src/hb-ot-kern-table.hh - third_party/harfbuzz - Git at Google

 /*
  * Copyright © 2017  Google, Inc.
  *
  *  This is part of HarfBuzz, a text shaping 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.
  *
  * Google Author(s): Behdad Esfahbod
  */

 #ifndef HB_OT_KERN_TABLE_HH
 #define HB_OT_KERN_TABLE_HH

 #include "hb-open-type-private.hh"

 namespace OT {


 /*
  * kern -- Kerning
  */

 #define HB_OT_TAG_kern HB_TAG('k','e','r','n')

 struct hb_glyph_pair_t
 {
   hb_codepoint_t left;
   hb_codepoint_t right;
 };

 struct KernPair
 {
   inline int get_kerning (void) const
   { return value; }

   inline int cmp (const hb_glyph_pair_t &o) const
   {
     int ret = left.cmp (o.left);
     if (ret) return ret;
     return right.cmp (o.right);
   }

   inline bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
     return_trace (c->check_struct (this));
   }

   protected:
   GlyphID	left;
   GlyphID	right;
   FWORD		value;
   public:
   DEFINE_SIZE_STATIC (6);
 };

 struct KernSubTableFormat0
 {
   inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right) const
   {
     hb_glyph_pair_t pair = {left, right};
     int i = pairs.bsearch (pair);
     if (i == -1)
       return 0;
     return pairs[i].get_kerning ();
   }

   inline bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
     return_trace (pairs.sanitize (c));
   }

   protected:
   BinSearchArrayOf<KernPair> pairs;	/* Array of kerning pairs. */
   public:
   DEFINE_SIZE_ARRAY (8, pairs);
 };

 struct KernClassTable
 {
   inline unsigned int get_class (hb_codepoint_t g) const { return classes[g - firstGlyph]; }

   inline bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
     return_trace (firstGlyph.sanitize (c) && classes.sanitize (c));
   }

   protected:
   HBUINT16		firstGlyph;	/* First glyph in class range. */
   ArrayOf<HBUINT16>	classes;	/* Glyph classes. */
   public:
   DEFINE_SIZE_ARRAY (4, classes);
 };

 struct KernSubTableFormat2
 {
   inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right, const char *end) const
   {
     unsigned int l = (this+leftClassTable).get_class (left);
     unsigned int r = (this+rightClassTable).get_class (right);
     unsigned int offset = l * rowWidth + r * sizeof (FWORD);
     const FWORD *arr = &(this+array);
     if (unlikely ((const void *) arr < (const void *) this || (const void *) arr >= (const void *) end))
       return 0;
     const FWORD *v = &StructAtOffset<FWORD> (arr, offset);
     if (unlikely ((const void *) v < (const void *) arr || (const void *) (v + 1) > (const void *) end))
       return 0;
     return *v;
   }

   inline bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
     return_trace (rowWidth.sanitize (c) &&
 		  leftClassTable.sanitize (c, this) &&
 		  rightClassTable.sanitize (c, this) &&
 		  array.sanitize (c, this));
   }

   protected:
   HBUINT16	rowWidth;	/* The width, in bytes, of a row in the table. */
   OffsetTo<KernClassTable>
 		leftClassTable;	/* Offset from beginning of this subtable to
 				 * left-hand class table. */
   OffsetTo<KernClassTable>
 		rightClassTable;/* Offset from beginning of this subtable to
 				 * right-hand class table. */
   OffsetTo<FWORD>
 		array;		/* Offset from beginning of this subtable to
 				 * the start of the kerning array. */
   public:
   DEFINE_SIZE_MIN (8);
 };

 struct KernSubTable
 {
   inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right, const char *end, unsigned int format) const
   {
     switch (format) {
     case 0: return u.format0.get_kerning (left, right);
     case 2: return u.format2.get_kerning (left, right, end);
     default:return 0;
     }
   }

   inline bool sanitize (hb_sanitize_context_t *c, unsigned int format) const
   {
     TRACE_SANITIZE (this);
     switch (format) {
     case 0: return_trace (u.format0.sanitize (c));
     case 2: return_trace (u.format2.sanitize (c));
     default:return_trace (true);
     }
   }

   protected:
   union {
   KernSubTableFormat0	format0;
   KernSubTableFormat2	format2;
   } u;
   public:
   DEFINE_SIZE_MIN (0);
 };


 template <typename T>
 struct KernSubTableWrapper
 {
   /* https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern */
   inline const T* thiz (void) const { return static_cast<const T *> (this); }

   inline bool is_horizontal (void) const
   { return (thiz()->coverage & T::COVERAGE_CHECK_FLAGS) == T::COVERAGE_CHECK_HORIZONTAL; }

