text: /*
   * Copyright © 2018  Google, Inc.
   *
   *  This is part of HarfBuzz, a text shaping library.
   *
   * Permission is hereby granted, without written agreement and without
   * license or royalty fees, to use, copy, modify, and distribute this
   * software and its documentation for any purpose, provided that the
   * above copyright notice and the following two paragraphs appear in
   * all copies of this software.
   *
   * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
   * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
   * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
   * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
   * DAMAGE.
   *
   * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
   * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
   * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
   * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
   * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
   *
   * Google Author(s): Behdad Esfahbod
   */
  
  #ifndef HB_META_HH
  #define HB_META_HH
  
  #include "hb.hh"
  
  
  /*
   * C++ template meta-programming & fundamentals used with them.
   */
  
  /* Void!  For when we need a expression-type of void. */
  struct hb_empty_t {};
  
  /* https://en.cppreference.com/w/cpp/types/void_t */
  template<typename... Ts> struct _hb_void_t { typedef void type; };
  template<typename... Ts> using hb_void_t = typename _hb_void_t<Ts...>::type;
  
  template<typename Head, typename... Ts> struct _hb_head_t { typedef Head type; };
  template<typename... Ts> using hb_head_t = typename _hb_head_t<Ts...>::type;
  
  template <typename T, T v> struct hb_integral_constant { static constexpr T value = v; };
  template <bool b> using hb_bool_constant = hb_integral_constant<bool, b>;
  using hb_true_type = hb_bool_constant<true>;
  using hb_false_type = hb_bool_constant<false>;
  
  
  /* Basic type SFINAE. */
  
  template <bool B, typename T = void> struct hb_enable_if {};
  template <typename T>                struct hb_enable_if<true, T> { typedef T type; };
  #define hb_enable_if(Cond) typename hb_enable_if<(Cond)>::type* = nullptr
  /* Concepts/Requires alias: */
  #define hb_requires(Cond) hb_enable_if((Cond))
  
  template <typename T, typename T2> struct hb_is_same : hb_false_type {};
  template <typename T>              struct hb_is_same<T, T> : hb_true_type {};
  #define hb_is_same(T, T2) hb_is_same<T, T2>::value
  
  /* Function overloading SFINAE and priority. */
  
  #define HB_RETURN(Ret, E) -> hb_head_t<Ret, decltype ((E))> { return (E); }
  #define HB_AUTO_RETURN(E) -> decltype ((E)) { return (E); }
  #define HB_VOID_RETURN(E) -> hb_void_t<decltype ((E))> { (E); }
  
  template <unsigned Pri> struct hb_priority : hb_priority<Pri - 1> {};
  template <>             struct hb_priority<0> {};
  #define hb_prioritize hb_priority<16> ()
  
  #define HB_FUNCOBJ(x) static_const x HB_UNUSED
  
  
  template <typename T> struct hb_type_identity_t { typedef T type; };
  template <typename T> using hb_type_identity = typename hb_type_identity_t<T>::type;
  
  struct
  {
    template <typename T> constexpr T*
    operator () (T& arg) const
    {
  #pragma GCC diagnostic push
  #pragma GCC diagnostic ignored "-Wcast-align"
      /* https://en.cppreference.com/w/cpp/memory/addressof */
      return reinterpret_cast<T*> (
  	     &const_cast<char&> (
  		reinterpret_cast<const volatile char&> (arg)));
  #pragma GCC diagnostic pop
    }
  }
  HB_FUNCOBJ (hb_addressof);
  
  template <typename T> static inline T hb_declval ();
  #define hb_declval(T) (hb_declval<T> ())
  
