ladybird/Userland/Libraries/LibJS/Runtime/FinalizationRegistry.cpp

/*
 * Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/FinalizationRegistry.h>

namespace JS {

FinalizationRegistry* FinalizationRegistry::create(GlobalObject& global_object, FunctionObject& cleanup_callback)
{
    return global_object.heap().allocate<FinalizationRegistry>(global_object, cleanup_callback, *global_object.finalization_registry_prototype());
}

FinalizationRegistry::FinalizationRegistry(FunctionObject& cleanup_callback, Object& prototype)
    : Object(prototype)
    , WeakContainer(heap())
    , m_cleanup_callback(&cleanup_callback)
{
}

FinalizationRegistry::~FinalizationRegistry()
{
}

void FinalizationRegistry::add_finalization_record(Cell& target, Value held_value, Object* unregister_token)
{
    VERIFY(!held_value.is_empty());
    m_records.append({ &target, held_value, unregister_token });
}

bool FinalizationRegistry::remove_by_token(Object& unregister_token)
{
    auto removed = false;
    for (auto it = m_records.begin(); it != m_records.end(); ++it) {
        if (it->unregister_token == &unregister_token) {
            it.remove(m_records);
            removed = true;
        }
    }
    return removed;
}

void FinalizationRegistry::remove_dead_cells(Badge<Heap>)
{
    auto any_cells_were_removed = false;
    for (auto& record : m_records) {
        if (!record.target || record.target->state() == Cell::State::Live)
            continue;
        record.target = nullptr;
        any_cells_were_removed = true;
        break;
    }
    if (any_cells_were_removed)
        vm().enqueue_finalization_registry_cleanup_job(*this);
}

// 9.13 CleanupFinalizationRegistry ( finalizationRegistry ), https://tc39.es/ecma262/#sec-cleanup-finalization-registry
ThrowCompletionOr<void> FinalizationRegistry::cleanup(FunctionObject* callback)
{
    // 1. Assert: finalizationRegistry has [[Cells]] and [[CleanupCallback]] internal slots.
    // Note: Ensured by type.

    // 2. Let callback be finalizationRegistry.[[CleanupCallback]].
    auto cleanup_callback = callback ?: m_cleanup_callback;

    // 3. While finalizationRegistry.[[Cells]] contains a Record cell such that cell.[[WeakRefTarget]] is empty, an implementation may perform the following steps:
    for (auto it = m_records.begin(); it != m_records.end(); ++it) {
        // a. Choose any such cell.
        if (it->target != nullptr)
            continue;
        auto cell = *it;

        // b. Remove cell from finalizationRegistry.[[Cells]].
        it.remove(m_records);

        // c. Perform ? HostCallJobCallback(callback, undefined, « cell.[[HeldValue]] »).
        (void)TRY(call(global_object(), *cleanup_callback, js_undefined(), cell.held_value));
    }

    // 4. Return NormalCompletion(empty).
    return {};
}

void FinalizationRegistry::visit_edges(Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_cleanup_callback);
    for (auto& record : m_records) {
        visitor.visit(record.held_value);
        visitor.visit(record.unregister_token);
    }
}

}