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

 /*
  * Copyright © 2015  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_GLYF_TABLE_HH
 #define HB_OT_GLYF_TABLE_HH

 #include "hb-open-type.hh"
 #include "hb-ot-head-table.hh"
 #include "hb-subset-glyf.hh"

 namespace OT {


 /*
  * loca -- Index to Location
  * https://docs.microsoft.com/en-us/typography/opentype/spec/loca
  */
 #define HB_OT_TAG_loca HB_TAG('l','o','c','a')


 struct loca
 {
   friend struct glyf;

   static const hb_tag_t tableTag = HB_OT_TAG_loca;

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

   protected:
   UnsizedArrayOf<HBUINT8>	dataZ;		/* Location data. */
   DEFINE_SIZE_ARRAY (0, dataZ);
 };


 /*
  * glyf -- TrueType Glyph Data
  * https://docs.microsoft.com/en-us/typography/opentype/spec/glyf
  */
 #define HB_OT_TAG_glyf HB_TAG('g','l','y','f')


 struct glyf
 {
   static const hb_tag_t tableTag = HB_OT_TAG_glyf;

   inline bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
     /* We don't check for anything specific here.  The users of the
      * struct do all the hard work... */
     return_trace (true);
   }

   inline bool subset (hb_subset_plan_t *plan) const
   {
     hb_blob_t *glyf_prime = nullptr;
     hb_blob_t *loca_prime = nullptr;

     bool success = true;
     bool use_short_loca = false;
     if (hb_subset_glyf_and_loca (plan, &use_short_loca, &glyf_prime, &loca_prime)) {
       success = success && plan->add_table (HB_OT_TAG_glyf, glyf_prime);
       success = success && plan->add_table (HB_OT_TAG_loca, loca_prime);
       success = success && _add_head_and_set_loca_version (plan, use_short_loca);
     } else {
       success = false;
     }
     hb_blob_destroy (loca_prime);
     hb_blob_destroy (glyf_prime);

     return success;
   }

   static bool
   _add_head_and_set_loca_version (hb_subset_plan_t *plan, bool use_short_loca)
   {
     hb_blob_t *head_blob = hb_sanitize_context_t().reference_table<head> (plan->source);
     hb_blob_t *head_prime_blob = hb_blob_copy_writable_or_fail (head_blob);
     hb_blob_destroy (head_blob);

     if (unlikely (!head_prime_blob))
       return false;

     head *head_prime = (head *) hb_blob_get_data_writable (head_prime_blob, nullptr);
     head_prime->indexToLocFormat.set (use_short_loca ? 0 : 1);
     bool success = plan->add_table (HB_OT_TAG_head, head_prime_blob);

     hb_blob_destroy (head_prime_blob);
     return success;
   }

   struct GlyphHeader
   {
     HBINT16		numberOfContours;	/* If the number of contours is
                                                  * greater than or equal to zero,
                                                  * this is a simple glyph; if negative,
                                                  * this is a composite glyph. */
     FWORD		xMin;			/* Minimum x for coordinate data. */
     FWORD		yMin;			/* Minimum y for coordinate data. */
     FWORD		xMax;			/* Maximum x for coordinate data. */
     FWORD		yMax;			/* Maximum y for coordinate data. */

     DEFINE_SIZE_STATIC (10);
   };

   struct CompositeGlyphHeader
   {
     enum composite_glyph_flag_t {
       ARG_1_AND_2_ARE_WORDS =      0x0001,
       ARGS_ARE_XY_VALUES =         0x0002,
       ROUND_XY_TO_GRID =           0x0004,
       WE_HAVE_A_SCALE =            0x0008,
       MORE_COMPONENTS =            0x0020,
       WE_HAVE_AN_X_AND_Y_SCALE =   0x0040,
       WE_HAVE_A_TWO_BY_TWO =       0x0080,
       WE_HAVE_INSTRUCTIONS =       0x0100,
       USE_MY_METRICS =             0x0200,
       OVERLAP_COMPOUND =           0x0400,
       SCALED_COMPONENT_OFFSET =    0x0800,
       UNSCALED_COMPONENT_OFFSET =  0x1000
     };

