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

 /*
  * Copyright © 2015  Google, Inc.
  * Copyright © 2019  Ebrahim Byagowi
  *
  *  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, Garret Rieger, Roderick Sheeter
  */

 #ifndef HB_OT_GLYF_TABLE_HH
 #define HB_OT_GLYF_TABLE_HH

 #include "hb-open-type.hh"
 #include "hb-ot-head-table.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 constexpr hb_tag_t tableTag = HB_OT_TAG_loca;

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

   protected:
   UnsizedArrayOf<HBUINT8>
 		dataZ;	/* Location data. */
   public:
   DEFINE_SIZE_MIN (0);  /* In reality, this is UNBOUNDED() type; but since we always
 			 * check the size externally, allow Null() object of it by
 			 * defining it _MIN instead. */
 };


 /*
  * 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 constexpr hb_tag_t tableTag = HB_OT_TAG_glyf;

   bool sanitize (hb_sanitize_context_t *c HB_UNUSED) 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);
   }

   template<typename Iterator,
 	   hb_requires (hb_is_source_of (Iterator, unsigned int))>
   static bool
   _add_loca_and_head (hb_subset_plan_t * plan, Iterator padded_offsets)
   {
     unsigned max_offset = + padded_offsets | hb_reduce(hb_add, 0);
     unsigned num_offsets = padded_offsets.len () + 1;
     bool use_short_loca = max_offset < 0x1FFFF;
     unsigned entry_size = use_short_loca ? 2 : 4;
     char *loca_prime_data = (char *) calloc (entry_size, num_offsets);

     if (unlikely (!loca_prime_data)) return false;

     DEBUG_MSG (SUBSET, nullptr, "loca entry_size %d num_offsets %d "
 				"max_offset %d size %d",
 	       entry_size, num_offsets, max_offset, entry_size * num_offsets);

     if (use_short_loca)
       _write_loca (padded_offsets, 1, hb_array ((HBUINT16*) loca_prime_data, num_offsets));
     else
       _write_loca (padded_offsets, 0, hb_array ((HBUINT32*) loca_prime_data, num_offsets));

     hb_blob_t * loca_blob = hb_blob_create (loca_prime_data,
 					    entry_size * num_offsets,
 					    HB_MEMORY_MODE_WRITABLE,
 					    loca_prime_data,
 					    free);

     bool result = plan->add_table (HB_OT_TAG_loca, loca_blob)
 		  && _add_head_and_set_loca_version(plan, use_short_loca);

     hb_blob_destroy (loca_blob);
     return result;
   }

   template<typename IteratorIn, typename IteratorOut,
 	   hb_requires (hb_is_source_of (IteratorIn, unsigned int)),
 	   hb_requires (hb_is_sink_of (IteratorOut, unsigned))>
   static void
   _write_loca (IteratorIn it, unsigned right_shift, IteratorOut dest)
   {
     unsigned int offset = 0;
     dest << 0;
     + it
     | hb_map ([=, &offset] (unsigned int padded_size)
 	      {
 		offset += padded_size;
 		DEBUG_MSG (SUBSET, nullptr, "loca entry offset %d", offset);
 		return offset >> right_shift;
 	      })
     | hb_sink (dest)
     ;
   }

   // requires source of SubsetGlyph complains the identifier isn't declared
   template <typename Iterator>
   bool serialize (hb_serialize_context_t *c,
 		  Iterator it,
 		  const hb_subset_plan_t *plan)
   {
     TRACE_SERIALIZE (this);

     + it
     | hb_apply ([=] (const SubsetGlyph& _) { _.serialize (c, plan); })
     ;

     return_trace (true);
   }

   bool subset (hb_subset_context_t *c) const
   {
     TRACE_SUBSET (this);

     glyf *glyf_prime = c->serializer->start_embed <glyf> ();
     if (unlikely (!c->serializer->check_success (glyf_prime))) return_trace (false);

     // Byte region(s) per glyph to output
     // unpadded, hints removed if so requested
     // If we fail to process a glyph we produce an empty (0-length) glyph
     hb_vector_t<SubsetGlyph> glyphs;
     _populate_subset_glyphs (c->plan, &glyphs);

     glyf_prime->serialize (c->serializer, hb_iter (glyphs), c->plan);

     auto padded_offsets =
     + hb_iter (glyphs)
     | hb_map (&SubsetGlyph::padded_size)
     ;

     if (c->serializer->in_error ()) return_trace (false);
     return_trace (c->serializer->check_success (_add_loca_and_head (c->plan,
 								    padded_offsets)));
   }

   template <typename SubsetGlyph>
   void
   _populate_subset_glyphs (const hb_subset_plan_t * plan,
 			   hb_vector_t<SubsetGlyph> * glyphs /* OUT */) const
   {
     OT::glyf::accelerator_t glyf;
     glyf.init (plan->source);

