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
33 /*
34 * C++ template meta-programming & fundamentals used with them.
35 */
36
37 /* Void! For when we need a expression-type of void. */
38 struct hb_empty_t {};
39
40 /* https://en.cppreference.com/w/cpp/types/void_t */
41 template<typename... Ts> struct _hb_void_t { typedef void type; };
42 template<typename... Ts> using hb_void_t = typename _hb_void_t<Ts...>::type;
43
44 template<typename Head, typename... Ts> struct _hb_head_t { typedef Head type; };
45 template<typename... Ts> using hb_head_t = typename _hb_head_t<Ts...>::type;
46
47 template <typename T, T v> struct hb_integral_constant { static constexpr T value = v; };
48 template <bool b> using hb_bool_constant = hb_integral_constant<bool, b>;
49 using hb_true_type = hb_bool_constant<true>;
50 using hb_false_type = hb_bool_constant<false>;
51
52 /* Static-assert as expression. */
53 template <bool cond> struct static_assert_expr;
54 template <> struct static_assert_expr<true> : hb_false_type {};
55 #define static_assert_expr(C) static_assert_expr<C>::value
56
57 /* Basic type SFINAE. */
58
59 template <bool B, typename T = void> struct hb_enable_if {};
60 template <typename T> struct hb_enable_if<true, T> { typedef T type; };
61 #define hb_enable_if(Cond) typename hb_enable_if<(Cond)>::type* = nullptr
62 /* Concepts/Requires alias: */
63 #define hb_requires(Cond) hb_enable_if((Cond))
64
65 template <typename T, typename T2> struct hb_is_same : hb_false_type {};
66 template <typename T> struct hb_is_same<T, T> : hb_true_type {};
67 #define hb_is_same(T, T2) hb_is_same<T, T2>::value
68
69 /* Function overloading SFINAE and priority. */
70
71 #define HB_RETURN(Ret, E) -> hb_head_t<Ret, decltype ((E))> { return (E); }
72 #define HB_AUTO_RETURN(E) -> decltype ((E)) { return (E); }
73 #define HB_VOID_RETURN(E) -> hb_void_t<decltype ((E))> { (E); }
74
75 template <unsigned Pri> struct hb_priority : hb_priority<Pri - 1> {};
76 template <> struct hb_priority<0> {};
77 #define hb_prioritize hb_priority<16> ()
78
79 #define HB_FUNCOBJ(x) static_const x HB_UNUSED
80
81
82 template <typename T> struct hb_type_identity_t { typedef T type; };
83 template <typename T> using hb_type_identity = typename hb_type_identity_t<T>::type;
84
85 struct
86 {
87 template <typename T> constexpr T*
operator ()__anon4a9e87de010888 operator () (T& arg) const
89 {
90 #pragma GCC diagnostic push
91 #pragma GCC diagnostic ignored "-Wcast-align"
92 /* https://en.cppreference.com/w/cpp/memory/addressof */
93 return reinterpret_cast<T*> (
94 &const_cast<char&> (
95 reinterpret_cast<const volatile char&> (arg)));
96 #pragma GCC diagnostic pop
97 }
98 }
99 HB_FUNCOBJ (hb_addressof);
100
101 template <typename T> static inline T hb_declval ();
102 #define hb_declval(T) (hb_declval<T> ())
103
104 template <typename T> struct hb_match_const : hb_type_identity_t<T>, hb_bool_constant<false>{};
105 template <typename T> struct hb_match_const<const T> : hb_type_identity_t<T>, hb_bool_constant<true> {};
106 template <typename T> using hb_remove_const = typename hb_match_const<T>::type;
107 template <typename T> using hb_add_const = const T;
108 #define hb_is_const(T) hb_match_const<T>::value
109 template <typename T> struct hb_match_reference : hb_type_identity_t<T>, hb_bool_constant<false>{};
110 template <typename T> struct hb_match_reference<T &> : hb_type_identity_t<T>, hb_bool_constant<true> {};
111 template <typename T> struct hb_match_reference<T &&> : hb_type_identity_t<T>, hb_bool_constant<true> {};
112 template <typename T> using hb_remove_reference = typename hb_match_reference<T>::type;
113 template <typename T> auto _hb_try_add_lvalue_reference (hb_priority<1>) -> hb_type_identity<T&>;
