hb-ot-layout-common-private.hh revision 67bb9e8cea49a44be6996515e1c7d8cdc95a77e6 
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  private:
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 (unlikely (lookupFlag & LookupFlag::UseMarkFilteringSet))
317    {
318      USHORT &markFilteringSet = StructAfter<USHORT> (subTable);
319      if (!markFilteringSet.sanitize (c)) return TRACE_RETURN (false);
320    }
321    return TRACE_RETURN (true);
322  }
323
324  USHORT	lookupType;		/* Different enumerations for GSUB and GPOS */
325  USHORT	lookupFlag;		/* Lookup qualifiers */
326  ArrayOf<Offset>
327		subTable;		/* Array of SubTables */
328  USHORT	markFilteringSetX[VAR];	/* Index (base 0) into GDEF mark glyph sets
329					 * structure. This field is only present if bit
330					 * UseMarkFilteringSet of lookup flags is set. */
331  public:
332  DEFINE_SIZE_ARRAY2 (6, subTable, markFilteringSetX);
333};
334
335typedef OffsetListOf<Lookup> LookupList;
336
337
338/*
339 * Coverage Table
340 */
341
342struct CoverageFormat1
343{
344  friend struct Coverage;
345
346  private:
347  inline unsigned int get_coverage (hb_codepoint_t glyph_id) const
348  {
349    int i = glyphArray.search (glyph_id);
350    if (i != -1)
351        return i;
352    return NOT_COVERED;
353  }
354
355  inline bool sanitize (hb_sanitize_context_t *c) {
356    TRACE_SANITIZE ();
357    return TRACE_RETURN (glyphArray.sanitize (c));
358  }
359
360  inline bool intersects_coverage (const hb_set_t *glyphs, unsigned int index) const {
361    return glyphs->has (glyphArray[index]);
362  }
363
364  inline void add_coverage (hb_set_t *glyphs) const {
365    unsigned int count = glyphArray.len;
366    for (unsigned int i = 0; i < count; i++)
367      glyphs->add (glyphArray[i]);
368  }
369
370  struct Iter {
371    inline void init (const struct CoverageFormat1 &c_) { c = &c_; i = 0; };
372    inline bool more (void) { return i < c->glyphArray.len; }
373    inline void next (void) { i++; }
374    inline uint16_t get_glyph (void) { return c->glyphArray[i]; }
375    inline uint16_t get_coverage (void) { return i; }
376
377    private:
378    const struct CoverageFormat1 *c;
379    unsigned int i;
380  };
381
382  private:
383  USHORT	coverageFormat;	/* Format identifier--format = 1 */
384  SortedArrayOf<GlyphID>
385		glyphArray;	/* Array of GlyphIDs--in numerical order */
386  public:
387  DEFINE_SIZE_ARRAY (4, glyphArray);
388};
389
390struct CoverageFormat2
391{
392  friend struct Coverage;
393
394  private:
395  inline unsigned int get_coverage (hb_codepoint_t glyph_id) const
396  {
397    int i = rangeRecord.search (glyph_id);
398    if (i != -1) {
399      const RangeRecord &range = rangeRecord[i];
400      return (unsigned int) range.value + (glyph_id - range.start);
401    }
402    return NOT_COVERED;
403  }
404
405  inline bool sanitize (hb_sanitize_context_t *c) {
406    TRACE_SANITIZE ();
407    return TRACE_RETURN (rangeRecord.sanitize (c));
408  }
409
410  inline bool intersects_coverage (const hb_set_t *glyphs, unsigned int index) const {
411    unsigned int i;
412    unsigned int count = rangeRecord.len;
413    for (i = 0; i < count; i++) {
414      const RangeRecord &range = rangeRecord[i];
415      if (range.value <= index &&
416	  index < (unsigned int) range.value + (range.end - range.start) &&
417	  range.intersects (glyphs))
418        return true;
419      else if (index < range.value)
420        return false;
421    }
422    return false;
423  }
424
425  inline void add_coverage (hb_set_t *glyphs) const {
426    unsigned int count = rangeRecord.len;
427    for (unsigned int i = 0; i < count; i++)
428      rangeRecord[i].add_coverage (glyphs);
429  }
430
431  struct Iter {
432    inline void init (const CoverageFormat2 &c_) {
433      c = &c_;
434      coverage = 0;
435      i = 0;
436      j = c->rangeRecord.len ? c_.rangeRecord[0].start : 0;
437    }
438    inline bool more (void) { return i < c->rangeRecord.len; }
439    inline void next (void) {
440      coverage++;
441      if (j == c->rangeRecord[i].end) {
442        i++;
443	if (more ())
444	  j = c->rangeRecord[i].start;
445	return;
446      }
447      j++;
448    }
449    inline uint16_t get_glyph (void) { return j; }
450    inline uint16_t get_coverage (void) { return coverage; }
451
452    private:
453    const struct CoverageFormat2 *c;
454    unsigned int i, j, coverage;
455  };
456
457  private:
458  USHORT	coverageFormat;	/* Format identifier--format = 2 */