     + hb_range (plan->num_output_glyphs ())
     | hb_map ([&] (hb_codepoint_t new_gid)
 	      {
 		SubsetGlyph subset_glyph = {0};
 		subset_glyph.new_gid = new_gid;

 		// should never fail: all old gids should be mapped
 		if (!plan->old_gid_for_new_gid (new_gid, &subset_glyph.old_gid))
 		  return subset_glyph;

 		subset_glyph.source_glyph = glyf.bytes_for_glyph ((const char *) this,
 								  subset_glyph.old_gid);
 		if (plan->drop_hints) subset_glyph.drop_hints (glyf);
 		else subset_glyph.dest_start = subset_glyph.source_glyph;

 		return subset_glyph;
 	      })
     | hb_sink (glyphs)
     ;

     glyf.fini ();
   }

   static void
   _fix_component_gids (const hb_subset_plan_t *plan,
 		       hb_bytes_t glyph)
   {
     OT::glyf::CompositeGlyphHeader::Iterator iterator;
     if (OT::glyf::CompositeGlyphHeader::get_iterator (&glyph,
 						      glyph.length,
 						      &iterator))
     {
       do
       {
 	hb_codepoint_t new_gid;
 	if (!plan->new_gid_for_old_gid (iterator.current->glyphIndex,
 					&new_gid))
 	  continue;
 	((OT::glyf::CompositeGlyphHeader *) iterator.current)->glyphIndex = new_gid;
       } while (iterator.move_to_next ());
     }
   }

   static void
   _zero_instruction_length (hb_bytes_t glyph)
   {
     const GlyphHeader &glyph_header = *glyph.as<GlyphHeader> ();
     if (!glyph_header.is_simple_glyph ()) return;  // only for simple glyphs

     unsigned int instruction_len_offset = glyph_header.simple_instruction_len_offset ();
     const HBUINT16 &instruction_len = StructAtOffset<HBUINT16> (&glyph,
 								instruction_len_offset);
     (HBUINT16 &) instruction_len = 0;
   }

   static bool _remove_composite_instruction_flag (hb_bytes_t glyph)
   {
     const GlyphHeader &glyph_header = *glyph.as<GlyphHeader> ();
     if (!glyph_header.is_composite_glyph ()) return true;  // only for composites

     /* remove WE_HAVE_INSTRUCTIONS from flags in dest */
     OT::glyf::CompositeGlyphHeader::Iterator composite_it;
     if (unlikely (!OT::glyf::CompositeGlyphHeader::get_iterator (&glyph, glyph.length,
 								 &composite_it)))
       return false;
     const OT::glyf::CompositeGlyphHeader *composite_header;
     do
     {
       composite_header = composite_it.current;
       OT::HBUINT16 *flags = const_cast<OT::HBUINT16 *> (&composite_header->flags);
       *flags = (uint16_t) *flags & ~OT::glyf::CompositeGlyphHeader::WE_HAVE_INSTRUCTIONS;
     } while (composite_it.move_to_next ());
     return true;
   }

   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 = 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
   {
     unsigned int simple_instruction_len_offset () const
     { return static_size + 2 * numberOfContours; }

     unsigned int simple_length (unsigned int instruction_len) const
     { return simple_instruction_len_offset () + 2 + instruction_len; }

     bool is_composite_glyph () const { return numberOfContours < 0; }
     bool is_simple_glyph () const    { return numberOfContours > 0; }

     void get_extents (hb_glyph_extents_t *extents) const
     {
       extents->x_bearing = hb_min (xMin, xMax);
       extents->y_bearing = hb_max (yMin, yMax);
       extents->width     = hb_max (xMin, xMax) - extents->x_bearing;
       extents->height    = hb_min (yMin, yMax) - extents->y_bearing;
     }

     bool has_data () const { return numberOfContours; }

     protected:
     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. */
     public:
     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;
     GlyphID  glyphIndex;

     unsigned int get_size () const
     {
       unsigned int size = min_size;
       // arg1 and 2 are int16
       if (flags & ARG_1_AND_2_ARE_WORDS) size += 4;
       // arg1 and 2 are int8
       else size += 2;

       // One x 16 bit (scale)
       if (flags & WE_HAVE_A_SCALE) size += 2;
       // Two x 16 bit (xscale, yscale)
       else if (flags & WE_HAVE_AN_X_AND_Y_SCALE) size += 4;
       // Four x 16 bit (xscale, scale01, scale10, yscale)
       else if (flags & WE_HAVE_A_TWO_BY_TWO) size += 8;

       return size;
     }

     // TODO rewrite using new iterator framework if possible
     struct Iterator
     {
       const char *glyph_start;
       const char *glyph_end;
       const CompositeGlyphHeader *current;

