src/hb-ot-layout-gsubgpos-private.h - third_party/harfbuzz - Git at Google

 /*
  * Copyright (C) 2007,2008,2009  Red Hat, Inc.
  *
  *  This is part of HarfBuzz, an OpenType Layout engine library.
  *
  * Permission is hereby granted, without written agreement and without
  * license or royalty fees, to use, copy, modify, and distribute this
  * software and its documentation for any purpose, provided that the
  * above copyright notice and the following two paragraphs appear in
  * all copies of this software.
  *
  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
  * DAMAGE.
  *
  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  *
  * Red Hat Author(s): Behdad Esfahbod
  */

 #ifndef HB_OT_LAYOUT_GSUBGPOS_PRIVATE_H
 #define HB_OT_LAYOUT_GSUBGPOS_PRIVATE_H

 #include "hb-ot-layout-gdef-private.h"
 #include "harfbuzz-buffer-private.h" /* XXX */


 #define LOOKUP_ARGS_DEF \
 	hb_ot_layout_t *layout, \
 	hb_buffer_t    *buffer, \
 	unsigned int    context_length HB_GNUC_UNUSED, \
 	unsigned int    nesting_level_left HB_GNUC_UNUSED, \
 	unsigned int    lookup_flag, \
 	unsigned int    property HB_GNUC_UNUSED /* propety of first glyph */
 #define LOOKUP_ARGS \
 	layout, \
 	buffer, \
 	context_length, \
 	nesting_level_left, \
 	lookup_flag, \
 	property


 typedef bool (*match_func_t) (hb_codepoint_t glyph_id, const USHORT &value, char *data);
 typedef bool (*apply_lookup_func_t) (LOOKUP_ARGS_DEF, unsigned int lookup_index);

 struct ContextFuncs {
   match_func_t match;
   apply_lookup_func_t apply;
 };

 static inline bool match_glyph (hb_codepoint_t glyph_id, const USHORT &value, char *data) {
   return glyph_id == value;
 }

 static inline bool match_class (hb_codepoint_t glyph_id, const USHORT &value, char *data) {
   const ClassDef &class_def = * (const ClassDef *) data;
   return class_def.get_class (glyph_id) == value;
 }

 static inline bool match_coverage (hb_codepoint_t glyph_id, const USHORT &value, char *data) {
   const OffsetTo<Coverage> &coverage = * (const OffsetTo<Coverage> *) &value;
   return (data+coverage) (glyph_id) != NOT_COVERED;
 }

 struct LookupRecord {

   USHORT	sequenceIndex;		/* Index into current glyph
 					 * sequence--first glyph = 0 */
   USHORT	lookupListIndex;	/* Lookup to apply to that
 					 * position--zero--based */
 };
 ASSERT_SIZE (LookupRecord, 4);


 /* Contextual lookups */

 struct ContextLookupContext {
   ContextFuncs funcs;
   char *match_data;
 };

 static inline bool context_lookup (LOOKUP_ARGS_DEF,
 				   USHORT inputCount, /* Including the first glyph (not matched) */
 				   const USHORT input[], /* Array of input values--start with second glyph */
 				   USHORT lookupCount,
 				   const LookupRecord lookupRecord[], /* Array of LookupRecords--in design order */
 				   ContextLookupContext &context) {

   unsigned int i, j;
   unsigned int count = inputCount;

   if (HB_UNLIKELY (buffer->in_pos + count > buffer->in_length ||
 		   context_length < count))
     return false; /* Not enough glyphs in input or context */

   /* XXX context_length should also be checked when skipping glyphs, right?
    * What does context_length really mean, anyway? */

   for (i = 1, j = buffer->in_pos + 1; i < count; i++, j++) {
     while (!_hb_ot_layout_check_glyph_property (layout, IN_ITEM (j), lookup_flag, &property)) {
       if (HB_UNLIKELY (j + count - i == buffer->in_length))
 	return false;
       j++;
     }

     if (HB_LIKELY (context.funcs.match (IN_GLYPH(j), input[i - 1], context.match_data)))
       return false;
   }

   /* XXX right? or j - buffer_inpos? */
   context_length = count;

   /* XXX We have to jump non-matching glyphs when applying too, right? */
   /* XXX We don't support lookupRecord arrays that are not increasing:
    *     Should be easy for in_place ones at least. */
   unsigned int record_count = lookupCount;
   const LookupRecord *record = lookupRecord;
   for (i = 0; i < count;)
   {
     if (record_count && i == record->sequenceIndex)
     {
       unsigned int old_pos = buffer->in_pos;

