1/*
2 * Copyright © 2007,2008,2009,2010 Red Hat, Inc.
3 * Copyright © 2012,2018 Google, Inc.
4 *
5 * This is part of HarfBuzz, a text shaping library.
6 *
7 * Permission is hereby granted, without written agreement and without
8 * license or royalty fees, to use, copy, modify, and distribute this
9 * software and its documentation for any purpose, provided that the
10 * above copyright notice and the following two paragraphs appear in
11 * all copies of this software.
12 *
13 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
14 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
15 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
16 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
17 * DAMAGE.
18 *
19 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
20 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
21 * FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
22 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
23 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
24 *
25 * Red Hat Author(s): Behdad Esfahbod
26 * Google Author(s): Behdad Esfahbod
27 */
28
29#ifndef HB_MACHINERY_HH
30#define HB_MACHINERY_HH
31
32#include "hb.hh"
33#include "hb-blob.hh"
34
35#include "hb-dispatch.hh"
36#include "hb-sanitize.hh"
37#include "hb-serialize.hh"
38
39
40/*
41 * Casts
42 */
43
44/* StructAtOffset<T>(P,Ofs) returns the struct T& that is placed at memory
45 * location pointed to by P plus Ofs bytes. */
46template<typename Type>
47static inline const Type& StructAtOffset(const void *P, unsigned int offset)
48{ return * reinterpret_cast<const Type*> ((const char *) P + offset); }
49template<typename Type>
50static inline Type& StructAtOffset(void *P, unsigned int offset)
51{ return * reinterpret_cast<Type*> ((char *) P + offset); }
52template<typename Type>
53static inline const Type& StructAtOffsetUnaligned(const void *P, unsigned int offset)
54{
55#pragma GCC diagnostic push
56#pragma GCC diagnostic ignored "-Wcast-align"
57 return * reinterpret_cast<const Type*> ((const char *) P + offset);
58#pragma GCC diagnostic pop
59}
60template<typename Type>
61static inline Type& StructAtOffsetUnaligned(void *P, unsigned int offset)
62{
63#pragma GCC diagnostic push
64#pragma GCC diagnostic ignored "-Wcast-align"
65 return * reinterpret_cast<Type*> ((char *) P + offset);
66#pragma GCC diagnostic pop
67}
68
69/* StructAfter<T>(X) returns the struct T& that is placed after X.
70 * Works with X of variable size also. X must implement get_size() */
71template<typename Type, typename TObject>
72static inline const Type& StructAfter(const TObject &X)
73{ return StructAtOffset<Type>(&X, X.get_size()); }
74template<typename Type, typename TObject>
75static inline Type& StructAfter(TObject &X)
76{ return StructAtOffset<Type>(&X, X.get_size()); }
77
78
79/*
80 * Size checking
81 */
82
83/* Check _assertion in a method environment */
84#define _DEFINE_INSTANCE_ASSERTION1(_line, _assertion) \
85 void _instance_assertion_on_line_##_line () const \
86 { static_assert ((_assertion), ""); }
87# define _DEFINE_INSTANCE_ASSERTION0(_line, _assertion) _DEFINE_INSTANCE_ASSERTION1 (_line, _assertion)
88# define DEFINE_INSTANCE_ASSERTION(_assertion) _DEFINE_INSTANCE_ASSERTION0 (__LINE__, _assertion)
89
90/* Check that _code compiles in a method environment */
91#define _DEFINE_COMPILES_ASSERTION1(_line, _code) \
92 void _compiles_assertion_on_line_##_line () const \
93 { _code; }
94# define _DEFINE_COMPILES_ASSERTION0(_line, _code) _DEFINE_COMPILES_ASSERTION1 (_line, _code)
95# define DEFINE_COMPILES_ASSERTION(_code) _DEFINE_COMPILES_ASSERTION0 (__LINE__, _code)
96
97
98#define DEFINE_SIZE_STATIC(size) \
99 DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size)) \
100 unsigned int get_size () const { return (size); } \
101 static constexpr unsigned null_size = (size); \
102 static constexpr unsigned min_size = (size); \
103 static constexpr unsigned static_size = (size)
104
105#define DEFINE_SIZE_UNION(size, _member) \
106 DEFINE_COMPILES_ASSERTION ((void) this->u._member.static_size) \
107 DEFINE_INSTANCE_ASSERTION (sizeof(this->u._member) == (size)) \
108 static constexpr unsigned null_size = (size); \
109 static constexpr unsigned min_size = (size)
110
111#define DEFINE_SIZE_MIN(size) \
112 DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
113 static constexpr unsigned null_size = (size); \
114 static constexpr unsigned min_size = (size)
115
116#define DEFINE_SIZE_UNBOUNDED(size) \
117 DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
118 static constexpr unsigned min_size = (size)
119
120#define DEFINE_SIZE_ARRAY(size, array) \
121 DEFINE_COMPILES_ASSERTION ((void) (array)[0].static_size) \
122 DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size) + (HB_VAR_ARRAY+0) * sizeof ((array)[0])) \
123 static constexpr unsigned null_size = (size); \
124 static constexpr unsigned min_size = (size)
125
126#define DEFINE_SIZE_ARRAY_SIZED(size, array) \
127 unsigned int get_size () const { return (size - (array).min_size + (array).get_size ()); } \
128 DEFINE_SIZE_ARRAY(size, array)
129
130
131
132/*
133 * Lazy loaders.
