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comparison mupdf-source/thirdparty/harfbuzz/src/hb-null.hh @ 2:b50eed0cc0ef upstream

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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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1:1d09e1dec1d9 2:b50eed0cc0ef
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_NULL_HH
28 #define HB_NULL_HH
29
30 #include "hb.hh"
31 #include "hb-meta.hh"
32
33
34 /*
35 * Static pools
36 */
37
38 /* Global nul-content Null pool. Enlarge as necessary. */
39
40 #define HB_NULL_POOL_SIZE 448
41
42 template <typename T, typename>
43 struct _hb_has_min_size : hb_false_type {};
44 template <typename T>
45 struct _hb_has_min_size<T, hb_void_t<decltype (T::min_size)>>
46 : hb_true_type {};
47 template <typename T>
48 using hb_has_min_size = _hb_has_min_size<T, void>;
49 #define hb_has_min_size(T) hb_has_min_size<T>::value
50
51 template <typename T, typename>
52 struct _hb_has_null_size : hb_false_type {};
53 template <typename T>
54 struct _hb_has_null_size<T, hb_void_t<decltype (T::null_size)>>
55 : hb_true_type {};
56 template <typename T>
57 using hb_has_null_size = _hb_has_null_size<T, void>;
58 #define hb_has_null_size(T) hb_has_null_size<T>::value
59
60 /* Use SFINAE to sniff whether T has min_size; in which case return the larger
61 * of sizeof(T) and T::null_size, otherwise return sizeof(T).
62 *
63 * The main purpose of this is to let structs communicate that they are not nullable,
64 * by defining min_size but *not* null_size. */
65
66 /* The hard way...
67 * https://stackoverflow.com/questions/7776448/sfinae-tried-with-bool-gives-compiler-error-template-argument-tvalue-invol
68 */
69
70 template <typename T, typename>
71 struct _hb_null_size : hb_integral_constant<unsigned, sizeof (T)> {};
72 template <typename T>
73 struct _hb_null_size<T, hb_void_t<decltype (T::min_size)>>
74 : hb_integral_constant<unsigned,
75 (sizeof (T) > T::null_size ? sizeof (T) : T::null_size)> {};
76 template <typename T>
77 using hb_null_size = _hb_null_size<T, void>;
78 #define hb_null_size(T) hb_null_size<T>::value
79
80 /* These doesn't belong here, but since is copy/paste from above, put it here. */
81
82 /* hb_static_size (T)
83 * Returns T::static_size if T::min_size is defined, or sizeof (T) otherwise. */
84
85 template <typename T, typename>
86 struct _hb_static_size : hb_integral_constant<unsigned, sizeof (T)> {};
87 template <typename T>
88 struct _hb_static_size<T, hb_void_t<decltype (T::min_size)>> : hb_integral_constant<unsigned, T::static_size> {};
89 template <typename T>
90 using hb_static_size = _hb_static_size<T, void>;
91 #define hb_static_size(T) hb_static_size<T>::value
92
93 template <typename T, typename>
94 struct _hb_min_size : hb_integral_constant<unsigned, sizeof (T)> {};
95 template <typename T>
96 struct _hb_min_size<T, hb_void_t<decltype (T::min_size)>> : hb_integral_constant<unsigned, T::min_size> {};
97 template <typename T>
98 using hb_min_size = _hb_min_size<T, void>;
99 #define hb_min_size(T) hb_min_size<T>::value
100
101
102 /*
103 * Null()
104 */
105
106 extern HB_INTERNAL
107 uint64_t const _hb_NullPool[(HB_NULL_POOL_SIZE + sizeof (uint64_t) - 1) / sizeof (uint64_t)];
108
109 /* Generic nul-content Null objects. */
110 template <typename Type>
111 struct Null {
112 static Type const & get_null ()
113 {
114 static_assert (hb_null_size (Type) <= HB_NULL_POOL_SIZE, "Increase HB_NULL_POOL_SIZE.");
115 return *reinterpret_cast<Type const *> (_hb_NullPool);
116 }
117 };
118 template <typename QType>
119 struct NullHelper
120 {
121 typedef hb_remove_const<hb_remove_reference<QType>> Type;
122 static const Type & get_null () { return Null<Type>::get_null (); }
123 };
124 #define Null(Type) NullHelper<Type>::get_null ()
125
126 /* Specializations for arbitrary-content Null objects expressed in bytes. */