       /* Apply a lookup */
       bool done = context.funcs.apply (LOOKUP_ARGS, record->lookupListIndex);

       record++;
       record_count--;
       i += buffer->in_pos - old_pos;

       if (!done)
 	goto not_applied;
     }
     else
     {
     not_applied:
       /* No lookup applied for this index */
       _hb_buffer_next_glyph (buffer);
       i++;
     }
   }

   return true;
 }

 struct Rule {

   friend struct RuleSet;

   private:
   inline bool apply (LOOKUP_ARGS_DEF, ContextLookupContext &context) const {
     const LookupRecord *record = (const LookupRecord *) ((const char *) input + sizeof (input[0]) * (inputCount ? inputCount - 1 : 0));
     return context_lookup (LOOKUP_ARGS,
 			   inputCount,
 			   input,
 			   lookupCount,
 			   record,
 			   context);
   }

   private:
   USHORT	inputCount;		/* Total number of glyphs in input
 					 * glyph sequence--includes the  first
 					 * glyph */
   USHORT	lookupCount;		/* Number of LookupRecords */
   USHORT	input[];		/* Array of match inputs--start with
 					 * second glyph */
   LookupRecord	lookupRecordX[];	/* Array of LookupRecords--in
 					 * design order */
 };
 ASSERT_SIZE (Rule, 4);

 struct RuleSet {

   inline bool apply (LOOKUP_ARGS_DEF, ContextLookupContext &context) const {

     unsigned int num_rules = rule.len;
     for (unsigned int i = 0; i < num_rules; i++) {
       if ((this+rule[i]).apply (LOOKUP_ARGS, context))
         return true;
     }

     return false;
   }

   private:
   OffsetArrayOf<Rule>
 		rule;			/* Array of Rule tables
 					 * ordered by preference */
 };


 struct ContextFormat1 {

   friend struct Context;

   private:
   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {

     unsigned int index = (this+coverage) (IN_CURGLYPH ());
     if (G_LIKELY (index == NOT_COVERED))
       return false;

     const RuleSet &rule_set = this+ruleSet[index];
     struct ContextLookupContext context = {
       {match_glyph, apply_func},
       NULL
     };
     return rule_set.apply (LOOKUP_ARGS, context);
   }

   private:
   USHORT	format;			/* Format identifier--format = 1 */
   OffsetTo<Coverage>
 		coverage;		/* Offset to Coverage table--from
 					 * beginning of table */
   OffsetArrayOf<RuleSet>
 		ruleSet;		/* Array of RuleSet tables
 					 * ordered by Coverage Index */
 };
 ASSERT_SIZE (ContextFormat1, 6);


 struct ContextFormat2 {

   friend struct Context;

   private:
   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {

     unsigned int index = (this+coverage) (IN_CURGLYPH ());
     if (G_LIKELY (index == NOT_COVERED))
       return false;

     const ClassDef &class_def = this+classDef;
     index = class_def (IN_CURGLYPH ());
     const RuleSet &rule_set = this+ruleSet[index];
     /* LONGTERMTODO: Old code fetches glyph classes at most once and caches
      * them across subrule lookups.  Not sure it's worth it.
      */
     struct ContextLookupContext context = {
      {match_class, apply_func},
       (char *) &class_def
     };
     return rule_set.apply (LOOKUP_ARGS, context);
   }

   private:
   USHORT	format;			/* Format identifier--format = 2 */
   OffsetTo<Coverage>
 		coverage;		/* Offset to Coverage table--from
 					 * beginning of table */
   OffsetTo<ClassDef>
 		classDef;		/* Offset to glyph ClassDef table--from
 					 * beginning of table */
   OffsetArrayOf<RuleSet>
 		ruleSet;		/* Array of RuleSet tables
 					 * ordered by class */
 };
 ASSERT_SIZE (ContextFormat2, 8);


 struct ContextFormat3 {

   friend struct Context;

   private:

   inline bool apply_coverage (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
     const LookupRecord *record = (const LookupRecord *) ((const char *) coverage + sizeof (coverage[0]) * glyphCount);
     struct ContextLookupContext context = {
       {match_coverage, apply_func},
       (char *) this
     };
     return context_lookup (LOOKUP_ARGS,
 			   glyphCount,
 			   (const USHORT *) (coverage + 1),
 			   lookupCount,
 			   record,
 			   context);
   }

