hb-ot-layout-common-private.hh revision 30ec9002d84e8b49290e782e6192069821ffa942 
1/*
2 * Copyright © 2007,2008,2009  Red Hat, Inc.
3 * Copyright © 2010,2012  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_OT_LAYOUT_COMMON_PRIVATE_HH
30#define HB_OT_LAYOUT_COMMON_PRIVATE_HH
31
32#include "hb-ot-layout-private.hh"
33#include "hb-open-type-private.hh"
34#include "hb-set-private.hh"
35
36
37#define NOT_COVERED		((unsigned int) 0x110000)
38#define MAX_NESTING_LEVEL	8
39
40
41
42/*
43 *
44 * OpenType Layout Common Table Formats
45 *
46 */
47
48
49/*
50 * Script, ScriptList, LangSys, Feature, FeatureList, Lookup, LookupList
51 */
52
53template <typename Type>
54struct Record
55{
56  inline int cmp (hb_tag_t a) const {
57    return tag.cmp (a);
58  }
59
60  inline bool sanitize (hb_sanitize_context_t *c, void *base) {
61    TRACE_SANITIZE ();
62    return TRACE_RETURN (c->check_struct (this) && offset.sanitize (c, base));
63  }
64
65  Tag		tag;		/* 4-byte Tag identifier */
66  OffsetTo<Type>
67		offset;		/* Offset from beginning of object holding
68				 * the Record */
69  public:
70  DEFINE_SIZE_STATIC (6);
71};
72
73template <typename Type>
74struct RecordArrayOf : SortedArrayOf<Record<Type> > {
75  inline const Tag& get_tag (unsigned int i) const
76  {
77    /* We cheat slightly and don't define separate Null objects
78     * for Record types.  Instead, we return the correct Null(Tag)
79     * here. */
80    if (unlikely (i >= this->len)) return Null(Tag);
81    return (*this)[i].tag;
82  }
83  inline unsigned int get_tags (unsigned int start_offset,
84				unsigned int *record_count /* IN/OUT */,
85				hb_tag_t     *record_tags /* OUT */) const
86  {
87    if (record_count) {
88      const Record<Type> *arr = this->sub_array (start_offset, record_count);
89      unsigned int count = *record_count;
90      for (unsigned int i = 0; i < count; i++)
91	record_tags[i] = arr[i].tag;
92    }
93    return this->len;
94  }
95  inline bool find_index (hb_tag_t tag, unsigned int *index) const
96  {
97    int i = this->search (tag);
98    if (i != -1) {
99        if (index) *index = i;
100        return true;
101    } else {
102      if (index) *index = Index::NOT_FOUND_INDEX;
103      return false;
104    }
105  }
106};
107
108template <typename Type>
109struct RecordListOf : RecordArrayOf<Type>
110{
111  inline const Type& operator [] (unsigned int i) const
112  { return this+RecordArrayOf<Type>::operator [](i).offset; }
113
114  inline bool sanitize (hb_sanitize_context_t *c) {
115    TRACE_SANITIZE ();
116    return TRACE_RETURN (RecordArrayOf<Type>::sanitize (c, this));
117  }
118};
119
120
121struct RangeRecord
122{
123  inline int cmp (hb_codepoint_t g) const {
124    hb_codepoint_t a = start, b = end;
125    return g < a ? -1 : g <= b ? 0 : +1 ;
126  }
127
128  inline bool sanitize (hb_sanitize_context_t *c) {
129    TRACE_SANITIZE ();
130    return TRACE_RETURN (c->check_struct (this));
131  }
132
133  inline bool intersects (const hb_set_t *glyphs) const {
134    return glyphs->intersects (start, end);
135  }
136
137  inline void add_coverage (hb_set_t *glyphs) const {
138    glyphs->add_range (start, end);
139  }
140
141  GlyphID	start;		/* First GlyphID in the range */
142  GlyphID	end;		/* Last GlyphID in the range */
143  USHORT	value;		/* Value */
144  public:
145  DEFINE_SIZE_STATIC (6);
146};
147DEFINE_NULL_DATA (RangeRecord, "\000\001");
148
149
150struct IndexArray : ArrayOf<Index>
151{
152  inline unsigned int get_indexes (unsigned int start_offset,
153				   unsigned int *_count /* IN/OUT */,
154				   unsigned int *_indexes /* OUT */) const
155  {
156    if (_count) {
157      const USHORT *arr = this->sub_array (start_offset, _count);
158      unsigned int count = *_count;
