hb-ot-layout-gsubgpos.hh

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/*

 * Copyright © 2007,2008,2009,2010  Red Hat, Inc.

 * Copyright © 2010,2012  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.

 * Red Hat Author(s): Behdad Esfahbod

 * Google Author(s): Behdad Esfahbod

*/

#ifndef HB_OT_LAYOUT_GSUBGPOS_HH

#define HB_OT_LAYOUT_GSUBGPOS_HH

#include "hb.hh"

#include "hb-buffer.hh"

#include "hb-map.hh"

#include "hb-set.hh"

#include "hb-ot-map.hh"

#include "hb-ot-layout-common.hh"

#include "hb-ot-layout-gdef-table.hh"

namespace OT {

struct hb_intersects_context_t :

       hb_dispatch_context_t<hb_intersects_context_t, bool>

  template <typename T>

  return_t dispatch (const T &obj) { return obj.intersects (this->glyphs); }

  static return_t default_return_value () { return false; }

  bool stop_sublookup_iteration (return_t r) const { return r; }

  const hb_set_t *glyphs;

  hb_intersects_context_t (const hb_set_t *glyphs_) :

                            glyphs (glyphs_) {}

};

struct hb_have_non_1to1_context_t :

       hb_dispatch_context_t<hb_have_non_1to1_context_t, bool>

  template <typename T>

  return_t dispatch (const T &obj) { return obj.may_have_non_1to1 (); }

  static return_t default_return_value () { return false; }

  bool stop_sublookup_iteration (return_t r) const { return r; }

};

struct hb_closure_context_t :

       hb_dispatch_context_t<hb_closure_context_t>

  typedef return_t (*recurse_func_t) (hb_closure_context_t *c, unsigned lookup_index, hb_set_t *covered_seq_indicies, unsigned seq_index, unsigned end_index);

  template <typename T>

  return_t dispatch (const T &obj) { obj.closure (this); return hb_empty_t (); }

  static return_t default_return_value () { return hb_empty_t (); }

  void recurse (unsigned lookup_index, hb_set_t *covered_seq_indicies, unsigned seq_index, unsigned end_index)

    if (unlikely (nesting_level_left == 0 || !recurse_func))

      return;

    nesting_level_left--;

    recurse_func (this, lookup_index, covered_seq_indicies, seq_index, end_index);

    nesting_level_left++;

  void reset_lookup_visit_count ()

  { lookup_count = 0; }

  bool lookup_limit_exceeded ()

  { return lookup_count > HB_MAX_LOOKUP_VISIT_COUNT; }

  bool should_visit_lookup (unsigned int lookup_index)

    if (lookup_count++ > HB_MAX_LOOKUP_VISIT_COUNT)

      return false;

    if (is_lookup_done (lookup_index))

      return false;

    return true;

  bool is_lookup_done (unsigned int lookup_index)

    if (unlikely (done_lookups_glyph_count->in_error () ||

		  done_lookups_glyph_set->in_error ()))

      return true;

    /* Have we visited this lookup with the current set of glyphs? */

    if (done_lookups_glyph_count->get (lookup_index) != glyphs->get_population ())

      done_lookups_glyph_count->set (lookup_index, glyphs->get_population ());

      if (!done_lookups_glyph_set->has (lookup_index))

	if (unlikely (!done_lookups_glyph_set->set (lookup_index, hb::unique_ptr<hb_set_t> {hb_set_create ()})))

	  return true;

      done_lookups_glyph_set->get (lookup_index)->clear ();

    hb_set_t *covered_glyph_set = done_lookups_glyph_set->get (lookup_index);

    if (unlikely (covered_glyph_set->in_error ()))

      return true;

    if (parent_active_glyphs ().is_subset (*covered_glyph_set))

      return true;

    covered_glyph_set->union_ (parent_active_glyphs ());

    return false;

  const hb_set_t& previous_parent_active_glyphs () {

    if (active_glyphs_stack.length <= 1)

      return *glyphs;

    return active_glyphs_stack[active_glyphs_stack.length - 2];

  const hb_set_t& parent_active_glyphs ()

    if (!active_glyphs_stack)

      return *glyphs;

    return active_glyphs_stack.tail ();

  hb_set_t* push_cur_active_glyphs ()

    hb_set_t *s = active_glyphs_stack.push ();

    if (unlikely (active_glyphs_stack.in_error ()))

      return nullptr;

    return s;

  bool pop_cur_done_glyphs ()

    if (!active_glyphs_stack)

      return false;

    active_glyphs_stack.pop ();

    return true;

  hb_face_t *face;

  hb_set_t *glyphs;

  hb_set_t output[1];

  hb_vector_t<hb_set_t> active_glyphs_stack;

  recurse_func_t recurse_func = nullptr;

  unsigned int nesting_level_left;

  hb_closure_context_t (hb_face_t *face_,

			hb_set_t *glyphs_,

			hb_map_t *done_lookups_glyph_count_,

			hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *done_lookups_glyph_set_,

			unsigned int nesting_level_left_ = HB_MAX_NESTING_LEVEL) :

			  face (face_),

			  glyphs (glyphs_),

			  nesting_level_left (nesting_level_left_),

			  done_lookups_glyph_count (done_lookups_glyph_count_),

			  done_lookups_glyph_set (done_lookups_glyph_set_)

{}

  ~hb_closure_context_t () { flush (); }

  void set_recurse_func (recurse_func_t func) { recurse_func = func; }

  void flush ()

    output->del_range (face->get_num_glyphs (), HB_SET_VALUE_INVALID);	/* Remove invalid glyphs. */

    glyphs->union_ (*output);

    output->clear ();

    active_glyphs_stack.pop ();

    active_glyphs_stack.reset ();

  private:

  hb_map_t *done_lookups_glyph_count;

  hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *done_lookups_glyph_set;

  unsigned int lookup_count = 0;

