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-iter.hh"
36#include "hb-vector.hh"
37
38
39/*
40 * Casts
41 */
42
43/* Cast to struct T, reference to reference */
44template<typename Type, typename TObject>
45static inline const Type& CastR(const TObject &X)
46{ return reinterpret_cast<const Type&> (X); }
47template<typename Type, typename TObject>
48static inline Type& CastR(TObject &X)
49{ return reinterpret_cast<Type&> (X); }
50
51/* Cast to struct T, pointer to pointer */
52template<typename Type, typename TObject>
53static inline const Type* CastP(const TObject *X)
54{ return reinterpret_cast<const Type*> (X); }
55template<typename Type, typename TObject>
56static inline Type* CastP(TObject *X)
57{ return reinterpret_cast<Type*> (X); }
58
59/* StructAtOffset<T>(P,Ofs) returns the struct T& that is placed at memory
60 * location pointed to by P plus Ofs bytes. */
61template<typename Type>
62static inline const Type& StructAtOffset(const void *P, unsigned int offset)
63{ return * reinterpret_cast<const Type*> ((const char *) P + offset); }
64template<typename Type>
65static inline Type& StructAtOffset(void *P, unsigned int offset)
66{ return * reinterpret_cast<Type*> ((char *) P + offset); }
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() */
70template<typename Type, typename TObject>
71static inline const Type& StructAfter(const TObject &X)
72{ return StructAtOffset<Type>(&X, X.get_size()); }
73template<typename Type, typename TObject>
74static inline Type& StructAfter(TObject &X)
75{ return StructAtOffset<Type>(&X, X.get_size()); }
76
77
78/*
79 * Size checking
80 */
81
82/* Check _assertion in a method environment */
83#define _DEFINE_INSTANCE_ASSERTION1(_line, _assertion) \
84 inline void _instance_assertion_on_line_##_line (void) const \
85 { \
86 static_assert ((_assertion), ""); \
87 ASSERT_INSTANCE_POD (*this); /* Make sure it's POD. */ \
88 }
89# define _DEFINE_INSTANCE_ASSERTION0(_line, _assertion) _DEFINE_INSTANCE_ASSERTION1 (_line, _assertion)
90# define DEFINE_INSTANCE_ASSERTION(_assertion) _DEFINE_INSTANCE_ASSERTION0 (__LINE__, _assertion)
91
92/* Check that _code compiles in a method environment */
93#define _DEFINE_COMPILES_ASSERTION1(_line, _code) \
94 inline void _compiles_assertion_on_line_##_line (void) const \
95 { _code; }
96# define _DEFINE_COMPILES_ASSERTION0(_line, _code) _DEFINE_COMPILES_ASSERTION1 (_line, _code)
97# define DEFINE_COMPILES_ASSERTION(_code) _DEFINE_COMPILES_ASSERTION0 (__LINE__, _code)
98
99
100#define DEFINE_SIZE_STATIC(size) \
101 DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size)); \
102 enum { static_size = (size) }; \
103 enum { min_size = (size) }; \
104 inline unsigned int get_size (void) const { return (size); }
105
106#define DEFINE_SIZE_UNION(size, _member) \
107 DEFINE_INSTANCE_ASSERTION (0*sizeof(this->u._member.static_size) + sizeof(this->u._member) == (size)); \
108 static const unsigned int min_size = (size)
109
110#define DEFINE_SIZE_MIN(size) \
111 DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)); \
112 static const unsigned int min_size = (size)
113
114#define DEFINE_SIZE_ARRAY(size, array) \
115 DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size) + VAR * sizeof (array[0])); \
116 DEFINE_COMPILES_ASSERTION ((void) array[0].static_size) \
117 enum { min_size = (size) }; \
118
119#define DEFINE_SIZE_ARRAY_SIZED(size, array) \
120 DEFINE_SIZE_ARRAY(size, array); \
121 inline unsigned int get_size (void) const { return (size - array[0].min_size + array.get_size ()); }
122
123#define DEFINE_SIZE_ARRAY2(size, array1, array2) \
124 DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size) + sizeof (this->array1[0]) + sizeof (this->array2[0])); \
125 DEFINE_COMPILES_ASSERTION ((void) array1[0].static_size; (void) array2[0].static_size) \
