hb-meta.hh (11086B)
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 <memory> 33 #include <type_traits> 34 #include <utility> 35 36 37 /* 38 * C++ template meta-programming & fundamentals used with them. 39 */ 40 41 /* Void! For when we need a expression-type of void. */ 42 struct hb_empty_t {}; 43 44 /* https://en.cppreference.com/w/cpp/types/void_t */ 45 template<typename... Ts> struct _hb_void_t { typedef void type; }; 46 template<typename... Ts> using hb_void_t = typename _hb_void_t<Ts...>::type; 47 48 template<typename Head, typename... Ts> struct _hb_head_t { typedef Head type; }; 49 template<typename... Ts> using hb_head_t = typename _hb_head_t<Ts...>::type; 50 51 template <typename T, T v> struct hb_integral_constant { static constexpr T value = v; }; 52 template <bool b> using hb_bool_constant = hb_integral_constant<bool, b>; 53 using hb_true_type = hb_bool_constant<true>; 54 using hb_false_type = hb_bool_constant<false>; 55 56 /* Static-assert as expression. */ 57 template <bool cond> struct static_assert_expr; 58 template <> struct static_assert_expr<true> : hb_false_type {}; 59 #define static_assert_expr(C) static_assert_expr<C>::value 60 61 /* Basic type SFINAE. */ 62 63 template <bool B, typename T = void> struct hb_enable_if {}; 64 template <typename T> struct hb_enable_if<true, T> { typedef T type; }; 65 #define hb_enable_if(Cond) typename hb_enable_if<(Cond)>::type* = nullptr 66 /* Concepts/Requires alias: */ 67 #define hb_requires(Cond) hb_enable_if((Cond)) 68 69 template <typename T, typename T2> struct hb_is_same : hb_false_type {}; 70 template <typename T> struct hb_is_same<T, T> : hb_true_type {}; 71 #define hb_is_same(T, T2) hb_is_same<T, T2>::value 72 73 /* Function overloading SFINAE and priority. */ 74 75 #define HB_RETURN(Ret, E) -> hb_head_t<Ret, decltype ((E))> { return (E); } 76 #define HB_AUTO_RETURN(E) -> decltype ((E)) { return (E); } 77 #define HB_VOID_RETURN(E) -> hb_void_t<decltype ((E))> { (E); } 78 79 template <unsigned Pri> struct hb_priority : hb_priority<Pri - 1> {}; 80 template <> struct hb_priority<0> {}; 81 #define hb_prioritize hb_priority<16> () 82 83 #define HB_FUNCOBJ(x) static_const x HB_UNUSED 84 85 86 template <typename T> struct hb_type_identity_t { typedef T type; }; 87 template <typename T> using hb_type_identity = typename hb_type_identity_t<T>::type; 88 89 template <typename T> static inline T hb_declval (); 90 #define hb_declval(T) (hb_declval<T> ()) 91 92 template <typename T> struct hb_match_const : hb_type_identity_t<T>, hb_false_type {}; 93 template <typename T> struct hb_match_const<const T> : hb_type_identity_t<T>, hb_true_type {}; 94 template <typename T> using hb_remove_const = typename hb_match_const<T>::type; 95 96 template <typename T> struct hb_match_reference : hb_type_identity_t<T>, hb_false_type {}; 97 template <typename T> struct hb_match_reference<T &> : hb_type_identity_t<T>, hb_true_type {}; 98 template <typename T> struct hb_match_reference<T &&> : hb_type_identity_t<T>, hb_true_type {}; 99 template <typename T> using hb_remove_reference = typename hb_match_reference<T>::type; 100 template <typename T> auto _hb_try_add_lvalue_reference (hb_priority<1>) -> hb_type_identity<T&>; 101 template <typename T> auto _hb_try_add_lvalue_reference (hb_priority<0>) -> hb_type_identity<T>; 102 template <typename T> using hb_add_lvalue_reference = decltype (_hb_try_add_lvalue_reference<T> (hb_prioritize)); 103 template <typename T> auto _hb_try_add_rvalue_reference (hb_priority<1>) -> hb_type_identity<T&&>; 104 template <typename T> auto _hb_try_add_rvalue_reference (hb_priority<0>) -> hb_type_identity<T>; 105 template <typename T> using hb_add_rvalue_reference = decltype (_hb_try_add_rvalue_reference<T> (hb_prioritize)); 106 107 template <typename T> struct hb_match_pointer : hb_type_identity_t<T>, hb_false_type {}; 108 template <typename T> struct hb_match_pointer<T *> : hb_type_identity_t<T>, hb_true_type {}; 109 template <typename T> using hb_remove_pointer = typename hb_match_pointer<T>::type; 110 template <typename T> auto _hb_try_add_pointer (hb_priority<1>) -> hb_type_identity<hb_remove_reference<T>*>; 111 template <typename T> auto _hb_try_add_pointer (hb_priority<1>) -> hb_type_identity<T>; 112 template <typename T> using hb_add_pointer = decltype (_hb_try_add_pointer<T> (hb_prioritize)); 113 114 115 template <typename T> using hb_decay = typename std::decay<T>::type; 116 117 #define hb_is_convertible(From,To) std::is_convertible<From, To>::value 118 119 template <typename From, typename To> 120 using hb_is_cr_convertible = hb_bool_constant< 121 hb_is_same (hb_decay<From>, hb_decay<To>) && 122 (!std::is_const<From>::value || std::is_const<To>::value) && 123 (!std::is_reference<To>::value || std::is_const<To>::value || std::is_reference<To>::value) 124 >; 125 #define hb_is_cr_convertible(From,To) hb_is_cr_convertible<From, To>::value 126 127 128 struct 129 { 130 template <typename T> constexpr auto 131 operator () (T&& v) const HB_AUTO_RETURN (std::forward<T> (v)) 132 133 template <typename T> constexpr auto 134 operator () (T *v) const HB_AUTO_RETURN (*v) 135 136 template <typename T> constexpr auto 137 operator () (const hb::shared_ptr<T>& v) const HB_AUTO_RETURN (*v) 138 139 template <typename T> constexpr auto 140 operator () (hb::shared_ptr<T>& v) const HB_AUTO_RETURN (*v) 141 142 template <typename T> constexpr auto 143 operator () (const hb::unique_ptr<T>& v) const HB_AUTO_RETURN (*v) 144 145 template <typename T> constexpr auto 146 operator () (hb::unique_ptr<T>& v) const HB_AUTO_RETURN (*v) 147 } 148 HB_FUNCOBJ (hb_deref); 149 150 template <typename T> 151 struct hb_reference_wrapper 152 { 153 hb_reference_wrapper (T v) : v (v) {} 154 bool operator == (const hb_reference_wrapper& o) const { return v == o.v; } 155 bool operator != (const hb_reference_wrapper& o) const { return v != o.v; } 156 operator T& () { return v; } 157 T& get () { return v; } 158 T v; 159 }; 160 template <typename T> 161 struct hb_reference_wrapper<T&> 162 { 163 hb_reference_wrapper (T& v) : v (std::addressof (v)) {} 164 bool operator == (const hb_reference_wrapper& o) const { return v == o.v; } 165 bool operator != (const hb_reference_wrapper& o) const { return v != o.v; } 166 operator T& () { return *v; } 167 T& get () { return *v; } 168 T* v; 169 }; 170 171 172 /* Type traits */ 173 174 template <typename T> struct hb_int_min; 175 template <> struct hb_int_min<char> : hb_integral_constant<char, CHAR_MIN> {}; 176 template <> struct hb_int_min<signed char> : hb_integral_constant<signed char, SCHAR_MIN> {}; 177 template <> struct hb_int_min<unsigned char> : hb_integral_constant<unsigned char, 0> {}; 178 template <> struct hb_int_min<signed short> : hb_integral_constant<signed short, SHRT_MIN> {}; 179 template <> struct hb_int_min<unsigned short> : hb_integral_constant<unsigned short, 0> {}; 180 template <> struct hb_int_min<signed int> : hb_integral_constant<signed int, INT_MIN> {}; 181 template <> struct hb_int_min<unsigned