MegEngine/src/core/include/megbrain/utils/metahelper.h

/**
 * \file src/core/include/megbrain/utils/metahelper.h
 * MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
 *
 * Copyright (c) 2014-2021 Megvii Inc. All rights reserved.
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 */

#pragma once

#include "megbrain/exception.h"
#include "megbrain/utils/hash.h"
#include "megbrain/utils/thin/function.h"
#include "megbrain/utils/thin/hash_table.h"

#include <algorithm>
#include <string>
#include <type_traits>
#include <unordered_set>
#include <utility>

namespace mgb {

/*!
 * \brief an object to represent a type
 *
 * MegBrain has a lightweight RTTI system. Each type is represented by the
 * address of a Typeinfo object, which is stored in the .bss segment.
 *
 * MGB_TYPEINFO_OBJ_DECL should be placed into the definition of classes that
 * need compile-time type support.
 *
 * For classes that need RTTI, they should be derived from DynTypeObj and
 * include MGB_DYN_TYPE_OBJ_FINAL_DECL in the definition.
 */
struct Typeinfo {
    //! name of the corresponding type; nullptr if MGB_VERBOSE_TYPEINFO_NAME==0
    const char* const name;

    /*!
     * \brief whether this is the type of given object
     * \tparam T a class with static typeinfo() method
     */
    template <typename T>
    bool is() const {
        return T::typeinfo() == this;
    }
};

/*!
 * \brief base class to emulate RTTI without compiler support
 */
class DynTypeObj {
public:
    virtual Typeinfo* dyn_typeinfo() const = 0;

    //! cast this to a final object (no type check is performed)
    template <class T>
    T& cast_final() {
        return *static_cast<T*>(this);
    }

    template <class T>
    const T& cast_final() const {
        return const_cast<DynTypeObj*>(this)->cast_final<T>();
    }

    //! cast this to a final object with type check
    template <class T>
    T& cast_final_safe() {
        mgb_assert(
                T::typeinfo() == dyn_typeinfo(), "can not convert type %s to %s",
                dyn_typeinfo()->name, T::typeinfo()->name);
        return cast_final<T>();
    }

    template <class T>
    const T& cast_final_safe() const {
        return const_cast<DynTypeObj*>(this)->cast_final_safe<T>();
    }

    //! cast this to a final object if type matches; return nullptr if not
    template <class T>
    T* try_cast_final() {
        return T::typeinfo() == dyn_typeinfo() ? static_cast<T*>(this) : nullptr;
    }

    template <class T>
    const T* try_cast_final() const {
        return const_cast<DynTypeObj*>(this)->try_cast_final<T>();
    }

    //! check whether this is same to given type
    template <class T>
    bool same_type() const {
        return dyn_typeinfo() == T::typeinfo();
    }

protected:
    ~DynTypeObj() = default;
};

//! define to template param so MGB_DYN_TYPE_OBJ_FINAL_IMPL for templates can
//! work
#define _MGB_DYN_TYPE_OBJ_FINAL_IMPL_TPL

//! put in the declaration of a class that only needs static typeinfo()
#define MGB_TYPEINFO_OBJ_DECL                                          \
public:                                                                \
    static inline ::mgb::Typeinfo* typeinfo() { return &sm_typeinfo; } \
                                                                       \
private:                                                               \
    static ::mgb::Typeinfo sm_typeinfo

#define MGB_TYPEINFO_OBJ_DECL_WITH_EXPORT                              \
public:                                                                \
    static inline ::mgb::Typeinfo* typeinfo() { return &sm_typeinfo; } \
                                                                       \
private:                                                               \
    static MGE_WIN_DECLSPEC_DATA ::mgb::Typeinfo sm_typeinfo

#if MGB_VERBOSE_TYPEINFO_NAME
//! get class name from class object
#define _MGB_TYPEINFO_CLASS_NAME(_cls) #_cls
#else
#define _MGB_TYPEINFO_CLASS_NAME(_cls) ""
#endif