126 static const unsigned int min_size = (size)
127
128
129/*
130 * Dispatch
131 */
132
133template <typename Context, typename Return, unsigned int MaxDebugDepth>
134struct hb_dispatch_context_t
135{
136 enum { max_debug_depth = MaxDebugDepth };
137 typedef Return return_t;
138 template <typename T, typename F>
139 inline bool may_dispatch (const T *obj, const F *format) { return true; }
140 static return_t no_dispatch_return_value (void) { return Context::default_return_value (); }
141};
142
143
144/*
145 * Sanitize
146 *
147 *
148 * === Introduction ===
149 *
150 * The sanitize machinery is at the core of our zero-cost font loading. We
151 * mmap() font file into memory and create a blob out of it. Font subtables
152 * are returned as a readonly sub-blob of the main font blob. These table
153 * blobs are then sanitized before use, to ensure invalid memory access does
154 * not happen. The toplevel sanitize API use is like, eg. to load the 'head'
155 * table:
156 *
157 * hb_blob_t *head_blob = hb_sanitize_context_t ().reference_table<OT::head> (face);
158 *
159 * The blob then can be converted to a head table struct with:
160 *
161 * const head *head_table = head_blob->as<head> ();
162 *
163 * What the reference_table does is, to call hb_face_reference_table() to load
164 * the table blob, sanitize it and return either the sanitized blob, or empty
165 * blob if sanitization failed. The blob->as() function returns the null
166 * object of its template type argument if the blob is empty. Otherwise, it
167 * just casts the blob contents to the desired type.
168 *
169 * Sanitizing a blob of data with a type T works as follows (with minor
170 * simplification):
171 *
172 * - Cast blob content to T*, call sanitize() method of it,
173 * - If sanitize succeeded, return blob.
174 * - Otherwise, if blob is not writable, try making it writable,
175 * or copy if cannot be made writable in-place,
176 * - Call sanitize() again. Return blob if sanitize succeeded.
177 * - Return empty blob otherwise.
178 *
179 *
180 * === The sanitize() contract ===
181 *
182 * The sanitize() method of each object type shall return true if it's safe to
183 * call other methods of the object, and false otherwise.
184 *
185 * Note that what sanitize() checks for might align with what the specification
186 * describes as valid table data, but does not have to be. In particular, we
187 * do NOT want to be pedantic and concern ourselves with validity checks that
188 * are irrelevant to our use of the table. On the contrary, we want to be
189 * lenient with error handling and accept invalid data to the extent that it
190 * does not impose extra burden on us.
191 *
192 * Based on the sanitize contract, one can see that what we check for depends
193 * on how we use the data in other table methods. Ie. if other table methods
194 * assume that offsets do NOT point out of the table data block, then that's
195 * something sanitize() must check for (GSUB/GPOS/GDEF/etc work this way). On
196 * the other hand, if other methods do such checks themselves, then sanitize()
197 * does not have to bother with them (glyf/local work this way). The choice
198 * depends on the table structure and sanitize() performance. For example, to
199 * check glyf/loca offsets in sanitize() would cost O(num-glyphs). We try hard
200 * to avoid such costs during font loading. By postponing such checks to the
201 * actual glyph loading, we reduce the sanitize cost to O(1) and total runtime
202 * cost to O(used-glyphs). As such, this is preferred.
203 *
204 * The same argument can be made re GSUB/GPOS/GDEF, but there, the table
205 * structure is so complicated that by checking all offsets at sanitize() time,
206 * we make the code much simpler in other methods, as offsets and referenced
207 * objectes do not need to be validated at each use site.