};

struct hb_closure_lookups_context_t :

       hb_dispatch_context_t<hb_closure_lookups_context_t>

  typedef return_t (*recurse_func_t) (hb_closure_lookups_context_t *c, unsigned lookup_index);

  template <typename T>

  return_t dispatch (const T &obj) { obj.closure_lookups (this); return hb_empty_t (); }

  static return_t default_return_value () { return hb_empty_t (); }

  void recurse (unsigned lookup_index)

    if (unlikely (nesting_level_left == 0 || !recurse_func))

      return;

    /* Return if new lookup was recursed to before. */

    if (lookup_limit_exceeded ()

        || visited_lookups->in_error ()

        || visited_lookups->has (lookup_index))

      // Don't increment lookup count here, that will be done in the call to closure_lookups()

      // made by recurse_func.

      return;

    nesting_level_left--;

    recurse_func (this, lookup_index);

    nesting_level_left++;

  void set_lookup_visited (unsigned lookup_index)

  { visited_lookups->add (lookup_index); }

  void set_lookup_inactive (unsigned lookup_index)

  { inactive_lookups->add (lookup_index); }

  bool lookup_limit_exceeded ()

    bool ret = lookup_count > HB_MAX_LOOKUP_VISIT_COUNT;

    if (ret)

      DEBUG_MSG (SUBSET, nullptr, "lookup visit count limit exceeded in lookup closure!");

    return ret; }

  bool is_lookup_visited (unsigned lookup_index)

    if (unlikely (lookup_count++ > HB_MAX_LOOKUP_VISIT_COUNT))

      DEBUG_MSG (SUBSET, nullptr, "total visited lookup count %u exceeds max limit, lookup %u is dropped.",

                 lookup_count, lookup_index);

      return true;

    if (unlikely (visited_lookups->in_error ()))

      return true;

    return visited_lookups->has (lookup_index);

  hb_face_t *face;

  const hb_set_t *glyphs;

  recurse_func_t recurse_func;

  unsigned int nesting_level_left;

  hb_closure_lookups_context_t (hb_face_t *face_,

				const hb_set_t *glyphs_,

				hb_set_t *visited_lookups_,

				hb_set_t *inactive_lookups_,

				unsigned nesting_level_left_ = HB_MAX_NESTING_LEVEL) :

				face (face_),

				glyphs (glyphs_),

				recurse_func (nullptr),

				nesting_level_left (nesting_level_left_),

				visited_lookups (visited_lookups_),

				inactive_lookups (inactive_lookups_),

				lookup_count (0) {}

  void set_recurse_func (recurse_func_t func) { recurse_func = func; }

  private:

  hb_set_t *visited_lookups;

  hb_set_t *inactive_lookups;

  unsigned int lookup_count;

};

struct hb_would_apply_context_t :

       hb_dispatch_context_t<hb_would_apply_context_t, bool>

  template <typename T>

  return_t dispatch (const T &obj) { return obj.would_apply (this); }

  static return_t default_return_value () { return false; }

  bool stop_sublookup_iteration (return_t r) const { return r; }

  hb_face_t *face;

  const hb_codepoint_t *glyphs;

  unsigned int len;

  bool zero_context;

  hb_would_apply_context_t (hb_face_t *face_,

			    const hb_codepoint_t *glyphs_,

			    unsigned int len_,

			    bool zero_context_) :

			      face (face_),

			      glyphs (glyphs_),

			      len (len_),

			      zero_context (zero_context_) {}

};

struct hb_collect_glyphs_context_t :

       hb_dispatch_context_t<hb_collect_glyphs_context_t>

  typedef return_t (*recurse_func_t) (hb_collect_glyphs_context_t *c, unsigned int lookup_index);

  template <typename T>

  return_t dispatch (const T &obj) { obj.collect_glyphs (this); return hb_empty_t (); }

  static return_t default_return_value () { return hb_empty_t (); }

  void recurse (unsigned int lookup_index)

    if (unlikely (nesting_level_left == 0 || !recurse_func))

      return;

    /* Note that GPOS sets recurse_func to nullptr already, so it doesn't get

     * past the previous check.  For GSUB, we only want to collect the output

     * glyphs in the recursion.  If output is not requested, we can go home now.

     * Note further, that the above is not exactly correct.  A recursed lookup

     * is allowed to match input that is not matched in the context, but that's

     * not how most fonts are built.  It's possible to relax that and recurse

     * with all sets here if it proves to be an issue.

*/

    if (output == hb_set_get_empty ())

      return;

    /* Return if new lookup was recursed to before. */

    if (recursed_lookups->has (lookup_index))

      return;

    hb_set_t *old_before = before;

    hb_set_t *old_input  = input;

    hb_set_t *old_after  = after;

    before = input = after = hb_set_get_empty ();

    nesting_level_left--;

    recurse_func (this, lookup_index);

    nesting_level_left++;

    before = old_before;

    input  = old_input;

    after  = old_after;

    recursed_lookups->add (lookup_index);

  hb_face_t *face;

  hb_set_t *before;

  hb_set_t *input;

  hb_set_t *after;

  hb_set_t *output;

  recurse_func_t recurse_func;

  hb_set_t *recursed_lookups;

  unsigned int nesting_level_left;

  hb_collect_glyphs_context_t (hb_face_t *face_,

			       hb_set_t  *glyphs_before, /* OUT.  May be NULL */

			       hb_set_t  *glyphs_input,  /* OUT.  May be NULL */

			       hb_set_t  *glyphs_after,  /* OUT.  May be NULL */

			       hb_set_t  *glyphs_output, /* OUT.  May be NULL */

			       unsigned int nesting_level_left_ = HB_MAX_NESTING_LEVEL) :

			      face (face_),

			      before (glyphs_before ? glyphs_before : hb_set_get_empty ()),

			      input  (glyphs_input  ? glyphs_input  : hb_set_get_empty ()),

			      after  (glyphs_after  ? glyphs_after  : hb_set_get_empty ()),

			      output (glyphs_output ? glyphs_output : hb_set_get_empty ()),

			      recurse_func (nullptr),

			      recursed_lookups (hb_set_create ()),

			      nesting_level_left (nesting_level_left_) {}

  ~hb_collect_glyphs_context_t () { hb_set_destroy (recursed_lookups); }

  void set_recurse_func (recurse_func_t func) { recurse_func = func; }

};

template <typename set_t>

struct hb_collect_coverage_context_t :

       hb_dispatch_context_t<hb_collect_coverage_context_t<set_t>, const Coverage &>

  typedef const Coverage &return_t; // Stoopid that we have to dupe this here.