     HBUINT16 flags;
     HBUINT16 glyphIndex;

     inline unsigned int get_size (void) const
     {
       unsigned int size = min_size;
       if (flags & ARG_1_AND_2_ARE_WORDS) {
         // arg1 and 2 are int16
         size += 4;
       } else {
         // arg1 and 2 are int8
         size += 2;
       }
       if (flags & WE_HAVE_A_SCALE) {
         // One x 16 bit (scale)
         size += 2;
       } else if (flags & WE_HAVE_AN_X_AND_Y_SCALE) {
         // Two x 16 bit (xscale, yscale)
         size += 4;
       } else if (flags & WE_HAVE_A_TWO_BY_TWO) {
         // Four x 16 bit (xscale, scale01, scale10, yscale)
         size += 8;
       }
       return size;
     }

     struct Iterator
     {
       const char *glyph_start;
       const char *glyph_end;
       const CompositeGlyphHeader *current;

       inline bool move_to_next ()
       {
 	if (current->flags & CompositeGlyphHeader::MORE_COMPONENTS)
 	{
 	  const CompositeGlyphHeader *possible =
 	    &StructAfter<CompositeGlyphHeader, CompositeGlyphHeader> (*current);
 	  if (!in_range (possible))
 	    return false;
 	  current = possible;
 	  return true;
 	}
 	return false;
       }

       inline bool in_range (const CompositeGlyphHeader *composite) const
       {
 	return (const char *) composite >= glyph_start
 	  && ((const char *) composite + CompositeGlyphHeader::min_size) <= glyph_end
 	  && ((const char *) composite + composite->get_size()) <= glyph_end;
       }
     };

     static inline bool get_iterator (const char * glyph_data,
 				     unsigned int length,
 				     CompositeGlyphHeader::Iterator *iterator /* OUT */)
     {
       if (length < GlyphHeader::static_size)
 	return false; /* Empty glyph; zero extents. */

       const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (glyph_data, 0);
       if (glyph_header.numberOfContours < 0)
       {
         const CompositeGlyphHeader *possible =
 	  &StructAfter<CompositeGlyphHeader, GlyphHeader> (glyph_header);

 	iterator->glyph_start = glyph_data;
 	iterator->glyph_end = (const char *) glyph_data + length;
 	if (!iterator->in_range (possible))
           return false;
         iterator->current = possible;
         return true;
       }

       return false;
     }

     DEFINE_SIZE_MIN (4);
   };

   struct accelerator_t
   {
     inline void init (hb_face_t *face)
     {
       memset (this, 0, sizeof (accelerator_t));

       hb_blob_t *head_blob = hb_sanitize_context_t().reference_table<head> (face);
       const head *head_table = head_blob->as<head> ();
       if (head_table->indexToLocFormat > 1 || head_table->glyphDataFormat != 0)
       {
 	/* Unknown format.  Leave num_glyphs=0, that takes care of disabling us. */
 	hb_blob_destroy (head_blob);
 	return;
       }
       short_offset = 0 == head_table->indexToLocFormat;
       hb_blob_destroy (head_blob);

       loca_blob = hb_sanitize_context_t().reference_table<loca> (face);
       loca_table = loca_blob->as<loca> ();
       glyf_blob = hb_sanitize_context_t().reference_table<glyf> (face);
       glyf_table = glyf_blob->as<glyf> ();

       num_glyphs = MAX (1u, hb_blob_get_length (loca_blob) / (short_offset ? 2 : 4)) - 1;
       glyf_len = hb_blob_get_length (glyf_blob);
     }

     inline void fini (void)
     {
       hb_blob_destroy (loca_blob);
       hb_blob_destroy (glyf_blob);
     }

