gfx/harfbuzz/src/hb-machinery.hh

   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
  38
  39 /*
  40  * Casts
  41  */
  42
  43 /* StructAtOffset<T>(P,Ofs) returns the struct T& that is placed at memory
  44  * location pointed to by P plus Ofs bytes. */
  45 template<typename Type>
  46 static inline const Type& StructAtOffset(const void *P, unsigned int offset)
  47 { return * reinterpret_cast<const Type*> ((const char *) P + offset); }
  48 template<typename Type>
  49 static inline Type& StructAtOffset(void *P, unsigned int offset)
  50 { return * reinterpret_cast<Type*> ((char *) P + offset); }
  51 template<typename Type>
  52 static inline const Type& StructAtOffsetUnaligned(const void *P, unsigned int offset)
  53 {
  54 #pragma GCC diagnostic push
  55 #pragma GCC diagnostic ignored "-Wcast-align"
  56   return * reinterpret_cast<const Type*> ((const char *) P + offset);
  57 #pragma GCC diagnostic pop
  58 }
  59 template<typename Type>
  60 static inline Type& StructAtOffsetUnaligned(void *P, unsigned int offset)
  61 {
  62 #pragma GCC diagnostic push
  63 #pragma GCC diagnostic ignored "-Wcast-align"
  64   return * reinterpret_cast<Type*> ((char *) P + offset);
  65 #pragma GCC diagnostic pop
  66 }
  67
  68 /* StructAfter<T>(X) returns the struct T& that is placed after X.
  69  * Works with X of variable size also.  X must implement get_size() */
  70 template<typename Type, typename TObject>
  71 static inline const Type& StructAfter(const TObject &X)
  72 { return StructAtOffset<Type>(&X, X.get_size()); }
  73 template<typename Type, typename TObject>
  74 static inline Type& StructAfter(TObject &X)
  75 { return StructAtOffset<Type>(&X, X.get_size()); }
  76
  77
  78 /*
  79  * Size checking
  80  */
  81
  82 /* Size signifying variable-sized array */
  83 #ifndef HB_VAR_ARRAY
  84 #define HB_VAR_ARRAY 1
  85 #endif
  86
  87 /* Check _assertion in a method environment */
  88 #define _DEFINE_INSTANCE_ASSERTION1(_line, _assertion) \
  89   void _instance_assertion_on_line_##_line () const \
  90   { static_assert ((_assertion), ""); }
  91 # define _DEFINE_INSTANCE_ASSERTION0(_line, _assertion) _DEFINE_INSTANCE_ASSERTION1 (_line, _assertion)
  92 # define DEFINE_INSTANCE_ASSERTION(_assertion) _DEFINE_INSTANCE_ASSERTION0 (__LINE__, _assertion)
  93
  94 /* Check that _code compiles in a method environment */
  95 #define _DEFINE_COMPILES_ASSERTION1(_line, _code) \
  96   void _compiles_assertion_on_line_##_line () const \
  97   { _code; }
  98 # define _DEFINE_COMPILES_ASSERTION0(_line, _code) _DEFINE_COMPILES_ASSERTION1 (_line, _code)
  99 # define DEFINE_COMPILES_ASSERTION(_code) _DEFINE_COMPILES_ASSERTION0 (__LINE__, _code)
 100
 101
 102 #define DEFINE_SIZE_STATIC(size) \
 103   DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size)) \
 104   unsigned int get_size () const { return (size); } \
 105   static constexpr unsigned null_size = (size); \
 106   static constexpr unsigned min_size = (size); \
 107   static constexpr unsigned static_size = (size)
 108
 109 #define DEFINE_SIZE_UNION(size, _member) \
 110   DEFINE_COMPILES_ASSERTION ((void) this->u._member.static_size) \
 111   DEFINE_INSTANCE_ASSERTION (sizeof(this->u._member) == (size)) \
 112   static constexpr unsigned null_size = (size); \
 113   static constexpr unsigned min_size = (size)
 114
 115 #define DEFINE_SIZE_MIN(size) \
 116   DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
 117   static constexpr unsigned null_size = (size); \
 118   static constexpr unsigned min_size = (size)
 119
 120 #define DEFINE_SIZE_UNBOUNDED(size) \
 121   DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
 122   static constexpr unsigned min_size = (size)
 123
 124 #define DEFINE_SIZE_ARRAY(size, array) \
 125   DEFINE_COMPILES_ASSERTION ((void) (array)[0].static_size) \
 126   DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size) + (HB_VAR_ARRAY+0) * sizeof ((array)[0])) \
 127   static constexpr unsigned null_size = (size); \
 128   static constexpr unsigned min_size = (size)
 129
 130 #define DEFINE_SIZE_ARRAY_SIZED(size, array) \
 131   unsigned int get_size () const { return (size - (array).min_size + (array).get_size ()); } \
 132   DEFINE_SIZE_ARRAY(size, array)
 133
 134
 135
 136 /*
 137  * Lazy loaders.