int> : hb_integral_constant<unsigned int, 0> {}; 182 template <> struct hb_int_min<signed long> : hb_integral_constant<signed long, LONG_MIN> {}; 183 template <> struct hb_int_min<unsigned long> : hb_integral_constant<unsigned long, 0> {}; 184 template <> struct hb_int_min<signed long long> : hb_integral_constant<signed long long, LLONG_MIN> {}; 185 template <> struct hb_int_min<unsigned long long> : hb_integral_constant<unsigned long long, 0> {}; 186 template <typename T> struct hb_int_min<T *> : hb_integral_constant<T *, nullptr> {}; 187 #define hb_int_min(T) hb_int_min<T>::value 188 template <typename T> struct hb_int_max; 189 template <> struct hb_int_max<char> : hb_integral_constant<char, CHAR_MAX> {}; 190 template <> struct hb_int_max<signed char> : hb_integral_constant<signed char, SCHAR_MAX> {}; 191 template <> struct hb_int_max<unsigned char> : hb_integral_constant<unsigned char, UCHAR_MAX> {}; 192 template <> struct hb_int_max<signed short> : hb_integral_constant<signed short, SHRT_MAX> {}; 193 template <> struct hb_int_max<unsigned short> : hb_integral_constant<unsigned short, USHRT_MAX> {}; 194 template <> struct hb_int_max<signed int> : hb_integral_constant<signed int, INT_MAX> {}; 195 template <> struct hb_int_max<unsigned int> : hb_integral_constant<unsigned int, UINT_MAX> {}; 196 template <> struct hb_int_max<signed long> : hb_integral_constant<signed long, LONG_MAX> {}; 197 template <> struct hb_int_max<unsigned long> : hb_integral_constant<unsigned long, ULONG_MAX> {}; 198 template <> struct hb_int_max<signed long long> : hb_integral_constant<signed long long, LLONG_MAX> {}; 199 template <> struct hb_int_max<unsigned long long> : hb_integral_constant<unsigned long long, ULLONG_MAX> {}; 200 #define hb_int_max(T) hb_int_max<T>::value 201 202 #if defined(__GNUC__) && __GNUC__ < 5 && !defined(__clang__) 203 #define hb_is_trivially_copyable(T) __has_trivial_copy(T) 204 #define hb_is_trivially_copy_assignable(T) __has_trivial_assign(T) 205 #define hb_is_trivially_constructible(T) __has_trivial_constructor(T) 206 #define hb_is_trivially_copy_constructible(T) __has_trivial_copy_constructor(T) 207 #define hb_is_trivially_destructible(T) __has_trivial_destructor(T) 208 #else 209 #define hb_is_trivially_copyable(T) std::is_trivially_copyable<T>::value 210 #define hb_is_trivially_copy_assignable(T) std::is_trivially_copy_assignable<T>::value 211 #define hb_is_trivially_constructible(T) std::is_trivially_constructible<T>::value 212 #define hb_is_trivially_copy_constructible(T) std::is_trivially_copy_constructible<T>::value 213 #define hb_is_trivially_destructible(T) std::is_trivially_destructible<T>::value 214 #endif 215 216 /* Class traits. */ 217 218 #define HB_DELETE_COPY_ASSIGN(TypeName) \ 219 TypeName(const TypeName&) = delete; \ 220 void operator=(const TypeName&) = delete 221 #define HB_DELETE_CREATE_COPY_ASSIGN(TypeName) \ 222 TypeName() = delete; \ 223 TypeName(const TypeName&) = delete; \ 224 void operator=(const TypeName&) = delete 225 226 /* hb_unwrap_type (T) 227 * If T has no T::type, returns T. Otherwise calls itself on T::type recursively. 228 */ 229 230 template <typename T, typename> 231 struct _hb_unwrap_type : hb_type_identity_t<T> {}; 232 template <typename T> 233 struct _hb_unwrap_type<T, hb_void_t<typename T::type>> : _hb_unwrap_type<typename T::type, void> {}; 234 template <typename T> 235 using hb_unwrap_type = _hb_unwrap_type<T, void>; 236 #define hb_unwrap_type(T) typename hb_unwrap_type<T>::type 237 238 #endif /* HB_META_HH */