   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {

     unsigned int index = (this+coverage[0]) (IN_CURGLYPH ());
     if (G_LIKELY (index == NOT_COVERED))
       return false;

     return apply_coverage (LOOKUP_ARGS, apply_func);
   }

   private:
   USHORT	format;			/* Format identifier--format = 3 */
   USHORT	glyphCount;		/* Number of glyphs in the input glyph
 					 * sequence */
   USHORT	lookupCount;		/* Number of LookupRecords */
   OffsetTo<Coverage>
 		coverage[];		/* Array of offsets to Coverage
 					 * table in glyph sequence order */
   LookupRecord	lookupRecordX[];	/* Array of LookupRecords--in
 					 * design order */
 };
 ASSERT_SIZE (ContextFormat3, 6);

 struct Context {

   protected:
   bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
     switch (u.format) {
     case 1: return u.format1->apply (LOOKUP_ARGS, apply_func);
     case 2: return u.format2->apply (LOOKUP_ARGS, apply_func);
     case 3: return u.format3->apply (LOOKUP_ARGS, apply_func);
     default:return false;
     }
   }

   private:
   union {
   USHORT		format;		/* Format identifier */
   ContextFormat1	format1[];
   ContextFormat2	format2[];
   ContextFormat3	format3[];
   } u;
 };
 ASSERT_SIZE (Context, 2);


 /* Chaining Contextual lookups */

 struct ChainContextLookupContext {
   ContextFuncs funcs;
   char *match_data[3];
 };


 struct ChainRule {

   friend struct ChainRuleSet;

   private:
   inline bool apply (LOOKUP_ARGS_DEF, ChainContextLookupContext &context) const {
     return false;
 //    const LookupRecord *record = (const LookupRecord *) ((const char *) input + sizeof (input[0]) * (inputCount ? inputCount - 1 : 0));
 //    return context_lookup (LOOKUP_ARGS,
 //			   inputCount,
 //			   input,
 //			   lookupCount,
 //			   record,
 //			   context);
   }


   private:
   USHORT	backtrackCount;		/* Total number of glyphs in the
 					 * backtrack sequence (number of
 					 * glyphs to be matched before the
 					 * first glyph) */
   USHORT	backtrack[];		/* Array of backtracking values
 					 * (to be matched before the input
 					 * sequence) */
   USHORT	inputCountX;		/* Total number of values in the input
 					 * sequence (includes the first glyph) */
   USHORT	inputX[];		/* Array of input values (start with
 					 * second glyph) */
   USHORT	lookaheadCountX;	/* Total number of glyphs in the look
 					 * ahead sequence (number of glyphs to
 					 * be matched after the input sequence) */
   USHORT	lookaheadX[];		/* Array of lookahead values's (to be
 					 * matched after the input sequence) */
   USHORT	lookupCountX;		/* Number of LookupRecords */
   LookupRecord	lookupRecordX[];	/* Array of LookupRecords--in
 					 * design order) */
 };
 ASSERT_SIZE (ChainRule, 8);

 struct ChainRuleSet {

   inline bool apply (LOOKUP_ARGS_DEF, ChainContextLookupContext &context) const {

     unsigned int num_rules = rule.len;
     for (unsigned int i = 0; i < num_rules; i++) {
       if ((this+rule[i]).apply (LOOKUP_ARGS, context))
         return true;
     }

     return false;
   }

   private:
   OffsetArrayOf<ChainRule>
 		rule;			/* Array of ChainRule tables
 					 * ordered by preference */
 };
 ASSERT_SIZE (ChainRuleSet, 2);

 struct ChainContextFormat1 {

   friend struct ChainContext;

   private:
   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {

     unsigned int index = (this+coverage) (IN_CURGLYPH ());
     if (G_LIKELY (index == NOT_COVERED))
       return false;

     const ChainRuleSet &rule_set = this+ruleSet[index];
     struct ChainContextLookupContext context = {
       {match_glyph, apply_func},
       {NULL, NULL, NULL}
     };
     return rule_set.apply (LOOKUP_ARGS, context);
   }
   private:
   USHORT	format;			/* Format identifier--format = 1 */
   OffsetTo<Coverage>
 		coverage;		/* Offset to Coverage table--from
 					 * beginning of table */
   OffsetArrayOf<ChainRuleSet>
 		ruleSet;		/* Array of ChainRuleSet tables
 					 * ordered by Coverage Index */
 };
 ASSERT_SIZE (ChainContextFormat1, 6);

 struct ChainContextFormat2 {

   friend struct ChainContext;

   private:
   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {

     unsigned int index = (this+coverage) (IN_CURGLYPH ());
     if (G_LIKELY (index == NOT_COVERED))
       return false;

     const ClassDef &backtrack_class_def = this+backtrackClassDef;
     const ClassDef &input_class_def = this+inputClassDef;
     const ClassDef &lookahead_class_def = this+lookaheadClassDef;

     index = input_class_def (IN_CURGLYPH ());
     const ChainRuleSet &rule_set = this+ruleSet[index];
     /* LONGTERMTODO: Old code fetches glyph classes at most once and caches
      * them across subrule lookups.  Not sure it's worth it.
      */
     struct ChainContextLookupContext context = {
      {match_class, apply_func},
      {(char *) &backtrack_class_def,
       (char *) &input_class_def,
       (char *) &lookahead_class_def}
     };
     return rule_set.apply (LOOKUP_ARGS, context);
   }