  template <typename T> struct hb_match_const		: hb_type_identity_t<T>, hb_bool_constant<false>{};
  template <typename T> struct hb_match_const<const T>	: hb_type_identity_t<T>, hb_bool_constant<true>	{};
  template <typename T> using hb_remove_const = typename hb_match_const<T>::type;
  template <typename T> using hb_add_const = const T;
  #define hb_is_const(T) hb_match_const<T>::value
  template <typename T> struct hb_match_reference		: hb_type_identity_t<T>, hb_bool_constant<false>{};
  template <typename T> struct hb_match_reference<T &>	: hb_type_identity_t<T>, hb_bool_constant<true>	{};
  template <typename T> struct hb_match_reference<T &&>	: hb_type_identity_t<T>, hb_bool_constant<true>	{};
  template <typename T> using hb_remove_reference = typename hb_match_reference<T>::type;
  template <typename T> auto _hb_try_add_lvalue_reference (hb_priority<1>) -> hb_type_identity<T&>;
  template <typename T> auto _hb_try_add_lvalue_reference (hb_priority<0>) -> hb_type_identity<T>;
  template <typename T> using hb_add_lvalue_reference = decltype (_hb_try_add_lvalue_reference<T> (hb_prioritize));
  template <typename T> auto _hb_try_add_rvalue_reference (hb_priority<1>) -> hb_type_identity<T&&>;
  template <typename T> auto _hb_try_add_rvalue_reference (hb_priority<0>) -> hb_type_identity<T>;
  template <typename T> using hb_add_rvalue_reference = decltype (_hb_try_add_rvalue_reference<T> (hb_prioritize));
  #define hb_is_reference(T) hb_match_reference<T>::value
  template <typename T> struct hb_match_pointer		: hb_type_identity_t<T>, hb_bool_constant<false>{};
  template <typename T> struct hb_match_pointer<T *>	: hb_type_identity_t<T>, hb_bool_constant<true>	{};
  template <typename T> using hb_remove_pointer = typename hb_match_pointer<T>::type;
  template <typename T> auto _hb_try_add_pointer (hb_priority<1>) -> hb_type_identity<hb_remove_reference<T>*>;
  template <typename T> auto _hb_try_add_pointer (hb_priority<1>) -> hb_type_identity<T>;
  template <typename T> using hb_add_pointer = decltype (_hb_try_add_pointer<T> (hb_prioritize));
  #define hb_is_pointer(T) hb_match_pointer<T>::value
  
  
  /* TODO Add feature-parity to std::decay. */
  template <typename T> using hb_decay = hb_remove_const<hb_remove_reference<T>>;
  
  
  template<bool B, class T, class F>
  struct _hb_conditional { typedef T type; };
  template<class T, class F>
  struct _hb_conditional<false, T, F> { typedef F type; };
  template<bool B, class T, class F>
  using hb_conditional = typename _hb_conditional<B, T, F>::type;
  
  
  template <typename From, typename To>
  struct hb_is_convertible
  {
    private:
    static constexpr bool   from_void = hb_is_same (void, hb_decay<From>);
    static constexpr bool     to_void = hb_is_same (void, hb_decay<To>  );
    static constexpr bool either_void = from_void || to_void;
    static constexpr bool   both_void = from_void && to_void;
  
    static hb_true_type impl2 (hb_conditional<to_void, int, To>);
  
    template <typename T>
    static auto impl (hb_priority<1>) -> decltype (impl2 (hb_declval (T)));
    template <typename T>
    static hb_false_type impl (hb_priority<0>);
    public:
    static constexpr bool value = both_void ||
  		       (!either_void &&
  			decltype (impl<hb_conditional<from_void, int, From>> (hb_prioritize))::value);
  };
  #define hb_is_convertible(From,To) hb_is_convertible<From, To>::value
  
  template <typename Base, typename Derived>
  using hb_is_base_of = hb_is_convertible<hb_decay<Derived> *, hb_decay<Base> *>;
  #define hb_is_base_of(Base,Derived) hb_is_base_of<Base, Derived>::value
  
  template <typename From, typename To>
  using hb_is_cr_convertible = hb_bool_constant<
    hb_is_same (hb_decay<From>, hb_decay<To>) &&
    (!hb_is_const (From) || hb_is_const (To)) &&
    (!hb_is_reference (To) || hb_is_const (To) || hb_is_reference (To))
  >;
  #define hb_is_cr_convertible(From,To) hb_is_cr_convertible<From, To>::value
  
