1 /* 2 * Copyright © 2018 Google, Inc. 3 * 4 * This is part of HarfBuzz, a text shaping library. 5 * 6 * Permission is hereby granted, without written agreement and without 7 * license or royalty fees, to use, copy, modify, and distribute this 8 * software and its documentation for any purpose, provided that the 9 * above copyright notice and the following two paragraphs appear in 10 * all copies of this software. 11 * 12 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR 13 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES 14 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN 15 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH 16 * DAMAGE. 17 * 18 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, 19 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND 20 * FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS 21 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO 22 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. 23 * 24 * Google Author(s): Behdad Esfahbod 25 */ 26 27 #ifndef HB_META_HH 28 #define HB_META_HH 29 30 #include "hb.hh" 31 32 #include <type_traits> 33 #include <utility> 34 35 36 /* 37 * C++ template meta-programming & fundamentals used with them. 38 */ 39 40 /* Void! For when we need a expression-type of void. */ 41 struct hb_empty_t {}; 42 43 /* https://en.cppreference.com/w/cpp/types/void_t */ 44 template<typename... Ts> struct _hb_void_t { typedef void type; }; 45 template<typename... Ts> using hb_void_t = typename _hb_void_t<Ts...>::type; 46 47 template<typename Head, typename... Ts> struct _hb_head_t { typedef Head type; }; 48 template<typename... Ts> using hb_head_t = typename _hb_head_t<Ts...>::type; 49 50 template <typename T, T v> struct hb_integral_constant { static constexpr T value = v; }; 51 template <bool b> using hb_bool_constant = hb_integral_constant<bool, b>; 52 using hb_true_type = hb_bool_constant<true>; 53 using hb_false_type = hb_bool_constant<false>; 54 55 /* Static-assert as expression. */ 56 template <bool cond> struct static_assert_expr; 57 template <> struct static_assert_expr<true> : hb_false_type {}; 58 #define static_assert_expr(C) static_assert_expr<C>::value 59 60 /* Basic type SFINAE. */ 61 62 template <bool B, typename T = void> struct hb_enable_if {}; 63 template <typename T> struct hb_enable_if<true, T> { typedef T type; }; 64 #define hb_enable_if(Cond) typename hb_enable_if<(Cond)>::type* = nullptr 65 /* Concepts/Requires alias: */ 66 #define hb_requires(Cond) hb_enable_if((Cond)) 67 68 template <typename T, typename T2> struct hb_is_same : hb_false_type {}; 69 template <typename T> struct hb_is_same<T, T> : hb_true_type {}; 70 #define hb_is_same(T, T2) hb_is_same<T, T2>::value 71 72 /* Function overloading SFINAE and priority. */ 73 74 #define HB_RETURN(Ret, E) -> hb_head_t<Ret, decltype ((E))> { return (E); } 75 #define HB_AUTO_RETURN(E) -> decltype ((E)) { return (E); } 76 #define HB_VOID_RETURN(E) -> hb_void_t<decltype ((E))> { (E); } 77 78 template <unsigned Pri> struct hb_priority : hb_priority<Pri - 1> {}; 79 template <> struct hb_priority<0> {}; 80 #define hb_prioritize hb_priority<16> () 81 82 #define HB_FUNCOBJ(x) static_const x HB_UNUSED 83 84 85 template <typename T> struct hb_type_identity_t { typedef T type; }; 86 template <typename T> using hb_type_identity = typename hb_type_identity_t<T>::type; 87 88 struct 89 { 90 template <typename T> constexpr T* operator ()__anon68fac5d2010891 operator () (T& arg) const 92 { 93 #pragma GCC diagnostic push 94 #pragma GCC diagnostic ignored "-Wcast-align" 95 /* https://en.cppreference.com/w/cpp/memory/addressof */ 96 return reinterpret_cast<T*> ( 97 &const_cast<char&> ( 98 reinterpret_cast<const volatile char&> (arg))); 99 #pragma GCC diagnostic pop 100 } 101 } 102 HB_FUNCOBJ (hb_addressof); 103 104 template <typename