//! put in the impl file of a class that needs static typeinfo()
#define MGB_TYPEINFO_OBJ_IMPL(_cls)  \
    _MGB_DYN_TYPE_OBJ_FINAL_IMPL_TPL \
    ::mgb::Typeinfo _cls::sm_typeinfo { _MGB_TYPEINFO_CLASS_NAME(_cls) }

//! put in the declaration of a final class inherited from DynTypeObj
#define MGB_DYN_TYPE_OBJ_FINAL_DECL                       \
public:                                                   \
    ::mgb::Typeinfo* dyn_typeinfo() const override final; \
    MGB_TYPEINFO_OBJ_DECL

#define MGB_DYN_TYPE_OBJ_FINAL_DECL_WITH_EXPORT                                \
public:                                                                        \
    MGE_WIN_DECLSPEC_FUC ::mgb::Typeinfo* dyn_typeinfo() const override final; \
    MGB_TYPEINFO_OBJ_DECL_WITH_EXPORT

//! put in the impl file of a final class inherited from DynTypeObj
#define MGB_DYN_TYPE_OBJ_FINAL_IMPL(_cls)                                \
    _MGB_DYN_TYPE_OBJ_FINAL_IMPL_TPL                                     \
    ::mgb::Typeinfo* _cls::dyn_typeinfo() const { return &sm_typeinfo; } \
    MGB_TYPEINFO_OBJ_IMPL(_cls)

/*!
 * \brief base class for non-copyable objects
 */
class NonCopyableObj {
    NonCopyableObj(const NonCopyableObj&) = delete;
    NonCopyableObj& operator=(const NonCopyableObj&) = delete;

public:
    NonCopyableObj() = default;
};

template <typename T>
class ReverseAdaptor {
    T& m_t;

public:
    ReverseAdaptor(T& t) : m_t(t) {}

    typename T::reverse_iterator begin() { return m_t.rbegin(); }

    typename T::reverse_iterator end() { return m_t.rend(); }
};

template <typename T>
class ConstReverseAdaptor {
    const T& m_t;

public:
    ConstReverseAdaptor(const T& t) : m_t(t) {}

    typename T::const_reverse_iterator begin() { return m_t.crbegin(); }

    typename T::const_reverse_iterator end() { return m_t.crend(); }
};

template <typename T>
ReverseAdaptor<T> reverse_adaptor(T& t) {
    return {t};
}

template <typename T>
ConstReverseAdaptor<T> reverse_adaptor(const T& t) {
    return {t};
}

/*!
 * \brief insertion sort for small arrays, to reduce code size
 * \tparam Iter iterator type, which must support ==, ++, --
 * \tparam Cmp comparator for strict less-than
 */
template <
        typename Iter,
        class Cmp = std::less<typename std::iterator_traits<Iter>::value_type>>
void small_sort(Iter begin, Iter end, const Cmp& cmp = {}) {
    if (begin == end)
        return;
    Iter i = begin;
    ++i;
    for (; !(i == end); ++i) {
        auto pivot = std::move(*i);
        Iter j = i;
        for (;;) {
            if (begin == j)
                break;
            Iter jnext = j;
            --j;
            if (cmp(pivot, *j)) {
                *jnext = std::move(*j);
            } else {
                j = jnext;
                break;
            }
        }
        *j = std::move(pivot);
    }
}

/*!
 * \brief find key in container with out-of-boundary check
 */
template <class Container, class Key>
typename Container::iterator safe_find(Container& container, const Key& key) {
    typename Container::iterator iter = container.find(key);
    mgb_assert(iter != container.end());
    return iter;
}

/*!
 * \brief find key in container with out-of-boundary check
 */
template <class Container, class Key>
typename Container::const_iterator safe_find(
        const Container& container, const Key& key) {
    typename Container::const_iterator iter = container.find(key);
    mgb_assert(iter != container.end());
    return iter;
}

/*!
 * \brief find key in vector with out-of-boundary check
 */
template <class T, class Key>
typename SmallVector<T>::iterator safe_find(SmallVector<T>& container, const Key& key) {
    typename SmallVector<T>::iterator iter =
            std::find(container.begin(), container.end(), key);
    mgb_assert(iter != container.end());
    return iter;
}

