viscosity/engine/core/object/ref_counted.cpp

/**************************************************************************/
/*  ref_counted.cpp                                                       */
/**************************************************************************/
/*                         This file is part of:                          */
/*                             GODOT ENGINE                               */
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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#include "ref_counted.h"

#include "core/object/class_db.h"
#include "core/object/script_instance.h"

bool RefCounted::init_ref() {
	if (reference()) {
		if (!is_referenced() && refcount_init.unref()) {
			unreference(); // first referencing is already 1, so compensate for the ref above
		}

		return true;
	} else {
		return false;
	}
}

void RefCounted::deinit_ref() {
	// Somewhat unsafe since we're doing tests in sync, but it's probably fine
	// since this function is called from the creation thread, so nobody else should have access.

	// If this succeeds, refcount_init is 2 (or more).
	// This would be unexpected, since callers should already have consumed it, or never established it.
	// It's a little unsafe to bring it above 1, since it means init_ref must be called more than once,
	// but the alternative would be decrementing refcount instead, which is also unsafe since the object
	// might unexpectedly destruct early. Better to risk zombying than to risk a crash.
	if (!refcount_init.ref()) {
		// refcount_init already dead, must re-establish (expected).
		refcount_init.init(1);
	}
}

void RefCounted::_bind_methods() {
	ClassDB::bind_method(D_METHOD("init_ref"), &RefCounted::init_ref);
	ClassDB::bind_method(D_METHOD("reference"), &RefCounted::reference);
	ClassDB::bind_method(D_METHOD("unreference"), &RefCounted::unreference);
	ClassDB::bind_method(D_METHOD("get_reference_count"), &RefCounted::get_reference_count);
}

int RefCounted::get_reference_count() const {
	return refcount.get();
}

bool RefCounted::reference() {
	uint32_t rc_val = refcount.refval();
	bool success = rc_val != 0;

	if (success && rc_val <= 2 /* higher is not relevant */) {
		if (get_script_instance()) {
			get_script_instance()->refcount_incremented();
		}
		if (_get_extension() && _get_extension()->reference) {
			_get_extension()->reference(_get_extension_instance());
		}

		_instance_binding_reference(true);
	}

	return success;
}

bool RefCounted::unreference() {
	dereference_count.increment();
	uint32_t rc_val = refcount.unrefval();
	bool die = rc_val == 0;

	if (rc_val <= 1 /* higher is not relevant */) {
		if (get_script_instance()) {
			bool script_ret = get_script_instance()->refcount_decremented();
			die = die && script_ret;
		}
		if (_get_extension() && _get_extension()->unreference) {
			_get_extension()->unreference(_get_extension_instance());
		}

		bool binding_ret = _instance_binding_reference(false);
		die = die && binding_ret;
	}

	dereference_count.decrement();

	// If we are going to be destroyed we need to ensure that no other thread
	// is still inside our critical section. If they are they might see
	// a (partially) destroyed Object for get_script_instance, _get_extension,
	// or _instance_binding_reference.
	if (die) {
		// It is unlikely that we will spin here for very long.
		// Only threads that see die == true will spin, which should only
		// ever be one. Only threads seeing rc_val == 1 and rc_val == 0
		// will do anything at all in the critical section.
		while (dereference_count.get()) {
			// Spin
		}
	}

	return die;
}

RefCounted::RefCounted() :
		Object(true) {
	_define_ancestry(AncestralClass::REF_COUNTED);
	refcount.init();
	refcount_init.init();
	dereference_count.set(0);
}

Variant WeakRef::get_ref() const {
	if (ref.is_null()) {
		return Variant();
	}

	Object *obj = ObjectDB::get_instance(ref);
	if (!obj) {
		return Variant();
	}
	RefCounted *r = cast_to<RefCounted>(obj);
	if (r) {
		return Ref<RefCounted>(r);
	}

	return obj;
}

void WeakRef::set_obj(Object *p_object) {
	ref = p_object ? p_object->get_instance_id() : ObjectID();
}

void WeakRef::set_ref(const Ref<RefCounted> &p_ref) {
	ref = p_ref.is_valid() ? p_ref->get_instance_id() : ObjectID();
}

void WeakRef::_bind_methods() {
	ClassDB::bind_method(D_METHOD("get_ref"), &WeakRef::get_ref);
}