any_regular.hpp

/*
    Copyright 2013 Adobe
    Distributed under the Boost Software License, Version 1.0.
    (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
*/
/**************************************************************************************************/


#ifndef ADOBE_ANY_REGULAR_HPP
#define ADOBE_ANY_REGULAR_HPP

#include <adobe/config.hpp>

#include <adobe/any_regular_fwd.hpp>

#include <cstdint>
#include <type_traits>

#include <boost/concept_check.hpp>
#include <boost/mpl/bool.hpp>
#include <boost/mpl/if.hpp>
#include <boost/noncopyable.hpp>
#include <boost/operators.hpp>
#include <boost/type_traits/has_nothrow_copy.hpp>

#include <adobe/conversion.hpp>
#include <adobe/empty.hpp>
#include <adobe/memory.hpp>
#include <adobe/regular_concept.hpp>
#include <adobe/serializable.hpp>
#include <adobe/typeinfo.hpp>

#include <adobe/implementation/swap.hpp>

#if defined(ADOBE_STD_SERIALIZATION)
#include <adobe/iomanip.hpp>
#endif

/**************************************************************************************************/

namespace adobe {

/*!
\defgroup any_regular any_regular_t
\ingroup runtime_concepts abi_safe
*/


/*!
\fn adobe::any_regular_t::any_regular_t(const T& x)

\param x Value to copy as the instance value of this object.

\note
    What is stored is a copy of <code>x</code> promoted to <code>promote<T>::type</code>.
*/

/*!
\fn const typename promote<T>::type& adobe::any_regular_t::cast() const

\return
    A refernce to a promoted type for <code>T</code> containing the <code>any_regular_t</code>'s
instance value.

\exception
    adobe::bad_cast Thrown if <code>adobe::promote<T></code> does not match the stored instance
type.
*/

/*!
\fn typename promote<T>::type& adobe::any_regular_t::cast()

\return
    A refernce to a promoted type for <code>T</code> containing the <code>any_regular_t</code>'s
instance value.

\exception
    adobe::bad_cast Thrown if <code>adobe::promote<T></code> does not match the stored instance
type.
*/

/*!
\fn bool adobe::any_regular_t::cast(T& x) const

\param
    x Value that will be set to the value stored in the any_regular_t.

\return
    <code>true</code> if x was set successfully, <code>false</code> otherwise.

\exception
    Undefined Will relay anything thrown by <code>x.operator=()</code>.
*/

/*!
\fn adobe::any_regular_t& adobe::any_regular_t::assign(const T& x)

\param x The new value to assign to this any_regular_t.

\return
    The any_regular_t with its new value set.
*/

/*!
\fn const adobe::type_info_t& adobe::any_regular_t::type() const

\return
    The information returned by <code>typeid()</code> for the instance value.
*/

/*!
\class adobe::any_regular_t::transform
\ingroup any_regular

\brief Function object used in binding for instance value access.
*/

/*!
\typedef adobe::any_regular_t::transform::result_type

The promoted value type from T that will be returned by this function object's
<code>operator()</code>s.
*/

/*!
\typedef adobe::any_regular_t::transform::argument_type

Parameter type required by this function object's <code>operator()</code>s.
*/

/*!
\fn promote<T>::type& adobe::any_regular_t::transform::operator()(any_regular_t &x) const

\param x The value from which the result is to be obtained.

\return
    A reference to the instance value stored in this any_regular_t.
*/

/*!
\fn const promote<T>::type& adobe::any_regular_t::transform::operator()(const any_regular_t &x)
const

\param x The value from which the result is to be obtained.