/*!
 * \brief find key in container with out-of-boundary check
 */
template <class T, class Key>
typename SmallVector<T>::const_iterator safe_find(
        const SmallVector<T>& container, const Key& key) {
    typename SmallVector<T>::const_iterator iter =
            std::find(container.begin(), container.end(), key);
    mgb_assert(iter != container.end());
    return iter;
}

/*!
 * \brief find in vector
 */
template <class Key>
typename std::vector<Key>::iterator find(std::vector<Key>& vec, const Key& key) {
    return std::find(vec.begin(), vec.end(), key);
}

/*!
 * \brief find in vector
 */
template <class Key>
typename std::vector<Key>::const_iterator find(
        const std::vector<Key>& vec, const Key& key) {
    return std::find(vec.begin(), vec.end(), key);
}

/*!
 * \brief explicit hash specification for std::vector
 */
template <class Key>
struct HashTrait<std::vector<Key>> {
    static size_t eval(const std::vector<Key>& val) {
        size_t rst = hash(val.size());
        for (auto&& i : val)
            rst = hash_pair_combine(rst, ::mgb::hash(i));
        return rst;
    }
};

//! like python dict.get(key, default)
template <class Map>
const typename Map::value_type::second_type& get_map_with_default(
        const Map& map, const typename Map::value_type::first_type& key,
        const typename Map::value_type::second_type& default_ = {}) {
    auto iter = map.find(key);
    return iter == map.end() ? default_ : iter->second;
}

/*!
 * \brief raw memory storage for incomplete type Obj; Obj only needs to be
 *      complete in ctor and dtor
 */
template <class Obj, size_t SIZE, size_t ALIGN>
class alignas(ALIGN) IncompleteObjStorage {
    uint8_t m_mem[SIZE];

public:
    IncompleteObjStorage() {
        static_assert(
                sizeof(Obj) <= SIZE && !(ALIGN % alignof(Obj)),
                "SIZE and ALIGN do not match Obj");
        new (m_mem) Obj;
    }

    IncompleteObjStorage(const IncompleteObjStorage& rhs) {
        new (m_mem) Obj(rhs.get());
    }
    IncompleteObjStorage(IncompleteObjStorage&& rhs) noexcept {
        new (m_mem) Obj(std::move(rhs.get()));
    }

    IncompleteObjStorage& operator=(const IncompleteObjStorage& rhs) {
        get() = rhs.get();
        return *this;
    }

    IncompleteObjStorage& operator=(IncompleteObjStorage&& rhs) noexcept {
        get() = std::move(rhs.get());
        return *this;
    }

    ~IncompleteObjStorage() noexcept { get().~Obj(); }

    Obj& get() { return *aliased_ptr<Obj>(m_mem); }

    const Obj& get() const { return const_cast<IncompleteObjStorage*>(this)->get(); }
};

//! use size and align of another object
template <class Obj, class Mock>
using IncompleteObjStorageMock = IncompleteObjStorage<Obj, sizeof(Mock), alignof(Mock)>;

/*!
 * \brief container for arbitrary objects
 *
 * This container keeps a reference to added objects and allows retriving by
 * type. Objects of the same type form a stack, and supports add/pop.
 *
 * NOTE: This object is not thread-safe.
 */
class UserDataContainer {
public:
    /*!
     * \brief base class for all user data
     *
     * Note that the impls must provide static typeinfo() (i.e. use
     * MGB_TYPEINFO_OBJ_DECL and MGB_TYPEINFO_OBJ_IMPL)
     */
    class UserData {
    public:
        virtual ~UserData() = default;
    };

    MGE_WIN_DECLSPEC_FUC ~UserDataContainer() noexcept;

    /*!
     * \brief register new user data
     */
    template <typename T>
    T* add_user_data(std::shared_ptr<T> data) {
        static_assert(
                std::is_base_of<UserData, T>::value, "must be derived from UserData");
        auto ptr = data.get();
        do_add(T::typeinfo(), std::move(data));
        return ptr;
    }