   private:
   USHORT	format;			/* Format identifier--format = 2 */
   OffsetTo<Coverage>
 		coverage;		/* Offset to Coverage table--from
 					 * beginning of table */
   OffsetTo<ClassDef>
 		backtrackClassDef;	/* Offset to glyph ClassDef table
 					 * containing backtrack sequence
 					 * data--from beginning of table */
   OffsetTo<ClassDef>
 		inputClassDef;		/* Offset to glyph ClassDef
 					 * table containing input sequence
 					 * data--from beginning of table */
   OffsetTo<ClassDef>
 		lookaheadClassDef;	/* Offset to glyph ClassDef table
 					 * containing lookahead sequence
 					 * data--from beginning of table */
   OffsetArrayOf<ChainRuleSet>
 		ruleSet;		/* Array of ChainRuleSet tables
 					 * ordered by class */
 };
 ASSERT_SIZE (ChainContextFormat2, 12);

 struct ChainContextFormat3 {

   friend struct ChainContext;

   private:

   inline bool apply_coverage (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 //    const LookupRecord *record = (const LookupRecord *) ((const char *) coverage + sizeof (coverage[0]) * glyphCount);
     struct ChainContextLookupContext context = {
       {match_coverage, apply_func},
       {(char *) this, (char *) this, (char *) this}
     };
     /*
     return context_lookup (LOOKUP_ARGS,
 			   glyphCount,
 			   (const USHORT *) (coverage + 1),
 			   lookupCount,
 			   record,
 			   context);
 			   */
     return false;
   }

   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {

     /* XXX */
     unsigned int index = 0;//(this+coverage[0]) (IN_CURGLYPH ());
     if (G_LIKELY (index == NOT_COVERED))
       return false;

     return apply_coverage (LOOKUP_ARGS, apply_func);
   }

   private:
   USHORT	format;			/* Format identifier--format = 3 */
   USHORT	backtrackGlyphCount;	/* Number of glyphs in the backtracking
 					 * sequence */
   Offset	backtrackCoverage[];	/* Array of offsets to coverage tables
 					 * in backtracking sequence, in  glyph
 					 * sequence order */
   USHORT	inputGlyphCountX;	/* Number of glyphs in input sequence */
   Offset	inputCoverageX[];	/* Array of offsets to coverage
 					 * tables in input sequence, in glyph
 					 * sequence order */
   USHORT	lookaheadGlyphCountX;	/* Number of glyphs in lookahead
 					 * sequence */
   Offset	lookaheadCoverageX[];	/* Array of offsets to coverage tables
 					 * in lookahead sequence, in glyph
 					 * sequence order */
   USHORT	lookupCountX;		/* Number of LookupRecords */
   LookupRecord	lookupRecordX[];	/* Array of LookupRecords--in
 					 * design order */
 };
 ASSERT_SIZE (ChainContextFormat3, 10);

 struct ChainContext {

   protected:
   bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
     switch (u.format) {
     case 1: return u.format1->apply (LOOKUP_ARGS, apply_func);
     case 2: return u.format2->apply (LOOKUP_ARGS, apply_func);
     case 3: return u.format3->apply (LOOKUP_ARGS, apply_func);
     default:return false;
     }
   }

   private:
   union {
   USHORT		format;	/* Format identifier */
   ChainContextFormat1	format1[];
   ChainContextFormat2	format2[];
   ChainContextFormat3	format3[];
   } u;
 };
 ASSERT_SIZE (ChainContext, 2);


 /*
  * GSUB/GPOS Common
  */

 struct GSUBGPOS {
   static const hb_tag_t GSUBTag		= HB_TAG ('G','S','U','B');
   static const hb_tag_t GPOSTag		= HB_TAG ('G','P','O','S');

   STATIC_DEFINE_GET_FOR_DATA (GSUBGPOS);
   /* XXX check version here? */

   DEFINE_TAG_LIST_INTERFACE (Script,  script );	/* get_script_count (), get_script (i), get_script_tag (i) */
   DEFINE_TAG_LIST_INTERFACE (Feature, feature);	/* get_feature_count(), get_feature(i), get_feature_tag(i) */
   DEFINE_LIST_INTERFACE     (Lookup,  lookup );	/* get_lookup_count (), get_lookup (i) */

   // LONGTERMTODO bsearch
   DEFINE_TAG_FIND_INTERFACE (Script,  script );	/* find_script_index (), get_script_by_tag (tag) */
   DEFINE_TAG_FIND_INTERFACE (Feature, feature);	/* find_feature_index(), get_feature_by_tag(tag) */

   private:
   Fixed_Version	version;	/* Version of the GSUB/GPOS table--initially set
 				 * to 0x00010000 */
   OffsetTo<ScriptList>
 		scriptList;  	/* ScriptList table */
   OffsetTo<FeatureList>
 		featureList; 	/* FeatureList table */
   OffsetTo<LookupList>
 		lookupList; 	/* LookupList table */
 };
 ASSERT_SIZE (GSUBGPOS, 10);


