Atmosphere/libraries/libmesosphere/include/mesosphere/kern_k_class_token.hpp

/*
 * Copyright (c) 2018-2020 Atmosphère-NX
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#pragma once
#include <mesosphere/kern_common.hpp>
#include <mesosphere/kern_k_typed_address.hpp>

namespace ams::kern {

    class KAutoObject;

    class KClassTokenGenerator {
        public:
            using TokenBaseType = u16;
        public:
            static constexpr size_t BaseClassBits = 8;
            static constexpr size_t FinalClassBits = (sizeof(TokenBaseType) * CHAR_BIT) - BaseClassBits;
            /* One bit per base class. */
            static constexpr size_t NumBaseClasses = BaseClassBits;
            /* Final classes are permutations of three bits. */
            static constexpr size_t NumFinalClasses = [] {
                TokenBaseType index = 0;
                for (size_t i = 0; i < FinalClassBits; i++) {
                    for (size_t j = i + 1; j < FinalClassBits; j++) {
                        for (size_t k = j + 1; k < FinalClassBits; k++) {
                            index++;
                        }
                    }
                }
                return index;
            }();
        private:
            template<TokenBaseType Index>
            static constexpr inline TokenBaseType BaseClassToken = BIT(Index);

            template<TokenBaseType Index>
            static constexpr inline TokenBaseType FinalClassToken = [] {
                TokenBaseType index = 0;
                for (size_t i = 0; i < FinalClassBits; i++) {
                    for (size_t j = i + 1; j < FinalClassBits; j++) {
                        for (size_t k = j + 1; k < FinalClassBits; k++) {
                            if ((index++) == Index) {
                                return ((1ul << i) | (1ul << j) | (1ul << k)) << BaseClassBits;
                            }
                        }
                    }
                }
                __builtin_unreachable();
            }();

            template<typename T>
            static constexpr inline TokenBaseType GetClassToken() {
                static_assert(std::is_base_of<KAutoObject, T>::value);
                if constexpr (std::is_same<T, KAutoObject>::value) {
                    static_assert(T::ObjectType == ObjectType::KAutoObject);
                    return 0;
                } else if constexpr (!std::is_final<T>::value) {
                    static_assert(ObjectType::BaseClassesStart <= T::ObjectType && T::ObjectType < ObjectType::BaseClassesEnd);
                    constexpr auto ClassIndex = static_cast<TokenBaseType>(T::ObjectType) - static_cast<TokenBaseType>(ObjectType::BaseClassesStart);
                    return BaseClassToken<ClassIndex> | GetClassToken<typename T::BaseClass>();
                } else if constexpr (ObjectType::FinalClassesStart <= T::ObjectType && T::ObjectType < ObjectType::FinalClassesEnd) {
                    constexpr auto ClassIndex = static_cast<TokenBaseType>(T::ObjectType) - static_cast<TokenBaseType>(ObjectType::FinalClassesStart);
                    return FinalClassToken<ClassIndex> | GetClassToken<typename T::BaseClass>();
                } else {
                    static_assert(!std::is_same<T, T>::value, "GetClassToken: Invalid Type");
                }
            };
        public:
            enum class ObjectType {
                KAutoObject,

                BaseClassesStart,

                KSynchronizationObject = BaseClassesStart,
                KReadableEvent,

                BaseClassesEnd,

                FinalClassesStart = BaseClassesEnd,

                KInterruptEvent = FinalClassesStart,
                KDebug,
                KThread,
                KServerPort,
                KServerSession,
                KClientPort,
                KClientSession,
                KProcess,
                KResourceLimit,
                KLightSession,
                KPort,
                KSession,
                KSharedMemory,
                KEvent,
                KWritableEvent,
                KLightClientSession,
                KLightServerSession,
                KTransferMemory,
                KDeviceAddressSpace,
                KSessionRequest,
                KCodeMemory,

                /* NOTE: True order for these has not been determined yet. */
                KAlpha,
                KBeta,

                FinalClassesEnd = FinalClassesStart + NumFinalClasses,
            };

            template<typename T>
            static constexpr inline TokenBaseType ClassToken = GetClassToken<T>();
    };

    using ClassTokenType = KClassTokenGenerator::TokenBaseType;

    template<typename T>
    static constexpr inline ClassTokenType ClassToken = KClassTokenGenerator::ClassToken<T>;

}