       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;
       }

       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 bool get_iterator (const char * glyph_data,
 			      unsigned int length,
 			      CompositeGlyphHeader::Iterator *iterator /* OUT */)
     {
       const GlyphHeader &glyph_header = *hb_bytes_t (glyph_data, length).as<GlyphHeader> ();
       if (!glyph_header.has_data ()) return false; /* Empty glyph; zero extents. */

       if (glyph_header.is_composite_glyph ())
       {
 	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
   {
     void init (hb_face_t *face)
     {
       memset (this, 0, sizeof (accelerator_t));

       const OT::head &head = *face->table.head;
       if (head.indexToLocFormat > 1 || head.glyphDataFormat != 0)
 	/* Unknown format.  Leave num_glyphs=0, that takes care of disabling us. */
 	return;
       short_offset = 0 == head.indexToLocFormat;

       loca_table = hb_sanitize_context_t ().reference_table<loca> (face);
       glyf_table = hb_sanitize_context_t ().reference_table<glyf> (face);

       num_glyphs = hb_max (1u, loca_table.get_length () / (short_offset ? 2 : 4)) - 1;
     }

     void fini ()
     {
       loca_table.destroy ();
       glyf_table.destroy ();
     }

     /*
      * 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.
      */
     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_ON_CURVE = 0x01,
       FLAG_X_SHORT = 0x02,
       FLAG_Y_SHORT = 0x04,
       FLAG_REPEAT = 0x08,
       FLAG_X_SAME = 0x10,
       FLAG_Y_SAME = 0x20,
       FLAG_RESERVED1 = 0x40,
       FLAG_RESERVED2 = 0x80
     };

     /* based on FontTools _g_l_y_f.py::trim */
     bool remove_padding (unsigned int start_offset,
 			 unsigned int *end_offset) const
     {
       const char *glyph = ((const char *) glyf_table) + start_offset;
       unsigned int glyph_length = *end_offset - start_offset;
       const GlyphHeader &glyph_header = *hb_bytes_t (glyph, glyph_length).as<GlyphHeader> ();
       if (!glyph_header.has_data ()) return true;

       const char *glyph_end = glyph + glyph_length;
       if (glyph_header.is_composite_glyph ())
 	/* Trimming for composites not implemented.
 	 * If removing hints it falls out of that. */
 	return true;
       else
       {
 	/* simple glyph w/contours, possibly trimmable */
 	glyph += glyph_header.simple_instruction_len_offset ();

 	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;
     }

     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_table.get_length ())
 	return false;

       return true;
     }

     bool get_instruction_length (hb_bytes_t glyph,
 				 unsigned int * length /* OUT */) const
     {
       const GlyphHeader &glyph_header = *glyph.as<GlyphHeader> ();
       /* Empty glyph; no instructions. */
       if (!glyph_header.has_data ())
       {
 	*length = 0;
 	// only 0 byte glyphs are healthy when missing GlyphHeader
 	return glyph.length == 0;
       }
       if (glyph_header.is_composite_glyph ())
       {
 	unsigned int start = glyph.length;
 	unsigned int end = glyph.length;
 	unsigned int glyph_offset = &glyph - glyf_table;
 	CompositeGlyphHeader::Iterator composite_it;
 	if (unlikely (!CompositeGlyphHeader::get_iterator (&glyph, glyph.length,
 							   &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)
 	  start = ((char *) last - (char *) glyf_table->dataZ.arrayZ)
 		+ last->get_size () - glyph_offset;
 	if (unlikely (start > end))
 	{
 	  DEBUG_MSG (SUBSET, nullptr, "Invalid instruction offset, %d is outside "
 				      "%d byte buffer", start, glyph.length);
 	  return false;
 	}
 	*length = end - start;
       }
       else
       {
 	unsigned int instruction_len_offset = glyph_header.simple_instruction_len_offset ();
 	if (unlikely (instruction_len_offset + 2 > glyph.length))
 	{
 	  DEBUG_MSG (SUBSET, nullptr, "Glyph size is too short, missing field "
 				      "instructionLength.");
 	  return false;
 	}

 	const HBUINT16 &instruction_len = StructAtOffset<HBUINT16> (&glyph,
 								    instruction_len_offset);
 	/* Out of bounds of the current glyph */
 	if (unlikely (glyph_header.simple_length (instruction_len) > glyph.length))
 	{
 	  DEBUG_MSG (SUBSET, nullptr, "The instructions array overruns the "
 				      "glyph's boundaries.");
 	  return false;
 	}
 	*length = (uint16_t) instruction_len;
       }
       return true;
     }