T> static inline T hb_declval (); 105 #define hb_declval(T) (hb_declval<T> ()) 106 107 template <typename T> struct hb_match_const : hb_type_identity_t<T>, hb_false_type {}; 108 template <typename T> struct hb_match_const<const T> : hb_type_identity_t<T>, hb_true_type {}; 109 template <typename T> using hb_remove_const = typename hb_match_const<T>::type; 110 template <typename T> using hb_add_const = const T; 111 #define hb_is_const(T) hb_match_const<T>::value 112 template <typename T> struct hb_match_reference : hb_type_identity_t<T>, hb_false_type {}; 113 template <typename T> struct hb_match_reference<T &> : hb_type_identity_t<T>, hb_true_type {}; 114 template <typename T> struct hb_match_reference<T &&> : hb_type_identity_t<T>, hb_true_type {}; 115 template <typename T> using hb_remove_reference = typename hb_match_reference<T>::type; 116 template <typename T> auto _hb_try_add_lvalue_reference (hb_priority<1>) -> hb_type_identity<T&>; 117 template <typename T> auto _hb_try_add_lvalue_reference (hb_priority<0>) -> hb_type_identity<T>; 118 template <typename T> using hb_add_lvalue_reference = decltype (_hb_try_add_lvalue_reference<T> (hb_prioritize)); 119 template <typename T> auto _hb_try_add_rvalue_reference (hb_priority<1>) -> hb_type_identity<T&&>; 120 template <typename T> auto _hb_try_add_rvalue_reference (hb_priority<0>) -> hb_type_identity<T>; 121 template <typename T> using hb_add_rvalue_reference = decltype (_hb_try_add_rvalue_reference<T> (hb_prioritize)); 122 #define hb_is_reference(T) hb_match_reference<T>::value 123 template <typename T> struct hb_match_pointer : hb_type_identity_t<T>, hb_false_type {}; 124 template <typename T> struct hb_match_pointer<T *> : hb_type_identity_t<T>, hb_true_type {}; 125 template <typename T> using hb_remove_pointer = typename hb_match_pointer<T>::type; 126 template <typename T> auto _hb_try_add_pointer (hb_priority<1>) -> hb_type_identity<hb_remove_reference<T>*>; 127 template <typename T> auto _hb_try_add_pointer (hb_priority<1>) -> hb_type_identity<T>; 128 template <typename T> using hb_add_pointer = decltype (_hb_try_add_pointer<T> (hb_prioritize)); 129 #define hb_is_pointer(T) hb_match_pointer<T>::value 130 131 132 /* TODO Add feature-parity to std::decay. */ 133 template <typename T> using hb_decay = hb_remove_const<hb_remove_reference<T>>; 134 135 #define hb_is_convertible(From,To) std::is_convertible<From, To>::value 136 137 template <typename From, typename To> 138 using hb_is_cr_convertible = hb_bool_constant< 139 hb_is_same (hb_decay<From>, hb_decay<To>) && 140 (!hb_is_const (From) || hb_is_const (To)) && 141 (!hb_is_reference (To) || hb_is_const (To) || hb_is_reference (To)) 142 >; 143 #define hb_is_cr_convertible(From,To) hb_is_cr_convertible<From, To>::value 144 145 146 struct 147 { 148 template <typename T> constexpr auto 149 operator () (T&& v) const HB_AUTO_RETURN (std::forward<T> (v)) 150 151 template <typename T> constexpr auto 152 operator () (T *v) const HB_AUTO_RETURN (*v) 153 } 154 HB_FUNCOBJ (hb_deref); 155 156 struct 157 { 158 template <typename T> constexpr auto 159 operator () (T&& v) const HB_AUTO_RETURN (std::forward<T> (v)) 160 161 template <typename T> constexpr auto 162 operator () (T& v) const HB_AUTO_RETURN (hb_addressof (v)) 163 } 164 HB_FUNCOBJ (hb_ref); 165 166 template <typename T> 167 struct hb_reference_wrapper 168 { hb_reference_wrapperhb_reference_wrapper169 hb_reference_wrapper (T v) : v (v) {} operator ==hb_reference_wrapper170 bool operator == (const hb_reference_wrapper& o) const { return v == o.v; } operator !=hb_reference_wrapper171 bool operator != (const hb_reference_wrapper& o) const { return v != o.v; } operator Thb_reference_wrapper172 operator T () const { return v; } gethb_reference_wrapper173 T get () const { return v; } 174 T v; 175 }; 176 template <typename T> 177 struct hb_reference_wrapper<T&> 178 { hb_reference_wrapperhb_reference_wrapper179 hb_reference_wrapper (T& v) : v (hb_addressof (v)) {} operator ==hb_reference_wrapper180 bool operator == (const hb_reference_wrapper& o) const { return v == o.v; } operator !