  template <typename T>

  return_t dispatch (const T &obj) { return obj.get_coverage (); }

  static return_t default_return_value () { return Null (Coverage); }

  bool stop_sublookup_iteration (return_t r) const

    r.collect_coverage (set);

    return false;

  hb_collect_coverage_context_t (set_t *set_) :

				   set (set_) {}

  set_t *set;

};

struct hb_ot_apply_context_t :

       hb_dispatch_context_t<hb_ot_apply_context_t, bool, HB_DEBUG_APPLY>

  struct matcher_t

    typedef bool (*match_func_t) (hb_glyph_info_t &info, unsigned value, const void *data);

    void set_ignore_zwnj (bool ignore_zwnj_) { ignore_zwnj = ignore_zwnj_; }

    void set_ignore_zwj (bool ignore_zwj_) { ignore_zwj = ignore_zwj_; }

    void set_ignore_hidden (bool ignore_hidden_) { ignore_hidden = ignore_hidden_; }

    void set_lookup_props (unsigned int lookup_props_) { lookup_props = lookup_props_; }

    void set_mask (hb_mask_t mask_) { mask = mask_; }

    void set_per_syllable (bool per_syllable_) { per_syllable = per_syllable_; }

    void set_syllable (uint8_t syllable_)  { syllable = per_syllable ? syllable_ : 0; }

    void set_match_func (match_func_t match_func_,

			 const void *match_data_)

    { match_func = match_func_; match_data = match_data_; }

    enum may_match_t {

      MATCH_NO,

      MATCH_YES,

      MATCH_MAYBE

};

#ifndef HB_OPTIMIZE_SIZE

    HB_ALWAYS_INLINE

#endif

    may_match_t may_match (hb_glyph_info_t &info,

			   hb_codepoint_t glyph_data) const

      if (!(info.mask & mask) ||

	  (syllable && syllable != info.syllable ()))

	return MATCH_NO;

      if (match_func)

	return match_func (info, glyph_data, match_data) ? MATCH_YES : MATCH_NO;

      return MATCH_MAYBE;

    enum may_skip_t {

      SKIP_NO,

      SKIP_YES,

      SKIP_MAYBE

};

#ifndef HB_OPTIMIZE_SIZE

    HB_ALWAYS_INLINE

#endif

    may_skip_t may_skip (const hb_ot_apply_context_t *c,

			 const hb_glyph_info_t       &info) const

      if (!c->check_glyph_property (&info, lookup_props))

	return SKIP_YES;

      if (unlikely (_hb_glyph_info_is_default_ignorable (&info) &&

		    (ignore_zwnj || !_hb_glyph_info_is_zwnj (&info)) &&

		    (ignore_zwj || !_hb_glyph_info_is_zwj (&info)) &&

		    (ignore_hidden || !_hb_glyph_info_is_hidden (&info))))

	return SKIP_MAYBE;

      return SKIP_NO;

    protected:

    unsigned int lookup_props = 0;

    hb_mask_t mask = -1;

    bool ignore_zwnj = false;

    bool ignore_zwj = false;

    bool ignore_hidden = false;

    bool per_syllable = false;

    uint8_t syllable = 0;

    match_func_t match_func = nullptr;

    const void *match_data = nullptr;

};

  struct skipping_iterator_t

    void init (hb_ot_apply_context_t *c_, bool context_match = false)

      c = c_;

      end = c->buffer->len;

      match_glyph_data16 = nullptr;

#ifndef HB_NO_BEYOND_64K

      match_glyph_data24 = nullptr;

#endif

      matcher.set_match_func (nullptr, nullptr);

      matcher.set_lookup_props (c->lookup_props);

      /* Ignore ZWNJ if we are matching GPOS, or matching GSUB context and asked to. */

      matcher.set_ignore_zwnj (c->table_index == 1 || (context_match && c->auto_zwnj));

      /* Ignore ZWJ if we are matching context, or asked to. */

      matcher.set_ignore_zwj  (context_match || c->auto_zwj);

      /* Ignore hidden glyphs (like CGJ) during GPOS. */

      matcher.set_ignore_hidden (c->table_index == 1);

      matcher.set_mask (context_match ? -1 : c->lookup_mask);

      /* Per syllable matching is only for GSUB. */

      matcher.set_per_syllable (c->table_index == 0 && c->per_syllable);

      matcher.set_syllable (0);

    void set_lookup_props (unsigned int lookup_props)

      matcher.set_lookup_props (lookup_props);

    void set_match_func (matcher_t::match_func_t match_func_,

			 const void *match_data_)

      matcher.set_match_func (match_func_, match_data_);

    void set_glyph_data (const HBUINT16 glyph_data[])

      match_glyph_data16 = glyph_data;

#ifndef HB_NO_BEYOND_64K

      match_glyph_data24 = nullptr;

#endif

#ifndef HB_NO_BEYOND_64K

    void set_glyph_data (const HBUINT24 glyph_data[])

      match_glyph_data16 = nullptr;

      match_glyph_data24 = glyph_data;

#endif

#ifndef HB_OPTIMIZE_SIZE

    HB_ALWAYS_INLINE

#endif

    void reset (unsigned int start_index_)

      idx = start_index_;

      end = c->buffer->len;

      matcher.set_syllable (start_index_ == c->buffer->idx ? c->buffer->cur().syllable () : 0);

#ifndef HB_OPTIMIZE_SIZE

    HB_ALWAYS_INLINE

#endif

    void reset_fast (unsigned int start_index_)

      // Doesn't set end or syllable. Used by GPOS which doesn't care / change.

      idx = start_index_;

    void reject ()

      backup_glyph_data ();

    matcher_t::may_skip_t

#ifndef HB_OPTIMIZE_SIZE

    HB_ALWAYS_INLINE

#endif

    may_skip (const hb_glyph_info_t &info) const

    { return matcher.may_skip (c, info); }

    enum match_t {

      MATCH,

      NOT_MATCH,

      SKIP

};