208 */
209
210/* This limits sanitizing time on really broken fonts. */
211#ifndef HB_SANITIZE_MAX_EDITS
212#define HB_SANITIZE_MAX_EDITS 32
213#endif
214#ifndef HB_SANITIZE_MAX_OPS_FACTOR
215#define HB_SANITIZE_MAX_OPS_FACTOR 8
216#endif
217#ifndef HB_SANITIZE_MAX_OPS_MIN
218#define HB_SANITIZE_MAX_OPS_MIN 16384
219#endif
220
221struct hb_sanitize_context_t :
222 hb_dispatch_context_t<hb_sanitize_context_t, bool, HB_DEBUG_SANITIZE>
223{
224 inline hb_sanitize_context_t (void) :
225 debug_depth (0),
226 start (nullptr), end (nullptr),
227 writable (false), edit_count (0), max_ops (0),
228 blob (nullptr),
229 num_glyphs (65536),
230 num_glyphs_set (false) {}
231
232 inline const char *get_name (void) { return "SANITIZE"; }
233 template <typename T, typename F>
234 inline bool may_dispatch (const T *obj, const F *format)
235 { return format->sanitize (this); }
236 template <typename T>
237 inline return_t dispatch (const T &obj) { return obj.sanitize (this); }
238 static return_t default_return_value (void) { return true; }
239 static return_t no_dispatch_return_value (void) { return false; }
240 bool stop_sublookup_iteration (const return_t r) const { return !r; }
241
242 inline void init (hb_blob_t *b)
243 {
244 this->blob = hb_blob_reference (b);
245 this->writable = false;
246 }
247
248 inline void set_num_glyphs (unsigned int num_glyphs_)
249 {
250 num_glyphs = num_glyphs_;
251 num_glyphs_set = true;
252 }
253 inline unsigned int get_num_glyphs (void) { return num_glyphs; }
254
255 inline void start_processing (void)
256 {
257 this->start = this->blob->data;
258 this->end = this->start + this->blob->length;
259 assert (this->start <= this->end); /* Must not overflow. */
260 this->max_ops = MAX ((unsigned int) (this->end - this->start) * HB_SANITIZE_MAX_OPS_FACTOR,
261 (unsigned) HB_SANITIZE_MAX_OPS_MIN);
262 this->edit_count = 0;
263 this->debug_depth = 0;
264
265 DEBUG_MSG_LEVEL (SANITIZE, start, 0, +1,
266 "start [%p..%p] (%lu bytes)",
267 this->start, this->end,
268 (unsigned long) (this->end - this->start));
269 }
270
271 inline void end_processing (void)
272 {
273 DEBUG_MSG_LEVEL (SANITIZE, this->start, 0, -1,
274 "end [%p..%p] %u edit requests",
275 this->start, this->end, this->edit_count);
276
277 hb_blob_destroy (this->blob);
278 this->blob = nullptr;
279 this->start = this->end = nullptr;
280 }
281
282 inline bool check_range (const void *base, unsigned int len) const
283 {
284 const char *p = (const char *) base;
285 bool ok = this->max_ops-- > 0 &&
286 this->start <= p &&
287 p <= this->end &&
288 (unsigned int) (this->end - p) >= len;
289
290 DEBUG_MSG_LEVEL (SANITIZE, p, this->debug_depth+1, 0,
291 "check_range [%p..%p] (%d bytes) in [%p..%p] -> %s",
292 p, p + len, len,
293 this->start, this->end,
294 ok ? "OK" : "OUT-OF-RANGE");
295
296 return likely (ok);
297 }
298
299 inline bool check_array (const void *base, unsigned int record_size, unsigned int len) const
300 {
301 const char *p = (const char *) base;
302 bool overflows = hb_unsigned_mul_overflows (len, record_size);
303 unsigned int array_size = record_size * len;
304 bool ok = !overflows && this->check_range (base, array_size);
305
306 DEBUG_MSG_LEVEL (SANITIZE, p, this->debug_depth+1, 0,
307 "check_array [%p..%p] (%d*%d=%d bytes) in [%p..%p] -> %s",
308 p, p + (record_size * len), record_size, len, (unsigned int) array_size,
309 this->start, this->end,
310 overflows ? "OVERFLOWS" : ok ? "OK" : "OUT-OF-RANGE");
311
312 return likely (ok);
313 }
314
315 template <typename Type>
316 inline bool check_struct (const Type *obj) const
317 {
318 return likely (this->check_range (obj, obj->min_size));
319 }
320
321 inline bool may_edit (const void *base, unsigned int len)
322 {
323 if (this->edit_count >= HB_SANITIZE_MAX_EDITS)
324 return false;
325