  /* std::move and std::forward */
  
  template <typename T>
  static constexpr hb_remove_reference<T>&& hb_move (T&& t) { return (hb_remove_reference<T>&&) (t); }
  
  template <typename T>
  static constexpr T&& hb_forward (hb_remove_reference<T>& t) { return (T&&) t; }
  template <typename T>
  static constexpr T&& hb_forward (hb_remove_reference<T>&& t) { return (T&&) t; }
  
  struct
  {
    template <typename T> constexpr auto
    operator () (T&& v) const HB_AUTO_RETURN (hb_forward<T> (v))
  
    template <typename T> constexpr auto
    operator () (T *v) const HB_AUTO_RETURN (*v)
  }
  HB_FUNCOBJ (hb_deref);
  
  struct
  {
    template <typename T> constexpr auto
    operator () (T&& v) const HB_AUTO_RETURN (hb_forward<T> (v))
  
    template <typename T> constexpr auto
    operator () (T& v) const HB_AUTO_RETURN (hb_addressof (v))
  }
  HB_FUNCOBJ (hb_ref);
  
  template <typename T>
  struct hb_reference_wrapper
  {
    hb_reference_wrapper (T v) : v (v) {}
    bool operator == (const hb_reference_wrapper& o) const { return v == o.v; }
    bool operator != (const hb_reference_wrapper& o) const { return v != o.v; }
    operator T () const { return v; }
    T get () const { return v; }
    T v;
  };
  template <typename T>
  struct hb_reference_wrapper<T&>
  {
    hb_reference_wrapper (T& v) : v (hb_addressof (v)) {}
    bool operator == (const hb_reference_wrapper& o) const { return v == o.v; }
    bool operator != (const hb_reference_wrapper& o) const { return v != o.v; }
    operator T& () const { return *v; }
    T& get () const { return *v; }
    T* v;
  };
  
  
  template <typename T>
  using hb_is_integral = hb_bool_constant<
    hb_is_same (hb_decay<T>, char) ||
    hb_is_same (hb_decay<T>, signed char) ||
    hb_is_same (hb_decay<T>, unsigned char) ||
    hb_is_same (hb_decay<T>, signed int) ||
    hb_is_same (hb_decay<T>, unsigned int) ||
    hb_is_same (hb_decay<T>, signed short) ||
    hb_is_same (hb_decay<T>, unsigned short) ||
    hb_is_same (hb_decay<T>, signed long) ||
    hb_is_same (hb_decay<T>, unsigned long) ||
    hb_is_same (hb_decay<T>, signed long long) ||
    hb_is_same (hb_decay<T>, unsigned long long) ||
    false
  >;
  #define hb_is_integral(T) hb_is_integral<T>::value
  template <typename T>
  using hb_is_floating_point = hb_bool_constant<
    hb_is_same (hb_decay<T>, float) ||
    hb_is_same (hb_decay<T>, double) ||
    hb_is_same (hb_decay<T>, long double) ||
    false
  >;
  #define hb_is_floating_point(T) hb_is_floating_point<T>::value
  template <typename T>
  using hb_is_arithmetic = hb_bool_constant<
    hb_is_integral (T) ||
    hb_is_floating_point (T) ||
    false
  >;
  #define hb_is_arithmetic(T) hb_is_arithmetic<T>::value
  
  
  template <typename T>
  using hb_is_signed = hb_conditional<hb_is_arithmetic (T),
  				    hb_bool_constant<(T) -1 < (T) 0>,
  				    hb_false_type>;
  #define hb_is_signed(T) hb_is_signed<T>::value
  template <typename T>
  using hb_is_unsigned = hb_conditional<hb_is_arithmetic (T),
  				      hb_bool_constant<(T) 0 < (T) -1>,
  				      hb_false_type>;
  #define hb_is_unsigned(T) hb_is_unsigned<T>::value
  