\return
    A reference to the instance value stored in this any_regular_t.
*/

/**************************************************************************************************/

namespace implementation {

enum { vtable_version = 2 };

/**************************************************************************************************/

struct any_regular_interface_t;

struct vtable_t {
    typedef any_regular_interface_t interface_type;

    std::uintptr_t version;
    void (*destruct)(const interface_type&);
    const std::type_info& (*type_info)(const interface_type&);
    interface_type* (*clone)(const interface_type&, void*);
    interface_type* (*move_clone)(interface_type&, void*);
    void (*assign)(interface_type&, const interface_type&);
    bool (*equals)(const interface_type&, const interface_type&);
    void (*exchange)(interface_type&, interface_type&);
    void (*serialize)(const interface_type&, std::ostream&);
};

// Ensure that the vtable_t has a fixed layout regardless of alignment or packing.

static_assert(sizeof(vtable_t) == 9 * sizeof(void*));

/**************************************************************************************************/

union pad_vtable_t {
    const vtable_t* vtable_m;
    double pad_m; // unused padding
};

static_assert(sizeof(pad_vtable_t) == sizeof(double));

/**************************************************************************************************/

struct any_regular_interface_t {
    typedef any_regular_interface_t interface_type;

    any_regular_interface_t(const vtable_t& x) { object_m.vtable_m = &x; }

    pad_vtable_t object_m;

    void destruct() const { return object_m.vtable_m->destruct(*this); }
    const std::type_info& type_info() const { return object_m.vtable_m->type_info(*this); }
    interface_type* clone(void* x) const { return object_m.vtable_m->clone(*this, x); }
    interface_type* move_clone(void* x) { return object_m.vtable_m->move_clone(*this, x); }
    void assign(const interface_type& x) { object_m.vtable_m->assign(*this, x); }
    bool equals(const interface_type& x) const { return object_m.vtable_m->equals(*this, x); }
    void exchange(interface_type& x) { object_m.vtable_m->exchange(*this, x); }
    void serialize(std::ostream& s) const { object_m.vtable_m->serialize(*this, s); }
};

/**************************************************************************************************/

template <typename T> // T models Regular
struct any_regular_model_local : any_regular_interface_t, boost::noncopyable {
    typedef any_regular_interface_t interface_type;

    T object_m;

    static const vtable_t vtable_s;

    any_regular_model_local() : interface_type(vtable_s), object_m() {}

    explicit any_regular_model_local(T x) : interface_type(vtable_s), object_m(std::move(x)) {}

    static const any_regular_model_local& self(const interface_type& x) {
        return static_cast<const any_regular_model_local&>(x);
    }

    static any_regular_model_local& self(interface_type& x) {
        return static_cast<any_regular_model_local&>(x);
    }

    static const std::type_info& type_info(const interface_type&) { return typeid(T); }

    static void destruct(const interface_type& x) { self(x).~any_regular_model_local(); }

    static interface_type* clone(const interface_type& x, void* storage) {
        return ::new (storage) any_regular_model_local(self(x).object_m);
    }

    static interface_type* move_clone(interface_type& x, void* storage) {
        return ::new (storage) any_regular_model_local(std::move(self(x).object_m));
    }

    static void assign(interface_type& x, const interface_type& y) {
        self(x).object_m = self(y).object_m;
    }

    static bool equals(const interface_type& x, const interface_type& y) {
        return self(x).object_m == self(y).object_m;
    }

    static void exchange(interface_type& x, interface_type& y) {
        swap(self(x).object_m, self(y).object_m);
    }

    static void serialize(const interface_type& x, std::ostream& s) { s << format(self(x).get()); }

    const T& get() const { return object_m; }
    T& get() { return object_m; }
};

static_assert(sizeof(any_regular_model_local<double>) == 16);

template <typename T>
const vtable_t any_regular_model_local<T>::vtable_s = {
    vtable_version,
    &any_regular_model_local::destruct,
    &any_regular_model_local::type_info,
    &any_regular_model_local::clone,
    &any_regular_model_local::move_clone,
    &any_regular_model_local::assign,
    &any_regular_model_local::equals,
    &any_regular_model_local::exchange,
    &any_regular_model_local::serialize,
};

template <typename T> // T models Regular
struct any_regular_model_remote : any_regular_interface_t, boost::noncopyable {
    BOOST_CLASS_REQUIRE(T, adobe, RegularConcept);

    typedef any_regular_interface_t interface_type;