   inline bool is_override (void) const
   { return bool (thiz()->coverage & T::COVERAGE_OVERRIDE_FLAG); }

   inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right, const char *end) const
   { return thiz()->subtable.get_kerning (left, right, end, thiz()->format); }

   inline int get_h_kerning (hb_codepoint_t left, hb_codepoint_t right, const char *end) const
   { return is_horizontal () ? get_kerning (left, right, end) : 0; }

   inline unsigned int get_size (void) const { return thiz()->length; }

   inline bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
     return_trace (c->check_struct (thiz()) &&
 		  thiz()->length >= thiz()->min_size &&
 		  c->check_array (thiz(), 1, thiz()->length) &&
 		  thiz()->subtable.sanitize (c, thiz()->format));
   }
 };

 template <typename T>
 struct KernTable
 {
   /* https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern */
   inline const T* thiz (void) const { return static_cast<const T *> (this); }

   inline int get_h_kerning (hb_codepoint_t left, hb_codepoint_t right, unsigned int table_length) const
   {
     int v = 0;
     const typename T::SubTableWrapper *st = CastP<typename T::SubTableWrapper> (thiz()->data);
     unsigned int count = thiz()->nTables;
     for (unsigned int i = 0; i < count; i++)
     {
       if (st->is_override ())
         v = 0;
       v += st->get_h_kerning (left, right, table_length + (const char *) this);
       st = &StructAfter<typename T::SubTableWrapper> (*st);
     }
     return v;
   }

   inline bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
     if (unlikely (!c->check_struct (thiz()) ||
 		  thiz()->version != T::VERSION))
       return_trace (false);

     const typename T::SubTableWrapper *st = CastP<typename T::SubTableWrapper> (thiz()->data);
     unsigned int count = thiz()->nTables;
     for (unsigned int i = 0; i < count; i++)
     {
       if (unlikely (!st->sanitize (c)))
 	return_trace (false);
       st = &StructAfter<typename T::SubTableWrapper> (*st);
     }

     return_trace (true);
   }
 };

 struct KernOT : KernTable<KernOT>
 {
   friend struct KernTable<KernOT>;

   static const uint16_t VERSION = 0x0000u;

   struct SubTableWrapper : KernSubTableWrapper<SubTableWrapper>
   {
     friend struct KernSubTableWrapper<SubTableWrapper>;

     enum coverage_flags_t {
       COVERAGE_DIRECTION_FLAG	= 0x01u,
       COVERAGE_MINIMUM_FLAG	= 0x02u,
       COVERAGE_CROSSSTREAM_FLAG	= 0x04u,
       COVERAGE_OVERRIDE_FLAG	= 0x08u,

       COVERAGE_VARIATION_FLAG	= 0x00u, /* Not supported. */

       COVERAGE_CHECK_FLAGS	= 0x07u,
       COVERAGE_CHECK_HORIZONTAL	= 0x01u
     };

     protected:
     HBUINT16	versionZ;	/* Unused. */
     HBUINT16	length;		/* Length of the subtable (including this header). */
     HBUINT8	format;		/* Subtable format. */
     HBUINT8	coverage;	/* Coverage bits. */
     KernSubTable subtable;	/* Subtable data. */
     public:
     DEFINE_SIZE_MIN (6);
   };

   protected:
   HBUINT16	version;	/* Version--0x0000u */
   HBUINT16	nTables;	/* Number of subtables in the kerning table. */
   HBUINT8		data[VAR];
   public:
   DEFINE_SIZE_ARRAY (4, data);
 };

 struct KernAAT : KernTable<KernAAT>
 {
   friend struct KernTable<KernAAT>;

   static const uint32_t VERSION = 0x00010000u;

   struct SubTableWrapper : KernSubTableWrapper<SubTableWrapper>
   {
     friend struct KernSubTableWrapper<SubTableWrapper>;

     enum coverage_flags_t {
       COVERAGE_DIRECTION_FLAG	= 0x80u,
       COVERAGE_CROSSSTREAM_FLAG	= 0x40u,
       COVERAGE_VARIATION_FLAG	= 0x20u,