114 template <typename T> auto _hb_try_add_lvalue_reference (hb_priority<0>) -> hb_type_identity<T>;
115 template <typename T> using hb_add_lvalue_reference = decltype (_hb_try_add_lvalue_reference<T> (hb_prioritize));
116 template <typename T> auto _hb_try_add_rvalue_reference (hb_priority<1>) -> hb_type_identity<T&&>;
117 template <typename T> auto _hb_try_add_rvalue_reference (hb_priority<0>) -> hb_type_identity<T>;
118 template <typename T> using hb_add_rvalue_reference = decltype (_hb_try_add_rvalue_reference<T> (hb_prioritize));
119 #define hb_is_reference(T) hb_match_reference<T>::value
120 template <typename T> struct hb_match_pointer : hb_type_identity_t<T>, hb_bool_constant<false>{};
121 template <typename T> struct hb_match_pointer<T *> : hb_type_identity_t<T>, hb_bool_constant<true> {};
122 template <typename T> using hb_remove_pointer = typename hb_match_pointer<T>::type;
123 template <typename T> auto _hb_try_add_pointer (hb_priority<1>) -> hb_type_identity<hb_remove_reference<T>*>;
124 template <typename T> auto _hb_try_add_pointer (hb_priority<1>) -> hb_type_identity<T>;
125 template <typename T> using hb_add_pointer = decltype (_hb_try_add_pointer<T> (hb_prioritize));
126 #define hb_is_pointer(T) hb_match_pointer<T>::value
127
128
129 /* TODO Add feature-parity to std::decay. */
130 template <typename T> using hb_decay = hb_remove_const<hb_remove_reference<T>>;
131
132
133 template<bool B, class T, class F>
134 struct _hb_conditional { typedef T type; };
135 template<class T, class F>
136 struct _hb_conditional<false, T, F> { typedef F type; };
137 template<bool B, class T, class F>
138 using hb_conditional = typename _hb_conditional<B, T, F>::type;
139
140
141 template <typename From, typename To>
142 struct hb_is_convertible
143 {
144 private:
145 static constexpr bool from_void = hb_is_same (void, hb_decay<From>);
146 static constexpr bool to_void = hb_is_same (void, hb_decay<To> );
147 static constexpr bool either_void = from_void || to_void;
148 static constexpr bool both_void = from_void && to_void;
149
150 static hb_true_type impl2 (hb_conditional<to_void, int, To>);
151
152 template <typename T>
153 static auto impl (hb_priority<1>) -> decltype (impl2 (hb_declval (T)));
154 template <typename T>
155 static hb_false_type impl (hb_priority<0>);
156 public:
157 static constexpr bool value = both_void ||
158 (!either_void &&
159 decltype (impl<hb_conditional<from_void, int, From>> (hb_prioritize))::value);
160 };
161 #define hb_is_convertible(From,To) hb_is_convertible<From, To>::value
162
163 template <typename Base, typename Derived>
164 using hb_is_base_of = hb_is_convertible<hb_decay<Derived> *, hb_decay<Base> *>;
165 #define hb_is_base_of(Base,Derived) hb_is_base_of<Base, Derived>::value
166
167 template <typename From, typename To>
168 using hb_is_cr_convertible = hb_bool_constant<
169 hb_is_same (hb_decay<From>, hb_decay<To>) &&
170 (!hb_is_const (From) || hb_is_const (To)) &&
171 (!hb_is_reference (To) || hb_is_const (To) || hb_is_reference (To))
172 >;
173 #define hb_is_cr_convertible(From,To) hb_is_cr_convertible<From, To>::value
174
175 /* std::move and std::forward */
176
177 template <typename T>
hb_move(T && t)178 static constexpr hb_remove_reference<T>&& hb_move (T&& t) { return (hb_remove_reference<T>&&) (t); }
179
180 template <typename T>
hb_forward(hb_remove_reference<T> & t)181 static constexpr T&& hb_forward (hb_remove_reference<T>& t) { return (T&&) t; }
182 template <typename T>
hb_forward(hb_remove_reference<T> && t)183 static constexpr T&& hb_forward (hb_remove_reference<T>&& t) { return (T&&) t; }
184
185 struct
186 {
187 template <typename T> constexpr auto