#ifndef HB_OPTIMIZE_SIZE

    HB_ALWAYS_INLINE

#endif

    match_t match (hb_glyph_info_t &info)

      matcher_t::may_skip_t skip = matcher.may_skip (c, info);

      if (unlikely (skip == matcher_t::SKIP_YES))

	return SKIP;

      matcher_t::may_match_t match = matcher.may_match (info, get_glyph_data ());

      if (match == matcher_t::MATCH_YES ||

	  (match == matcher_t::MATCH_MAYBE &&

	   skip == matcher_t::SKIP_NO))

	return MATCH;

      if (skip == matcher_t::SKIP_NO)

        return NOT_MATCH;

      return SKIP;

#ifndef HB_OPTIMIZE_SIZE

    HB_ALWAYS_INLINE

#endif

    bool next (unsigned *unsafe_to = nullptr)

      const signed stop = (signed) end - 1;

      while ((signed) idx < stop)

	idx++;

	switch (match (c->buffer->info[idx]))

	  case MATCH:

	    advance_glyph_data ();

	    return true;

	  case NOT_MATCH:

	    if (unsafe_to)

	      *unsafe_to = idx + 1;

	    return false;

	  case SKIP:

	    continue;

      if (unsafe_to)

        *unsafe_to = end;

      return false;

#ifndef HB_OPTIMIZE_SIZE

    HB_ALWAYS_INLINE

#endif

    bool prev (unsigned *unsafe_from = nullptr)

      const unsigned stop = 0;

      while (idx > stop)

	idx--;

	switch (match (c->buffer->out_info[idx]))

	  case MATCH:

	    advance_glyph_data ();

	    return true;

	  case NOT_MATCH:

	    if (unsafe_from)

	      *unsafe_from = hb_max (1u, idx) - 1u;

	    return false;

	  case SKIP:

	    continue;

      if (unsafe_from)

        *unsafe_from = 0;

      return false;

    HB_ALWAYS_INLINE

    hb_codepoint_t

    get_glyph_data ()

      if (match_glyph_data16) return *match_glyph_data16;

#ifndef HB_NO_BEYOND_64K

      else

      if (match_glyph_data24) return *match_glyph_data24;

#endif

      return 0;

    HB_ALWAYS_INLINE

    void

    advance_glyph_data ()

      if (match_glyph_data16) match_glyph_data16++;

#ifndef HB_NO_BEYOND_64K

      else

      if (match_glyph_data24) match_glyph_data24++;

#endif

    void

    backup_glyph_data ()

      if (match_glyph_data16) match_glyph_data16--;

#ifndef HB_NO_BEYOND_64K

      else

      if (match_glyph_data24) match_glyph_data24--;

#endif

    unsigned int idx;

    protected:

    hb_ot_apply_context_t *c;

    matcher_t matcher;

    const HBUINT16 *match_glyph_data16;

#ifndef HB_NO_BEYOND_64K

    const HBUINT24 *match_glyph_data24;

#endif

    unsigned int end;

};

  const char *get_name () { return "APPLY"; }

  typedef return_t (*recurse_func_t) (hb_ot_apply_context_t *c, unsigned int lookup_index);

  template <typename T>

  return_t dispatch (const T &obj) { return obj.apply (this); }

  static return_t default_return_value () { return false; }

  bool stop_sublookup_iteration (return_t r) const { return r; }

  return_t recurse (unsigned int sub_lookup_index)

    if (unlikely (nesting_level_left == 0 || !recurse_func || buffer->max_ops-- <= 0))

      buffer->shaping_failed = true;

      return default_return_value ();

    nesting_level_left--;

    bool ret = recurse_func (this, sub_lookup_index);

    nesting_level_left++;

    return ret;

  skipping_iterator_t iter_input, iter_context;

  unsigned int table_index; /* GSUB/GPOS */

  hb_font_t *font;

  hb_face_t *face;

  hb_buffer_t *buffer;

  hb_sanitize_context_t sanitizer;

  recurse_func_t recurse_func = nullptr;

  const GDEF &gdef;

  const GDEF::accelerator_t &gdef_accel;

  const ItemVariationStore &var_store;

  ItemVariationStore::cache_t *var_store_cache;

  hb_set_digest_t digest;

  hb_direction_t direction;

  hb_mask_t lookup_mask = 1;

  unsigned int lookup_index = (unsigned) -1;

  unsigned int lookup_props = 0;

  unsigned int nesting_level_left = HB_MAX_NESTING_LEVEL;

  bool has_glyph_classes;

  bool auto_zwnj = true;

  bool auto_zwj = true;

  bool per_syllable = false;

  bool random = false;

  unsigned new_syllables = (unsigned) -1;

  signed last_base = -1; // GPOS uses

  unsigned last_base_until = 0; // GPOS uses

  hb_ot_apply_context_t (unsigned int table_index_,

			 hb_font_t *font_,

			 hb_buffer_t *buffer_,

			 hb_blob_t *table_blob_) :

			table_index (table_index_),

			font (font_), face (font->face), buffer (buffer_),

			sanitizer (table_blob_),

			gdef (

#ifndef HB_NO_OT_LAYOUT

			      *face->table.GDEF->table

#else

			      Null (GDEF)

#endif

),

			gdef_accel (

#ifndef HB_NO_OT_LAYOUT

			      *face->table.GDEF

#else

			      Null (GDEF::accelerator_t)

#endif

),

			var_store (gdef.get_var_store ()),

			var_store_cache (

#ifndef HB_NO_VAR

					 table_index == 1 && font->num_coords ? var_store.create_cache () : nullptr

#else

					 nullptr

#endif

),

			digest (buffer_->digest ()),

			direction (buffer_->props.direction),

			has_glyph_classes (gdef.has_glyph_classes ())

  { init_iters (); }

  ~hb_ot_apply_context_t ()

#ifndef HB_NO_VAR

    ItemVariationStore::destroy_cache (var_store_cache);