134 */
135
136template <typename Data, unsigned int WheresData>
137struct hb_data_wrapper_t
138{
139 static_assert (WheresData > 0, "");
140
141 Data * get_data () const
142 { return *(((Data **) (void *) this) - WheresData); }
143
144 bool is_inert () const { return !get_data (); }
145
146 template <typename Stored, typename Subclass>
147 Stored * call_create () const { return Subclass::create (get_data ()); }
148};
149template <>
150struct hb_data_wrapper_t<void, 0>
151{
152 bool is_inert () const { return false; }
153
154 template <typename Stored, typename Funcs>
155 Stored * call_create () const { return Funcs::create (); }
156};
157
158template <typename T1, typename T2> struct hb_non_void_t { typedef T1 value; };
159template <typename T2> struct hb_non_void_t<void, T2> { typedef T2 value; };
160
161template <typename Returned,
162 typename Subclass = void,
163 typename Data = void,
164 unsigned int WheresData = 0,
165 typename Stored = Returned>
166struct hb_lazy_loader_t : hb_data_wrapper_t<Data, WheresData>
167{
168 typedef typename hb_non_void_t<Subclass,
169 hb_lazy_loader_t<Returned,Subclass,Data,WheresData,Stored>
170 >::value Funcs;
171
172 void init0 () {} /* Init, when memory is already set to 0. No-op for us. */
173 void init () { instance.set_relaxed (nullptr); }
174 void fini () { do_destroy (instance.get ()); }
175
176 void free_instance ()
177 {
178 retry:
179 Stored *p = instance.get ();
180 if (unlikely (p && !cmpexch (p, nullptr)))
181 goto retry;
182 do_destroy (p);
183 }
184
185 static void do_destroy (Stored *p)
186 {
187 if (p && p != const_cast<Stored *> (Funcs::get_null ()))
188 Funcs::destroy (p);
189 }
190
191 const Returned * operator -> () const { return get (); }
192 const Returned & operator * () const { return *get (); }
193 explicit operator bool () const
194 { return get_stored () != Funcs::get_null (); }
195 template <typename C> operator const C * () const { return get (); }
196
197 Stored * get_stored () const
198 {
199 retry:
200 Stored *p = this->instance.get ();
201 if (unlikely (!p))
202 {
203 if (unlikely (this->is_inert ()))
204 return const_cast<Stored *> (Funcs::get_null ());
205
206 p = this->template call_create<Stored, Funcs> ();
207 if (unlikely (!p))
208 p = const_cast<Stored *> (Funcs::get_null ());
209
210 if (unlikely (!cmpexch (nullptr, p)))
211 {
212 do_destroy (p);
213 goto retry;
214 }
215 }
216 return p;
217 }
218 Stored * get_stored_relaxed () const
219 {
220 return this->instance.get_relaxed ();
221 }
222
223 bool cmpexch (Stored *current, Stored *value) const
224 {
225 /* This *must* be called when there are no other threads accessing. */
226 return this->instance.cmpexch (current, value);
227 }
228
229 const Returned * get () const { return Funcs::convert (get_stored ()); }
230 const Returned * get_relaxed () const { return Funcs::convert (get_stored_relaxed ()); }
231 Returned * get_unconst () const { return const_cast<Returned *> (Funcs::convert (get_stored ())); }
232
233 /* To be possibly overloaded by subclasses. */
234 static Returned* convert (Stored *p) { return p; }
235
236 /* By default null/init/fini the object. */
237 static const Stored* get_null () { return &Null (Stored); }
238 static Stored *create (Data *data)
239 {
240 Stored *p = (Stored *) calloc (1, sizeof (Stored));
241 if (likely (p))
242 p->init (data);
243 return p;
244 }
245 static Stored *create ()
246 {
247 Stored *p = (Stored *) calloc (1, sizeof (Stored));
248 if (likely (p))
249 p->init ();
250 return p;
251 }
252 static void destroy (Stored *p)
253 {
254 p->fini ();
255 free (p);
256 }
257
258// private:
259 /* Must only have one pointer. */
260 hb_atomic_ptr_t<Stored *> instance;
261};
262
263/* Specializations. */
264
265template <typename T, unsigned int WheresFace>
266struct hb_face_lazy_loader_t : hb_lazy_loader_t<T,
267 hb_face_lazy_loader_t<T, WheresFace>,
268 hb_face_t, WheresFace> {};
269
270template <typename T, unsigned int WheresFace>
271struct hb_table_lazy_loader_t : hb_lazy_loader_t<T,
272 hb_table_lazy_loader_t<T, WheresFace>,
273 hb_face_t, WheresFace,
274 hb_blob_t>
275{
276 static hb_blob_t *create (hb_face_t *face)
277 { return hb_sanitize_context_t ().reference_table<T> (face); }
278 static void destroy (hb_blob_t *p) { hb_blob_destroy (p); }
279
280 static const hb_blob_t *get_null ()
281 { return hb_blob_get_empty (); }
282
283 static const T* convert (const hb_blob_t *blob)
284 { return blob->as<T> (); }
285
286 hb_blob_t* get_blob () const { return this->get_stored (); }
287};
288
289template <typename Subclass>
290struct hb_font_funcs_lazy_loader_t : hb_lazy_loader_t<hb_font_funcs_t, Subclass>
291{
292 static void destroy (hb_font_funcs_t *p)
293 { hb_font_funcs_destroy (p); }
294 static const hb_font_funcs_t *get_null ()
295 { return hb_font_funcs_get_empty (); }
296};
297template <typename Subclass>
298struct hb_unicode_funcs_lazy_loader_t : hb_lazy_loader_t<hb_unicode_funcs_t, Subclass>
299{
300 static void destroy (hb_unicode_funcs_t *p)
301 { hb_unicode_funcs_destroy (p); }
302 static const hb_unicode_funcs_t *get_null ()
303 { return hb_unicode_funcs_get_empty (); }
304};
305
306
307#endif /* HB_MACHINERY_HH */
308