188 operator () (T&& v) const HB_AUTO_RETURN (hb_forward<T> (v))
189
190 template <typename T> constexpr auto
191 operator () (T *v) const HB_AUTO_RETURN (*v)
192 }
193 HB_FUNCOBJ (hb_deref);
194
195 struct
196 {
197 template <typename T> constexpr auto
198 operator () (T&& v) const HB_AUTO_RETURN (hb_forward<T> (v))
199
200 template <typename T> constexpr auto
201 operator () (T& v) const HB_AUTO_RETURN (hb_addressof (v))
202 }
203 HB_FUNCOBJ (hb_ref);
204
205 template <typename T>
206 struct hb_reference_wrapper
207 {
hb_reference_wrapperhb_reference_wrapper208 hb_reference_wrapper (T v) : v (v) {}
operator ==hb_reference_wrapper209 bool operator == (const hb_reference_wrapper& o) const { return v == o.v; }
operator !=hb_reference_wrapper210 bool operator != (const hb_reference_wrapper& o) const { return v != o.v; }
operator Thb_reference_wrapper211 operator T () const { return v; }
gethb_reference_wrapper212 T get () const { return v; }
213 T v;
214 };
215 template <typename T>
216 struct hb_reference_wrapper<T&>
217 {
hb_reference_wrapperhb_reference_wrapper218 hb_reference_wrapper (T& v) : v (hb_addressof (v)) {}
operator ==hb_reference_wrapper219 bool operator == (const hb_reference_wrapper& o) const { return v == o.v; }
operator !=hb_reference_wrapper220 bool operator != (const hb_reference_wrapper& o) const { return v != o.v; }
operator T&hb_reference_wrapper221 operator T& () const { return *v; }
gethb_reference_wrapper222 T& get () const { return *v; }
223 T* v;
224 };
225
226
227 /* Type traits */
228
229 template <typename T>
230 using hb_is_integral = hb_bool_constant<
231 hb_is_same (hb_decay<T>, char) ||
232 hb_is_same (hb_decay<T>, signed char) ||
233 hb_is_same (hb_decay<T>, unsigned char) ||
234 hb_is_same (hb_decay<T>, signed int) ||
235 hb_is_same (hb_decay<T>, unsigned int) ||
236 hb_is_same (hb_decay<T>, signed short) ||
237 hb_is_same (hb_decay<T>, unsigned short) ||
238 hb_is_same (hb_decay<T>, signed long) ||
239 hb_is_same (hb_decay<T>, unsigned long) ||
240 hb_is_same (hb_decay<T>, signed long long) ||
241 hb_is_same (hb_decay<T>, unsigned long long) ||
242 false
243 >;
244 #define hb_is_integral(T) hb_is_integral<T>::value
245 template <typename T>
246 using hb_is_floating_point = hb_bool_constant<
247 hb_is_same (hb_decay<T>, float) ||
248 hb_is_same (hb_decay<T>, double) ||
249 hb_is_same (hb_decay<T>, long double) ||
250 false
251 >;
252 #define hb_is_floating_point(T) hb_is_floating_point<T>::value
253 template <typename T>
254 using hb_is_arithmetic = hb_bool_constant<
255 hb_is_integral (T) ||
256 hb_is_floating_point (T) ||
257 false
258 >;
259 #define hb_is_arithmetic(T) hb_is_arithmetic<T>::value
260
261
262 template <typename T>
263 using hb_is_signed = hb_conditional<hb_is_arithmetic (T),
264 hb_bool_constant<(T) -1 < (T) 0>,
265 hb_false_type>;
266 #define hb_is_signed(T) hb_is_signed<T>::value
267 template <typename T>
268 using hb_is_unsigned = hb_conditional<hb_is_arithmetic (T),
269 hb_bool_constant<(T) 0 < (T) -1>,
270 hb_false_type>;
271 #define hb_is_unsigned(T) hb_is_unsigned<T>::value
272
273 template <typename T> struct hb_int_min;
274 template <> struct hb_int_min<char> : hb_integral_constant<char, CHAR_MIN> {};
275 template <> struct hb_int_min<signed char> : hb_integral_constant<signed char, SCHAR_MIN> {};
276 template <> struct hb_int_min<unsigned char> : hb_integral_constant<unsigned char, 0> {};
277 template <> struct hb_int_min<signed short> : hb_integral_constant<signed short, SHRT_MIN> {};
278 template <> struct hb_int_min<unsigned short> : hb_integral_constant<unsigned short, 0> {};
279 template <> struct hb_int_min<signed int> : hb_integral_constant<signed int, INT_MIN> {};