127 #define DECLARE_NULL_NAMESPACE_BYTES(Namespace, Type) \
128 } /* Close namespace. */ \
129 extern HB_INTERNAL const unsigned char _hb_Null_##Namespace##_##Type[hb_null_size (Namespace::Type)]; \
130 template <> \
131 struct Null<Namespace::Type> { \
132 static Namespace::Type const & get_null () { \
133 return *reinterpret_cast<const Namespace::Type *> (_hb_Null_##Namespace##_##Type); \
134 } \
135 }; \
136 namespace Namespace { \
137 static_assert (true, "") /* Require semicolon after. */
138 #define DECLARE_NULL_NAMESPACE_BYTES_TEMPLATE1(Namespace, Type, Size) \
139 } /* Close namespace. */ \
140 extern HB_INTERNAL const unsigned char _hb_Null_##Namespace##_##Type[Size]; \
141 template <typename Spec> \
142 struct Null<Namespace::Type<Spec>> { \
143 static Namespace::Type<Spec> const & get_null () { \
144 return *reinterpret_cast<const Namespace::Type<Spec> *> (_hb_Null_##Namespace##_##Type); \
145 } \
146 }; \
147 namespace Namespace { \
148 static_assert (true, "") /* Require semicolon after. */
149 #define DEFINE_NULL_NAMESPACE_BYTES(Namespace, Type) \
150 const unsigned char _hb_Null_##Namespace##_##Type[sizeof (_hb_Null_##Namespace##_##Type)]
151
152 /* Specializations for arbitrary-content Null objects expressed as struct initializer. */
153 #define DECLARE_NULL_INSTANCE(Type) \
154 extern HB_INTERNAL const Type _hb_Null_##Type; \
155 template <> \
156 struct Null<Type> { \
157 static Type const & get_null () { \
158 return _hb_Null_##Type; \
159 } \
160 }; \
161 static_assert (true, "") /* Require semicolon after. */
162 #define DEFINE_NULL_INSTANCE(Type) \
163 const Type _hb_Null_##Type
164
165 /* Global writable pool. Enlarge as necessary. */
166
167 /* To be fully correct, CrapPool must be thread_local. However, we do not rely on CrapPool
168 * for correct operation. It only exist to catch and divert program logic bugs instead of
169 * causing bad memory access. So, races there are not actually introducing incorrectness
170 * in the code. Has ~12kb binary size overhead to have it, also clang build fails with it. */
171 extern HB_INTERNAL
172 /*thread_local*/ uint64_t _hb_CrapPool[(HB_NULL_POOL_SIZE + sizeof (uint64_t) - 1) / sizeof (uint64_t)];
173
174 /* CRAP pool: Common Region for Access Protection. */
175 template <typename Type>
176 static inline Type& Crap () {
177 static_assert (hb_null_size (Type) <= HB_NULL_POOL_SIZE, "Increase HB_NULL_POOL_SIZE.");
178 Type *obj = reinterpret_cast<Type *> (_hb_CrapPool);
179 memcpy (obj, &Null (Type), sizeof (*obj));
180 return *obj;
181 }
182 template <typename QType>
183 struct CrapHelper
184 {
185 typedef hb_remove_const<hb_remove_reference<QType>> Type;
186 static Type & get_crap () { return Crap<Type> (); }
187 };
188 #define Crap(Type) CrapHelper<Type>::get_crap ()
189
190 template <typename Type>
191 struct CrapOrNullHelper {
192 static Type & get () { return Crap (Type); }
193 };
194 template <typename Type>
195 struct CrapOrNullHelper<const Type> {
196 static const Type & get () { return Null (Type); }
197 };
198 #define CrapOrNull(Type) CrapOrNullHelper<Type>::get ()
199
200
201 /*
202 * hb_nonnull_ptr_t
203 */
204
205 template <typename P>
206 struct hb_nonnull_ptr_t
207 {
208 typedef hb_remove_pointer<P> T;
209
210 hb_nonnull_ptr_t (T *v_ = nullptr) : v (v_) {}
211 T * operator = (T *v_) { return v = v_; }
212 T * operator -> () const { return get (); }
213 T & operator * () const { return *get (); }
214 T ** operator & () const { return &v; }
215 /* Only auto-cast to const types. */
216 template <typename C> operator const C * () const { return get (); }
217 operator const char * () const { return (const char *) get (); }
218 T * get () const { return v ? v : const_cast<T *> (&Null (T)); }
219 T * get_raw () const { return v; }
220
221 private:
222 T *v;
223 };
224
225
226 #endif /* HB_NULL_HH */