#endif

  void init_iters ()

    iter_input.init (this, false);

    iter_context.init (this, true);

  void set_lookup_mask (hb_mask_t mask, bool init = true) { lookup_mask = mask; last_base = -1; last_base_until = 0; if (init) init_iters (); }

  void set_auto_zwj (bool auto_zwj_, bool init = true) { auto_zwj = auto_zwj_; if (init) init_iters (); }

  void set_auto_zwnj (bool auto_zwnj_, bool init = true) { auto_zwnj = auto_zwnj_; if (init) init_iters (); }

  void set_per_syllable (bool per_syllable_, bool init = true) { per_syllable = per_syllable_; if (init) init_iters (); }

  void set_random (bool random_) { random = random_; }

  void set_recurse_func (recurse_func_t func) { recurse_func = func; }

  void set_lookup_index (unsigned int lookup_index_) { lookup_index = lookup_index_; }

  void set_lookup_props (unsigned int lookup_props_) { lookup_props = lookup_props_; init_iters (); }

  uint32_t random_number ()

    /* http://www.cplusplus.com/reference/random/minstd_rand/ */

    buffer->random_state = buffer->random_state * 48271 % 2147483647;

    return buffer->random_state;

  bool match_properties_mark (hb_codepoint_t  glyph,

			      unsigned int    glyph_props,

			      unsigned int    match_props) const

    /* If using mark filtering sets, the high short of

     * match_props has the set index.

*/

    if (match_props & LookupFlag::UseMarkFilteringSet)

      return gdef_accel.mark_set_covers (match_props >> 16, glyph);

    /* The second byte of match_props has the meaning

     * "ignore marks of attachment type different than

     * the attachment type specified."

*/

    if (match_props & LookupFlag::MarkAttachmentType)

      return (match_props & LookupFlag::MarkAttachmentType) == (glyph_props & LookupFlag::MarkAttachmentType);

    return true;

#ifndef HB_OPTIMIZE_SIZE

  HB_ALWAYS_INLINE

#endif

  bool check_glyph_property (const hb_glyph_info_t *info,

			     unsigned int  match_props) const

    unsigned int glyph_props = _hb_glyph_info_get_glyph_props (info);

    /* Not covered, if, for example, glyph class is ligature and

     * match_props includes LookupFlags::IgnoreLigatures

*/

    if (glyph_props & match_props & LookupFlag::IgnoreFlags)

      return false;

    if (unlikely (glyph_props & HB_OT_LAYOUT_GLYPH_PROPS_MARK))

      return match_properties_mark (info->codepoint, glyph_props, match_props);

    return true;

  void _set_glyph_class (hb_codepoint_t glyph_index,

			  unsigned int class_guess = 0,

			  bool ligature = false,

			  bool component = false)

    digest.add (glyph_index);

    if (new_syllables != (unsigned) -1)

      buffer->cur().syllable() = new_syllables;

    unsigned int props = _hb_glyph_info_get_glyph_props (&buffer->cur());

    props |= HB_OT_LAYOUT_GLYPH_PROPS_SUBSTITUTED;

    if (ligature)

      props |= HB_OT_LAYOUT_GLYPH_PROPS_LIGATED;

      /* In the only place that the MULTIPLIED bit is used, Uniscribe

       * seems to only care about the "last" transformation between

       * Ligature and Multiple substitutions.  Ie. if you ligate, expand,

       * and ligate again, it forgives the multiplication and acts as

       * if only ligation happened.  As such, clear MULTIPLIED bit.

*/

      props &= ~HB_OT_LAYOUT_GLYPH_PROPS_MULTIPLIED;

    if (component)

      props |= HB_OT_LAYOUT_GLYPH_PROPS_MULTIPLIED;

    if (likely (has_glyph_classes))

      props &= HB_OT_LAYOUT_GLYPH_PROPS_PRESERVE;

      _hb_glyph_info_set_glyph_props (&buffer->cur(), props | gdef_accel.get_glyph_props (glyph_index));

    else if (class_guess)

      props &= HB_OT_LAYOUT_GLYPH_PROPS_PRESERVE;

      _hb_glyph_info_set_glyph_props (&buffer->cur(), props | class_guess);

    else

      _hb_glyph_info_set_glyph_props (&buffer->cur(), props);

  void replace_glyph (hb_codepoint_t glyph_index)

    _set_glyph_class (glyph_index);

    (void) buffer->replace_glyph (glyph_index);

  void replace_glyph_inplace (hb_codepoint_t glyph_index)

    _set_glyph_class (glyph_index);

    buffer->cur().codepoint = glyph_index;

  void replace_glyph_with_ligature (hb_codepoint_t glyph_index,

				    unsigned int class_guess)

    _set_glyph_class (glyph_index, class_guess, true);

    (void) buffer->replace_glyph (glyph_index);

  void output_glyph_for_component (hb_codepoint_t glyph_index,

				   unsigned int class_guess)

    _set_glyph_class (glyph_index, class_guess, false, true);

    (void) buffer->output_glyph (glyph_index);

};

struct hb_accelerate_subtables_context_t :

       hb_dispatch_context_t<hb_accelerate_subtables_context_t>

  template <typename Type>

  static inline bool apply_to (const void *obj, hb_ot_apply_context_t *c)

    const Type *typed_obj = (const Type *) obj;

    return typed_obj->apply (c);

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

  template <typename T>

  static inline auto apply_cached_ (const T *obj, hb_ot_apply_context_t *c, hb_priority<1>) HB_RETURN (bool, obj->apply_cached (c) )

  template <typename T>

  static inline auto apply_cached_ (const T *obj, hb_ot_apply_context_t *c, hb_priority<0>) HB_RETURN (bool, obj->apply (c) )

  template <typename Type>

  static inline bool apply_cached_to (const void *obj, hb_ot_apply_context_t *c)

    const Type *typed_obj = (const Type *) obj;

    return apply_cached_ (typed_obj, c, hb_prioritize);

  template <typename T>

  static inline auto cache_func_ (const T *obj, hb_ot_apply_context_t *c, bool enter, hb_priority<1>) HB_RETURN (bool, obj->cache_func (c, enter) )

  template <typename T>

  static inline bool cache_func_ (const T *obj, hb_ot_apply_context_t *c, bool enter, hb_priority<0>) { return false; }

  template <typename Type>

  static inline bool cache_func_to (const void *obj, hb_ot_apply_context_t *c, bool enter)

    const Type *typed_obj = (const Type *) obj;

    return cache_func_ (typed_obj, c, enter, hb_prioritize);