     /*
      * Returns true if the referenced glyph is a valid glyph and a composite glyph.
      * If true is returned a pointer to the composite glyph will be written into
      * composite.
      */
     inline bool get_composite (hb_codepoint_t glyph,
 			       CompositeGlyphHeader::Iterator *composite /* OUT */) const
     {
       if (unlikely (!num_glyphs))
 	return false;

       unsigned int start_offset, end_offset;
       if (!get_offsets (glyph, &start_offset, &end_offset))
         return false; /* glyph not found */

       return CompositeGlyphHeader::get_iterator ((const char*) this->glyf_table + start_offset,
 						 end_offset - start_offset,
 						 composite);
     }

     enum simple_glyph_flag_t {
       FLAG_X_SHORT = 0x02,
       FLAG_Y_SHORT = 0x04,
       FLAG_REPEAT = 0x08,
       FLAG_X_SAME = 0x10,
       FLAG_Y_SAME = 0x20
     };

     /* based on FontTools _g_l_y_f.py::trim */
     inline bool remove_padding(unsigned int start_offset,
                                unsigned int *end_offset) const
     {
       if (*end_offset - start_offset < GlyphHeader::static_size)
         return true;

       const char *glyph = ((const char *) glyf_table) + start_offset;
       const char * const glyph_end = glyph + (*end_offset - start_offset);
       const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (glyph, 0);
       int16_t num_contours = (int16_t) glyph_header.numberOfContours;

       if (num_contours < 0)
         /* Trimming for composites not implemented.
          * If removing hints it falls out of that. */
         return true;
       else if (num_contours > 0)
       {
         /* simple glyph w/contours, possibly trimmable */
         glyph += GlyphHeader::static_size + 2 * num_contours;

         if (unlikely (glyph + 2 >= glyph_end)) return false;
         uint16_t nCoordinates = (uint16_t) StructAtOffset<HBUINT16>(glyph - 2, 0) + 1;
         uint16_t nInstructions = (uint16_t) StructAtOffset<HBUINT16>(glyph, 0);

         glyph += 2 + nInstructions;
         if (unlikely (glyph + 2 >= glyph_end)) return false;

         unsigned int coordBytes = 0;
         unsigned int coordsWithFlags = 0;
         while (glyph < glyph_end)
         {
           uint8_t flag = (uint8_t) *glyph;
           glyph++;

           unsigned int repeat = 1;
           if (flag & FLAG_REPEAT)
           {
             if (glyph >= glyph_end)
             {
               DEBUG_MSG(SUBSET, nullptr, "Bad flag");
               return false;
             }
             repeat = ((uint8_t) *glyph) + 1;
             glyph++;
           }

           unsigned int xBytes, yBytes;
           xBytes = yBytes = 0;
           if (flag & FLAG_X_SHORT)
             xBytes = 1;
           else if ((flag & FLAG_X_SAME) == 0)
             xBytes = 2;

           if (flag & FLAG_Y_SHORT)
             yBytes = 1;
           else if ((flag & FLAG_Y_SAME) == 0)
             yBytes = 2;

           coordBytes += (xBytes + yBytes) * repeat;
           coordsWithFlags += repeat;
           if (coordsWithFlags >= nCoordinates)
             break;
         }

         if (coordsWithFlags != nCoordinates)
         {
           DEBUG_MSG(SUBSET, nullptr, "Expect %d coords to have flags, got flags for %d", nCoordinates, coordsWithFlags);
           return false;
         }
         glyph += coordBytes;

         if (glyph < glyph_end)
           *end_offset -= glyph_end - glyph;
       }
       return true;
     }

     inline bool get_offsets (hb_codepoint_t  glyph,
                              unsigned int   *start_offset /* OUT */,
                              unsigned int   *end_offset   /* OUT */) const
     {
       if (unlikely (glyph >= num_glyphs))
 	return false;

       if (short_offset)
       {
         const HBUINT16 *offsets = (const HBUINT16 *) loca_table->dataZ.arrayZ;
 	*start_offset = 2 * offsets[glyph];
 	*end_offset   = 2 * offsets[glyph + 1];
       }
       else
       {
         const HBUINT32 *offsets = (const HBUINT32 *) loca_table->dataZ.arrayZ;