    struct object_t;
    typedef capture_allocator<object_t> allocator_type;

    struct object_t : boost::noncopyable {
        aligned_storage<allocator_type> alloc_m;
        T data_m;
    };

    static object_t* new_move(T& x) {
        allocator_type a;
        object_t* result = a.allocate(1);
        construct_at(&result->alloc_m, aligned_storage<allocator_type>(a));
        construct_at(&result->data_m, std::move(x));
        return result;
    }

    object_t* object_ptr_m;

    static const vtable_t vtable_s;

    explicit any_regular_model_remote(T x) : interface_type(vtable_s), object_ptr_m(new_move(x)) {}

    any_regular_model_remote(any_regular_model_remote&& x) noexcept
        : interface_type(vtable_s), object_ptr_m(x.object_ptr_m) {
        x.object_ptr_m = 0;
    }

    ~any_regular_model_remote() {
        if (object_ptr_m) {
            allocator_type a = object_ptr_m->alloc_m.get();
            destroy(&object_ptr_m->alloc_m);
            destroy(&object_ptr_m->data_m);
            a.deallocate(object_ptr_m, 1);
        }
    }

    static const any_regular_model_remote& self(const interface_type& x) {
        return static_cast<const any_regular_model_remote&>(x);
    }

    static any_regular_model_remote& self(interface_type& x) {
        return static_cast<any_regular_model_remote&>(x);
    }

    static const std::type_info& type_info(const interface_type&) { return typeid(T); }

    static void destruct(const interface_type& x) { return self(x).~any_regular_model_remote(); }

    static interface_type* clone(const interface_type& x, void* storage) {
        return ::new (storage) any_regular_model_remote(self(x).get());
    }

    static interface_type* move_clone(interface_type& x, void* storage) {
        return ::new (storage) any_regular_model_remote(std::move(self(x)));
    }

    static void assign(interface_type& x, const interface_type& y) {
        self(x).get() = self(y).get();
    }

    static bool equals(const interface_type& x, const interface_type& y) {
        return self(x).get() == self(y).get();
    }

    static void exchange(interface_type& x, interface_type& y) {
        return swap(self(x).object_ptr_m, self(y).object_ptr_m);
    }

    static void serialize(const interface_type& x, std::ostream& s) { s << format(self(x).get()); }

    const T& get() const { return object_ptr_m->data_m; }
    T& get() { return object_ptr_m->data_m; }
};

static_assert(sizeof(any_regular_model_remote<double>) <= 16);

template <typename T>
const vtable_t any_regular_model_remote<T>::vtable_s = {
    vtable_version,
    &any_regular_model_remote::destruct,
    &any_regular_model_remote::type_info,
    &any_regular_model_remote::clone,
    &any_regular_model_remote::move_clone,
    &any_regular_model_remote::assign,
    &any_regular_model_remote::equals,
    &any_regular_model_remote::exchange,
    &any_regular_model_remote::serialize,
};

/**************************************************************************************************/

} // namespace implementation

/**************************************************************************************************/

namespace version_1 {

/**************************************************************************************************/

/*!
\ingroup any_regular

\brief A runtime polymorphic type similar to boost::any which can hold any type which models
    \ref concept_regular_type.

\model_of
    - \ref concept_movable

\details
\par Type Promotion
    \c any_regular_t leverages \c adobe::promote while storing instance values.
    \todo The reliance of any_regular_t on type promotion is current problematic and really
    ammounts to a poor-mans approach to refinements. In this case the desired functionality is
to
    be able to extract something which models a number regardless of the actual numeric type
    stored. The feature becomes especially important if serialization happens between the
    writer and reader. This is still an open problem.

\par Getting a Value
    \c any_regular_t uses <code>cast<>()</code> to get its instance value. It behaves like
    an explicit cast getting a any_regular_t out will always succeed and simply returns the same
    any_regular_t.

\par Setting a Value
    \c any_regular_t uses <code>assign<>()</code> to set its instance value. It behaves like
    an explicit assignment. Assigning an any_regular_t into a any_regular_t simply assigns the
    values; it does not introduce another layer of indirection.