326 const char *p = (const char *) base;
327 this->edit_count++;
328
329 DEBUG_MSG_LEVEL (SANITIZE, p, this->debug_depth+1, 0,
330 "may_edit(%u) [%p..%p] (%d bytes) in [%p..%p] -> %s",
331 this->edit_count,
332 p, p + len, len,
333 this->start, this->end,
334 this->writable ? "GRANTED" : "DENIED");
335
336 return this->writable;
337 }
338
339 template <typename Type, typename ValueType>
340 inline bool try_set (const Type *obj, const ValueType &v) {
341 if (this->may_edit (obj, obj->static_size)) {
342 const_cast<Type *> (obj)->set (v);
343 return true;
344 }
345 return false;
346 }
347
348 template <typename Type>
349 inline hb_blob_t *sanitize_blob (hb_blob_t *blob)
350 {
351 bool sane;
352
353 init (blob);
354
355 retry:
356 DEBUG_MSG_FUNC (SANITIZE, start, "start");
357
358 start_processing ();
359
360 if (unlikely (!start))
361 {
362 end_processing ();
363 return blob;
364 }
365
366 Type *t = CastP<Type> (const_cast<char *> (start));
367
368 sane = t->sanitize (this);
369 if (sane)
370 {
371 if (edit_count)
372 {
373 DEBUG_MSG_FUNC (SANITIZE, start, "passed first round with %d edits; going for second round", edit_count);
374
375 /* sanitize again to ensure no toe-stepping */
376 edit_count = 0;
377 sane = t->sanitize (this);
378 if (edit_count) {
379 DEBUG_MSG_FUNC (SANITIZE, start, "requested %d edits in second round; FAILLING", edit_count);
380 sane = false;
381 }
382 }
383 }
384 else
385 {
386 if (edit_count && !writable) {
387 start = hb_blob_get_data_writable (blob, nullptr);
388 end = start + blob->length;
389
390 if (start)
391 {
392 writable = true;
393 /* ok, we made it writable by relocating. try again */
394 DEBUG_MSG_FUNC (SANITIZE, start, "retry");
395 goto retry;
396 }
397 }
398 }
399
400 end_processing ();
401
402 DEBUG_MSG_FUNC (SANITIZE, start, sane ? "PASSED" : "FAILED");
403 if (sane)
404 {
405 hb_blob_make_immutable (blob);
406 return blob;
407 }
408 else
409 {
410 hb_blob_destroy (blob);
411 return hb_blob_get_empty ();
412 }
413 }
414
415 template <typename Type>
416 inline hb_blob_t *reference_table (const hb_face_t *face, hb_tag_t tableTag = Type::tableTag)
417 {
418 if (!num_glyphs_set)
419 set_num_glyphs (hb_face_get_glyph_count (face));
420 return sanitize_blob<Type> (hb_face_reference_table (face, tableTag));
421 }
422
423 mutable unsigned int debug_depth;
424 const char *start, *end;
425 private:
426 bool writable;
427 unsigned int edit_count;
428 mutable int max_ops;
429 hb_blob_t *blob;
430 unsigned int num_glyphs;
431 bool num_glyphs_set;
432};
433
434
435/*
436 * Serialize
437 */
438
439struct hb_serialize_context_t
440{
441 inline hb_serialize_context_t (void *start_, unsigned int size)
442 {
443 this->start = (char *) start_;
444 this->end = this->start + size;
445 reset ();
446 }
447
448 inline void reset (void)
449 {
450 this->ran_out_of_room = false;
451 this->head = this->start;
452 this->debug_depth = 0;
453 }
454
455 inline bool err (bool e) { return this->ran_out_of_room = this->ran_out_of_room || e; }
456
457 /* To be called around main operation. */
458 template <typename Type>
459 inline Type *start_serialize (void)
460 {
461 DEBUG_MSG_LEVEL (SERIALIZE, this->start, 0, +1,
462 "start [%p..%p] (%lu bytes)",
463 this->start, this->end,
464 (unsigned long) (this->end - this->start));
465
466 return start_embed<Type> ();
467 }
468 inline void end_serialize (void)
469 {
470 DEBUG_MSG_LEVEL (SERIALIZE, this->start, 0, -1,
471 "end [%p..%p] serialized %d bytes; %s",
472 this->start, this->end,
473 (int) (this->head - this->start),
474 this->ran_out_of_room ? "RAN OUT OF ROOM" : "did not ran out of room");
475 }
476
477 inline unsigned int length (void) const { return this->head - this->start; }
478
479 inline void align (unsigned int alignment)
480 {
481 unsigned int l = length () % alignment;