    /*!
     * \brief remove most recently added user data of a specific type
     * \return number of items removed
     */
    template <typename T>
    int pop_user_data() {
        static_assert(
                std::is_base_of<UserData, T>::value, "must be derived from UserData");
        return do_pop(T::typeinfo());
    }

    /*!
     * \brief get user data
     * \return pair of (data object array ptr, number of data objects)
     */
    template <typename T>
    std::pair<T* const*, size_t> get_user_data() const {
        static_assert(
                std::is_base_of<UserData, T>::value, "must be derived from UserData");
        auto ret = do_get(T::typeinfo());
        return {reinterpret_cast<T* const*>(ret.first), ret.second};
    }

    /*!
     * \brief get user data or create a new one; the registry for this user
     *      data type must contain only one instance
     */
    template <typename T, typename Maker>
    T* get_user_data_or_create(Maker&& maker) {
        static_assert(
                std::is_base_of<UserData, T>::value, "must be derived from UserData");
        auto type = T::typeinfo();
        if (!m_storage.count(type)) {
            do_add(type, maker());
        }
        return static_cast<T*>(do_get_one(type));
    }

    //! get_user_data_or_create(), with std::make_shared as maker
    template <typename T>
    T* get_user_data_or_create() {
        return get_user_data_or_create<T>(std::make_shared<T>);
    }

    void clear_all_user_data();

    void swap(UserDataContainer& other) {
        m_refkeeper.swap(other.m_refkeeper);
        m_storage.swap(other.m_storage);
    }

private:
    MGE_WIN_DECLSPEC_FUC void do_add(Typeinfo* type, std::shared_ptr<UserData> ptr);
    MGE_WIN_DECLSPEC_FUC std::pair<void* const*, size_t> do_get(Typeinfo* type) const;
    MGE_WIN_DECLSPEC_FUC void* do_get_one(Typeinfo* type) const;
    MGE_WIN_DECLSPEC_FUC int do_pop(Typeinfo* type);

    //! use a set to help erase
    std::unordered_set<std::shared_ptr<UserData>> m_refkeeper;
    ThinHashMap<Typeinfo*, SmallVector<void*, 1>> m_storage;
};

/*!
 * \brief continuation context, usually used for an async function
 * \tparam Args args to be passed to Next
 */
template <typename... Args>
class ContinuationCtx {
public:
    using Next = thin_function<void(Args...)>;
    using Err = thin_function<void(std::exception&)>;

    ContinuationCtx(const Next& next = {}, const Err& err = {})
            : m_next{next}, m_err{err} {}

    template <class... T>
    void next(T&&... args) const {
        if (m_next)
            m_next(std::forward<T>(args)...);
    }

    void err(std::exception& exc) const {
        if (m_err)
            m_err(exc);
    }

private:
    Next m_next;
    Err m_err;
};

//! a class that invokes given callbacks in the destructor
class CleanupCallback {
public:
    using Callback = thin_function<void()>;
    void add(Callback callback);

    ~CleanupCallback() noexcept(false);

private:
    SmallVector<Callback> m_callbacks;
};

}  // namespace mgb

#define MGB_DEFINE_CLS_WITH_SUPER_IMPL(_tpl, _name, _base, ...) \
    class _name : public _base, ##__VA_ARGS__ {                 \
    public:                                                     \
        using Super = _tpl _base;                               \
                                                                \
    private:

/*!
 * \brief define a class which has Super defined to base
 */
#define MGB_DEFINE_CLS_WITH_SUPER(_name, _base, ...) \
    MGB_DEFINE_CLS_WITH_SUPER_IMPL(, _name, _base, ##__VA_ARGS__)

/*!
 * \brief define a class which has Super defined to base
 *
 * Used when this class is a template and base class has template
 */
#define MGB_DEFINE_CLS_WITH_SUPER_TPL(_name, _base, ...) \
    MGB_DEFINE_CLS_WITH_SUPER_IMPL(typename, _name, _base, ##__VA_ARGS__)
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