280 template <> struct hb_int_min<unsigned int> : hb_integral_constant<unsigned int, 0> {};
281 template <> struct hb_int_min<signed long> : hb_integral_constant<signed long, LONG_MIN> {};
282 template <> struct hb_int_min<unsigned long> : hb_integral_constant<unsigned long, 0> {};
283 template <> struct hb_int_min<signed long long> : hb_integral_constant<signed long long, LLONG_MIN> {};
284 template <> struct hb_int_min<unsigned long long> : hb_integral_constant<unsigned long long, 0> {};
285 #define hb_int_min(T) hb_int_min<T>::value
286 template <typename T> struct hb_int_max;
287 template <> struct hb_int_max<char> : hb_integral_constant<char, CHAR_MAX> {};
288 template <> struct hb_int_max<signed char> : hb_integral_constant<signed char, SCHAR_MAX> {};
289 template <> struct hb_int_max<unsigned char> : hb_integral_constant<unsigned char, UCHAR_MAX> {};
290 template <> struct hb_int_max<signed short> : hb_integral_constant<signed short, SHRT_MAX> {};
291 template <> struct hb_int_max<unsigned short> : hb_integral_constant<unsigned short, USHRT_MAX> {};
292 template <> struct hb_int_max<signed int> : hb_integral_constant<signed int, INT_MAX> {};
293 template <> struct hb_int_max<unsigned int> : hb_integral_constant<unsigned int, UINT_MAX> {};
294 template <> struct hb_int_max<signed long> : hb_integral_constant<signed long, LONG_MAX> {};
295 template <> struct hb_int_max<unsigned long> : hb_integral_constant<unsigned long, ULONG_MAX> {};
296 template <> struct hb_int_max<signed long long> : hb_integral_constant<signed long long, LLONG_MAX> {};
297 template <> struct hb_int_max<unsigned long long> : hb_integral_constant<unsigned long long, ULLONG_MAX> {};
298 #define hb_int_max(T) hb_int_max<T>::value
299
300
301 /* Class traits. */
302
303 #define HB_DELETE_COPY_ASSIGN(TypeName) \
304 TypeName(const TypeName&) = delete; \
305 void operator=(const TypeName&) = delete
306 #define HB_DELETE_CREATE_COPY_ASSIGN(TypeName) \
307 TypeName() = delete; \
308 TypeName(const TypeName&) = delete; \
309 void operator=(const TypeName&) = delete
310
311 template <typename T, typename>
312 struct _hb_is_destructible : hb_false_type {};
313 template <typename T>
314 struct _hb_is_destructible<T, hb_void_t<decltype (hb_declval (T).~T ())>> : hb_true_type {};
315 template <typename T>
316 using hb_is_destructible = _hb_is_destructible<T, void>;
317 #define hb_is_destructible(T) hb_is_destructible<T>::value
318
319 template <typename T, typename, typename ...Ts>
320 struct _hb_is_constructible : hb_false_type {};
321 template <typename T, typename ...Ts>
322 struct _hb_is_constructible<T, hb_void_t<decltype (T (hb_declval (Ts)...))>, Ts...> : hb_true_type {};
323 template <typename T, typename ...Ts>
324 using hb_is_constructible = _hb_is_constructible<T, void, Ts...>;
325 #define hb_is_constructible(...) hb_is_constructible<__VA_ARGS__>::value
326
327 template <typename T>
328 using hb_is_default_constructible = hb_is_constructible<T>;
329 #define hb_is_default_constructible(T) hb_is_default_constructible<T>::value
330
331 template <typename T>
332 using hb_is_copy_constructible = hb_is_constructible<T, hb_add_lvalue_reference<hb_add_const<T>>>;
333 #define hb_is_copy_constructible(T) hb_is_copy_constructible<T>::value
334
335 template <typename T>
336 using hb_is_move_constructible = hb_is_constructible<T, hb_add_rvalue_reference<hb_add_const<T>>>;
337 #define hb_is_move_constructible(T) hb_is_move_constructible<T>::value
338
339 template <typename T, typename U, typename>
340 struct _hb_is_assignable : hb_false_type {};
341 template <typename T, typename U>
342 struct _hb_is_assignable<T, U, hb_void_t<decltype (hb_declval (T) = hb_declval (U))>> : hb_true_type {};
343 template <typename T, typename U>