  template <typename T> struct hb_int_min;
  template <> struct hb_int_min<char>			: hb_integral_constant<char,			CHAR_MIN>	{};
  template <> struct hb_int_min<signed char>		: hb_integral_constant<signed char,		SCHAR_MIN>	{};
  template <> struct hb_int_min<unsigned char>		: hb_integral_constant<unsigned char,		0>		{};
  template <> struct hb_int_min<signed short>		: hb_integral_constant<signed short,		SHRT_MIN>	{};
  template <> struct hb_int_min<unsigned short>		: hb_integral_constant<unsigned short,		0>		{};
  template <> struct hb_int_min<signed int>		: hb_integral_constant<signed int,		INT_MIN>	{};
  template <> struct hb_int_min<unsigned int>		: hb_integral_constant<unsigned int,		0>		{};
  template <> struct hb_int_min<signed long>		: hb_integral_constant<signed long,		LONG_MIN>	{};
  template <> struct hb_int_min<unsigned long>		: hb_integral_constant<unsigned long,		0>		{};
  template <> struct hb_int_min<signed long long>		: hb_integral_constant<signed long long,	LLONG_MIN>	{};
  template <> struct hb_int_min<unsigned long long>	: hb_integral_constant<unsigned long long,	0>		{};
  #define hb_int_min(T) hb_int_min<T>::value
  template <typename T> struct hb_int_max;
  template <> struct hb_int_max<char>			: hb_integral_constant<char,			CHAR_MAX>	{};
  template <> struct hb_int_max<signed char>		: hb_integral_constant<signed char,		SCHAR_MAX>	{};
  template <> struct hb_int_max<unsigned char>		: hb_integral_constant<unsigned char,		UCHAR_MAX>	{};
  template <> struct hb_int_max<signed short>		: hb_integral_constant<signed short,		SHRT_MAX>	{};
  template <> struct hb_int_max<unsigned short>		: hb_integral_constant<unsigned short,		USHRT_MAX>	{};
  template <> struct hb_int_max<signed int>		: hb_integral_constant<signed int,		INT_MAX>	{};
  template <> struct hb_int_max<unsigned int>		: hb_integral_constant<unsigned int,		UINT_MAX>	{};
  template <> struct hb_int_max<signed long>		: hb_integral_constant<signed long,		LONG_MAX>	{};
  template <> struct hb_int_max<unsigned long>		: hb_integral_constant<unsigned long,		ULONG_MAX>	{};
  template <> struct hb_int_max<signed long long>		: hb_integral_constant<signed long long,	LLONG_MAX>	{};
  template <> struct hb_int_max<unsigned long long>	: hb_integral_constant<unsigned long long,	ULLONG_MAX>	{};
  #define hb_int_max(T) hb_int_max<T>::value
  
  
  
  template <typename T, typename>
  struct _hb_is_destructible : hb_false_type {};
  template <typename T>
  struct _hb_is_destructible<T, hb_void_t<decltype (hb_declval (T).~T ())>> : hb_true_type {};
  template <typename T>
  using hb_is_destructible = _hb_is_destructible<T, void>;
  #define hb_is_destructible(T) hb_is_destructible<T>::value
  
  template <typename T, typename, typename ...Ts>
  struct _hb_is_constructible : hb_false_type {};
  template <typename T, typename ...Ts>
  struct _hb_is_constructible<T, hb_void_t<decltype (T (hb_declval (Ts)...))>, Ts...> : hb_true_type {};
  template <typename T, typename ...Ts>
  using hb_is_constructible = _hb_is_constructible<T, void, Ts...>;
  #define hb_is_constructible(...) hb_is_constructible<__VA_ARGS__>::value
  
  template <typename T>
  using hb_is_default_constructible = hb_is_constructible<T>;
  #define hb_is_default_constructible(T) hb_is_default_constructible<T>::value
  
  template <typename T>
  using hb_is_copy_constructible = hb_is_constructible<T, hb_add_lvalue_reference<hb_add_const<T>>>;
  #define hb_is_copy_constructible(T) hb_is_copy_constructible<T>::value
  
  template <typename T>
  using hb_is_move_constructible = hb_is_constructible<T, hb_add_rvalue_reference<hb_add_const<T>>>;
  #define hb_is_move_constructible(T) hb_is_move_constructible<T>::value
  