159      for (unsigned int i = 0; i < count; i++)
160	_indexes[i] = arr[i];
161    }
162    return this->len;
163  }
164};
165
166
167struct Script;
168struct LangSys;
169struct Feature;
170
171
172struct LangSys
173{
174  inline unsigned int get_feature_count (void) const
175  { return featureIndex.len; }
176  inline hb_tag_t get_feature_index (unsigned int i) const
177  { return featureIndex[i]; }
178  inline unsigned int get_feature_indexes (unsigned int start_offset,
179					   unsigned int *feature_count /* IN/OUT */,
180					   unsigned int *feature_indexes /* OUT */) const
181  { return featureIndex.get_indexes (start_offset, feature_count, feature_indexes); }
182
183  inline bool has_required_feature (void) const { return reqFeatureIndex != 0xffff; }
184  inline unsigned int get_required_feature_index (void) const
185  {
186    if (reqFeatureIndex == 0xffff)
187      return Index::NOT_FOUND_INDEX;
188   return reqFeatureIndex;;
189  }
190
191  inline bool sanitize (hb_sanitize_context_t *c) {
192    TRACE_SANITIZE ();
193    return TRACE_RETURN (c->check_struct (this) && featureIndex.sanitize (c));
194  }
195
196  Offset	lookupOrder;	/* = Null (reserved for an offset to a
197				 * reordering table) */
198  USHORT	reqFeatureIndex;/* Index of a feature required for this
199				 * language system--if no required features
200				 * = 0xFFFF */
201  IndexArray	featureIndex;	/* Array of indices into the FeatureList */
202  public:
203  DEFINE_SIZE_ARRAY (6, featureIndex);
204};
205DEFINE_NULL_DATA (LangSys, "\0\0\xFF\xFF");
206
207
208struct Script
209{
210  inline unsigned int get_lang_sys_count (void) const
211  { return langSys.len; }
212  inline const Tag& get_lang_sys_tag (unsigned int i) const
213  { return langSys.get_tag (i); }
214  inline unsigned int get_lang_sys_tags (unsigned int start_offset,
215					 unsigned int *lang_sys_count /* IN/OUT */,
216					 hb_tag_t     *lang_sys_tags /* OUT */) const
217  { return langSys.get_tags (start_offset, lang_sys_count, lang_sys_tags); }
218  inline const LangSys& get_lang_sys (unsigned int i) const
219  {
220    if (i == Index::NOT_FOUND_INDEX) return get_default_lang_sys ();
221    return this+langSys[i].offset;
222  }
223  inline bool find_lang_sys_index (hb_tag_t tag, unsigned int *index) const
224  { return langSys.find_index (tag, index); }
225
226  inline bool has_default_lang_sys (void) const { return defaultLangSys != 0; }
227  inline const LangSys& get_default_lang_sys (void) const { return this+defaultLangSys; }
228
229  inline bool sanitize (hb_sanitize_context_t *c) {
230    TRACE_SANITIZE ();
231    return TRACE_RETURN (defaultLangSys.sanitize (c, this) && langSys.sanitize (c, this));
232  }
233
234  protected:
235  OffsetTo<LangSys>
236		defaultLangSys;	/* Offset to DefaultLangSys table--from
237				 * beginning of Script table--may be Null */
238  RecordArrayOf<LangSys>
239		langSys;	/* Array of LangSysRecords--listed
240				 * alphabetically by LangSysTag */
241  public:
242  DEFINE_SIZE_ARRAY (4, langSys);
243};
244
245typedef RecordListOf<Script> ScriptList;
246
247
248struct Feature
249{
250  inline unsigned int get_lookup_count (void) const
251  { return lookupIndex.len; }
252  inline hb_tag_t get_lookup_index (unsigned int i) const
253  { return lookupIndex[i]; }
254  inline unsigned int get_lookup_indexes (unsigned int start_index,
255					  unsigned int *lookup_count /* IN/OUT */,
256					  unsigned int *lookup_tags /* OUT */) const
257  { return lookupIndex.get_indexes (start_index, lookup_count, lookup_tags); }
258
259  inline bool sanitize (hb_sanitize_context_t *c) {
260    TRACE_SANITIZE ();
261    return TRACE_RETURN (c->check_struct (this) && lookupIndex.sanitize (c));
262  }
263