 	*start_offset = offsets[glyph];
 	*end_offset   = offsets[glyph + 1];
       }

       if (*start_offset > *end_offset || *end_offset > glyf_len)
 	return false;

       return true;
     }

     inline bool get_instruction_offsets(unsigned int start_offset,
                                         unsigned int end_offset,
                                         unsigned int *instruction_start /* OUT */,
                                         unsigned int *instruction_end /* OUT */) const
     {
       if (end_offset - start_offset < GlyphHeader::static_size)
       {
         *instruction_start = 0;
         *instruction_end = 0;
         return true; /* Empty glyph; no instructions. */
       }
       const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (glyf_table, start_offset);
       int16_t num_contours = (int16_t) glyph_header.numberOfContours;
       if (num_contours < 0)
       {
         CompositeGlyphHeader::Iterator composite_it;
         if (unlikely (!CompositeGlyphHeader::get_iterator (
             (const char*) this->glyf_table + start_offset,
              end_offset - start_offset, &composite_it))) return false;
         const CompositeGlyphHeader *last;
         do {
           last = composite_it.current;
         } while (composite_it.move_to_next());

         if ( (uint16_t) last->flags & CompositeGlyphHeader::WE_HAVE_INSTRUCTIONS)
           *instruction_start = ((char *) last - (char *) glyf_table->dataZ.arrayZ) + last->get_size();
         else
           *instruction_start = end_offset;
         *instruction_end = end_offset;
         if (unlikely (*instruction_start > *instruction_end))
         {
           DEBUG_MSG(SUBSET, nullptr, "Invalid instruction offset, %d is outside [%d, %d]", *instruction_start, start_offset, end_offset);
           return false;
         }
       }
       else
       {
         unsigned int instruction_length_offset = start_offset + GlyphHeader::static_size + 2 * num_contours;
 	if (unlikely (instruction_length_offset + 2 > end_offset))
 	{
 	  DEBUG_MSG(SUBSET, nullptr, "Glyph size is too short, missing field instructionLength.");
 	  return false;
 	}

         const HBUINT16 &instruction_length = StructAtOffset<HBUINT16> (glyf_table, instruction_length_offset);
 	unsigned int start = instruction_length_offset + 2;
 	unsigned int end = start + (uint16_t) instruction_length;
 	if (unlikely (end > end_offset)) // Out of bounds of the current glyph
 	{
 	  DEBUG_MSG(SUBSET, nullptr, "The instructions array overruns the glyph's boundaries.");
 	  return false;
 	}

 	*instruction_start = start;
         *instruction_end = end;
       }
       return true;
     }

     inline bool get_extents (hb_codepoint_t glyph,
 			     hb_glyph_extents_t *extents) const
     {
       unsigned int start_offset, end_offset;
       if (!get_offsets (glyph, &start_offset, &end_offset))
         return false;

       if (end_offset - start_offset < GlyphHeader::static_size)
 	return true; /* Empty glyph; zero extents. */

       const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (glyf_table, start_offset);

       extents->x_bearing = MIN (glyph_header.xMin, glyph_header.xMax);
       extents->y_bearing = MAX (glyph_header.yMin, glyph_header.yMax);
       extents->width     = MAX (glyph_header.xMin, glyph_header.xMax) - extents->x_bearing;
       extents->height    = MIN (glyph_header.yMin, glyph_header.yMax) - extents->y_bearing;

       return true;
     }

     private:
     bool short_offset;
     unsigned int num_glyphs;
     const loca *loca_table;
     const glyf *glyf_table;
     hb_blob_t *loca_blob;
     hb_blob_t *glyf_blob;
     unsigned int glyf_len;
   };

   protected:
   UnsizedArrayOf<HBUINT8>	dataZ;		/* Glyphs data. */

   DEFINE_SIZE_ARRAY (0, dataZ);
 };

 struct glyf_accelerator_t : glyf::accelerator_t {};