459  SortedArrayOf<RangeRecord>
460		rangeRecord;	/* Array of glyph ranges--ordered by
461				 * Start GlyphID. rangeCount entries
462				 * long */
463  public:
464  DEFINE_SIZE_ARRAY (4, rangeRecord);
465};
466
467struct Coverage
468{
469  inline unsigned int operator () (hb_codepoint_t glyph_id) const { return get_coverage (glyph_id); }
470
471  inline unsigned int get_coverage (hb_codepoint_t glyph_id) const
472  {
473    switch (u.format) {
474    case 1: return u.format1.get_coverage(glyph_id);
475    case 2: return u.format2.get_coverage(glyph_id);
476    default:return NOT_COVERED;
477    }
478  }
479
480  inline bool sanitize (hb_sanitize_context_t *c) {
481    TRACE_SANITIZE ();
482    if (!u.format.sanitize (c)) return TRACE_RETURN (false);
483    switch (u.format) {
484    case 1: return TRACE_RETURN (u.format1.sanitize (c));
485    case 2: return TRACE_RETURN (u.format2.sanitize (c));
486    default:return TRACE_RETURN (true);
487    }
488  }
489
490  inline bool intersects (const hb_set_t *glyphs) const {
491    /* TODO speed this up */
492    Coverage::Iter iter;
493    for (iter.init (*this); iter.more (); iter.next ()) {
494      if (glyphs->has (iter.get_glyph ()))
495        return true;
496    }
497    return false;
498  }
499
500  inline bool intersects_coverage (const hb_set_t *glyphs, unsigned int index) const {
501    switch (u.format) {
502    case 1: return u.format1.intersects_coverage (glyphs, index);
503    case 2: return u.format2.intersects_coverage (glyphs, index);
504    default:return false;
505    }
506  }
507
508  inline void add_coverage (hb_set_t *glyphs) const {
509    switch (u.format) {
510    case 1: u.format1.add_coverage (glyphs); break;
511    case 2: u.format2.add_coverage (glyphs); break;
512    default:                                 break;
513    }
514  }
515
516  struct Iter {
517    Iter (void) : format (0) {};
518    inline void init (const Coverage &c_) {
519      format = c_.u.format;
520      switch (format) {
521      case 1: return u.format1.init (c_.u.format1);
522      case 2: return u.format2.init (c_.u.format2);
523      default:return;
524      }
525    }
526    inline bool more (void) {
527      switch (format) {
528      case 1: return u.format1.more ();
529      case 2: return u.format2.more ();
530      default:return true;
531      }
532    }
533    inline void next (void) {
534      switch (format) {
535      case 1: u.format1.next (); break;
536      case 2: u.format2.next (); break;
537      default:                   break;
538      }
539    }
540    inline uint16_t get_glyph (void) {
541      switch (format) {
542      case 1: return u.format1.get_glyph ();
543      case 2: return u.format2.get_glyph ();
544      default:return true;
545      }
546    }
547    inline uint16_t get_coverage (void) {
548      switch (format) {
549      case 1: return u.format1.get_coverage ();
550      case 2: return u.format2.get_coverage ();
551      default:return true;
552      }
553    }
554
555    private:
556    unsigned int format;
557    union {
558    CoverageFormat1::Iter	format1;
559    CoverageFormat2::Iter	format2;
560    } u;
561  };
562
563  private:
564  union {
565  USHORT		format;		/* Format identifier */
566  CoverageFormat1	format1;
567  CoverageFormat2	format2;
568  } u;
569  public:
570  DEFINE_SIZE_UNION (2, format);
571};
572
573
574/*
575 * Class Definition Table
576 */
577
578struct ClassDefFormat1
579{
580  friend struct ClassDef;
581
582  private:
583  inline unsigned int get_class (hb_codepoint_t glyph_id) const
584  {
585    if (unlikely ((unsigned int) (glyph_id - startGlyph) < classValue.len))
586      return classValue[glyph_id - startGlyph];
587    return 0;
588  }
589
590  inline bool sanitize (hb_sanitize_context_t *c) {
591    TRACE_SANITIZE ();
592    return TRACE_RETURN (c->check_struct (this) && classValue.sanitize (c));
593  }
594
595  inline bool intersects_class (const hb_set_t *glyphs, unsigned int klass) const {
596    unsigned int count = classValue.len;
597    for (unsigned int i = 0; i < count; i++)
598      if (classValue[i] == klass && glyphs->has (startGlyph + i))
599        return true;
600    return false;
601  }
602
603  USHORT	classFormat;		/* Format identifier--format = 1 */
604  GlyphID	startGlyph;		/* First GlyphID of the classValueArray */
605  ArrayOf<USHORT>
606		classValue;		/* Array of Class Values--one per GlyphID */
607  public:
608  DEFINE_SIZE_ARRAY (6, classValue);