264  Offset	featureParams;	/* Offset to Feature Parameters table (if one
265				 * has been defined for the feature), relative
266				 * to the beginning of the Feature Table; = Null
267				 * if not required */
268  IndexArray	 lookupIndex;	/* Array of LookupList indices */
269  public:
270  DEFINE_SIZE_ARRAY (4, lookupIndex);
271};
272
273typedef RecordListOf<Feature> FeatureList;
274
275
276struct LookupFlag : USHORT
277{
278  enum Flags {
279    RightToLeft		= 0x0001u,
280    IgnoreBaseGlyphs	= 0x0002u,
281    IgnoreLigatures	= 0x0004u,
282    IgnoreMarks		= 0x0008u,
283    IgnoreFlags		= 0x000Eu,
284    UseMarkFilteringSet	= 0x0010u,
285    Reserved		= 0x00E0u,
286    MarkAttachmentType	= 0xFF00u
287  };
288  public:
289  DEFINE_SIZE_STATIC (2);
290};
291
292struct Lookup
293{
294  inline unsigned int get_subtable_count (void) const { return subTable.len; }
295
296  inline unsigned int get_type (void) const { return lookupType; }
297
298  /* lookup_props is a 32-bit integer where the lower 16-bit is LookupFlag and
299   * higher 16-bit is mark-filtering-set if the lookup uses one.
300   * Not to be confused with glyph_props which is very similar. */
301  inline uint32_t get_props (void) const
302  {
303    unsigned int flag = lookupFlag;
304    if (unlikely (flag & LookupFlag::UseMarkFilteringSet))
305    {
306      const USHORT &markFilteringSet = StructAfter<USHORT> (subTable);
307      flag += (markFilteringSet << 16);
308    }
309    return flag;
310  }
311
312  inline bool sanitize (hb_sanitize_context_t *c) {
313    TRACE_SANITIZE ();
314    /* Real sanitize of the subtables is done by GSUB/GPOS/... */
315    if (!(c->check_struct (this) && subTable.sanitize (c))) return TRACE_RETURN (false);
316    if (!subTable.len) TRACE_RETURN (false);
317    if (unlikely (lookupFlag & LookupFlag::UseMarkFilteringSet))
318    {
319      USHORT &markFilteringSet = StructAfter<USHORT> (subTable);
320      if (!markFilteringSet.sanitize (c)) return TRACE_RETURN (false);
321    }
322    return TRACE_RETURN (true);
323  }
324
325  USHORT	lookupType;		/* Different enumerations for GSUB and GPOS */
326  USHORT	lookupFlag;		/* Lookup qualifiers */
327  ArrayOf<Offset>
328		subTable;		/* Array of SubTables */
329  USHORT	markFilteringSetX[VAR];	/* Index (base 0) into GDEF mark glyph sets
330					 * structure. This field is only present if bit
331					 * UseMarkFilteringSet of lookup flags is set. */
332  public:
333  DEFINE_SIZE_ARRAY2 (6, subTable, markFilteringSetX);
334};
335
336typedef OffsetListOf<Lookup> LookupList;
337
338
339/*
340 * Coverage Table
341 */
342
343struct CoverageFormat1
344{
345  friend struct Coverage;
346
347  private:
348  inline unsigned int get_coverage (hb_codepoint_t glyph_id) const
349  {
350    int i = glyphArray.search (glyph_id);
351    if (i != -1)
352        return i;
353    return NOT_COVERED;
354  }
355
356  inline bool sanitize (hb_sanitize_context_t *c) {
357    TRACE_SANITIZE ();
358    return TRACE_RETURN (glyphArray.sanitize (c));
359  }
360
361  inline bool intersects_coverage (const hb_set_t *glyphs, unsigned int index) const {
362    return glyphs->has (glyphArray[index]);
363  }
364
365  inline void add_coverage (hb_set_t *glyphs) const {
366    unsigned int count = glyphArray.len;
367    for (unsigned int i = 0; i < count; i++)
368      glyphs->add (glyphArray[i]);
369  }
370
371  struct Iter {
372    inline void init (const struct CoverageFormat1 &c_) { c = &c_; i = 0; };
373    inline bool more (void) { return i < c->glyphArray.len; }
374    inline void next (void) { i++; }
375    inline uint16_t get_glyph (void) { return c->glyphArray[i]; }
376    inline uint16_t get_coverage (void) { return i; }
377
378    private:
379    const struct CoverageFormat1 *c;
380    unsigned int i;
