  */
  
  FMySomething MySomething;
  MySomething.String = "Hello, こんにちは.";
  MySomething.DateTime = FDateTime::UtcNow();
  MySomething.Vector = FVector::UpVector();
  MySomething.ArrayI32 = { 123, -456, 789 };
  
  /* ... ( abbreviation ) ...  */
  
  std::stringstream buffer;
  {
    cereal::JSONOutputArchive a( buffer );
    a( cereal::make_nvp( "MySomething", MySomething ) );
  }
  const auto json = FString( buffer.str().data() );
  UE_LOG( LogTemp, Log, TEXT( "%s" ), *json )
  
  if
  ( !  FFileHelper::SaveStringToFile
          ( json
          , *( FPaths::ProjectDir / TEXT( "MySomething.json" ) )
          , FFileHelper::EEncodingOptions::ForceUTF8WithoutBOM )
  )
  {
    UE_LOG( LogTemp, Fatal, TEXT( "Save Error" ) );
  }

/* ... ( abbreviation ) ...  */

(†3): Step-5's expected result.

MySomething.json:

{
    "MySomething": {
        "String": "Hello, こんにちは.",
        "DateTime": "2018-03-29T17:59:50.595Z",
        "Vector": {
            "X": 0.0,
            "Y": 0.0,
            "Z": 1.0
        },
        "ArrayI32": [
            123,
            -456,
            789
        ]
    }
}

• See https://uscilab.github.io/cereal/quickstart.html if you need quickstart of cereal.
• See example/ if you need an example of all of supported type and easy testing.

• MIT

• Usagi Ito
  • [email protected]
  • https://github.com/usagi
  • https://discord.gg/QsDNMbN
  • https://www.reddit.com/user/luatichare
  • https://twitter.com/USAGI_WRP
  • https://www.facebook.com/usagi.wrp
  • https://www.instagram.com/usagi_wrp/