     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;

       hb_bytes_t ((const char *) glyf_table + start_offset,
 		  end_offset - start_offset).as<GlyphHeader> ()->get_extents (extents);
       return true;
     }

     hb_bytes_t bytes_for_glyph (const char *glyf, hb_codepoint_t gid)
     {
       unsigned int start_offset, end_offset;
       if (unlikely (!(get_offsets (gid, &start_offset, &end_offset) &&
 		      remove_padding (start_offset, &end_offset))))
       {
 	DEBUG_MSG (SUBSET, nullptr, "Unable to get offset or remove padding for %d", gid);
 	return hb_bytes_t ();
       }
       hb_bytes_t glyph_bytes = hb_bytes_t (glyf + start_offset, end_offset - start_offset);
       if (!glyph_bytes.as<GlyphHeader> ()->has_data ())
       {
 	DEBUG_MSG (SUBSET, nullptr, "Empty or invalid glyph size, %d", gid);
 	return hb_bytes_t ();
       }
       return glyph_bytes;
     }

     private:
     bool short_offset;
     unsigned int num_glyphs;
     hb_blob_ptr_t<loca> loca_table;
     hb_blob_ptr_t<glyf> glyf_table;
   };

   struct SubsetGlyph
   {
     hb_codepoint_t new_gid;
     hb_codepoint_t old_gid;
     hb_bytes_t source_glyph;
     hb_bytes_t dest_start;  /* region of source_glyph to copy first */
     hb_bytes_t dest_end;    /* region of source_glyph to copy second */

     bool serialize (hb_serialize_context_t *c,
 		    const hb_subset_plan_t *plan) const
     {
       TRACE_SERIALIZE (this);

       hb_bytes_t dest_glyph = dest_start.copy (c);
       dest_glyph = hb_bytes_t (&dest_glyph, dest_glyph.length + dest_end.copy (c).length);
       unsigned int pad_length = padding ();
       DEBUG_MSG (SUBSET, nullptr, "serialize %d byte glyph, width %d pad %d",
 		 dest_glyph.length, dest_glyph.length  + pad_length, pad_length);

       HBUINT8 pad;
       pad = 0;
       while (pad_length > 0)
       {
 	c->embed (pad);
 	pad_length--;
       }

       if (dest_glyph.length)
       {
 	_fix_component_gids (plan, dest_glyph);
 	if (plan->drop_hints)
 	{
 	  _zero_instruction_length (dest_glyph);
 	  c->check_success (_remove_composite_instruction_flag (dest_glyph));
 	}
       }

       return_trace (true);
     }

     void drop_hints (const OT::glyf::accelerator_t& glyf)
     {
       if (source_glyph.length == 0) return;

       unsigned int instruction_len = 0;
       if (!glyf.get_instruction_length (source_glyph, &instruction_len))
       {
 	DEBUG_MSG (SUBSET, nullptr, "Unable to read instruction length for new_gid %d",
 		   new_gid);
 	return ;
       }

       const GlyphHeader& header = *source_glyph.as<GlyphHeader> ();
       DEBUG_MSG (SUBSET, nullptr, "new_gid %d drop %d instruction bytes "
 				  "from %d byte source glyph",
 		 new_gid, instruction_len, source_glyph.length);
       if (header.is_composite_glyph ())
       {
 	/* just chop instructions off the end for composite glyphs */
 	dest_start = hb_bytes_t (&source_glyph, source_glyph.length - instruction_len);
       }
       else
       {
 	unsigned int glyph_length = header.simple_length (instruction_len);
 	dest_start = hb_bytes_t (&source_glyph, glyph_length - instruction_len);
 	dest_end = hb_bytes_t (&source_glyph + glyph_length,
 			       source_glyph.length - glyph_length);
 	DEBUG_MSG (SUBSET, nullptr, "source_len %d start len %d glyph_len %d "
 				    "instruction_len %d end len %d",
 		   source_glyph.length, dest_start.length, glyph_length,
 		   instruction_len, dest_end.length);
       }
     }

     unsigned int length () const      { return dest_start.length + dest_end.length; }
     /* pad to 2 to ensure 2-byte loca will be ok */
     unsigned int padding () const     { return length () % 2; }
     unsigned int padded_size () const { return length () + padding (); }
   };

   protected:
   UnsizedArrayOf<HBUINT8>
 		dataZ;	/* Glyphs data. */
   public:
   DEFINE_SIZE_MIN (0);	/* In reality, this is UNBOUNDED() type; but since we always
 			 * check the size externally, allow Null() object of it by
 			 * defining it _MIN instead. */
 };

 struct glyf_accelerator_t : glyf::accelerator_t {};

