[K/N] Support of collectReferenceFieldValues function

kotlin-native/runtime/src/main/cpp/TypeInfo.cpp

@@ -16,6 +16,9 @@
 
 #include "KAssert.h"
 #include "TypeInfo.h"
+#include "Memory.h"
+#include "Types.h"
+#include "KString.h"
 
 extern "C" {
 
@@ -39,4 +42,14 @@ InterfaceTableRecord const* LookupInterfaceTableRecord(InterfaceTableRecord cons
   return interfaceTable + l;
 }
 
+RUNTIME_NOTHROW int Kotlin_internal_reflect_getObjectReferenceFieldsCount(ObjHeader* object) {
+    auto *info = object->type_info();
+    if (info->IsArray()) return 0;
+    return info->objOffsetsCount_;
+}
+
+RUNTIME_NOTHROW OBJ_GETTER(Kotlin_internal_reflect_getObjectReferenceFieldByIndex, ObjHeader* object, int index) {
+    RETURN_OBJ(*reinterpret_cast<ObjHeader**>(reinterpret_cast<uintptr_t>(object) + object->type_info()->objOffsets_[index]));
+}
+
 }

kotlin-native/runtime/src/main/kotlin/kotlin/native/internal/Utils.kt

@@ -19,3 +19,36 @@ internal fun debugDescription(kClass: KClass<*>, identity: Int): String {
     val identityStr = unsignedIdentity.toString(16)
     return "$className@$identityStr"
 }
+
+@GCUnsafeCall("Kotlin_internal_reflect_getObjectReferenceFieldsCount")
+private external fun getObjectReferenceFieldsCount(o: Any): Int
+@GCUnsafeCall("Kotlin_internal_reflect_getObjectReferenceFieldByIndex")
+private external fun getObjectReferenceFieldByIndex(o: Any, index: Int): Any?
+
+/**
+ * Returns [List] of non-null reference fields of the object.
+ *
+ * This function is intended to be used for testing and debugging purposes.
+ * - It heavily relies on internal ABI details. No compatibility guarantees on exact list contents are provided.
+ * - Order and representation of object's fields are subject to change.
+ * - Performance characteristics of the implementation
+ *
+ * Limitations:
+ *  - Primitives (unboxed [Int], [Double], [Float], etc.) are not included in the result.
+ *  - Non-boxed value classes over primitives are not included in the result.
+ *  - Non-boxed value classes over references are included in the result as the underlying reference type.
+ *  - Synthetic fields (e.g. special fields for delegation) are included in the result.
+ *  - There is no way to find which reference in the result corresponds to which field.
+ *
+ *  For `Array<T>` list of all its non-null elements is returned.
+ *  For primitive arrays ([IntArray], [DoubleArray], [FloatArray], etc.) empty list is returned.
+ */
+@InternalForKotlinNative
+public fun Any.collectReferenceFieldValues() : List<Any> {
+    return when {
+        this is Array<*> -> this.filterNotNull()
+        else -> (0 until getObjectReferenceFieldsCount(this@collectReferenceFieldValues)).mapNotNull {
+            getObjectReferenceFieldByIndex(this@collectReferenceFieldValues, it)
+        }
+    }
+}