 138  *
 139  * The lazy-loaders are thread-safe pointer-like objects that create their
 140  * instead on-demand.  They also support access to a "data" object that is
 141  * necessary for creating their instance.  The data object, if specified,
 142  * is accessed via pointer math, located at a location before the position
 143  * of the loader itself.  This avoids having to store a pointer to data
 144  * for every lazy-loader.  Multiple lazy-loaders can access the same data.
 145  */
 146
 147 template <typename Data, unsigned int WheresData>
 148 struct hb_data_wrapper_t
 149 {
 150   static_assert (WheresData > 0, "");
 151
 152   Data * get_data () const
 153   { return *(((Data **) (void *) this) - WheresData); }
 154
 155   bool is_inert () const { return !get_data (); }
 156
 157   template <typename Stored, typename Subclass>
 158   Stored * call_create () const { return Subclass::create (get_data ()); }
 159 };
 160 template <>
 161 struct hb_data_wrapper_t<void, 0>
 162 {
 163   bool is_inert () const { return false; }
 164
 165   template <typename Stored, typename Funcs>
 166   Stored * call_create () const { return Funcs::create (); }
 167 };
 168
 169 template <typename T1, typename T2> struct hb_non_void_t { typedef T1 value; };
 170 template <typename T2> struct hb_non_void_t<void, T2> { typedef T2 value; };
 171
 172 template <typename Returned,
 173           typename Subclass = void,
 174           typename Data = void,
 175           unsigned int WheresData = 0,
 176           typename Stored = Returned>
 177 struct hb_lazy_loader_t : hb_data_wrapper_t<Data, WheresData>
 178 {
 179   typedef typename hb_non_void_t<Subclass,
 180                                  hb_lazy_loader_t<Returned,Subclass,Data,WheresData,Stored>
 181                                 >::value Funcs;
 182
 183   hb_lazy_loader_t () = default;
 184   hb_lazy_loader_t (const hb_lazy_loader_t &other) = delete;
 185
 186   void init0 () {} /* Init, when memory is already set to 0. No-op for us. */
 187   void init ()  { instance.set_relaxed (nullptr); }
 188   void fini ()  { do_destroy (instance.get_acquire ()); init (); }
 189
 190   void free_instance ()
 191   {
 192   retry:
 193     Stored *p = instance.get_acquire ();
 194     if (unlikely (p && !cmpexch (p, nullptr)))
 195       goto retry;
 196     do_destroy (p);
 197   }
 198
 199   static void do_destroy (Stored *p)
 200   {
 201     if (p && p != const_cast<Stored *> (Funcs::get_null ()))
 202       Funcs::destroy (p);
 203   }
 204
 205   const Returned * operator -> () const { return get (); }
 206   template <typename U = Returned, hb_enable_if (!hb_is_same (U, void))>
 207   const U & operator * () const  { return *get (); }
 208   explicit operator bool () const
 209   { return get_stored () != Funcs::get_null (); }
 210   template <typename C> operator const C * () const { return get (); }
 211
 212   Stored * get_stored () const
 213   {
 214   retry:
 215     Stored *p = this->instance.get_acquire ();
 216     if (unlikely (!p))
 217     {
 218       if (unlikely (this->is_inert ()))
 219         return const_cast<Stored *> (Funcs::get_null ());
 220
 221       p = this->template call_create<Stored, Funcs> ();
 222       if (unlikely (!p))
 223         p = const_cast<Stored *> (Funcs::get_null ());
 224
 225       if (unlikely (!cmpexch (nullptr, p)))
 226       {
 227         do_destroy (p);
 228         goto retry;
 229       }
 230     }
 231     return p;
 232   }
 233   Stored * get_stored_relaxed () const
 234   {
 235     return this->instance.get_relaxed ();
 236   }
 237
 238   bool cmpexch (Stored *current, Stored *value) const