 } /* namespace OT */


 #endif /* HB_OT_GLYF_TABLE_HH */
	/*
	* Copyright © 2015 Google, Inc.
	* Copyright © 2019 Ebrahim Byagowi
	*
	* 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, Garret Rieger, Roderick Sheeter
	*/

	#ifndef HB_OT_GLYF_TABLE_HH
	#define HB_OT_GLYF_TABLE_HH

	#include "hb-open-type.hh"
	#include "hb-ot-head-table.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 constexpr hb_tag_t tableTag = HB_OT_TAG_loca;

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

	protected:
	UnsizedArrayOf<HBUINT8>
	dataZ; /* Location data. */
	public:
	DEFINE_SIZE_MIN (0); /* In reality, this is UNBOUNDED() type; but since we always
	* check the size externally, allow Null() object of it by
	* defining it _MIN instead. */
	};


	/*
	* 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 constexpr hb_tag_t tableTag = HB_OT_TAG_glyf;

	bool sanitize (hb_sanitize_context_t *c HB_UNUSED) 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);
	}

	template<typename Iterator,
	hb_requires (hb_is_source_of (Iterator, unsigned int))>
	static bool
	_add_loca_and_head (hb_subset_plan_t * plan, Iterator padded_offsets)
	{
	unsigned max_offset = + padded_offsets \| hb_reduce(hb_add, 0);
	unsigned num_offsets = padded_offsets.len () + 1;
	bool use_short_loca = max_offset < 0x1FFFF;
	unsigned entry_size = use_short_loca ? 2 : 4;
	char loca_prime_data = (char ) calloc (entry_size, num_offsets);

	if (unlikely (!loca_prime_data)) return false;

	DEBUG_MSG (SUBSET, nullptr, "loca entry_size %d num_offsets %d "
	"max_offset %d size %d",
	entry_size, num_offsets, max_offset, entry_size * num_offsets);

	if (use_short_loca)
	_write_loca (padded_offsets, 1, hb_array ((HBUINT16*) loca_prime_data, num_offsets));
	else
	_write_loca (padded_offsets, 0, hb_array ((HBUINT32*) loca_prime_data, num_offsets));

	hb_blob_t * loca_blob = hb_blob_create (loca_prime_data,
	entry_size * num_offsets,
	HB_MEMORY_MODE_WRITABLE,
	loca_prime_data,
	free);

	bool result = plan->add_table (HB_OT_TAG_loca, loca_blob)
	&& _add_head_and_set_loca_version(plan, use_short_loca);

	hb_blob_destroy (loca_blob);
	return result;
	}

	template<typename IteratorIn, typename IteratorOut,
	hb_requires (hb_is_source_of (IteratorIn, unsigned int)),
	hb_requires (hb_is_sink_of (IteratorOut, unsigned))>
	static void
	_write_loca (IteratorIn it, unsigned right_shift, IteratorOut dest)
	{
	unsigned int offset = 0;
	dest << 0;
	+ it
	\| hb_map ([=, &offset] (unsigned int padded_size)
	{
	offset += padded_size;
	DEBUG_MSG (SUBSET, nullptr, "loca entry offset %d", offset);
	return offset >> right_shift;
	})
	\| hb_sink (dest)
	;
	}

	// requires source of SubsetGlyph complains the identifier isn't declared
	template <typename Iterator>
	bool serialize (hb_serialize_context_t *c,
	Iterator it,
	const hb_subset_plan_t *plan)
	{
	TRACE_SERIALIZE (this);

	+ it
	\| hb_apply ([=] (const SubsetGlyph& _) { _.serialize (c, plan); })
	;

	return_trace (true);
	}

	bool subset (hb_subset_context_t *c) const
	{
	TRACE_SUBSET (this);

	glyf *glyf_prime = c->serializer->start_embed <glyf> ();
	if (unlikely (!c->serializer->check_success (glyf_prime))) return_trace (false);

	// Byte region(s) per glyph to output
	// unpadded, hints removed if so requested
	// If we fail to process a glyph we produce an empty (0-length) glyph
	hb_vector_t<SubsetGlyph> glyphs;
	_populate_subset_glyphs (c->plan, &glyphs);

	glyf_prime->serialize (c->serializer, hb_iter (glyphs), c->plan);

	auto padded_offsets =
	+ hb_iter (glyphs)
	\| hb_map (&SubsetGlyph::padded_size)
	;

	if (c->serializer->in_error ()) return_trace (false);
	return_trace (c->serializer->check_success (_add_loca_and_head (c->plan,
	padded_offsets)));
	}

	template <typename SubsetGlyph>
	void
	_populate_subset_glyphs (const hb_subset_plan_t * plan,
	hb_vector_t<SubsetGlyph> * glyphs /* OUT */) const
	{
	OT::glyf::accelerator_t glyf;
	glyf.init (plan->source);