#endif

  typedef bool (*hb_apply_func_t) (const void *obj, hb_ot_apply_context_t *c);

  typedef bool (*hb_cache_func_t) (const void *obj, hb_ot_apply_context_t *c, bool enter);

  struct hb_applicable_t

    friend struct hb_accelerate_subtables_context_t;

    friend struct hb_ot_layout_lookup_accelerator_t;

    template <typename T>

    void init (const T &obj_,

	       hb_apply_func_t apply_func_

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

	       , hb_apply_func_t apply_cached_func_

	       , hb_cache_func_t cache_func_

#endif

      obj = &obj_;

      apply_func = apply_func_;

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

      apply_cached_func = apply_cached_func_;

      cache_func = cache_func_;

#endif

      digest.init ();

      obj_.get_coverage ().collect_coverage (&digest);

    bool apply (hb_ot_apply_context_t *c) const

      return digest.may_have (c->buffer->cur().codepoint) && apply_func (obj, c);

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

    bool apply_cached (hb_ot_apply_context_t *c) const

      return digest.may_have (c->buffer->cur().codepoint) &&  apply_cached_func (obj, c);

    bool cache_enter (hb_ot_apply_context_t *c) const

      return cache_func (obj, c, true);

    void cache_leave (hb_ot_apply_context_t *c) const

      cache_func (obj, c, false);

#endif

    private:

    const void *obj;

    hb_apply_func_t apply_func;

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

    hb_apply_func_t apply_cached_func;

    hb_cache_func_t cache_func;

#endif

    hb_set_digest_t digest;

};

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

  template <typename T>

  auto cache_cost (const T &obj, hb_priority<1>) HB_AUTO_RETURN ( obj.cache_cost () )

  template <typename T>

  auto cache_cost (const T &obj, hb_priority<0>) HB_AUTO_RETURN ( 0u )

#endif

  /* Dispatch interface. */

  template <typename T>

  return_t dispatch (const T &obj)

    hb_applicable_t *entry = &array[i++];

    entry->init (obj,

		 apply_to<T>

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

		 , apply_cached_to<T>

		 , cache_func_to<T>

#endif

);

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

    /* Cache handling

     * We allow one subtable from each lookup to use a cache. The assumption

     * being that multiple subtables of the same lookup cannot use a cache

     * because the resources they would use will collide.  As such, we ask

     * each subtable to tell us how much it costs (which a cache would avoid),

     * and we allocate the cache opportunity to the costliest subtable.

*/

    unsigned cost = cache_cost (obj, hb_prioritize);

    if (cost > cache_user_cost)

      cache_user_idx = i - 1;

      cache_user_cost = cost;

#endif

    return hb_empty_t ();

  static return_t default_return_value () { return hb_empty_t (); }

  hb_accelerate_subtables_context_t (hb_applicable_t *array_) :

				     array (array_) {}

  hb_applicable_t *array;

  unsigned i = 0;

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

  unsigned cache_user_idx = (unsigned) -1;

  unsigned cache_user_cost = 0;

#endif

};

typedef bool (*intersects_func_t) (const hb_set_t *glyphs, unsigned value, const void *data, void *cache);

typedef void (*intersected_glyphs_func_t) (const hb_set_t *glyphs, const void *data, unsigned value, hb_set_t *intersected_glyphs, void *cache);

typedef void (*collect_glyphs_func_t) (hb_set_t *glyphs, unsigned value, const void *data);

typedef bool (*match_func_t) (hb_glyph_info_t &info, unsigned value, const void *data);

struct ContextClosureFuncs

  intersects_func_t intersects;

  intersected_glyphs_func_t intersected_glyphs;

};

struct ContextCollectGlyphsFuncs

  collect_glyphs_func_t collect;

};

struct ContextApplyFuncs

  match_func_t match;

};

struct ChainContextApplyFuncs

  match_func_t match[3];

};

static inline bool intersects_glyph (const hb_set_t *glyphs, unsigned value, const void *data HB_UNUSED, void *cache HB_UNUSED)

  return glyphs->has (value);

static inline bool intersects_class (const hb_set_t *glyphs, unsigned value, const void *data, void *cache)

  const ClassDef &class_def = *reinterpret_cast<const ClassDef *>(data);

  hb_map_t *map = (hb_map_t *) cache;

  hb_codepoint_t *cached_v;

  if (map->has (value, &cached_v))

    return *cached_v;

  bool v = class_def.intersects_class (glyphs, value);

  map->set (value, v);

  return v;

static inline bool intersects_coverage (const hb_set_t *glyphs, unsigned value, const void *data, void *cache HB_UNUSED)

  Offset16To<Coverage> coverage;

  coverage = value;

  return (data+coverage).intersects (glyphs);

static inline void intersected_glyph (const hb_set_t *glyphs HB_UNUSED, const void *data, unsigned value, hb_set_t *intersected_glyphs, HB_UNUSED void *cache)

  unsigned g = reinterpret_cast<const HBUINT16 *>(data)[value];

  intersected_glyphs->add (g);

using intersected_class_cache_t = hb_hashmap_t<unsigned, hb_set_t>;

static inline void intersected_class_glyphs (const hb_set_t *glyphs, const void *data, unsigned value, hb_set_t *intersected_glyphs, void *cache)

  const ClassDef &class_def = *reinterpret_cast<const ClassDef *>(data);

  intersected_class_cache_t *map = (intersected_class_cache_t *) cache;

  hb_set_t *cached_v;

  if (map->has (value, &cached_v))

    intersected_glyphs->union_ (*cached_v);

    return;

  hb_set_t v;

  class_def.intersected_class_glyphs (glyphs, value, &v);

  intersected_glyphs->union_ (v);

  map->set (value, std::move (v));

static inline void intersected_coverage_glyphs (const hb_set_t *glyphs, const void *data, unsigned value, hb_set_t *intersected_glyphs, HB_UNUSED void *cache)