344 using hb_is_assignable = _hb_is_assignable<T, U, void>;
345 #define hb_is_assignable(T,U) hb_is_assignable<T, U>::value
346
347 template <typename T>
348 using hb_is_copy_assignable = hb_is_assignable<hb_add_lvalue_reference<T>,
349 hb_add_lvalue_reference<hb_add_const<T>>>;
350 #define hb_is_copy_assignable(T) hb_is_copy_assignable<T>::value
351
352 template <typename T>
353 using hb_is_move_assignable = hb_is_assignable<hb_add_lvalue_reference<T>,
354 hb_add_rvalue_reference<T>>;
355 #define hb_is_move_assignable(T) hb_is_move_assignable<T>::value
356
357 /* Trivial versions. */
358
359 template <typename T> union hb_trivial { T value; };
360
361 template <typename T>
362 using hb_is_trivially_destructible= hb_is_destructible<hb_trivial<T>>;
363 #define hb_is_trivially_destructible(T) hb_is_trivially_destructible<T>::value
364
365 /* Don't know how to do the following. */
366 //template <typename T, typename ...Ts>
367 //using hb_is_trivially_constructible= hb_is_constructible<hb_trivial<T>, hb_trivial<Ts>...>;
368 //#define hb_is_trivially_constructible(...) hb_is_trivially_constructible<__VA_ARGS__>::value
369
370 template <typename T>
371 using hb_is_trivially_default_constructible= hb_is_default_constructible<hb_trivial<T>>;
372 #define hb_is_trivially_default_constructible(T) hb_is_trivially_default_constructible<T>::value
373
374 template <typename T>
375 using hb_is_trivially_copy_constructible= hb_is_copy_constructible<hb_trivial<T>>;
376 #define hb_is_trivially_copy_constructible(T) hb_is_trivially_copy_constructible<T>::value
377
378 template <typename T>
379 using hb_is_trivially_move_constructible= hb_is_move_constructible<hb_trivial<T>>;
380 #define hb_is_trivially_move_constructible(T) hb_is_trivially_move_constructible<T>::value
381
382 /* Don't know how to do the following. */
383 //template <typename T, typename U>
384 //using hb_is_trivially_assignable= hb_is_assignable<hb_trivial<T>, hb_trivial<U>>;
385 //#define hb_is_trivially_assignable(T,U) hb_is_trivially_assignable<T, U>::value
386
387 template <typename T>
388 using hb_is_trivially_copy_assignable= hb_is_copy_assignable<hb_trivial<T>>;
389 #define hb_is_trivially_copy_assignable(T) hb_is_trivially_copy_assignable<T>::value
390
391 template <typename T>
392 using hb_is_trivially_move_assignable= hb_is_move_assignable<hb_trivial<T>>;
393 #define hb_is_trivially_move_assignable(T) hb_is_trivially_move_assignable<T>::value
394
395 template <typename T>
396 using hb_is_trivially_copyable= hb_bool_constant<
397 hb_is_trivially_destructible (T) &&
398 (!hb_is_move_assignable (T) || hb_is_trivially_move_assignable (T)) &&
399 (!hb_is_move_constructible (T) || hb_is_trivially_move_constructible (T)) &&
400 (!hb_is_copy_assignable (T) || hb_is_trivially_copy_assignable (T)) &&
401 (!hb_is_copy_constructible (T) || hb_is_trivially_copy_constructible (T)) &&
402 true
403 >;
404 #define hb_is_trivially_copyable(T) hb_is_trivially_copyable<T>::value
405
406 template <typename T>
407 using hb_is_trivial= hb_bool_constant<
408 hb_is_trivially_copyable (T) &&
409 hb_is_trivially_default_constructible (T)
410 >;
411 #define hb_is_trivial(T) hb_is_trivial<T>::value
412
413 /* hb_unwrap_type (T)
414 * If T has no T::type, returns T. Otherwise calls itself on T::type recursively.
415 */
416
417 template <typename T, typename>
418 struct _hb_unwrap_type : hb_type_identity_t<T> {};
419 template <typename T>
420 struct _hb_unwrap_type<T, hb_void_t<typename T::type>> : _hb_unwrap_type<typename T::type, void> {};
421 template <typename T>
422 using hb_unwrap_type = _hb_unwrap_type<T, void>;
423 #define hb_unwrap_type(T) typename hb_unwrap_type<T>::type
424
425 #endif /* HB_META_HH */
426