 } /* namespace OT */


 #endif /* HB_OT_GLYF_TABLE_HH */
	/*
	* Copyright © 2015 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_GLYF_TABLE_HH
	#define HB_OT_GLYF_TABLE_HH

	#include "hb-open-type.hh"
	#include "hb-ot-head-table.hh"
	#include "hb-subset-glyf.hh"

	namespace OT {


	/*
	* loca -- Index to Location
	* https://docs.microsoft.com/en-us/typography/opentype/spec/loca
	*/
	#define HB_OT_TAG_loca HB_TAG('l','o','c','a')


	struct loca
	{
	friend struct glyf;

	static const hb_tag_t tableTag = HB_OT_TAG_loca;

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

	protected:
	UnsizedArrayOf<HBUINT8> dataZ; /* Location data. */
	DEFINE_SIZE_ARRAY (0, dataZ);
	};


	/*
	* glyf -- TrueType Glyph Data
	* https://docs.microsoft.com/en-us/typography/opentype/spec/glyf
	*/
	#define HB_OT_TAG_glyf HB_TAG('g','l','y','f')


	struct glyf
	{
	static const hb_tag_t tableTag = HB_OT_TAG_glyf;

	inline bool sanitize (hb_sanitize_context_t *c) const
	{
	TRACE_SANITIZE (this);
	/* We don't check for anything specific here. The users of the
	* struct do all the hard work... */
	return_trace (true);
	}

	inline bool subset (hb_subset_plan_t *plan) const
	{
	hb_blob_t *glyf_prime = nullptr;
	hb_blob_t *loca_prime = nullptr;

	bool success = true;
	bool use_short_loca = false;
	if (hb_subset_glyf_and_loca (plan, &use_short_loca, &glyf_prime, &loca_prime)) {
	success = success && plan->add_table (HB_OT_TAG_glyf, glyf_prime);
	success = success && plan->add_table (HB_OT_TAG_loca, loca_prime);
	success = success && _add_head_and_set_loca_version (plan, use_short_loca);
	} else {
	success = false;
	}
	hb_blob_destroy (loca_prime);
	hb_blob_destroy (glyf_prime);

	return success;
	}

	static bool
	_add_head_and_set_loca_version (hb_subset_plan_t *plan, bool use_short_loca)
	{
	hb_blob_t *head_blob = hb_sanitize_context_t().reference_table<head> (plan->source);
	hb_blob_t *head_prime_blob = hb_blob_copy_writable_or_fail (head_blob);
	hb_blob_destroy (head_blob);

	if (unlikely (!head_prime_blob))
	return false;

	head head_prime = (head ) hb_blob_get_data_writable (head_prime_blob, nullptr);
	head_prime->indexToLocFormat.set (use_short_loca ? 0 : 1);
	bool success = plan->add_table (HB_OT_TAG_head, head_prime_blob);

	hb_blob_destroy (head_prime_blob);
	return success;
	}

	struct GlyphHeader
	{
	HBINT16 numberOfContours; /* If the number of contours is
	* greater than or equal to zero,
	* this is a simple glyph; if negative,
	* this is a composite glyph. */
	FWORD xMin; /* Minimum x for coordinate data. */
	FWORD yMin; /* Minimum y for coordinate data. */
	FWORD xMax; /* Maximum x for coordinate data. */
	FWORD yMax; /* Maximum y for coordinate data. */

	DEFINE_SIZE_STATIC (10);
	};

	struct CompositeGlyphHeader
	{
	enum composite_glyph_flag_t {
	ARG_1_AND_2_ARE_WORDS = 0x0001,
	ARGS_ARE_XY_VALUES = 0x0002,
	ROUND_XY_TO_GRID = 0x0004,
	WE_HAVE_A_SCALE = 0x0008,
	MORE_COMPONENTS = 0x0020,
	WE_HAVE_AN_X_AND_Y_SCALE = 0x0040,
	WE_HAVE_A_TWO_BY_TWO = 0x0080,
	WE_HAVE_INSTRUCTIONS = 0x0100,
	USE_MY_METRICS = 0x0200,
	OVERLAP_COMPOUND = 0x0400,
	SCALED_COMPONENT_OFFSET = 0x0800,
	UNSCALED_COMPONENT_OFFSET = 0x1000
	};