  Offset16To<Coverage> coverage;

  coverage = value;

  (data+coverage).intersect_set (*glyphs, *intersected_glyphs);

template <typename HBUINT>

static inline bool array_is_subset_of (const hb_set_t *glyphs,

				       unsigned int count,

				       const HBUINT values[],

				       intersects_func_t intersects_func,

				       const void *intersects_data,

				       void *cache)

  for (const auto &_ : + hb_iter (values, count))

    if (!intersects_func (glyphs, _, intersects_data, cache)) return false;

  return true;

static inline void collect_glyph (hb_set_t *glyphs, unsigned value, const void *data HB_UNUSED)

  glyphs->add (value);

static inline void collect_class (hb_set_t *glyphs, unsigned value, const void *data)

  const ClassDef &class_def = *reinterpret_cast<const ClassDef *>(data);

  class_def.collect_class (glyphs, value);

static inline void collect_coverage (hb_set_t *glyphs, unsigned value, const void *data)

  Offset16To<Coverage> coverage;

  coverage = value;

  (data+coverage).collect_coverage (glyphs);

template <typename HBUINT>

static inline void collect_array (hb_collect_glyphs_context_t *c HB_UNUSED,

				  hb_set_t *glyphs,

				  unsigned int count,

				  const HBUINT values[],

				  collect_glyphs_func_t collect_func,

				  const void *collect_data)

  return

  + hb_iter (values, count)

  | hb_apply ([&] (const HBUINT &_) { collect_func (glyphs, _, collect_data); })

static inline bool match_always (hb_glyph_info_t &info HB_UNUSED, unsigned value HB_UNUSED, const void *data HB_UNUSED)

  return true;

static inline bool match_glyph (hb_glyph_info_t &info, unsigned value, const void *data HB_UNUSED)

  return info.codepoint == value;

static inline bool match_class (hb_glyph_info_t &info, unsigned value, const void *data)

  const ClassDef &class_def = *reinterpret_cast<const ClassDef *>(data);

  return class_def.get_class (info.codepoint) == value;

static inline bool match_class_cached (hb_glyph_info_t &info, unsigned value, const void *data)

  unsigned klass = info.syllable();

  if (klass < 255)

    return klass == value;

  const ClassDef &class_def = *reinterpret_cast<const ClassDef *>(data);

  klass = class_def.get_class (info.codepoint);

  if (likely (klass < 255))

    info.syllable() = klass;

  return klass == value;

static inline bool match_class_cached1 (hb_glyph_info_t &info, unsigned value, const void *data)

  unsigned klass = info.syllable() & 0x0F;

  if (klass < 15)

    return klass == value;

  const ClassDef &class_def = *reinterpret_cast<const ClassDef *>(data);

  klass = class_def.get_class (info.codepoint);

  if (likely (klass < 15))

    info.syllable() = (info.syllable() & 0xF0) | klass;

  return klass == value;

static inline bool match_class_cached2 (hb_glyph_info_t &info, unsigned value, const void *data)

  unsigned klass = (info.syllable() & 0xF0) >> 4;

  if (klass < 15)

    return klass == value;

  const ClassDef &class_def = *reinterpret_cast<const ClassDef *>(data);

  klass = class_def.get_class (info.codepoint);

  if (likely (klass < 15))

    info.syllable() = (info.syllable() & 0x0F) | (klass << 4);

  return klass == value;

static inline bool match_coverage (hb_glyph_info_t &info, unsigned value, const void *data)

  Offset16To<Coverage> coverage;

  coverage = value;

  return (data+coverage).get_coverage (info.codepoint) != NOT_COVERED;

template <typename HBUINT>

static inline bool would_match_input (hb_would_apply_context_t *c,

				      unsigned int count, /* Including the first glyph (not matched) */

				      const HBUINT input[], /* Array of input values--start with second glyph */

				      match_func_t match_func,

				      const void *match_data)

  if (count != c->len)

    return false;

  for (unsigned int i = 1; i < count; i++)

    hb_glyph_info_t info;

    info.codepoint = c->glyphs[i];

    if (likely (!match_func (info, input[i - 1], match_data)))

      return false;

  return true;

template <typename HBUINT>

#ifndef HB_OPTIMIZE_SIZE

HB_ALWAYS_INLINE

#endif

static bool match_input (hb_ot_apply_context_t *c,

			 unsigned int count, /* Including the first glyph (not matched) */

			 const HBUINT input[], /* Array of input values--start with second glyph */

			 match_func_t match_func,

			 const void *match_data,

			 unsigned int *end_position,

			 unsigned int *match_positions,

			 unsigned int *p_total_component_count = nullptr)

  TRACE_APPLY (nullptr);

  if (unlikely (count > HB_MAX_CONTEXT_LENGTH)) return_trace (false);

  hb_buffer_t *buffer = c->buffer;

  hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c->iter_input;

  skippy_iter.reset (buffer->idx);

  skippy_iter.set_match_func (match_func, match_data);

  skippy_iter.set_glyph_data (input);

/*

   * This is perhaps the trickiest part of OpenType...  Remarks:

   * - If all components of the ligature were marks, we call this a mark ligature.

   * - If there is no GDEF, and the ligature is NOT a mark ligature, we categorize

   *   it as a ligature glyph.

   * - Ligatures cannot be formed across glyphs attached to different components

   *   of previous ligatures.  Eg. the sequence is LAM,SHADDA,LAM,FATHA,HEH, and

   *   LAM,LAM,HEH form a ligature, leaving SHADDA,FATHA next to eachother.

   *   However, it would be wrong to ligate that SHADDA,FATHA sequence.