482 if (l)
483 allocate_size<void> (alignment - l);
484 }
485
486 template <typename Type>
487 inline Type *start_embed (void) const
488 {
489 Type *ret = reinterpret_cast<Type *> (this->head);
490 return ret;
491 }
492
493 template <typename Type>
494 inline Type *allocate_size (unsigned int size)
495 {
496 if (unlikely (this->ran_out_of_room || this->end - this->head < ptrdiff_t (size))) {
497 this->ran_out_of_room = true;
498 return nullptr;
499 }
500 memset (this->head, 0, size);
501 char *ret = this->head;
502 this->head += size;
503 return reinterpret_cast<Type *> (ret);
504 }
505
506 template <typename Type>
507 inline Type *allocate_min (void)
508 {
509 return this->allocate_size<Type> (Type::min_size);
510 }
511
512 template <typename Type>
513 inline Type *embed (const Type &obj)
514 {
515 unsigned int size = obj.get_size ();
516 Type *ret = this->allocate_size<Type> (size);
517 if (unlikely (!ret)) return nullptr;
518 memcpy (ret, &obj, size);
519 return ret;
520 }
521
522 template <typename Type>
523 inline Type *extend_min (Type &obj)
524 {
525 unsigned int size = obj.min_size;
526 assert (this->start <= (char *) &obj && (char *) &obj <= this->head && (char *) &obj + size >= this->head);
527 if (unlikely (!this->allocate_size<Type> (((char *) &obj) + size - this->head))) return nullptr;
528 return reinterpret_cast<Type *> (&obj);
529 }
530
531 template <typename Type>
532 inline Type *extend (Type &obj)
533 {
534 unsigned int size = obj.get_size ();
535 assert (this->start < (char *) &obj && (char *) &obj <= this->head && (char *) &obj + size >= this->head);
536 if (unlikely (!this->allocate_size<Type> (((char *) &obj) + size - this->head))) return nullptr;
537 return reinterpret_cast<Type *> (&obj);
538 }
539
540 /* Output routines. */
541 template <typename Type>
542 inline Type *copy (void) const
543 {
544 assert (!this->ran_out_of_room);
545 unsigned int len = this->head - this->start;
546 void *p = malloc (len);
547 if (p)
548 memcpy (p, this->start, len);
549 return reinterpret_cast<Type *> (p);
550 }
551 inline hb_bytes_t copy_bytes (void) const
552 {
553 assert (!this->ran_out_of_room);
554 unsigned int len = this->head - this->start;
555 void *p = malloc (len);
556 if (p)
557 memcpy (p, this->start, len);
558 else
559 return hb_bytes_t ();
560 return hb_bytes_t (p, len);
561 }
562 inline hb_blob_t *copy_blob (void) const
563 {
564 assert (!this->ran_out_of_room);
565 return hb_blob_create (this->start,
566 this->head - this->start,
567 HB_MEMORY_MODE_DUPLICATE,
568 nullptr, nullptr);
569 }
570
571 public:
572 unsigned int debug_depth;
573 char *start, *end, *head;
574 bool ran_out_of_room;
575};
576
577
578/*
579 * Supplier
580 */
581
582template <typename Type>
583struct Supplier
584{
585 inline Supplier (const Type *array, unsigned int len_, unsigned int stride_=sizeof (Type))
586 {
587 head = array;
588 len = len_;
589 stride = stride_;
590 }
591 inline Supplier (const hb_vector_t<Type> *v)
592 {
593 head = v->arrayZ;
594 len = v->len;
595 stride = sizeof (Type);
596 }
597
598 inline const Type operator [] (unsigned int i) const
599 {
600 if (unlikely (i >= len)) return Type ();
601 return * (const Type *) (const void *) ((const char *) head + stride * i);
602 }
603
604 inline Supplier<Type> & operator += (unsigned int count)
605 {
606 if (unlikely (count > len))
607 count = len;
608 len -= count;
609 head = (const Type *) (const void *) ((const char *) head + stride * count);
610 return *this;
611 }
612
613 private:
614 inline Supplier (const Supplier<Type> &); /* Disallow copy */
615 inline Supplier<Type>& operator= (const Supplier<Type> &); /* Disallow copy */
616
617 unsigned int len;
618 unsigned int stride;
619 const Type *head;
620};
621
622
623/*
624 * Big-endian integers.