	+ hb_range (plan->num_output_glyphs ())
	\| hb_map ([&] (hb_codepoint_t new_gid)
	{
	SubsetGlyph subset_glyph = {0};
	subset_glyph.new_gid = new_gid;

	// should never fail: all old gids should be mapped
	if (!plan->old_gid_for_new_gid (new_gid, &subset_glyph.old_gid))
	return subset_glyph;

	subset_glyph.source_glyph = glyf.bytes_for_glyph ((const char *) this,
	subset_glyph.old_gid);
	if (plan->drop_hints) subset_glyph.drop_hints (glyf);
	else subset_glyph.dest_start = subset_glyph.source_glyph;

	return subset_glyph;
	})
	\| hb_sink (glyphs)
	;

	glyf.fini ();
	}

	static void
	_fix_component_gids (const hb_subset_plan_t *plan,
	hb_bytes_t glyph)
	{
	OT::glyf::CompositeGlyphHeader::Iterator iterator;
	if (OT::glyf::CompositeGlyphHeader::get_iterator (&glyph,
	glyph.length,
	&iterator))
	{
	do
	{
	hb_codepoint_t new_gid;
	if (!plan->new_gid_for_old_gid (iterator.current->glyphIndex,
	&new_gid))
	continue;
	((OT::glyf::CompositeGlyphHeader *) iterator.current)->glyphIndex = new_gid;
	} while (iterator.move_to_next ());
	}
	}

	static void
	_zero_instruction_length (hb_bytes_t glyph)
	{
	const GlyphHeader &glyph_header = *glyph.as<GlyphHeader> ();
	if (!glyph_header.is_simple_glyph ()) return; // only for simple glyphs

	unsigned int instruction_len_offset = glyph_header.simple_instruction_len_offset ();
	const HBUINT16 &instruction_len = StructAtOffset<HBUINT16> (&glyph,
	instruction_len_offset);
	(HBUINT16 &) instruction_len = 0;
	}

	static bool _remove_composite_instruction_flag (hb_bytes_t glyph)
	{
	const GlyphHeader &glyph_header = *glyph.as<GlyphHeader> ();
	if (!glyph_header.is_composite_glyph ()) return true; // only for composites

	/* remove WE_HAVE_INSTRUCTIONS from flags in dest */
	OT::glyf::CompositeGlyphHeader::Iterator composite_it;
	if (unlikely (!OT::glyf::CompositeGlyphHeader::get_iterator (&glyph, glyph.length,
	&composite_it)))
	return false;
	const OT::glyf::CompositeGlyphHeader *composite_header;
	do
	{
	composite_header = composite_it.current;
	OT::HBUINT16 flags = const_cast<OT::HBUINT16 > (&composite_header->flags);
	flags = (uint16_t) flags & ~OT::glyf::CompositeGlyphHeader::WE_HAVE_INSTRUCTIONS;
	} while (composite_it.move_to_next ());
	return true;
	}

	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 = 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
	{
	unsigned int simple_instruction_len_offset () const
	{ return static_size + 2 * numberOfContours; }

	unsigned int simple_length (unsigned int instruction_len) const
	{ return simple_instruction_len_offset () + 2 + instruction_len; }

	bool is_composite_glyph () const { return numberOfContours < 0; }
	bool is_simple_glyph () const { return numberOfContours > 0; }

	void get_extents (hb_glyph_extents_t *extents) const
	{
	extents->x_bearing = hb_min (xMin, xMax);
	extents->y_bearing = hb_max (yMin, yMax);
	extents->width = hb_max (xMin, xMax) - extents->x_bearing;
	extents->height = hb_min (yMin, yMax) - extents->y_bearing;
	}

	bool has_data () const { return numberOfContours; }

	protected:
	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. */
	public:
	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;
	GlyphID glyphIndex;

	unsigned int get_size () const
	{
	unsigned int size = min_size;
	// arg1 and 2 are int16
	if (flags & ARG_1_AND_2_ARE_WORDS) size += 4;
	// arg1 and 2 are int8
	else size += 2;

