Merge pull request #11 from Hopper262/pr-header-v3

Support extra field in GVAS version 3 (possibly a checksum)

UnrealEngine.Gvas/SaveGameHeader.cs

@@ -13,22 +13,27 @@ public class SaveGameHeader
  public CustomVersionSerializationFormat CustomVersionFormat { get; set; }
  public List<CustomVersion> CustomVersions { get; set; } = new();
  public string? SaveGameClassName { get; set; }
+ public long Unknown1 { get; set; }
 
  public static SaveGameHeader ReadFrom(BinaryReader reader)
  {
  var magic = reader.ReadChars(4);
  if (!magic.SequenceEqual(FileTypeTag))
  throw new SaveGameException("Invalid magic number in file header, expected: 'GVAS'.");
 
- return new SaveGameHeader
+ var header = new SaveGameHeader
  {
  SaveGameFileVersion = reader.ReadInt32(),
  PackageFileUE4Version = reader.ReadInt32(),
  SavedEngineVersion = EngineVersion.ReadFrom(reader),
  CustomVersionFormat = (CustomVersionSerializationFormat) reader.ReadInt32(),
  CustomVersions = Enumerable.Range(0, reader.ReadInt32()).Select(_ => CustomVersion.ReadFrom(reader)).ToList(),
- SaveGameClassName = reader.ReadFString()
+ SaveGameClassName = reader.ReadFString(),
+ Unknown1 = 0
  };
+ if (header.SaveGameFileVersion >= 3)
+ header.Unknown1 = reader.ReadInt64();
+ return header;
  }
 
  public void WriteTo(BinaryWriter writer)
@@ -42,5 +47,7 @@ public void WriteTo(BinaryWriter writer)
  foreach (var customVersion in CustomVersions)
  customVersion.WriteTo(writer);
  writer.WriteFString(SaveGameClassName);
+ if (SaveGameFileVersion >= 3)
+ writer.Write(Unknown1);
  }
 }