memotable.h

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// SPDX-FileCopyrightText: Copyright (C) 2016 swift Project Community / Contributors
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-swift-pilot-client-1
 
 
#ifndef SWIFT_MISC_MEMOTABLE_H
#define SWIFT_MISC_MEMOTABLE_H
 
#include "misc/dictionary.h"
#include "misc/sequence.h"
 
namespace swift::misc
{
    template <typename T>
    class CMemoTable
    {
    public:
        int getIndex(const T &value)
        {
            int &index = m_dict[value];
            if (!index)
            {
                m_list.push_back(value);
                index = m_list.size();
            }
            return index - 1;
        }
 
        const CSequence<T> &getTable() const { return m_list; }
 
    private:
        CSequence<T> m_list;
        CDictionary<T, int, QMap> m_dict;
    };
 
    template <typename... Ts>
    struct CMemoHelper
    {
        class CMemoizer : private CMemoTable<Ts>...
        {
        public:
            template <typename T>
            decltype(auto) maybeMemoize(const T &member)
            {
                if constexpr ((std::is_same_v<T, Ts> || ...)) { return this->CMemoTable<T>::getIndex(member); }
                else { return std::as_const(member); }
            }
 
            template <typename T>
            const CSequence<T> &getTable() const
            {
                return this->CMemoTable<T>::getTable();
            }
        };
 
        class CUnmemoizer : private CSequence<Ts>...
        {
        public:
            template <typename T>
            CSequence<T> &getTable()
            {
                return *this;
            }
 
            template <typename T>
            auto maybeUnmemoize(T &member) const
            {
                if constexpr ((std::is_same_v<T, Ts> || ...))
                {
                    struct Memo // clazy:exclude=rule-of-three
                    {
                        int index;
                        T &member;
                        const CSequence<T> &list;
                        int &get() { return index; }
                        ~Memo()
                        {
                            if (index >= 0) { member = list[index]; }
                        }
                    };
                    return Memo { -1, member, static_cast<const CSequence<T> &>(*this) };
                }
                else { return std::ref(member); }
            }
        };
    };
} // namespace swift::misc
 
#endif // SWIFT_MISC_MEMOTABLE_H