\par How does adobe::any_regular_t differ from boost::any?
    any_regular_t differs from <a href="http://www.boost.org/doc/html/any.html">
    <code>boost::any</code></a> in several ways:
        - any_regular_t models \ref stldoc_EqualityComparable, fully modeling a
            \ref concept_regular_type.
        - any_regular_t supports type promotion. See <code>adobe::promote</code> for more
details.
        - cast<>() results are returned by reference, making any_regular_t generally more
efficient.
        - small values (less than or equal to 64 bits) with a non-throwing copy constructor or
which
            model \ref concept_movable are stored without a free store allocation.

\note With currently compilers the trait
<a
href="http://www.boost.org/doc/libs/1_35_0/libs/type_traits/doc/html/boost_typetraits/reference/has_nothrow_copy.html">
<code>boost::has_no_throw_copy</code></a> must be manually declared for small types to be stored
without a free store allocation.

\see_also
    adobe::runtime_cast

\tutorial
    A tutorial for \ref asl_tutorials_value_t is available.
*/

class any_regular_t : boost::equality_comparable<any_regular_t, any_regular_t> {
    typedef implementation::any_regular_interface_t interface_type;
    typedef double storage_t[2];

#ifndef ADOBE_NO_DOCUMENTATION

    template <typename T>
    struct traits {
        typedef typename promote<T>::type promote_type;
        BOOST_CLASS_REQUIRE(promote_type, adobe, RegularConcept);

        typedef promote_type& reference_type;
        typedef const promote_type& const_reference_type;

        typedef implementation::any_regular_model_local<promote_type> regular_model_local_type;
        typedef implementation::any_regular_model_remote<promote_type> regular_model_remote_type;

        typedef boost::mpl::bool_<(sizeof(regular_model_local_type) <= sizeof(storage_t)) &&
                                  (boost::has_nothrow_copy<promote_type>::value ||
                                   std::is_nothrow_move_constructible<promote_type>::value)>
            use_local_type;

        typedef typename boost::mpl::if_<use_local_type, regular_model_local_type,
                                         regular_model_remote_type>::type model_type;

        typedef typename boost::mpl::if_c<std::is_same<promote_type, T>::value, reference_type,
                                          T>::type result_type;

        typedef typename boost::mpl::if_c<std::is_same<promote_type, T>::value,
                                          const_reference_type, T>::type const_result_type;
    };

    template <typename T>
    struct helper;
    template <typename T>
    friend struct helper;

#endif

public:
    /*!
    \name Movable Functions
    \see_only
        \ref concept_movable
    */
    /*!@{*/
    any_regular_t() { ::new (storage()) traits<empty_t>::model_type(); }

    any_regular_t(const any_regular_t& x) { x.object().clone(storage()); }

    any_regular_t(any_regular_t&& x) noexcept { x.object().move_clone(storage()); }

    any_regular_t& operator=(any_regular_t x) {
        object().destruct();
        x.object().move_clone(storage());
        return *this;
    }

    ~any_regular_t() { object().destruct(); }
    /*!@}*/

    /*!@{*/

    /*!
    \param x Value is promoted to type \c promote<T>::type and stored in the object.
    */

    template <typename T>
    any_regular_t(T x) {
        ::new (storage()) typename traits<T>::model_type(std::move(x));
    }

    /*!@}*/

    /*!@{*/

    /*!
    \param x
        If \c promote<T>::type is equal to \c T then the value stored will be assigned to \c x,
        otherwise \c x is unchanged

    \return
        \true if \c x was assigned to, \false otherwise.
    */

    template <typename T>
    bool cast(T& x) const {
        if (type_info() != typeid(typename promote<T>::type))
            return false;
        x = cast<T>();
        return true;
    }

    template <typename T>
    typename traits<T>::const_result_type cast() const {
        return helper<T>::cast(*this);
    }

    /*!
    \return
        A [const]referece to the stored value if \c T is equal to \c promote<T>::type otherwise
        \c static_cast<T>(value) where value is the stored value is return.