	HBUINT16 flags;
	HBUINT16 glyphIndex;

	inline unsigned int get_size (void) const
	{
	unsigned int size = min_size;
	if (flags & ARG_1_AND_2_ARE_WORDS) {
	// arg1 and 2 are int16
	size += 4;
	} else {
	// arg1 and 2 are int8
	size += 2;
	}
	if (flags & WE_HAVE_A_SCALE) {
	// One x 16 bit (scale)
	size += 2;
	} else if (flags & WE_HAVE_AN_X_AND_Y_SCALE) {
	// Two x 16 bit (xscale, yscale)
	size += 4;
	} else if (flags & WE_HAVE_A_TWO_BY_TWO) {
	// Four x 16 bit (xscale, scale01, scale10, yscale)
	size += 8;
	}
	return size;
	}

	struct Iterator
	{
	const char *glyph_start;
	const char *glyph_end;
	const CompositeGlyphHeader *current;

	inline bool move_to_next ()
	{
	if (current->flags & CompositeGlyphHeader::MORE_COMPONENTS)
	{
	const CompositeGlyphHeader *possible =
	&StructAfter<CompositeGlyphHeader, CompositeGlyphHeader> (*current);
	if (!in_range (possible))
	return false;
	current = possible;
	return true;
	}
	return false;
	}

	inline bool in_range (const CompositeGlyphHeader *composite) const
	{
	return (const char *) composite >= glyph_start
	&& ((const char *) composite + CompositeGlyphHeader::min_size) <= glyph_end
	&& ((const char *) composite + composite->get_size()) <= glyph_end;
	}
	};

	static inline bool get_iterator (const char * glyph_data,
	unsigned int length,
	CompositeGlyphHeader::Iterator iterator / OUT */)
	{
	if (length < GlyphHeader::static_size)
	return false; /* Empty glyph; zero extents. */

	const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (glyph_data, 0);
	if (glyph_header.numberOfContours < 0)
	{
	const CompositeGlyphHeader *possible =
	&StructAfter<CompositeGlyphHeader, GlyphHeader> (glyph_header);

	iterator->glyph_start = glyph_data;
	iterator->glyph_end = (const char *) glyph_data + length;
	if (!iterator->in_range (possible))
	return false;
	iterator->current = possible;
	return true;
	}

	return false;
	}

	DEFINE_SIZE_MIN (4);
	};

	struct accelerator_t
	{
	inline void init (hb_face_t *face)
	{
	memset (this, 0, sizeof (accelerator_t));

	hb_blob_t *head_blob = hb_sanitize_context_t().reference_table<head> (face);
	const head *head_table = head_blob->as<head> ();
	if (head_table->indexToLocFormat > 1 \|\| head_table->glyphDataFormat != 0)
	{
	/* Unknown format. Leave num_glyphs=0, that takes care of disabling us. */
	hb_blob_destroy (head_blob);
	return;
	}
	short_offset = 0 == head_table->indexToLocFormat;
	hb_blob_destroy (head_blob);

	loca_blob = hb_sanitize_context_t().reference_table<loca> (face);
	loca_table = loca_blob->as<loca> ();
	glyf_blob = hb_sanitize_context_t().reference_table<glyf> (face);
	glyf_table = glyf_blob->as<glyf> ();

	num_glyphs = MAX (1u, hb_blob_get_length (loca_blob) / (short_offset ? 2 : 4)) - 1;
	glyf_len = hb_blob_get_length (glyf_blob);
	}

	inline void fini (void)
	{
	hb_blob_destroy (loca_blob);
	hb_blob_destroy (glyf_blob);
	}