 239   {
 240     /* This function can only be safely called directly if no
 241      * other thread is accessing. */
 242     return this->instance.cmpexch (current, value);
 243   }
 244
 245   const Returned * get () const { return Funcs::convert (get_stored ()); }
 246   const Returned * get_relaxed () const { return Funcs::convert (get_stored_relaxed ()); }
 247   Returned * get_unconst () const { return const_cast<Returned *> (Funcs::convert (get_stored ())); }
 248
 249   /* To be possibly overloaded by subclasses. */
 250   static Returned* convert (Stored *p) { return p; }
 251
 252   /* By default null/init/fini the object. */
 253   static const Stored* get_null () { return &Null (Stored); }
 254   static Stored *create (Data *data)
 255   {
 256     Stored *p = (Stored *) hb_calloc (1, sizeof (Stored));
 257     if (likely (p))
 258       p = new (p) Stored (data);
 259     return p;
 260   }
 261   static Stored *create ()
 262   {
 263     Stored *p = (Stored *) hb_calloc (1, sizeof (Stored));
 264     if (likely (p))
 265       p = new (p) Stored ();
 266     return p;
 267   }
 268   static void destroy (Stored *p)
 269   {
 270     p->~Stored ();
 271     hb_free (p);
 272   }
 273
 274   private:
 275   /* Must only have one pointer. */
 276   hb_atomic_ptr_t<Stored *> instance;
 277 };
 278
 279 /* Specializations. */
 280
 281 template <typename T, unsigned int WheresFace>
 282 struct hb_face_lazy_loader_t : hb_lazy_loader_t<T,
 283                                                 hb_face_lazy_loader_t<T, WheresFace>,
 284                                                 hb_face_t, WheresFace>
 285 {
 286   // Hack; have them here for API parity with hb_table_lazy_loader_t
 287   hb_blob_t *get_blob () { return this->get ()->get_blob (); }
 288 };
 289
 290 template <typename T, unsigned int WheresFace, bool core=false>
 291 struct hb_table_lazy_loader_t : hb_lazy_loader_t<T,
 292                                                  hb_table_lazy_loader_t<T, WheresFace, core>,
 293                                                  hb_face_t, WheresFace,
 294                                                  hb_blob_t>
 295 {
 296   static hb_blob_t *create (hb_face_t *face)
 297   {
 298     hb_sanitize_context_t c;
 299     if (core)
 300       c.set_num_glyphs (0); // So we don't recurse ad infinitum, or doesn't need num_glyphs
 301     return c.reference_table<T> (face);
 302   }
 303   static void destroy (hb_blob_t *p) { hb_blob_destroy (p); }
 304
 305   static const hb_blob_t *get_null ()
 306   { return hb_blob_get_empty (); }
 307
 308   static const T* convert (const hb_blob_t *blob)
 309   { return blob->as<T> (); }
 310
 311   hb_blob_t* get_blob () const { return this->get_stored (); }
 312 };
 313
 314 #define HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T(Type) \
 315   template <typename Subclass> \
 316   struct hb_##Type##_funcs_lazy_loader_t : hb_lazy_loader_t<hb_##Type##_funcs_t, Subclass> \
 317   { \
 318     static void destroy (hb_##Type##_funcs_t *p) \
 319     { hb_##Type##_funcs_destroy (p); } \
 320     static const hb_##Type##_funcs_t *get_null () \
 321     { return hb_##Type##_funcs_get_empty (); } \
 322   }
 323
 324 HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (font);
 325 HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (unicode);
 326 HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (draw);
 327 HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (paint);
 328
 329 #undef HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T
 330
 331
 332 #endif /* HB_MACHINERY_HH */