625 */
626
627template <typename Type, int Bytes> struct BEInt;
628
629template <typename Type>
630struct BEInt<Type, 1>
631{
632 public:
633 inline void set (Type V)
634 {
635 v = V;
636 }
637 inline operator Type (void) const
638 {
639 return v;
640 }
641 private: uint8_t v;
642};
643template <typename Type>
644struct BEInt<Type, 2>
645{
646 public:
647 inline void set (Type V)
648 {
649 v[0] = (V >> 8) & 0xFF;
650 v[1] = (V ) & 0xFF;
651 }
652 inline operator Type (void) const
653 {
654 return (v[0] << 8)
655 + (v[1] );
656 }
657 private: uint8_t v[2];
658};
659template <typename Type>
660struct BEInt<Type, 3>
661{
662 public:
663 inline void set (Type V)
664 {
665 v[0] = (V >> 16) & 0xFF;
666 v[1] = (V >> 8) & 0xFF;
667 v[2] = (V ) & 0xFF;
668 }
669 inline operator Type (void) const
670 {
671 return (v[0] << 16)
672 + (v[1] << 8)
673 + (v[2] );
674 }
675 private: uint8_t v[3];
676};
677template <typename Type>
678struct BEInt<Type, 4>
679{
680 public:
681 inline void set (Type V)
682 {
683 v[0] = (V >> 24) & 0xFF;
684 v[1] = (V >> 16) & 0xFF;
685 v[2] = (V >> 8) & 0xFF;
686 v[3] = (V ) & 0xFF;
687 }
688 inline operator Type (void) const
689 {
690 return (v[0] << 24)
691 + (v[1] << 16)
692 + (v[2] << 8)
693 + (v[3] );
694 }
695 private: uint8_t v[4];
696};
697
698
699/*
700 * Lazy loaders.
701 */
702
703template <typename Data, unsigned int WheresData>
704struct hb_data_wrapper_t
705{
706 static_assert (WheresData > 0, "");
707
708 inline Data * get_data (void) const
709 {
710 return *(((Data **) (void *) this) - WheresData);
711 }
712
713 template <typename Stored, typename Subclass>
714 inline Stored * call_create (void) const
715 {
716 Data *data = this->get_data ();
717 return likely (data) ? Subclass::create (data) : nullptr;
718 }
719};
720template <>
721struct hb_data_wrapper_t<void, 0>
722{
723 template <typename Stored, typename Funcs>
724 inline Stored * call_create (void) const
725 {
726 return Funcs::create ();
727 }
728};
729
730template <typename T1, typename T2> struct hb_non_void_t { typedef T1 value; };
731template <typename T2> struct hb_non_void_t<void, T2> { typedef T2 value; };
732
733template <typename Returned,
734 typename Subclass = void,
735 typename Data = void,
736 unsigned int WheresData = 0,
737 typename Stored = Returned>
738struct hb_lazy_loader_t : hb_data_wrapper_t<Data, WheresData>
739{
740 typedef typename hb_non_void_t<Subclass,
741 hb_lazy_loader_t<Returned,Subclass,Data,WheresData,Stored>
742 >::value Funcs;
743
744 inline void init0 (void) {} /* Init, when memory is already set to 0. No-op for us. */
745 inline void init (void) { instance.set_relaxed (nullptr); }
746 inline void fini (void)
747 {
748 do_destroy (instance.get ());
749 }
750 inline void free_instance (void)
751 {
752 retry:
753 Stored *p = instance.get ();
754 if (unlikely (p && !this->instance.cmpexch (p, nullptr)))
755 goto retry;
756 do_destroy (p);
757 }
758
759 inline Stored * do_create (void) const
760 {
761 Stored *p = this->template call_create<Stored, Funcs> ();
762 if (unlikely (!p))
763 p = const_cast<Stored *> (Funcs::get_null ());
764 return p;
765 }
766 static inline void do_destroy (Stored *p)
767 {
768 if (p && p != Funcs::get_null ())
769 Funcs::destroy (p);
770 }
771
772 inline const Returned * operator -> (void) const { return get (); }
773 inline const Returned & operator * (void) const { return *get (); }
774
775 inline Data * get_data (void) const
776 {
777 return *(((Data **) this) - WheresData);
778 }
779
780 inline Stored * get_stored (void) const
781 {
782 retry:
783 Stored *p = this->instance.get ();
784 if (unlikely (!p))
785 {
786 p = do_create ();
787 if (unlikely (!this->instance.cmpexch (nullptr, p)))
788 {
789 do_destroy (p);
790 goto retry;
791 }
792 }
793 return p;
794 }
795 inline Stored * get_stored_relaxed (void) const
796 {
797 return this->instance.get_relaxed ();
798 }
799
800 inline void set_stored (Stored *instance_)
801 {
802 /* This *must* be called when there are no other threads accessing.