381  };
382
383  protected:
384  USHORT	coverageFormat;	/* Format identifier--format = 1 */
385  SortedArrayOf<GlyphID>
386		glyphArray;	/* Array of GlyphIDs--in numerical order */
387  public:
388  DEFINE_SIZE_ARRAY (4, glyphArray);
389};
390
391struct CoverageFormat2
392{
393  friend struct Coverage;
394
395  private:
396  inline unsigned int get_coverage (hb_codepoint_t glyph_id) const
397  {
398    int i = rangeRecord.search (glyph_id);
399    if (i != -1) {
400      const RangeRecord &range = rangeRecord[i];
401      return (unsigned int) range.value + (glyph_id - range.start);
402    }
403    return NOT_COVERED;
404  }
405
406  inline bool sanitize (hb_sanitize_context_t *c) {
407    TRACE_SANITIZE ();
408    return TRACE_RETURN (rangeRecord.sanitize (c));
409  }
410
411  inline bool intersects_coverage (const hb_set_t *glyphs, unsigned int index) const {
412    unsigned int i;
413    unsigned int count = rangeRecord.len;
414    for (i = 0; i < count; i++) {
415      const RangeRecord &range = rangeRecord[i];
416      if (range.value <= index &&
417	  index < (unsigned int) range.value + (range.end - range.start) &&
418	  range.intersects (glyphs))
419        return true;
420      else if (index < range.value)
421        return false;
422    }
423    return false;
424  }
425
426  inline void add_coverage (hb_set_t *glyphs) const {
427    unsigned int count = rangeRecord.len;
428    for (unsigned int i = 0; i < count; i++)
429      rangeRecord[i].add_coverage (glyphs);
430  }
431
432  struct Iter {
433    inline void init (const CoverageFormat2 &c_) {
434      c = &c_;
435      coverage = 0;
436      i = 0;
437      j = c->rangeRecord.len ? c_.rangeRecord[0].start : 0;
438    }
439    inline bool more (void) { return i < c->rangeRecord.len; }
440    inline void next (void) {
441      coverage++;
442      if (j == c->rangeRecord[i].end) {
443        i++;
444	if (more ())
445	  j = c->rangeRecord[i].start;
446	return;
447      }
448      j++;
449    }
450    inline uint16_t get_glyph (void) { return j; }
451    inline uint16_t get_coverage (void) { return coverage; }
452
453    private:
454    const struct CoverageFormat2 *c;
455    unsigned int i, j, coverage;
456  };
457
458  protected:
459  USHORT	coverageFormat;	/* Format identifier--format = 2 */
460  SortedArrayOf<RangeRecord>
461		rangeRecord;	/* Array of glyph ranges--ordered by
462				 * Start GlyphID. rangeCount entries
463				 * long */
464  public:
465  DEFINE_SIZE_ARRAY (4, rangeRecord);
466};
467
468struct Coverage
469{
470  inline unsigned int operator () (hb_codepoint_t glyph_id) const { return get_coverage (glyph_id); }
471
472  inline unsigned int get_coverage (hb_codepoint_t glyph_id) const
473  {
474    switch (u.format) {
475    case 1: return u.format1.get_coverage(glyph_id);
476    case 2: return u.format2.get_coverage(glyph_id);
477    default:return NOT_COVERED;
478    }
479  }
480
481  inline bool sanitize (hb_sanitize_context_t *c) {
482    TRACE_SANITIZE ();
483    if (!u.format.sanitize (c)) return TRACE_RETURN (false);
484    switch (u.format) {
485    case 1: return TRACE_RETURN (u.format1.sanitize (c));
486    case 2: return TRACE_RETURN (u.format2.sanitize (c));
487    default:return TRACE_RETURN (true);
488    }
489  }
490
491  inline bool intersects (const hb_set_t *glyphs) const {
492    /* TODO speed this up */
493    Coverage::Iter iter;
494    for (iter.init (*this); iter.more (); iter.next ()) {
495      if (glyphs->has (iter.get_glyph ()))
496        return true;
497    }
498    return false;
499  }
500
501  inline bool intersects_coverage (const hb_set_t *glyphs, unsigned int index) const {
502    switch (u.format) {
503    case 1: return u.format1.intersects_coverage (glyphs, index);