    \exception adobe::bad_cast
        Thrown if \c promote<T>::type does not match the store instance type.
    */

    template <typename T>
    typename traits<T>::result_type cast() {
        return helper<T>::cast(*this);
    }

    /*!@}*/

    /*!@{*/

    /*!

    \param x
        Assigned to the stored value.

    \return
        The any_regular_t with its new value.
    */

    template <typename T>
    any_regular_t& assign(T x) {
        object().destruct();
        ::new (storage()) typename traits<T>::model_type(std::move(x));
        return *this;
    }

    any_regular_t& assign(any_regular_t x) {
        object().destruct();
        x.object().move_clone(storage());
        return *this;
    }

    /*!@}*/

    /*!@{*/

    /*!
    \return
        The information returned by <code>adobe::type_info<T>()</code> for the stored value.
    */

    const std::type_info& type_info() const { return object().type_info(); }

    /*!
    \brief Function object used in binding for instance value access.
    */

    /*!@}*/


    template <typename T>
    struct transform {
        typedef typename traits<T>::promote_type result_type;

        typename traits<T>::result_type operator()(any_regular_t& x) const { return x.cast<T>(); }

        typename traits<T>::const_result_type operator()(const any_regular_t& x) const {
            return x.cast<T>();
        }
    };

#if defined(ADOBE_STD_SERIALIZATION)
    // Problem: We want 'any' to be serializable. But 'any' can be implicitly
    // constructed from a type T making it difficult to determine if T is
    // serializable or if T converted to an 'any' is serializable. We wrap the
    // serialization in an explicit_const_any_regular_t to consume the one
    // allowed implicit cast by the compiler, preventing an infinite recursion
    // of T being converted to an any_regular_t and then attempting to re-
    // serialize.
    struct explicit_const_any_regular_t {
        explicit_const_any_regular_t(const any_regular_t& x) : p_m(x) {}

        const any_regular_t& p_m;
    };

    friend std::ostream& operator<<(std::ostream& out, const explicit_const_any_regular_t& value) {
        value.p_m.object().serialize(out);

        return out;
    }
#endif

    friend bool operator==(const any_regular_t& x, const any_regular_t& y);
    friend void swap(any_regular_t& x, any_regular_t& y);

private:
    any_regular_t(interface_type&& x) noexcept { x.move_clone(storage()); }

    interface_type& object() { return *static_cast<interface_type*>(storage()); }
    const interface_type& object() const { return *static_cast<const interface_type*>(storage()); }

    void* storage() { return &data_m; }
    const void* storage() const { return &data_m; }

    storage_t data_m;

#ifndef ADOBE_NO_DOCUMENTATION

#ifdef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
public:
#else
    template <typename, typename>
    friend struct adobe::runtime_cast_t;
#endif

    template <typename T>
    T* ptr_cast() {
        return helper<T>::ptr_cast(*this);
    }

#endif
};

#ifndef ADOBE_NO_DOCUMENTATION

static_assert(sizeof(any_regular_t) == 16);

inline bool operator==(const any_regular_t& x, const any_regular_t& y) {
    return (x.type_info() == y.type_info()) && x.object().equals(y.object());
}

inline void swap(any_regular_t& x, any_regular_t& y) {
    any_regular_t::interface_type& a(x.object());
    any_regular_t::interface_type& b(y.object());

    if (a.type_info() == b.type_info()) {
        a.exchange(b);
        return;
    }

    // x->tmp
    any_regular_t tmp = std::move(a);
    a.destruct();

    // y->x
    b.move_clone(x.storage());
    b.destruct();

    // tmp->y
    tmp.object().move_clone(y.storage());
}

#endif

/**************************************************************************************************/