  template <typename T, typename U, typename>
  struct _hb_is_assignable : hb_false_type {};
  template <typename T, typename U>
  struct _hb_is_assignable<T, U, hb_void_t<decltype (hb_declval (T) = hb_declval (U))>> : hb_true_type {};
  template <typename T, typename U>
  using hb_is_assignable = _hb_is_assignable<T, U, void>;
  #define hb_is_assignable(T,U) hb_is_assignable<T, U>::value
  
  template <typename T>
  using hb_is_copy_assignable = hb_is_assignable<hb_add_lvalue_reference<T>,
  					       hb_add_lvalue_reference<hb_add_const<T>>>;
  #define hb_is_copy_assignable(T) hb_is_copy_assignable<T>::value
  
  template <typename T>
  using hb_is_move_assignable = hb_is_assignable<hb_add_lvalue_reference<T>,
  					       hb_add_rvalue_reference<T>>;
  #define hb_is_move_assignable(T) hb_is_move_assignable<T>::value
  
  /* Trivial versions. */
  
  template <typename T> union hb_trivial { T value; };
  
  /* Don't know how to do the following. */
  template <typename T>
  using hb_is_trivially_destructible= hb_is_destructible<hb_trivial<T>>;
  #define hb_is_trivially_destructible(T) hb_is_trivially_destructible<T>::value
  
  /* Don't know how to do the following. */
  //template <typename T, typename ...Ts>
  //using hb_is_trivially_constructible= hb_is_constructible<hb_trivial<T>, hb_trivial<Ts>...>;
  //#define hb_is_trivially_constructible(...) hb_is_trivially_constructible<__VA_ARGS__>::value
  
  template <typename T>
  using hb_is_trivially_default_constructible= hb_is_default_constructible<hb_trivial<T>>;
  #define hb_is_trivially_default_constructible(T) hb_is_trivially_default_constructible<T>::value
  
  template <typename T>
  using hb_is_trivially_copy_constructible= hb_is_copy_constructible<hb_trivial<T>>;
  #define hb_is_trivially_copy_constructible(T) hb_is_trivially_copy_constructible<T>::value
  
  template <typename T>
  using hb_is_trivially_move_constructible= hb_is_move_constructible<hb_trivial<T>>;
  #define hb_is_trivially_move_constructible(T) hb_is_trivially_move_constructible<T>::value
  
  /* Don't know how to do the following. */
  //template <typename T, typename U>
  //using hb_is_trivially_assignable= hb_is_assignable<hb_trivial<T>, hb_trivial<U>>;
  //#define hb_is_trivially_assignable(T,U) hb_is_trivially_assignable<T, U>::value
  
  template <typename T>
  using hb_is_trivially_copy_assignable= hb_is_copy_assignable<hb_trivial<T>>;
  #define hb_is_trivially_copy_assignable(T) hb_is_trivially_copy_assignable<T>::value
  
  template <typename T>
  using hb_is_trivially_move_assignable= hb_is_move_assignable<hb_trivial<T>>;
  #define hb_is_trivially_move_assignable(T) hb_is_trivially_move_assignable<T>::value
  
  template <typename T>
  using hb_is_trivially_copyable= hb_bool_constant<
    hb_is_trivially_destructible (T) &&
    (!hb_is_move_assignable (T) || hb_is_trivially_move_assignable (T)) &&
    (!hb_is_move_constructible (T) || hb_is_trivially_move_constructible (T)) &&
    (!hb_is_copy_assignable (T) || hb_is_trivially_copy_assignable (T)) &&
    (!hb_is_copy_constructible (T) || hb_is_trivially_copy_constructible (T)) &&
    true
  >;
  #define hb_is_trivially_copyable(T) hb_is_trivially_copyable<T>::value
  
  template <typename T>
  using hb_is_trivial= hb_bool_constant<
    hb_is_trivially_copyable (T) &&
    hb_is_trivially_default_constructible (T)
  >;
  #define hb_is_trivial(T) hb_is_trivial<T>::value
  
  
  #endif /* HB_META_HH */
  