	// One x 16 bit (scale)
	if (flags & WE_HAVE_A_SCALE) size += 2;
	// Two x 16 bit (xscale, yscale)
	else if (flags & WE_HAVE_AN_X_AND_Y_SCALE) size += 4;
	// Four x 16 bit (xscale, scale01, scale10, yscale)
	else if (flags & WE_HAVE_A_TWO_BY_TWO) size += 8;

	return size;
	}

	// TODO rewrite using new iterator framework if possible
	struct Iterator
	{
	const char *glyph_start;
	const char *glyph_end;
	const CompositeGlyphHeader *current;

	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;
	}

	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 bool get_iterator (const char * glyph_data,
	unsigned int length,
	CompositeGlyphHeader::Iterator iterator / OUT */)
	{
	const GlyphHeader &glyph_header = *hb_bytes_t (glyph_data, length).as<GlyphHeader> ();
	if (!glyph_header.has_data ()) return false; /* Empty glyph; zero extents. */

	if (glyph_header.is_composite_glyph ())
	{
	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
	{
	void init (hb_face_t *face)
	{
	memset (this, 0, sizeof (accelerator_t));

	const OT::head &head = *face->table.head;
	if (head.indexToLocFormat > 1 \|\| head.glyphDataFormat != 0)
	/* Unknown format. Leave num_glyphs=0, that takes care of disabling us. */
	return;
	short_offset = 0 == head.indexToLocFormat;

	loca_table = hb_sanitize_context_t ().reference_table<loca> (face);
	glyf_table = hb_sanitize_context_t ().reference_table<glyf> (face);

	num_glyphs = hb_max (1u, loca_table.get_length () / (short_offset ? 2 : 4)) - 1;
	}

	void fini ()
	{
	loca_table.destroy ();
	glyf_table.destroy ();
	}

	/*
	* 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.
	*/
	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_ON_CURVE = 0x01,
	FLAG_X_SHORT = 0x02,
	FLAG_Y_SHORT = 0x04,
	FLAG_REPEAT = 0x08,
	FLAG_X_SAME = 0x10,
	FLAG_Y_SAME = 0x20,
	FLAG_RESERVED1 = 0x40,
	FLAG_RESERVED2 = 0x80
	};

	/* based on FontTools _g_l_y_f.py::trim */
	bool remove_padding (unsigned int start_offset,
	unsigned int *end_offset) const
	{
	const char glyph = ((const char ) glyf_table) + start_offset;
	unsigned int glyph_length = *end_offset - start_offset;
	const GlyphHeader &glyph_header = *hb_bytes_t (glyph, glyph_length).as<GlyphHeader> ();
	if (!glyph_header.has_data ()) return true;

	const char *glyph_end = glyph + glyph_length;
	if (glyph_header.is_composite_glyph ())
	/* Trimming for composites not implemented.
	* If removing hints it falls out of that. */
	return true;
	else
	{
	/* simple glyph w/contours, possibly trimmable */
	glyph += glyph_header.simple_instruction_len_offset ();

	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;
	}

	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_table.get_length ())
	return false;

	return true;
	}

	bool get_instruction_length (hb_bytes_t glyph,
	unsigned int * length /* OUT */) const
	{
	const GlyphHeader &glyph_header = *glyph.as<GlyphHeader> ();
	/* Empty glyph; no instructions. */
	if (!glyph_header.has_data ())
	{
	*length = 0;
	// only 0 byte glyphs are healthy when missing GlyphHeader
	return glyph.length == 0;
	}
	if (glyph_header.is_composite_glyph ())
	{
	unsigned int start = glyph.length;
	unsigned int end = glyph.length;
	unsigned int glyph_offset = &glyph - glyf_table;
	CompositeGlyphHeader::Iterator composite_it;
	if (unlikely (!CompositeGlyphHeader::get_iterator (&glyph, glyph.length,
	&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)
	start = ((char ) last - (char ) glyf_table->dataZ.arrayZ)
	+ last->get_size () - glyph_offset;
	if (unlikely (start > end))
	{
	DEBUG_MSG (SUBSET, nullptr, "Invalid instruction offset, %d is outside "
	"%d byte buffer", start, glyph.length);
	return false;
	}
	*length = end - start;
	}
	else
	{
	unsigned int instruction_len_offset = glyph_header.simple_instruction_len_offset ();
	if (unlikely (instruction_len_offset + 2 > glyph.length))
	{
	DEBUG_MSG (SUBSET, nullptr, "Glyph size is too short, missing field "
	"instructionLength.");
	return false;
	}

	const HBUINT16 &instruction_len = StructAtOffset<HBUINT16> (&glyph,
	instruction_len_offset);
	/* Out of bounds of the current glyph */
	if (unlikely (glyph_header.simple_length (instruction_len) > glyph.length))
	{
	DEBUG_MSG (SUBSET, nullptr, "The instructions array overruns the "
	"glyph's boundaries.");
	return false;
	}
	*length = (uint16_t) instruction_len;
	}
	return true;
	}