       COVERAGE_OVERRIDE_FLAG	= 0x00u, /* Not supported. */

       COVERAGE_CHECK_FLAGS	= 0xE0u,
       COVERAGE_CHECK_HORIZONTAL	= 0x00u
     };

     protected:
     HBUINT32	length;		/* Length of the subtable (including this header). */
     HBUINT8	coverage;	/* Coverage bits. */
     HBUINT8	format;		/* Subtable format. */
     HBUINT16	tupleIndex;	/* The tuple index (used for variations fonts).
 				 * This value specifies which tuple this subtable covers. */
     KernSubTable subtable;	/* Subtable data. */
     public:
     DEFINE_SIZE_MIN (8);
   };

   protected:
   HBUINT32		version;	/* Version--0x00010000u */
   HBUINT32		nTables;	/* Number of subtables in the kerning table. */
   HBUINT8		data[VAR];
   public:
   DEFINE_SIZE_ARRAY (8, data);
 };

 struct kern
 {
   static const hb_tag_t tableTag = HB_OT_TAG_kern;

   inline int get_h_kerning (hb_codepoint_t left, hb_codepoint_t right, unsigned int table_length) const
   {
     switch (u.major) {
     case 0: return u.ot.get_h_kerning (left, right, table_length);
     case 1: return u.aat.get_h_kerning (left, right, table_length);
     default:return 0;
     }
   }

   inline bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
     if (!u.major.sanitize (c)) return_trace (false);
     switch (u.major) {
     case 0: return_trace (u.ot.sanitize (c));
     case 1: return_trace (u.aat.sanitize (c));
     default:return_trace (true);
     }
   }

   struct accelerator_t
   {
     inline void init (hb_face_t *face)
     {
       blob = Sanitizer<kern>().sanitize (face->reference_table (HB_OT_TAG_kern));
       table = Sanitizer<kern>::lock_instance (blob);
       table_length = hb_blob_get_length (blob);
     }
     inline void fini (void)
     {
       hb_blob_destroy (blob);
     }

     inline int get_h_kerning (hb_codepoint_t left, hb_codepoint_t right) const
     { return table->get_h_kerning (left, right, table_length); }

     private:
     hb_blob_t *blob;
     const kern *table;
     unsigned int table_length;
   };

   protected:
   union {
   HBUINT16		major;
   KernOT		ot;
   KernAAT		aat;
   } u;
   public:
   DEFINE_SIZE_UNION (2, major);
 };

 } /* namespace OT */


 #endif /* HB_OT_KERN_TABLE_HH */
	/*
	* Copyright © 2017 Google, Inc.
	*
	* This is part of HarfBuzz, a text shaping 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.
	*
	* Google Author(s): Behdad Esfahbod
	*/

	#ifndef HB_OT_KERN_TABLE_HH
	#define HB_OT_KERN_TABLE_HH

	#include "hb-open-type-private.hh"

	namespace OT {


	/*
	* kern -- Kerning
	*/

	#define HB_OT_TAG_kern HB_TAG('k','e','r','n')

	struct hb_glyph_pair_t
	{
	hb_codepoint_t left;
	hb_codepoint_t right;
	};

	struct KernPair
	{
	inline int get_kerning (void) const
	{ return value; }

	inline int cmp (const hb_glyph_pair_t &o) const
	{
	int ret = left.cmp (o.left);
	if (ret) return ret;
	return right.cmp (o.right);
	}

	inline bool sanitize (hb_sanitize_context_t *c) const
	{
	TRACE_SANITIZE (this);
	return_trace (c->check_struct (this));
	}

	protected:
	GlyphID left;
	GlyphID right;
	FWORD value;
	public:
	DEFINE_SIZE_STATIC (6);
	};

	struct KernSubTableFormat0
	{
	inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right) const
	{
	hb_glyph_pair_t pair = {left, right};
	int i = pairs.bsearch (pair);
	if (i == -1)
	return 0;
	return pairs[i].get_kerning ();
	}

	inline bool sanitize (hb_sanitize_context_t *c) const
	{
	TRACE_SANITIZE (this);
	return_trace (pairs.sanitize (c));
	}

	protected:
	BinSearchArrayOf<KernPair> pairs; /* Array of kerning pairs. */
	public:
	DEFINE_SIZE_ARRAY (8, pairs);
	};

	struct KernClassTable
	{
	inline unsigned int get_class (hb_codepoint_t g) const { return classes[g - firstGlyph]; }

	inline bool sanitize (hb_sanitize_context_t *c) const
	{
	TRACE_SANITIZE (this);
	return_trace (firstGlyph.sanitize (c) && classes.sanitize (c));
	}

	protected:
	HBUINT16 firstGlyph; /* First glyph in class range. */
	ArrayOf<HBUINT16> classes; /* Glyph classes. */
	public:
	DEFINE_SIZE_ARRAY (4, classes);
	};