#ifndef ADOBE_NO_DOCUMENTATION

template <typename T>
struct any_regular_t::helper {
    static inline T* ptr_cast(any_regular_t& r) {
        if (r.type_info() != typeid(T))
            return 0;
        return &reinterpret_cast<typename traits<T>::model_type&>(r.object()).get();
    }

    static inline typename traits<T>::const_result_type cast(const any_regular_t& r) {
        typedef typename traits<T>::promote_type promote_type;

        if (r.type_info() != typeid(promote_type))
            throw bad_cast(r.type_info(), typeid(promote_type));
        return static_cast<typename traits<T>::const_result_type>(
            reinterpret_cast<const typename traits<T>::model_type&>(r.object()).get());
    }

    static inline typename traits<T>::result_type cast(any_regular_t& r) {
        typedef typename traits<T>::promote_type promote_type;

        if (r.type_info() != typeid(promote_type))
            throw bad_cast(r.type_info(), typeid(promote_type));
        return static_cast<typename traits<T>::result_type>(
            reinterpret_cast<typename traits<T>::model_type&>(r.object()).get());
    }

    static inline any_regular_t& assign(any_regular_t& r, const T& x) {
        typedef typename promote<T>::type promote_type;

        if (r.type_info() == typeid(promote_type))
            r.cast<promote_type>() = static_cast<promote_type>(x);
        else {
            any_regular_t result(x);
            swap(r, result);
        }
        return r;
    }
};

/**************************************************************************************************/

template <>
struct any_regular_t::helper<any_regular_t> {
    static inline any_regular_t* ptr_cast(any_regular_t& r) { return &r; }

    static inline const any_regular_t& cast(const any_regular_t& r) { return r; }

    static inline any_regular_t& cast(any_regular_t& r) { return r; }
};

#endif

/**************************************************************************************************/

} // namespace version_1

/**************************************************************************************************/

/*!
    \return \true if \c x contains \c empty_t(), \false otherwise.

    \related adobe::version_1::any_regular_t
*/

inline bool empty(const any_regular_t& x) { return x.type_info() == typeid(empty_t); }

/**************************************************************************************************/

/*!
    \related adobe::version_1::any_regular_t
*/

/**************************************************************************************************/

template <typename R>
struct runtime_cast_t<R, const any_regular_t> {
    R operator()(const any_regular_t& x) const {
        typedef typename boost::remove_const<typename boost::remove_reference<R>::type>::type
            result_type;

        static_assert(boost::is_reference<R>::value);

        /* There is no auto-promotion through the new interface. Soon promotion will be disabled. */
        static_assert(std::is_same<typename promote<result_type>::type, result_type>::value);

        return x.cast<result_type>();
    }
};

/**************************************************************************************************/

template <typename R>
struct runtime_cast_t<R, any_regular_t> {
    R operator()(any_regular_t& x) const {
        typedef typename boost::remove_reference<R>::type result_type;

        static_assert(boost::is_reference<R>::value);

        /* There is no auto-promotion through the new interface. Soon promotion will be disabled. */
        static_assert(std::is_same<typename promote<result_type>::type, result_type>::value);

        return x.cast<result_type>();
    }
};

/**************************************************************************************************/

template <typename R>
struct runtime_cast_t<R, any_regular_t*> {
    R operator()(any_regular_t* x) const {
        typedef typename boost::remove_pointer<R>::type result_type;

        static_assert(boost::is_pointer<R>::value);

        /* There is no auto-promotion through the new interface. Soon promotion will be disabled. */
        static_assert(std::is_same<typename promote<result_type>::type, result_type>::value);

        return x->ptr_cast<result_type>();
    }
};

/**************************************************************************************************/

template <typename R>
struct runtime_cast_t<R, const any_regular_t*> {
    R operator()(const any_regular_t* x) const {
        typedef
            typename boost::remove_const<typename boost::remove_pointer<R>::type>::type result_type;

        static_assert(boost::is_pointer<R>::value);

        /* There is no auto-promotion through the new interface. Soon promotion will be disabled. */
        static_assert(std::is_same<typename promote<result_type>::type, result_type>::value);

        if (x->type_info() != typeid(result_type))
            return 0;
        return &x->cast<result_type>();
    }
};

/**************************************************************************************************/

} // namespace adobe

/**************************************************************************************************/

#endif

/**************************************************************************************************/