	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;

	hb_bytes_t ((const char *) glyf_table + start_offset,
	end_offset - start_offset).as<GlyphHeader> ()->get_extents (extents);
	return true;
	}

	hb_bytes_t bytes_for_glyph (const char *glyf, hb_codepoint_t gid)
	{
	unsigned int start_offset, end_offset;
	if (unlikely (!(get_offsets (gid, &start_offset, &end_offset) &&
	remove_padding (start_offset, &end_offset))))
	{
	DEBUG_MSG (SUBSET, nullptr, "Unable to get offset or remove padding for %d", gid);
	return hb_bytes_t ();
	}
	hb_bytes_t glyph_bytes = hb_bytes_t (glyf + start_offset, end_offset - start_offset);
	if (!glyph_bytes.as<GlyphHeader> ()->has_data ())
	{
	DEBUG_MSG (SUBSET, nullptr, "Empty or invalid glyph size, %d", gid);
	return hb_bytes_t ();
	}
	return glyph_bytes;
	}

	private:
	bool short_offset;
	unsigned int num_glyphs;
	hb_blob_ptr_t<loca> loca_table;
	hb_blob_ptr_t<glyf> glyf_table;
	};

	struct SubsetGlyph
	{
	hb_codepoint_t new_gid;
	hb_codepoint_t old_gid;
	hb_bytes_t source_glyph;
	hb_bytes_t dest_start; /* region of source_glyph to copy first */
	hb_bytes_t dest_end; /* region of source_glyph to copy second */

	bool serialize (hb_serialize_context_t *c,
	const hb_subset_plan_t *plan) const
	{
	TRACE_SERIALIZE (this);

	hb_bytes_t dest_glyph = dest_start.copy (c);
	dest_glyph = hb_bytes_t (&dest_glyph, dest_glyph.length + dest_end.copy (c).length);
	unsigned int pad_length = padding ();
	DEBUG_MSG (SUBSET, nullptr, "serialize %d byte glyph, width %d pad %d",
	dest_glyph.length, dest_glyph.length + pad_length, pad_length);

	HBUINT8 pad;
	pad = 0;
	while (pad_length > 0)
	{
	c->embed (pad);
	pad_length--;
	}

	if (dest_glyph.length)
	{
	_fix_component_gids (plan, dest_glyph);
	if (plan->drop_hints)
	{
	_zero_instruction_length (dest_glyph);
	c->check_success (_remove_composite_instruction_flag (dest_glyph));
	}
	}

	return_trace (true);
	}

	void drop_hints (const OT::glyf::accelerator_t& glyf)
	{
	if (source_glyph.length == 0) return;

	unsigned int instruction_len = 0;
	if (!glyf.get_instruction_length (source_glyph, &instruction_len))
	{
	DEBUG_MSG (SUBSET, nullptr, "Unable to read instruction length for new_gid %d",
	new_gid);
	return ;
	}

	const GlyphHeader& header = *source_glyph.as<GlyphHeader> ();
	DEBUG_MSG (SUBSET, nullptr, "new_gid %d drop %d instruction bytes "
	"from %d byte source glyph",
	new_gid, instruction_len, source_glyph.length);
	if (header.is_composite_glyph ())
	{
	/* just chop instructions off the end for composite glyphs */
	dest_start = hb_bytes_t (&source_glyph, source_glyph.length - instruction_len);
	}
	else
	{
	unsigned int glyph_length = header.simple_length (instruction_len);
	dest_start = hb_bytes_t (&source_glyph, glyph_length - instruction_len);
	dest_end = hb_bytes_t (&source_glyph + glyph_length,
	source_glyph.length - glyph_length);
	DEBUG_MSG (SUBSET, nullptr, "source_len %d start len %d glyph_len %d "
	"instruction_len %d end len %d",
	source_glyph.length, dest_start.length, glyph_length,
	instruction_len, dest_end.length);
	}
	}

	unsigned int length () const { return dest_start.length + dest_end.length; }
	/* pad to 2 to ensure 2-byte loca will be ok */
	unsigned int padding () const { return length () % 2; }
	unsigned int padded_size () const { return length () + padding (); }
	};

	protected:
	UnsizedArrayOf<HBUINT8>
	dataZ; /* Glyphs data. */
	public:
	DEFINE_SIZE_MIN (0); /* In reality, this is UNBOUNDED() type; but since we always
	* check the size externally, allow Null() object of it by
	* defining it _MIN instead. */
	};

	struct glyf_accelerator_t : glyf::accelerator_t {};

	} /* namespace OT */


	#endif /* HB_OT_GLYF_TABLE_HH */