 #endif /* HB_OT_LAYOUT_GSUBGPOS_PRIVATE_H */
	/*
	* Copyright (C) 2007,2008,2009 Red Hat, Inc.
	*
	* This is part of HarfBuzz, an OpenType Layout engine library.
	*
	* Permission is hereby granted, without written agreement and without
	* license or royalty fees, to use, copy, modify, and distribute this
	* software and its documentation for any purpose, provided that the
	* above copyright notice and the following two paragraphs appear in
	* all copies of this software.
	*
	* IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
	* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
	* ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
	* IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
	* DAMAGE.
	*
	* THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
	* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
	* FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
	* ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
	* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
	*
	* Red Hat Author(s): Behdad Esfahbod
	*/

	#ifndef HB_OT_LAYOUT_GSUBGPOS_PRIVATE_H
	#define HB_OT_LAYOUT_GSUBGPOS_PRIVATE_H

	#include "hb-ot-layout-gdef-private.h"
	#include "harfbuzz-buffer-private.h" /* XXX */


	#define LOOKUP_ARGS_DEF \
	hb_ot_layout_t *layout, \
	hb_buffer_t *buffer, \
	unsigned int context_length HB_GNUC_UNUSED, \
	unsigned int nesting_level_left HB_GNUC_UNUSED, \
	unsigned int lookup_flag, \
	unsigned int property HB_GNUC_UNUSED /* propety of first glyph */
	#define LOOKUP_ARGS \
	layout, \
	buffer, \
	context_length, \
	nesting_level_left, \
	lookup_flag, \
	property


	typedef bool (match_func_t) (hb_codepoint_t glyph_id, const USHORT &value, char data);
	typedef bool (*apply_lookup_func_t) (LOOKUP_ARGS_DEF, unsigned int lookup_index);

	struct ContextFuncs {
	match_func_t match;
	apply_lookup_func_t apply;
	};

	static inline bool match_glyph (hb_codepoint_t glyph_id, const USHORT &value, char *data) {
	return glyph_id == value;
	}

	static inline bool match_class (hb_codepoint_t glyph_id, const USHORT &value, char *data) {
	const ClassDef &class_def = * (const ClassDef *) data;
	return class_def.get_class (glyph_id) == value;
	}

	static inline bool match_coverage (hb_codepoint_t glyph_id, const USHORT &value, char *data) {
	const OffsetTo<Coverage> &coverage = * (const OffsetTo<Coverage> *) &value;
	return (data+coverage) (glyph_id) != NOT_COVERED;
	}

	struct LookupRecord {

	USHORT sequenceIndex; /* Index into current glyph
	* sequence--first glyph = 0 */
	USHORT lookupListIndex; /* Lookup to apply to that
	* position--zero--based */
	};
	ASSERT_SIZE (LookupRecord, 4);


	/* Contextual lookups */

	struct ContextLookupContext {
	ContextFuncs funcs;
	char *match_data;
	};

	static inline bool context_lookup (LOOKUP_ARGS_DEF,
	USHORT inputCount, /* Including the first glyph (not matched) */
	const USHORT input[], /* Array of input values--start with second glyph */
	USHORT lookupCount,
	const LookupRecord lookupRecord[], /* Array of LookupRecords--in design order */
	ContextLookupContext &context) {

	unsigned int i, j;
	unsigned int count = inputCount;

	if (HB_UNLIKELY (buffer->in_pos + count > buffer->in_length \|\|
	context_length < count))
	return false; /* Not enough glyphs in input or context */

	/* XXX context_length should also be checked when skipping glyphs, right?
	* What does context_length really mean, anyway? */

	for (i = 1, j = buffer->in_pos + 1; i < count; i++, j++) {
	while (!_hb_ot_layout_check_glyph_property (layout, IN_ITEM (j), lookup_flag, &property)) {
	if (HB_UNLIKELY (j + count - i == buffer->in_length))
	return false;
	j++;
	}

	if (HB_LIKELY (context.funcs.match (IN_GLYPH(j), input[i - 1], context.match_data)))
	return false;
	}

	/* XXX right? or j - buffer_inpos? */
	context_length = count;

	/* XXX We have to jump non-matching glyphs when applying too, right? */
	/* XXX We don't support lookupRecord arrays that are not increasing:
	* Should be easy for in_place ones at least. */
	unsigned int record_count = lookupCount;
	const LookupRecord *record = lookupRecord;
	for (i = 0; i < count;)
	{
	if (record_count && i == record->sequenceIndex)
	{
	unsigned int old_pos = buffer->in_pos;

