https://www.graalvm.org/ 
public interface com.oracle.svm.truffle.nfi.libffi.LibFFI$ffi_closure extends org.graalvm.word.PointerBase
  minor version: 0
  major version: 59
  flags: flags: (0x0601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT
  this_class: com.oracle.svm.truffle.nfi.libffi.LibFFI$ffi_closure
  super_class: java.lang.Object
{
}
SourceFile: "LibFFI.java"
NestHost: com.oracle.svm.truffle.nfi.libffi.LibFFI
InnerClasses:
  public abstract ffi_closure = com.oracle.svm.truffle.nfi.libffi.LibFFI$ffi_closure of com.oracle.svm.truffle.nfi.libffi.LibFFI
    RuntimeVisibleAnnotations: 
      org.graalvm.nativeimage.c.struct.CStruct(value = "ffi_closure")