=hb_reference_wrapper181 bool operator != (const hb_reference_wrapper& o) const { return v != o.v; } operator T&hb_reference_wrapper182 operator T& () const { return *v; } gethb_reference_wrapper183 T& get () const { return *v; } 184 T* v; 185 }; 186 187 188 /* Type traits */ 189 190 template <typename T> struct hb_int_min; 191 template <> struct hb_int_min<char> : hb_integral_constant<char, CHAR_MIN> {}; 192 template <> struct hb_int_min<signed char> : hb_integral_constant<signed char, SCHAR_MIN> {}; 193 template <> struct hb_int_min<unsigned char> : hb_integral_constant<unsigned char, 0> {}; 194 template <> struct hb_int_min<signed short> : hb_integral_constant<signed short, SHRT_MIN> {}; 195 template <> struct hb_int_min<unsigned short> : hb_integral_constant<unsigned short, 0> {}; 196 template <> struct hb_int_min<signed int> : hb_integral_constant<signed int, INT_MIN> {}; 197 template <> struct hb_int_min<unsigned int> : hb_integral_constant<unsigned int, 0> {}; 198 template <> struct hb_int_min<signed long> : hb_integral_constant<signed long, LONG_MIN> {}; 199 template <> struct hb_int_min<unsigned long> : hb_integral_constant<unsigned long, 0> {}; 200 template <> struct hb_int_min<signed long long> : hb_integral_constant<signed long long, LLONG_MIN> {}; 201 template <> struct hb_int_min<unsigned long long> : hb_integral_constant<unsigned long long, 0> {}; 202 template <typename T> struct hb_int_min<T *> : hb_integral_constant<T *, nullptr> {}; 203 #define hb_int_min(T) hb_int_min<T>::value 204 template <typename T> struct hb_int_max; 205 template <> struct hb_int_max<char> : hb_integral_constant<char, CHAR_MAX> {}; 206 template <> struct hb_int_max<signed char> : hb_integral_constant<signed char, SCHAR_MAX> {}; 207 template <> struct hb_int_max<unsigned char> : hb_integral_constant<unsigned char, UCHAR_MAX> {}; 208 template <> struct hb_int_max<signed short> : hb_integral_constant<signed short, SHRT_MAX> {}; 209 template <> struct hb_int_max<unsigned short> : hb_integral_constant<unsigned short, USHRT_MAX> {}; 210 template <> struct hb_int_max<signed int> : hb_integral_constant<signed int, INT_MAX> {}; 211 template <> struct hb_int_max<unsigned int> : hb_integral_constant<unsigned int, UINT_MAX> {}; 212 template <> struct hb_int_max<signed long> : hb_integral_constant<signed long, LONG_MAX> {}; 213 template <> struct hb_int_max<unsigned long> : hb_integral_constant<unsigned long, ULONG_MAX> {}; 214 template <> struct hb_int_max<signed long long> : hb_integral_constant<signed long long, LLONG_MAX> {}; 215 template <> struct hb_int_max<unsigned long long> : hb_integral_constant<unsigned long long, ULLONG_MAX> {}; 216 #define hb_int_max(T) hb_int_max<T>::value 217 218 219 /* Class traits. */ 220 221 #define HB_DELETE_COPY_ASSIGN(TypeName) \ 222 TypeName(const TypeName&) = delete; \ 223 void operator=(const TypeName&) = delete 224 #define HB_DELETE_CREATE_COPY_ASSIGN(TypeName) \ 225 TypeName() = delete; \ 226 TypeName(const TypeName&) = delete; \ 227 void operator=(const TypeName&) = delete 228 229 /* hb_unwrap_type (T) 230 * If T has no T::type, returns T. Otherwise calls itself on T::type recursively. 231 */ 232 233 template <typename T, typename> 234 struct _hb_unwrap_type : hb_type_identity_t<T> {}; 235 template <typename T> 236 struct _hb_unwrap_type<T, hb_void_t<typename T::type>> : _hb_unwrap_type<typename T::type, void> {}; 237 template <typename T> 238 using hb_unwrap_type = _hb_unwrap_type<T, void>; 239 #define hb_unwrap_type(T) typename hb_unwrap_type<T>::type 240 241 #endif /* HB_META_HH */ 242