504    case 2: return u.format2.intersects_coverage (glyphs, index);
505    default:return false;
506    }
507  }
508
509  inline void add_coverage (hb_set_t *glyphs) const {
510    switch (u.format) {
511    case 1: u.format1.add_coverage (glyphs); break;
512    case 2: u.format2.add_coverage (glyphs); break;
513    default:                                 break;
514    }
515  }
516
517  struct Iter {
518    Iter (void) : format (0) {};
519    inline void init (const Coverage &c_) {
520      format = c_.u.format;
521      switch (format) {
522      case 1: return u.format1.init (c_.u.format1);
523      case 2: return u.format2.init (c_.u.format2);
524      default:return;
525      }
526    }
527    inline bool more (void) {
528      switch (format) {
529      case 1: return u.format1.more ();
530      case 2: return u.format2.more ();
531      default:return true;
532      }
533    }
534    inline void next (void) {
535      switch (format) {
536      case 1: u.format1.next (); break;
537      case 2: u.format2.next (); break;
538      default:                   break;
539      }
540    }
541    inline uint16_t get_glyph (void) {
542      switch (format) {
543      case 1: return u.format1.get_glyph ();
544      case 2: return u.format2.get_glyph ();
545      default:return true;
546      }
547    }
548    inline uint16_t get_coverage (void) {
549      switch (format) {
550      case 1: return u.format1.get_coverage ();
551      case 2: return u.format2.get_coverage ();
552      default:return true;
553      }
554    }
555
556    private:
557    unsigned int format;
558    union {
559    CoverageFormat1::Iter	format1;
560    CoverageFormat2::Iter	format2;
561    } u;
562  };
563
564  protected:
565  union {
566  USHORT		format;		/* Format identifier */
567  CoverageFormat1	format1;
568  CoverageFormat2	format2;
569  } u;
570  public:
571  DEFINE_SIZE_UNION (2, format);
572};
573
574
575/*
576 * Class Definition Table
577 */
578
579struct ClassDefFormat1
580{
581  friend struct ClassDef;
582
583  private:
584  inline unsigned int get_class (hb_codepoint_t glyph_id) const
585  {
586    if (unlikely ((unsigned int) (glyph_id - startGlyph) < classValue.len))
587      return classValue[glyph_id - startGlyph];
588    return 0;
589  }
590
591  inline bool sanitize (hb_sanitize_context_t *c) {
592    TRACE_SANITIZE ();
593    return TRACE_RETURN (c->check_struct (this) && classValue.sanitize (c));
594  }
595
596  inline bool intersects_class (const hb_set_t *glyphs, unsigned int klass) const {
597    unsigned int count = classValue.len;
598    for (unsigned int i = 0; i < count; i++)
599      if (classValue[i] == klass && glyphs->has (startGlyph + i))
600        return true;
601    return false;
602  }
603
604  protected:
605  USHORT	classFormat;		/* Format identifier--format = 1 */
606  GlyphID	startGlyph;		/* First GlyphID of the classValueArray */
607  ArrayOf<USHORT>
608		classValue;		/* Array of Class Values--one per GlyphID */
609  public:
610  DEFINE_SIZE_ARRAY (6, classValue);
611};
612
613struct ClassDefFormat2
614{
615  friend struct ClassDef;
616
617  private:
618  inline unsigned int get_class (hb_codepoint_t glyph_id) const
619  {
620    int i = rangeRecord.search (glyph_id);
621    if (i != -1)
622      return rangeRecord[i].value;
623    return 0;
624  }
625
626  inline bool sanitize (hb_sanitize_context_t *c) {
627    TRACE_SANITIZE ();
628    return TRACE_RETURN (rangeRecord.sanitize (c));
629  }
630
631  inline bool intersects_class (const hb_set_t *glyphs, unsigned int klass) const {
632    unsigned int count = rangeRecord.len;
633    for (unsigned int i = 0; i < count; i++)
634      if (rangeRecord[i].value == klass && rangeRecord[i].intersects (glyphs))
635        return true;