	/*
	* Returns true if the referenced glyph is a valid glyph and a composite glyph.
	* If true is returned a pointer to the composite glyph will be written into
	* composite.
	*/
	inline bool get_composite (hb_codepoint_t glyph,
	CompositeGlyphHeader::Iterator composite / OUT */) const
	{
	if (unlikely (!num_glyphs))
	return false;

	unsigned int start_offset, end_offset;
	if (!get_offsets (glyph, &start_offset, &end_offset))
	return false; /* glyph not found */

	return CompositeGlyphHeader::get_iterator ((const char*) this->glyf_table + start_offset,
	end_offset - start_offset,
	composite);
	}

	enum simple_glyph_flag_t {
	FLAG_X_SHORT = 0x02,
	FLAG_Y_SHORT = 0x04,
	FLAG_REPEAT = 0x08,
	FLAG_X_SAME = 0x10,
	FLAG_Y_SAME = 0x20
	};

	/* based on FontTools _g_l_y_f.py::trim */
	inline bool remove_padding(unsigned int start_offset,
	unsigned int *end_offset) const
	{
	if (*end_offset - start_offset < GlyphHeader::static_size)
	return true;

	const char glyph = ((const char ) glyf_table) + start_offset;
	const char * const glyph_end = glyph + (*end_offset - start_offset);
	const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (glyph, 0);
	int16_t num_contours = (int16_t) glyph_header.numberOfContours;

	if (num_contours < 0)
	/* Trimming for composites not implemented.
	* If removing hints it falls out of that. */
	return true;
	else if (num_contours > 0)
	{
	/* simple glyph w/contours, possibly trimmable */
	glyph += GlyphHeader::static_size + 2 * num_contours;

	if (unlikely (glyph + 2 >= glyph_end)) return false;
	uint16_t nCoordinates = (uint16_t) StructAtOffset<HBUINT16>(glyph - 2, 0) + 1;
	uint16_t nInstructions = (uint16_t) StructAtOffset<HBUINT16>(glyph, 0);

	glyph += 2 + nInstructions;
	if (unlikely (glyph + 2 >= glyph_end)) return false;

	unsigned int coordBytes = 0;
	unsigned int coordsWithFlags = 0;
	while (glyph < glyph_end)
	{
	uint8_t flag = (uint8_t) *glyph;
	glyph++;

	unsigned int repeat = 1;
	if (flag & FLAG_REPEAT)
	{
	if (glyph >= glyph_end)
	{
	DEBUG_MSG(SUBSET, nullptr, "Bad flag");
	return false;
	}
	repeat = ((uint8_t) *glyph) + 1;
	glyph++;
	}

	unsigned int xBytes, yBytes;
	xBytes = yBytes = 0;
	if (flag & FLAG_X_SHORT)
	xBytes = 1;
	else if ((flag & FLAG_X_SAME) == 0)
	xBytes = 2;

	if (flag & FLAG_Y_SHORT)
	yBytes = 1;
	else if ((flag & FLAG_Y_SAME) == 0)
	yBytes = 2;

	coordBytes += (xBytes + yBytes) * repeat;
	coordsWithFlags += repeat;
	if (coordsWithFlags >= nCoordinates)
	break;
	}

	if (coordsWithFlags != nCoordinates)
	{
	DEBUG_MSG(SUBSET, nullptr, "Expect %d coords to have flags, got flags for %d", nCoordinates, coordsWithFlags);
	return false;
	}
	glyph += coordBytes;

	if (glyph < glyph_end)
	*end_offset -= glyph_end - glyph;
	}
	return true;
	}

	inline bool get_offsets (hb_codepoint_t glyph,
	unsigned int start_offset / OUT */,
	unsigned int end_offset / OUT */) const
	{
	if (unlikely (glyph >= num_glyphs))
	return false;

	if (short_offset)
	{
	const HBUINT16 offsets = (const HBUINT16 ) loca_table->dataZ.arrayZ;
	start_offset = 2 offsets[glyph];
	end_offset = 2 offsets[glyph + 1];
	}
	else
	{
	const HBUINT32 offsets = (const HBUINT32 ) loca_table->dataZ.arrayZ;