803 * However, to make TSan, etc, happy, we using cmpexch. */
804 retry:
805 Stored *p = this->instance.get ();
806 if (unlikely (!this->instance.cmpexch (p, instance_)))
807 goto retry;
808 do_destroy (p);
809 }
810
811 inline const Returned * get (void) const { return Funcs::convert (get_stored ()); }
812 inline const Returned * get_relaxed (void) const { return Funcs::convert (get_stored_relaxed ()); }
813 inline Returned * get_unconst (void) const { return const_cast<Returned *> (Funcs::convert (get_stored ())); }
814
815 /* To be possibly overloaded by subclasses. */
816 static inline Returned* convert (Stored *p) { return p; }
817
818 /* By default null/init/fini the object. */
819 static inline const Stored* get_null (void) { return &Null(Stored); }
820 static inline Stored *create (Data *data)
821 {
822 Stored *p = (Stored *) calloc (1, sizeof (Stored));
823 if (likely (p))
824 p->init (data);
825 return p;
826 }
827 static inline Stored *create (void)
828 {
829 Stored *p = (Stored *) calloc (1, sizeof (Stored));
830 if (likely (p))
831 p->init ();
832 return p;
833 }
834 static inline void destroy (Stored *p)
835 {
836 p->fini ();
837 free (p);
838 }
839
840 private:
841 /* Must only have one pointer. */
842 hb_atomic_ptr_t<Stored *> instance;
843};
844
845/* Specializations. */
846
847template <typename T, unsigned int WheresFace>
848struct hb_face_lazy_loader_t : hb_lazy_loader_t<T,
849 hb_face_lazy_loader_t<T, WheresFace>,
850 hb_face_t, WheresFace> {};
851
852template <typename T, unsigned int WheresFace>
853struct hb_table_lazy_loader_t : hb_lazy_loader_t<T,
854 hb_table_lazy_loader_t<T, WheresFace>,
855 hb_face_t, WheresFace,
856 hb_blob_t>
857{
858 static inline hb_blob_t *create (hb_face_t *face)
859 {
860 return hb_sanitize_context_t ().reference_table<T> (face);
861 }
862 static inline void destroy (hb_blob_t *p)
863 {
864 hb_blob_destroy (p);
865 }
866 static inline const hb_blob_t *get_null (void)
867 {
868 return hb_blob_get_empty ();
869 }
870 static inline const T* convert (const hb_blob_t *blob)
871 {
872 return blob->as<T> ();
873 }
874
875 inline hb_blob_t* get_blob (void) const
876 {
877 return this->get_stored ();
878 }
879};
880
881template <typename Subclass>
882struct hb_font_funcs_lazy_loader_t : hb_lazy_loader_t<hb_font_funcs_t, Subclass>
883{
884 static inline void destroy (hb_font_funcs_t *p)
885 {
886 hb_font_funcs_destroy (p);
887 }
888 static inline const hb_font_funcs_t *get_null (void)
889 {
890 return hb_font_funcs_get_empty ();
891 }
892};
893template <typename Subclass>
894struct hb_unicode_funcs_lazy_loader_t : hb_lazy_loader_t<hb_unicode_funcs_t, Subclass>
895{
896 static inline void destroy (hb_unicode_funcs_t *p)
897 {
898 hb_unicode_funcs_destroy (p);
899 }
900 static inline const hb_unicode_funcs_t *get_null (void)
901 {
902 return hb_unicode_funcs_get_empty ();
903 }
904};
905
906
907#endif /* HB_MACHINERY_HH */
908