	/* Apply a lookup */
	bool done = context.funcs.apply (LOOKUP_ARGS, record->lookupListIndex);

	record++;
	record_count--;
	i += buffer->in_pos - old_pos;

	if (!done)
	goto not_applied;
	}
	else
	{
	not_applied:
	/* No lookup applied for this index */
	_hb_buffer_next_glyph (buffer);
	i++;
	}
	}

	return true;
	}

	struct Rule {

	friend struct RuleSet;

	private:
	inline bool apply (LOOKUP_ARGS_DEF, ContextLookupContext &context) const {
	const LookupRecord record = (const LookupRecord ) ((const char ) input + sizeof (input[0]) (inputCount ? inputCount - 1 : 0));
	return context_lookup (LOOKUP_ARGS,
	inputCount,
	input,
	lookupCount,
	record,
	context);
	}

	private:
	USHORT inputCount; /* Total number of glyphs in input
	* glyph sequence--includes the first
	* glyph */
	USHORT lookupCount; /* Number of LookupRecords */
	USHORT input[]; /* Array of match inputs--start with
	* second glyph */
	LookupRecord lookupRecordX[]; /* Array of LookupRecords--in
	* design order */
	};
	ASSERT_SIZE (Rule, 4);

	struct RuleSet {

	inline bool apply (LOOKUP_ARGS_DEF, ContextLookupContext &context) const {

	unsigned int num_rules = rule.len;
	for (unsigned int i = 0; i < num_rules; i++) {
	if ((this+rule[i]).apply (LOOKUP_ARGS, context))
	return true;
	}

	return false;
	}

	private:
	OffsetArrayOf<Rule>
	rule; /* Array of Rule tables
	* ordered by preference */
	};


	struct ContextFormat1 {

	friend struct Context;

	private:
	inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {

	unsigned int index = (this+coverage) (IN_CURGLYPH ());
	if (G_LIKELY (index == NOT_COVERED))
	return false;

	const RuleSet &rule_set = this+ruleSet[index];
	struct ContextLookupContext context = {
	{match_glyph, apply_func},
	NULL
	};
	return rule_set.apply (LOOKUP_ARGS, context);
	}

	private:
	USHORT format; /* Format identifier--format = 1 */
	OffsetTo<Coverage>
	coverage; /* Offset to Coverage table--from
	* beginning of table */
	OffsetArrayOf<RuleSet>
	ruleSet; /* Array of RuleSet tables
	* ordered by Coverage Index */
	};
	ASSERT_SIZE (ContextFormat1, 6);


	struct ContextFormat2 {

	friend struct Context;

	private:
	inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {

	unsigned int index = (this+coverage) (IN_CURGLYPH ());
	if (G_LIKELY (index == NOT_COVERED))
	return false;

	const ClassDef &class_def = this+classDef;
	index = class_def (IN_CURGLYPH ());
	const RuleSet &rule_set = this+ruleSet[index];
	/* LONGTERMTODO: Old code fetches glyph classes at most once and caches
	* them across subrule lookups. Not sure it's worth it.
	*/
	struct ContextLookupContext context = {
	{match_class, apply_func},
	(char *) &class_def
	};
	return rule_set.apply (LOOKUP_ARGS, context);
	}

	private:
	USHORT format; /* Format identifier--format = 2 */
	OffsetTo<Coverage>
	coverage; /* Offset to Coverage table--from
	* beginning of table */
	OffsetTo<ClassDef>
	classDef; /* Offset to glyph ClassDef table--from
	* beginning of table */
	OffsetArrayOf<RuleSet>
	ruleSet; /* Array of RuleSet tables
	* ordered by class */
	};
	ASSERT_SIZE (ContextFormat2, 8);


	struct ContextFormat3 {

	friend struct Context;

	private:

	inline bool apply_coverage (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
	const LookupRecord record = (const LookupRecord ) ((const char ) coverage + sizeof (coverage[0]) glyphCount);
	struct ContextLookupContext context = {
	{match_coverage, apply_func},
	(char *) this
	};
	return context_lookup (LOOKUP_ARGS,
	glyphCount,
	(const USHORT *) (coverage + 1),
	lookupCount,
	record,
	context);
	}

	inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {

	unsigned int index = (this+coverage[0]) (IN_CURGLYPH ());
	if (G_LIKELY (index == NOT_COVERED))
	return false;

	return apply_coverage (LOOKUP_ARGS, apply_func);
	}

	private:
	USHORT format; /* Format identifier--format = 3 */
	USHORT glyphCount; /* Number of glyphs in the input glyph
	* sequence */
	USHORT lookupCount; /* Number of LookupRecords */
	OffsetTo<Coverage>
	coverage[]; /* Array of offsets to Coverage
	* table in glyph sequence order */
	LookupRecord lookupRecordX[]; /* Array of LookupRecords--in
	* design order */
	};
	ASSERT_SIZE (ContextFormat3, 6);