636    return false;
637  }
638
639  protected:
640  USHORT	classFormat;	/* Format identifier--format = 2 */
641  SortedArrayOf<RangeRecord>
642		rangeRecord;	/* Array of glyph ranges--ordered by
643				 * Start GlyphID */
644  public:
645  DEFINE_SIZE_ARRAY (4, rangeRecord);
646};
647
648struct ClassDef
649{
650  inline unsigned int operator () (hb_codepoint_t glyph_id) const { return get_class (glyph_id); }
651
652  inline unsigned int get_class (hb_codepoint_t glyph_id) const
653  {
654    switch (u.format) {
655    case 1: return u.format1.get_class(glyph_id);
656    case 2: return u.format2.get_class(glyph_id);
657    default:return 0;
658    }
659  }
660
661  inline bool sanitize (hb_sanitize_context_t *c) {
662    TRACE_SANITIZE ();
663    if (!u.format.sanitize (c)) return TRACE_RETURN (false);
664    switch (u.format) {
665    case 1: return TRACE_RETURN (u.format1.sanitize (c));
666    case 2: return TRACE_RETURN (u.format2.sanitize (c));
667    default:return TRACE_RETURN (true);
668    }
669  }
670
671  inline bool intersects_class (const hb_set_t *glyphs, unsigned int klass) const {
672    switch (u.format) {
673    case 1: return u.format1.intersects_class (glyphs, klass);
674    case 2: return u.format2.intersects_class (glyphs, klass);
675    default:return false;
676    }
677  }
678
679  protected:
680  union {
681  USHORT		format;		/* Format identifier */
682  ClassDefFormat1	format1;
683  ClassDefFormat2	format2;
684  } u;
685  public:
686  DEFINE_SIZE_UNION (2, format);
687};
688
689
690/*
691 * Device Tables
692 */
693
694struct Device
695{
696
697  inline hb_position_t get_x_delta (hb_font_t *font) const
698  { return get_delta (font->x_ppem, font->x_scale); }
699
700  inline hb_position_t get_y_delta (hb_font_t *font) const
701  { return get_delta (font->y_ppem, font->y_scale); }
702
703  inline int get_delta (unsigned int ppem, int scale) const
704  {
705    if (!ppem) return 0;
706
707    int pixels = get_delta_pixels (ppem);
708
709    if (!pixels) return 0;
710
711    return pixels * (int64_t) scale / ppem;
712  }
713
714
715  inline int get_delta_pixels (unsigned int ppem_size) const
716  {
717    unsigned int f = deltaFormat;
718    if (unlikely (f < 1 || f > 3))
719      return 0;
720
721    if (ppem_size < startSize || ppem_size > endSize)
722      return 0;
723
724    unsigned int s = ppem_size - startSize;
725
726    unsigned int byte = deltaValue[s >> (4 - f)];
727    unsigned int bits = (byte >> (16 - (((s & ((1 << (4 - f)) - 1)) + 1) << f)));
728    unsigned int mask = (0xFFFF >> (16 - (1 << f)));
729
730    int delta = bits & mask;
731
732    if ((unsigned int) delta >= ((mask + 1) >> 1))
733      delta -= mask + 1;
734
735    return delta;
736  }
737
738  inline unsigned int get_size (void) const
739  {
740    unsigned int f = deltaFormat;
741    if (unlikely (f < 1 || f > 3 || startSize > endSize)) return 3 * USHORT::static_size;
742    return USHORT::static_size * (4 + ((endSize - startSize) >> (4 - f)));
743  }
744
745  inline bool sanitize (hb_sanitize_context_t *c) {
746    TRACE_SANITIZE ();
747    return TRACE_RETURN (c->check_struct (this) && c->check_range (this, this->get_size ()));
748  }
749
750  protected:
751  USHORT	startSize;		/* Smallest size to correct--in ppem */
752  USHORT	endSize;		/* Largest size to correct--in ppem */
753  USHORT	deltaFormat;		/* Format of DeltaValue array data: 1, 2, or 3
754					 * 1	Signed 2-bit value, 8 values per uint16
755					 * 2	Signed 4-bit value, 4 values per uint16
756					 * 3	Signed 8-bit value, 2 values per uint16
757					 */
758  USHORT	deltaValue[VAR];	/* Array of compressed data */
759  public:
760  DEFINE_SIZE_ARRAY (6, deltaValue);
761};
762
763
764
765#endif /* HB_OT_LAYOUT_COMMON_PRIVATE_HH */
766