	struct KernSubTableFormat2
	{
	inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right, const char *end) const
	{
	unsigned int l = (this+leftClassTable).get_class (left);
	unsigned int r = (this+rightClassTable).get_class (right);
	unsigned int offset = l * rowWidth + r * sizeof (FWORD);
	const FWORD *arr = &(this+array);
	if (unlikely ((const void ) arr < (const void ) this \|\| (const void ) arr >= (const void ) end))
	return 0;
	const FWORD *v = &StructAtOffset<FWORD> (arr, offset);
	if (unlikely ((const void ) v < (const void ) arr \|\| (const void ) (v + 1) > (const void ) end))
	return 0;
	return *v;
	}

	inline bool sanitize (hb_sanitize_context_t *c) const
	{
	TRACE_SANITIZE (this);
	return_trace (rowWidth.sanitize (c) &&
	leftClassTable.sanitize (c, this) &&
	rightClassTable.sanitize (c, this) &&
	array.sanitize (c, this));
	}

	protected:
	HBUINT16 rowWidth; /* The width, in bytes, of a row in the table. */
	OffsetTo<KernClassTable>
	leftClassTable; /* Offset from beginning of this subtable to
	* left-hand class table. */
	OffsetTo<KernClassTable>
	rightClassTable;/* Offset from beginning of this subtable to
	* right-hand class table. */
	OffsetTo<FWORD>
	array; /* Offset from beginning of this subtable to
	* the start of the kerning array. */
	public:
	DEFINE_SIZE_MIN (8);
	};

	struct KernSubTable
	{
	inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right, const char *end, unsigned int format) const
	{
	switch (format) {
	case 0: return u.format0.get_kerning (left, right);
	case 2: return u.format2.get_kerning (left, right, end);
	default:return 0;
	}
	}

	inline bool sanitize (hb_sanitize_context_t *c, unsigned int format) const
	{
	TRACE_SANITIZE (this);
	switch (format) {
	case 0: return_trace (u.format0.sanitize (c));
	case 2: return_trace (u.format2.sanitize (c));
	default:return_trace (true);
	}
	}

	protected:
	union {
	KernSubTableFormat0 format0;
	KernSubTableFormat2 format2;
	} u;
	public:
	DEFINE_SIZE_MIN (0);
	};


	template <typename T>
	struct KernSubTableWrapper
	{
	/* https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern */
	inline const T* thiz (void) const { return static_cast<const T *> (this); }

	inline bool is_horizontal (void) const
	{ return (thiz()->coverage & T::COVERAGE_CHECK_FLAGS) == T::COVERAGE_CHECK_HORIZONTAL; }

	inline bool is_override (void) const
	{ return bool (thiz()->coverage & T::COVERAGE_OVERRIDE_FLAG); }

	inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right, const char *end) const
	{ return thiz()->subtable.get_kerning (left, right, end, thiz()->format); }

	inline int get_h_kerning (hb_codepoint_t left, hb_codepoint_t right, const char *end) const
	{ return is_horizontal () ? get_kerning (left, right, end) : 0; }

	inline unsigned int get_size (void) const { return thiz()->length; }

	inline bool sanitize (hb_sanitize_context_t *c) const
	{
	TRACE_SANITIZE (this);
	return_trace (c->check_struct (thiz()) &&
	thiz()->length >= thiz()->min_size &&
	c->check_array (thiz(), 1, thiz()->length) &&
	thiz()->subtable.sanitize (c, thiz()->format));
	}
	};

	template <typename T>
	struct KernTable
	{
	/* https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern */
	inline const T* thiz (void) const { return static_cast<const T *> (this); }

	inline int get_h_kerning (hb_codepoint_t left, hb_codepoint_t right, unsigned int table_length) const
	{
	int v = 0;
	const typename T::SubTableWrapper *st = CastP<typename T::SubTableWrapper> (thiz()->data);
	unsigned int count = thiz()->nTables;
	for (unsigned int i = 0; i < count; i++)
	{
	if (st->is_override ())
	v = 0;
	v += st->get_h_kerning (left, right, table_length + (const char *) this);
	st = &StructAfter<typename T::SubTableWrapper> (*st);
	}
	return v;
	}

	inline bool sanitize (hb_sanitize_context_t *c) const
	{
	TRACE_SANITIZE (this);
	if (unlikely (!c->check_struct (thiz()) \|\|
	thiz()->version != T::VERSION))
	return_trace (false);

	const typename T::SubTableWrapper *st = CastP<typename T::SubTableWrapper> (thiz()->data);
	unsigned int count = thiz()->nTables;
	for (unsigned int i = 0; i < count; i++)
	{
	if (unlikely (!st->sanitize (c)))
	return_trace (false);
	st = &StructAfter<typename T::SubTableWrapper> (*st);
	}

	return_trace (true);
	}
	};

	struct KernOT : KernTable<KernOT>
	{
	friend struct KernTable<KernOT>;

	static const uint16_t VERSION = 0x0000u;

	struct SubTableWrapper : KernSubTableWrapper<SubTableWrapper>
	{
	friend struct KernSubTableWrapper<SubTableWrapper>;

	enum coverage_flags_t {
	COVERAGE_DIRECTION_FLAG = 0x01u,
	COVERAGE_MINIMUM_FLAG = 0x02u,
	COVERAGE_CROSSSTREAM_FLAG = 0x04u,
	COVERAGE_OVERRIDE_FLAG = 0x08u,

