serenity/Libraries/LibJS/Runtime/Shape.cpp

/*
 * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <LibJS/Heap/DeferGC.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/Shape.h>

namespace JS {

Shape* Shape::create_unique_clone() const
{
    ASSERT(m_global_object);
    auto* new_shape = heap().allocate_without_global_object<Shape>(*m_global_object);
    new_shape->m_unique = true;
    new_shape->m_prototype = m_prototype;
    ensure_property_table();
    new_shape->ensure_property_table();
    (*new_shape->m_property_table) = *m_property_table;
    new_shape->m_property_count = new_shape->m_property_table->size();
    return new_shape;
}

Shape* Shape::create_put_transition(const StringOrSymbol& property_name, PropertyAttributes attributes)
{
    TransitionKey key { property_name, attributes };
    if (auto* existing_shape = m_forward_transitions.get(key).value_or(nullptr))
        return existing_shape;
    auto* new_shape = heap().allocate_without_global_object<Shape>(*this, property_name, attributes, TransitionType::Put);
    m_forward_transitions.set(key, new_shape);
    return new_shape;
}

Shape* Shape::create_configure_transition(const StringOrSymbol& property_name, PropertyAttributes attributes)
{
    TransitionKey key { property_name, attributes };
    if (auto* existing_shape = m_forward_transitions.get(key).value_or(nullptr))
        return existing_shape;
    auto* new_shape = heap().allocate_without_global_object<Shape>(*this, property_name, attributes, TransitionType::Configure);
    m_forward_transitions.set(key, new_shape);
    return new_shape;
}

Shape* Shape::create_prototype_transition(Object* new_prototype)
{
    return heap().allocate_without_global_object<Shape>(*this, new_prototype);
}

Shape::Shape(ShapeWithoutGlobalObjectTag)
{
}

Shape::Shape(GlobalObject& global_object)
    : m_global_object(&global_object)
{
}

Shape::Shape(Shape& previous_shape, const StringOrSymbol& property_name, PropertyAttributes attributes, TransitionType transition_type)
    : m_attributes(attributes)
    , m_transition_type(transition_type)
    , m_global_object(previous_shape.m_global_object)
    , m_previous(&previous_shape)
    , m_property_name(property_name)
    , m_prototype(previous_shape.m_prototype)
    , m_property_count(transition_type == TransitionType::Put ? previous_shape.m_property_count + 1 : previous_shape.m_property_count)
{
}

Shape::Shape(Shape& previous_shape, Object* new_prototype)
    : m_transition_type(TransitionType::Prototype)
    , m_global_object(previous_shape.m_global_object)
    , m_previous(&previous_shape)
    , m_prototype(new_prototype)
    , m_property_count(previous_shape.m_property_count)
{
}

Shape::~Shape()
{
}

void Shape::visit_edges(Cell::Visitor& visitor)
{
    Cell::visit_edges(visitor);
    visitor.visit(m_global_object);
    visitor.visit(m_prototype);
    visitor.visit(m_previous);
    m_property_name.visit_edges(visitor);
    for (auto& it : m_forward_transitions)
        visitor.visit(it.value);

    if (m_property_table) {
        for (auto& it : *m_property_table)
            it.key.visit_edges(visitor);
    }
}

Optional<PropertyMetadata> Shape::lookup(const StringOrSymbol& property_name) const
{
    if (m_property_count == 0)
        return {};
    auto property = property_table().get(property_name);
    if (!property.has_value())
        return {};
    return property;
}

const HashMap<StringOrSymbol, PropertyMetadata>& Shape::property_table() const
{
    ensure_property_table();
    return *m_property_table;
}

size_t Shape::property_count() const
{
    return m_property_count;
}

Vector<Shape::Property> Shape::property_table_ordered() const
{
    auto vec = Vector<Shape::Property>();
    vec.resize(property_count());

    for (auto& it : property_table()) {
        vec[it.value.offset] = { it.key, it.value };
    }

    return vec;
}

void Shape::ensure_property_table() const
{
    if (m_property_table)
        return;
    m_property_table = make<HashMap<StringOrSymbol, PropertyMetadata>>();

    u32 next_offset = 0;

    Vector<const Shape*, 64> transition_chain;
    for (auto* shape = m_previous; shape; shape = shape->m_previous) {
        if (shape->m_property_table) {
            *m_property_table = *shape->m_property_table;
            next_offset = shape->m_property_count;
            break;
        }
        transition_chain.append(shape);
    }
    transition_chain.append(this);

    for (ssize_t i = transition_chain.size() - 1; i >= 0; --i) {
        auto* shape = transition_chain[i];
        if (!shape->m_property_name.is_valid()) {
            // Ignore prototype transitions as they don't affect the key map.
            continue;
        }
        if (shape->m_transition_type == TransitionType::Put) {
            m_property_table->set(shape->m_property_name, { next_offset++, shape->m_attributes });
        } else if (shape->m_transition_type == TransitionType::Configure) {
            auto it = m_property_table->find(shape->m_property_name);
            ASSERT(it != m_property_table->end());
            it->value.attributes = shape->m_attributes;
        }
    }
}

void Shape::add_property_to_unique_shape(const StringOrSymbol& property_name, PropertyAttributes attributes)
{
    ASSERT(is_unique());
    ASSERT(m_property_table);
    ASSERT(!m_property_table->contains(property_name));
    m_property_table->set(property_name, { m_property_table->size(), attributes });
    ++m_property_count;
}

void Shape::reconfigure_property_in_unique_shape(const StringOrSymbol& property_name, PropertyAttributes attributes)
{
    ASSERT(is_unique());
    ASSERT(m_property_table);
    auto it = m_property_table->find(property_name);
    ASSERT(it != m_property_table->end());
    it->value.attributes = attributes;
    m_property_table->set(property_name, it->value);
}

void Shape::remove_property_from_unique_shape(const StringOrSymbol& property_name, size_t offset)
{
    ASSERT(is_unique());
    ASSERT(m_property_table);
    if (m_property_table->remove(property_name))
        --m_property_count;
    for (auto& it : *m_property_table) {
        ASSERT(it.value.offset != offset);
        if (it.value.offset > offset)
            --it.value.offset;
    }
}

void Shape::add_property_without_transition(const StringOrSymbol& property_name, PropertyAttributes attributes)
{
    ensure_property_table();
    if (m_property_table->set(property_name, { m_property_count, attributes }) == AK::HashSetResult::InsertedNewEntry)
        ++m_property_count;
}

}