	struct Context {

	protected:
	bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
	switch (u.format) {
	case 1: return u.format1->apply (LOOKUP_ARGS, apply_func);
	case 2: return u.format2->apply (LOOKUP_ARGS, apply_func);
	case 3: return u.format3->apply (LOOKUP_ARGS, apply_func);
	default:return false;
	}
	}

	private:
	union {
	USHORT format; /* Format identifier */
	ContextFormat1 format1[];
	ContextFormat2 format2[];
	ContextFormat3 format3[];
	} u;
	};
	ASSERT_SIZE (Context, 2);


	/* Chaining Contextual lookups */

	struct ChainContextLookupContext {
	ContextFuncs funcs;
	char *match_data[3];
	};


	struct ChainRule {

	friend struct ChainRuleSet;

	private:
	inline bool apply (LOOKUP_ARGS_DEF, ChainContextLookupContext &context) const {
	return false;
	// const LookupRecord record = (const LookupRecord ) ((const char ) input + sizeof (input[0]) (inputCount ? inputCount - 1 : 0));
	// return context_lookup (LOOKUP_ARGS,
	// inputCount,
	// input,
	// lookupCount,
	// record,
	// context);
	}


	private:
	USHORT backtrackCount; /* Total number of glyphs in the
	* backtrack sequence (number of
	* glyphs to be matched before the
	* first glyph) */
	USHORT backtrack[]; /* Array of backtracking values
	* (to be matched before the input
	* sequence) */
	USHORT inputCountX; /* Total number of values in the input
	* sequence (includes the first glyph) */
	USHORT inputX[]; /* Array of input values (start with
	* second glyph) */
	USHORT lookaheadCountX; /* Total number of glyphs in the look
	* ahead sequence (number of glyphs to
	* be matched after the input sequence) */
	USHORT lookaheadX[]; /* Array of lookahead values's (to be
	* matched after the input sequence) */
	USHORT lookupCountX; /* Number of LookupRecords */
	LookupRecord lookupRecordX[]; /* Array of LookupRecords--in
	* design order) */
	};
	ASSERT_SIZE (ChainRule, 8);

	struct ChainRuleSet {

	inline bool apply (LOOKUP_ARGS_DEF, ChainContextLookupContext &context) const {

	unsigned int num_rules = rule.len;
	for (unsigned int i = 0; i < num_rules; i++) {
	if ((this+rule[i]).apply (LOOKUP_ARGS, context))
	return true;
	}

	return false;
	}

	private:
	OffsetArrayOf<ChainRule>
	rule; /* Array of ChainRule tables
	* ordered by preference */
	};
	ASSERT_SIZE (ChainRuleSet, 2);

	struct ChainContextFormat1 {

	friend struct ChainContext;

	private:
	inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {

	unsigned int index = (this+coverage) (IN_CURGLYPH ());
	if (G_LIKELY (index == NOT_COVERED))
	return false;

	const ChainRuleSet &rule_set = this+ruleSet[index];
	struct ChainContextLookupContext context = {
	{match_glyph, apply_func},
	{NULL, NULL, NULL}
	};
	return rule_set.apply (LOOKUP_ARGS, context);
	}
	private:
	USHORT format; /* Format identifier--format = 1 */
	OffsetTo<Coverage>
	coverage; /* Offset to Coverage table--from
	* beginning of table */
	OffsetArrayOf<ChainRuleSet>
	ruleSet; /* Array of ChainRuleSet tables
	* ordered by Coverage Index */
	};
	ASSERT_SIZE (ChainContextFormat1, 6);

	struct ChainContextFormat2 {

	friend struct ChainContext;

	private:
	inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {

	unsigned int index = (this+coverage) (IN_CURGLYPH ());
	if (G_LIKELY (index == NOT_COVERED))
	return false;

	const ClassDef &backtrack_class_def = this+backtrackClassDef;
	const ClassDef &input_class_def = this+inputClassDef;
	const ClassDef &lookahead_class_def = this+lookaheadClassDef;

	index = input_class_def (IN_CURGLYPH ());
	const ChainRuleSet &rule_set = this+ruleSet[index];
	/* LONGTERMTODO: Old code fetches glyph classes at most once and caches
	* them across subrule lookups. Not sure it's worth it.
	*/
	struct ChainContextLookupContext context = {
	{match_class, apply_func},
	{(char *) &backtrack_class_def,
	(char *) &input_class_def,
	(char *) &lookahead_class_def}
	};
	return rule_set.apply (LOOKUP_ARGS, context);
	}