	COVERAGE_VARIATION_FLAG = 0x00u, /* Not supported. */

	COVERAGE_CHECK_FLAGS = 0x07u,
	COVERAGE_CHECK_HORIZONTAL = 0x01u
	};

	protected:
	HBUINT16 versionZ; /* Unused. */
	HBUINT16 length; /* Length of the subtable (including this header). */
	HBUINT8 format; /* Subtable format. */
	HBUINT8 coverage; /* Coverage bits. */
	KernSubTable subtable; /* Subtable data. */
	public:
	DEFINE_SIZE_MIN (6);
	};

	protected:
	HBUINT16 version; /* Version--0x0000u */
	HBUINT16 nTables; /* Number of subtables in the kerning table. */
	HBUINT8 data[VAR];
	public:
	DEFINE_SIZE_ARRAY (4, data);
	};

	struct KernAAT : KernTable<KernAAT>
	{
	friend struct KernTable<KernAAT>;

	static const uint32_t VERSION = 0x00010000u;

	struct SubTableWrapper : KernSubTableWrapper<SubTableWrapper>
	{
	friend struct KernSubTableWrapper<SubTableWrapper>;

	enum coverage_flags_t {
	COVERAGE_DIRECTION_FLAG = 0x80u,
	COVERAGE_CROSSSTREAM_FLAG = 0x40u,
	COVERAGE_VARIATION_FLAG = 0x20u,

	COVERAGE_OVERRIDE_FLAG = 0x00u, /* Not supported. */

	COVERAGE_CHECK_FLAGS = 0xE0u,
	COVERAGE_CHECK_HORIZONTAL = 0x00u
	};

	protected:
	HBUINT32 length; /* Length of the subtable (including this header). */
	HBUINT8 coverage; /* Coverage bits. */
	HBUINT8 format; /* Subtable format. */
	HBUINT16 tupleIndex; /* The tuple index (used for variations fonts).
	* This value specifies which tuple this subtable covers. */
	KernSubTable subtable; /* Subtable data. */
	public:
	DEFINE_SIZE_MIN (8);
	};

	protected:
	HBUINT32 version; /* Version--0x00010000u */
	HBUINT32 nTables; /* Number of subtables in the kerning table. */
	HBUINT8 data[VAR];
	public:
	DEFINE_SIZE_ARRAY (8, data);
	};

	struct kern
	{
	static const hb_tag_t tableTag = HB_OT_TAG_kern;

	inline int get_h_kerning (hb_codepoint_t left, hb_codepoint_t right, unsigned int table_length) const
	{
	switch (u.major) {
	case 0: return u.ot.get_h_kerning (left, right, table_length);
	case 1: return u.aat.get_h_kerning (left, right, table_length);
	default:return 0;
	}
	}

	inline bool sanitize (hb_sanitize_context_t *c) const
	{
	TRACE_SANITIZE (this);
	if (!u.major.sanitize (c)) return_trace (false);
	switch (u.major) {
	case 0: return_trace (u.ot.sanitize (c));
	case 1: return_trace (u.aat.sanitize (c));
	default:return_trace (true);
	}
	}

	struct accelerator_t
	{
	inline void init (hb_face_t *face)
	{
	blob = Sanitizer<kern>().sanitize (face->reference_table (HB_OT_TAG_kern));
	table = Sanitizer<kern>::lock_instance (blob);
	table_length = hb_blob_get_length (blob);
	}
	inline void fini (void)
	{
	hb_blob_destroy (blob);
	}

	inline int get_h_kerning (hb_codepoint_t left, hb_codepoint_t right) const
	{ return table->get_h_kerning (left, right, table_length); }

	private:
	hb_blob_t *blob;
	const kern *table;
	unsigned int table_length;
	};

	protected:
	union {
	HBUINT16 major;
	KernOT ot;
	KernAAT aat;
	} u;
	public:
	DEFINE_SIZE_UNION (2, major);
	};

	} /* namespace OT */


	#endif /* HB_OT_KERN_TABLE_HH */