	*start_offset = offsets[glyph];
	*end_offset = offsets[glyph + 1];
	}

	if (start_offset > end_offset \|\| *end_offset > glyf_len)
	return false;

	return true;
	}

	inline bool get_instruction_offsets(unsigned int start_offset,
	unsigned int end_offset,
	unsigned int instruction_start / OUT */,
	unsigned int instruction_end / OUT */) const
	{
	if (end_offset - start_offset < GlyphHeader::static_size)
	{
	*instruction_start = 0;
	*instruction_end = 0;
	return true; /* Empty glyph; no instructions. */
	}
	const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (glyf_table, start_offset);
	int16_t num_contours = (int16_t) glyph_header.numberOfContours;
	if (num_contours < 0)
	{
	CompositeGlyphHeader::Iterator composite_it;
	if (unlikely (!CompositeGlyphHeader::get_iterator (
	(const char*) this->glyf_table + start_offset,
	end_offset - start_offset, &composite_it))) return false;
	const CompositeGlyphHeader *last;
	do {
	last = composite_it.current;
	} while (composite_it.move_to_next());

	if ( (uint16_t) last->flags & CompositeGlyphHeader::WE_HAVE_INSTRUCTIONS)
	instruction_start = ((char ) last - (char *) glyf_table->dataZ.arrayZ) + last->get_size();
	else
	*instruction_start = end_offset;
	*instruction_end = end_offset;
	if (unlikely (instruction_start > instruction_end))
	{
	DEBUG_MSG(SUBSET, nullptr, "Invalid instruction offset, %d is outside [%d, %d]", *instruction_start, start_offset, end_offset);
	return false;
	}
	}
	else
	{
	unsigned int instruction_length_offset = start_offset + GlyphHeader::static_size + 2 * num_contours;
	if (unlikely (instruction_length_offset + 2 > end_offset))
	{
	DEBUG_MSG(SUBSET, nullptr, "Glyph size is too short, missing field instructionLength.");
	return false;
	}

	const HBUINT16 &instruction_length = StructAtOffset<HBUINT16> (glyf_table, instruction_length_offset);
	unsigned int start = instruction_length_offset + 2;
	unsigned int end = start + (uint16_t) instruction_length;
	if (unlikely (end > end_offset)) // Out of bounds of the current glyph
	{
	DEBUG_MSG(SUBSET, nullptr, "The instructions array overruns the glyph's boundaries.");
	return false;
	}

	*instruction_start = start;
	*instruction_end = end;
	}
	return true;
	}

	inline bool get_extents (hb_codepoint_t glyph,
	hb_glyph_extents_t *extents) const
	{
	unsigned int start_offset, end_offset;
	if (!get_offsets (glyph, &start_offset, &end_offset))
	return false;

	if (end_offset - start_offset < GlyphHeader::static_size)
	return true; /* Empty glyph; zero extents. */

	const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (glyf_table, start_offset);

	extents->x_bearing = MIN (glyph_header.xMin, glyph_header.xMax);
	extents->y_bearing = MAX (glyph_header.yMin, glyph_header.yMax);
	extents->width = MAX (glyph_header.xMin, glyph_header.xMax) - extents->x_bearing;
	extents->height = MIN (glyph_header.yMin, glyph_header.yMax) - extents->y_bearing;

	return true;
	}

	private:
	bool short_offset;
	unsigned int num_glyphs;
	const loca *loca_table;
	const glyf *glyf_table;
	hb_blob_t *loca_blob;
	hb_blob_t *glyf_blob;
	unsigned int glyf_len;
	};

	protected:
	UnsizedArrayOf<HBUINT8> dataZ; /* Glyphs data. */

	DEFINE_SIZE_ARRAY (0, dataZ);
	};

	struct glyf_accelerator_t : glyf::accelerator_t {};

	} /* namespace OT */


	#endif /* HB_OT_GLYF_TABLE_HH */