	private:
	USHORT format; /* Format identifier--format = 2 */
	OffsetTo<Coverage>
	coverage; /* Offset to Coverage table--from
	* beginning of table */
	OffsetTo<ClassDef>
	backtrackClassDef; /* Offset to glyph ClassDef table
	* containing backtrack sequence
	* data--from beginning of table */
	OffsetTo<ClassDef>
	inputClassDef; /* Offset to glyph ClassDef
	* table containing input sequence
	* data--from beginning of table */
	OffsetTo<ClassDef>
	lookaheadClassDef; /* Offset to glyph ClassDef table
	* containing lookahead sequence
	* data--from beginning of table */
	OffsetArrayOf<ChainRuleSet>
	ruleSet; /* Array of ChainRuleSet tables
	* ordered by class */
	};
	ASSERT_SIZE (ChainContextFormat2, 12);

	struct ChainContextFormat3 {

	friend struct ChainContext;

	private:

	inline bool apply_coverage (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
	// const LookupRecord record = (const LookupRecord ) ((const char ) coverage + sizeof (coverage[0]) glyphCount);
	struct ChainContextLookupContext context = {
	{match_coverage, apply_func},
	{(char ) this, (char ) this, (char *) this}
	};
	/*
	return context_lookup (LOOKUP_ARGS,
	glyphCount,
	(const USHORT *) (coverage + 1),
	lookupCount,
	record,
	context);
	*/
	return false;
	}

	inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {

	/* XXX */
	unsigned int index = 0;//(this+coverage[0]) (IN_CURGLYPH ());
	if (G_LIKELY (index == NOT_COVERED))
	return false;

	return apply_coverage (LOOKUP_ARGS, apply_func);
	}

	private:
	USHORT format; /* Format identifier--format = 3 */
	USHORT backtrackGlyphCount; /* Number of glyphs in the backtracking
	* sequence */
	Offset backtrackCoverage[]; /* Array of offsets to coverage tables
	* in backtracking sequence, in glyph
	* sequence order */
	USHORT inputGlyphCountX; /* Number of glyphs in input sequence */
	Offset inputCoverageX[]; /* Array of offsets to coverage
	* tables in input sequence, in glyph
	* sequence order */
	USHORT lookaheadGlyphCountX; /* Number of glyphs in lookahead
	* sequence */
	Offset lookaheadCoverageX[]; /* Array of offsets to coverage tables
	* in lookahead sequence, in glyph
	* sequence order */
	USHORT lookupCountX; /* Number of LookupRecords */
	LookupRecord lookupRecordX[]; /* Array of LookupRecords--in
	* design order */
	};
	ASSERT_SIZE (ChainContextFormat3, 10);

	struct ChainContext {

	protected:
	bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
	switch (u.format) {
	case 1: return u.format1->apply (LOOKUP_ARGS, apply_func);
	case 2: return u.format2->apply (LOOKUP_ARGS, apply_func);
	case 3: return u.format3->apply (LOOKUP_ARGS, apply_func);
	default:return false;
	}
	}

	private:
	union {
	USHORT format; /* Format identifier */
	ChainContextFormat1 format1[];
	ChainContextFormat2 format2[];
	ChainContextFormat3 format3[];
	} u;
	};
	ASSERT_SIZE (ChainContext, 2);


	/*
	* GSUB/GPOS Common
	*/

	struct GSUBGPOS {
	static const hb_tag_t GSUBTag = HB_TAG ('G','S','U','B');
	static const hb_tag_t GPOSTag = HB_TAG ('G','P','O','S');

	STATIC_DEFINE_GET_FOR_DATA (GSUBGPOS);
	/* XXX check version here? */

	DEFINE_TAG_LIST_INTERFACE (Script, script ); /* get_script_count (), get_script (i), get_script_tag (i) */
	DEFINE_TAG_LIST_INTERFACE (Feature, feature); /* get_feature_count(), get_feature(i), get_feature_tag(i) */
	DEFINE_LIST_INTERFACE (Lookup, lookup ); /* get_lookup_count (), get_lookup (i) */

	// LONGTERMTODO bsearch
	DEFINE_TAG_FIND_INTERFACE (Script, script ); /* find_script_index (), get_script_by_tag (tag) */
	DEFINE_TAG_FIND_INTERFACE (Feature, feature); /* find_feature_index(), get_feature_by_tag(tag) */

	private:
	Fixed_Version version; /* Version of the GSUB/GPOS table--initially set
	* to 0x00010000 */
	OffsetTo<ScriptList>
	scriptList; /* ScriptList table */
	OffsetTo<FeatureList>
	featureList; /* FeatureList table */
	OffsetTo<LookupList>
	lookupList; /* LookupList table */
	};
	ASSERT_SIZE (GSUBGPOS, 10);


	#endif /* HB_OT_LAYOUT_GSUBGPOS_PRIVATE_H */