609};
610
611struct ClassDefFormat2
612{
613  friend struct ClassDef;
614
615  private:
616  inline unsigned int get_class (hb_codepoint_t glyph_id) const
617  {
618    int i = rangeRecord.search (glyph_id);
619    if (i != -1)
620      return rangeRecord[i].value;
621    return 0;
622  }
623
624  inline bool sanitize (hb_sanitize_context_t *c) {
625    TRACE_SANITIZE ();
626    return TRACE_RETURN (rangeRecord.sanitize (c));
627  }
628
629  inline bool intersects_class (const hb_set_t *glyphs, unsigned int klass) const {
630    unsigned int count = rangeRecord.len;
631    for (unsigned int i = 0; i < count; i++)
632      if (rangeRecord[i].value == klass && rangeRecord[i].intersects (glyphs))
633        return true;
634    return false;
635  }
636
637  USHORT	classFormat;	/* Format identifier--format = 2 */
638  SortedArrayOf<RangeRecord>
639		rangeRecord;	/* Array of glyph ranges--ordered by
640				 * Start GlyphID */
641  public:
642  DEFINE_SIZE_ARRAY (4, rangeRecord);
643};
644
645struct ClassDef
646{
647  inline unsigned int operator () (hb_codepoint_t glyph_id) const { return get_class (glyph_id); }
648
649  inline unsigned int get_class (hb_codepoint_t glyph_id) const
650  {
651    switch (u.format) {
652    case 1: return u.format1.get_class(glyph_id);
653    case 2: return u.format2.get_class(glyph_id);
654    default:return 0;
655    }
656  }
657
658  inline bool sanitize (hb_sanitize_context_t *c) {
659    TRACE_SANITIZE ();
660    if (!u.format.sanitize (c)) return TRACE_RETURN (false);
661    switch (u.format) {
662    case 1: return TRACE_RETURN (u.format1.sanitize (c));
663    case 2: return TRACE_RETURN (u.format2.sanitize (c));
664    default:return TRACE_RETURN (true);
665    }
666  }
667
668  inline bool intersects_class (const hb_set_t *glyphs, unsigned int klass) const {
669    switch (u.format) {
670    case 1: return u.format1.intersects_class (glyphs, klass);
671    case 2: return u.format2.intersects_class (glyphs, klass);
672    default:return false;
673    }
674  }
675
676  private:
677  union {
678  USHORT		format;		/* Format identifier */
679  ClassDefFormat1	format1;
680  ClassDefFormat2	format2;
681  } u;
682  public:
683  DEFINE_SIZE_UNION (2, format);
684};
685
686
687/*
688 * Device Tables
689 */
690
691struct Device
692{
693
694  inline hb_position_t get_x_delta (hb_font_t *font) const
695  { return get_delta (font->x_ppem, font->x_scale); }
696
697  inline hb_position_t get_y_delta (hb_font_t *font) const
698  { return get_delta (font->y_ppem, font->y_scale); }
699
700  inline int get_delta (unsigned int ppem, int scale) const
701  {
702    if (!ppem) return 0;
703
704    int pixels = get_delta_pixels (ppem);
705
706    if (!pixels) return 0;
707
708    return pixels * (int64_t) scale / ppem;
709  }
710
711
712  inline int get_delta_pixels (unsigned int ppem_size) const
713  {
714    unsigned int f = deltaFormat;
715    if (unlikely (f < 1 || f > 3))
716      return 0;
717
718    if (ppem_size < startSize || ppem_size > endSize)
719      return 0;
720
721    unsigned int s = ppem_size - startSize;
722
723    unsigned int byte = deltaValue[s >> (4 - f)];
724    unsigned int bits = (byte >> (16 - (((s & ((1 << (4 - f)) - 1)) + 1) << f)));
725    unsigned int mask = (0xFFFF >> (16 - (1 << f)));
726
727    int delta = bits & mask;
728
729    if ((unsigned int) delta >= ((mask + 1) >> 1))
730      delta -= mask + 1;
731
732    return delta;
733  }
734
735  inline unsigned int get_size (void) const
736  {
737    unsigned int f = deltaFormat;
738    if (unlikely (f < 1 || f > 3 || startSize > endSize)) return 3 * USHORT::static_size;
739    return USHORT::static_size * (4 + ((endSize - startSize) >> (4 - f)));
740  }
741
742  inline bool sanitize (hb_sanitize_context_t *c) {
743    TRACE_SANITIZE ();
744    return TRACE_RETURN (c->check_struct (this) && c->check_range (this, this->get_size ()));
745  }
746
747  private:
748  USHORT	startSize;		/* Smallest size to correct--in ppem */
749  USHORT	endSize;		/* Largest size to correct--in ppem */
750  USHORT	deltaFormat;		/* Format of DeltaValue array data: 1, 2, or 3
751					 * 1	Signed 2-bit value, 8 values per uint16
752					 * 2	Signed 4-bit value, 4 values per uint16
753					 * 3	Signed 8-bit value, 2 values per uint16
754					 */
755  USHORT	deltaValue[VAR];	/* Array of compressed data */
756  public:
757  DEFINE_SIZE_ARRAY (6, deltaValue);
758};
759
760
761
762#endif /* HB_OT_LAYOUT_COMMON_PRIVATE_HH */
763