   *   There are a couple of exceptions to this:

   *   o If a ligature tries ligating with marks that belong to it itself, go ahead,

   *     assuming that the font designer knows what they are doing (otherwise it can

   *     break Indic stuff when a matra wants to ligate with a conjunct,

   *   o If two marks want to ligate and they belong to different components of the

   *     same ligature glyph, and said ligature glyph is to be ignored according to

   *     mark-filtering rules, then allow.

   *     https://github.com/harfbuzz/harfbuzz/issues/545

*/

  unsigned int total_component_count = 0;

  unsigned int first_lig_id = _hb_glyph_info_get_lig_id (&buffer->cur());

  unsigned int first_lig_comp = _hb_glyph_info_get_lig_comp (&buffer->cur());

  enum {

    LIGBASE_NOT_CHECKED,

    LIGBASE_MAY_NOT_SKIP,

    LIGBASE_MAY_SKIP

  } ligbase = LIGBASE_NOT_CHECKED;

  for (unsigned int i = 1; i < count; i++)

    unsigned unsafe_to;

    if (!skippy_iter.next (&unsafe_to))

      *end_position = unsafe_to;

      return_trace (false);

    match_positions[i] = skippy_iter.idx;

    unsigned int this_lig_id = _hb_glyph_info_get_lig_id (&buffer->info[skippy_iter.idx]);

    unsigned int this_lig_comp = _hb_glyph_info_get_lig_comp (&buffer->info[skippy_iter.idx]);

    if (first_lig_id && first_lig_comp)

      /* If first component was attached to a previous ligature component,

       * all subsequent components should be attached to the same ligature

       * component, otherwise we shouldn't ligate them... */

      if (first_lig_id != this_lig_id || first_lig_comp != this_lig_comp)

	/* ...unless, we are attached to a base ligature and that base

	 * ligature is ignorable. */

	if (ligbase == LIGBASE_NOT_CHECKED)

	  bool found = false;

	  const auto *out = buffer->out_info;

	  unsigned int j = buffer->out_len;

	  while (j && _hb_glyph_info_get_lig_id (&out[j - 1]) == first_lig_id)

	    if (_hb_glyph_info_get_lig_comp (&out[j - 1]) == 0)

	      j--;

	      found = true;

	      break;

	    j--;

	  if (found && skippy_iter.may_skip (out[j]) == hb_ot_apply_context_t::matcher_t::SKIP_YES)

	    ligbase = LIGBASE_MAY_SKIP;

	  else

	    ligbase = LIGBASE_MAY_NOT_SKIP;

	if (ligbase == LIGBASE_MAY_NOT_SKIP)

	  return_trace (false);

    else

      /* If first component was NOT attached to a previous ligature component,

       * all subsequent components should also NOT be attached to any ligature

       * component, unless they are attached to the first component itself! */

      if (this_lig_id && this_lig_comp && (this_lig_id != first_lig_id))

	return_trace (false);

    total_component_count += _hb_glyph_info_get_lig_num_comps (&buffer->info[skippy_iter.idx]);

  *end_position = skippy_iter.idx + 1;

  if (p_total_component_count)

    total_component_count += _hb_glyph_info_get_lig_num_comps (&buffer->cur());

    *p_total_component_count = total_component_count;

  match_positions[0] = buffer->idx;

  return_trace (true);

static inline bool ligate_input (hb_ot_apply_context_t *c,

				 unsigned int count, /* Including the first glyph */

				 const unsigned int *match_positions, /* Including the first glyph */

				 unsigned int match_end,

				 hb_codepoint_t lig_glyph,

				 unsigned int total_component_count)

  TRACE_APPLY (nullptr);

  hb_buffer_t *buffer = c->buffer;

  buffer->merge_clusters (buffer->idx, match_end);

  /* - If a base and one or more marks ligate, consider that as a base, NOT

   *   ligature, such that all following marks can still attach to it.

   *   https://github.com/harfbuzz/harfbuzz/issues/1109

   * - If all components of the ligature were marks, we call this a mark ligature.

   *   If it *is* a mark ligature, we don't allocate a new ligature id, and leave

   *   the ligature to keep its old ligature id.  This will allow it to attach to

   *   a base ligature in GPOS.  Eg. if the sequence is: LAM,LAM,SHADDA,FATHA,HEH,

   *   and LAM,LAM,HEH for a ligature, they will leave SHADDA and FATHA with a

   *   ligature id and component value of 2.  Then if SHADDA,FATHA form a ligature

   *   later, we don't want them to lose their ligature id/component, otherwise

   *   GPOS will fail to correctly position the mark ligature on top of the

   *   LAM,LAM,HEH ligature.  See:

   *     https://bugzilla.gnome.org/show_bug.cgi?id=676343

   * - If a ligature is formed of components that some of which are also ligatures

   *   themselves, and those ligature components had marks attached to *their*

   *   components, we have to attach the marks to the new ligature component

   *   positions!  Now *that*'s tricky!  And these marks may be following the

   *   last component of the whole sequence, so we should loop forward looking

   *   for them and update them.

   *   Eg. the sequence is LAM,LAM,SHADDA,FATHA,HEH, and the font first forms a

   *   'calt' ligature of LAM,HEH, leaving the SHADDA and FATHA with a ligature

   *   id and component == 1.  Now, during 'liga', the LAM and the LAM-HEH ligature

   *   form a LAM-LAM-HEH ligature.  We need to reassign the SHADDA and FATHA to

   *   the new ligature with a component value of 2.

   *   This in fact happened to a font...  See:

   *   https://bugzilla.gnome.org/show_bug.cgi?id=437633

*/

  bool is_base_ligature = _hb_glyph_info_is_base_glyph (&buffer->info[match_positions[0]]);

  bool is_mark_ligature = _hb_glyph_info_is_mark (&buffer->info[match_positions[0]]);

  for (unsigned int i = 1; i < count; i++)

    if (!_hb_glyph_info_is_mark (&buffer->info[match_positions[i]]))

      is_base_ligature = false;

      is_mark_ligature = false;

      break;

  bool is_ligature = !is_base_ligature && !is_mark_ligature;

  unsigned int klass = is_ligature ? HB_OT_LAYOUT_GLYPH_PROPS_LIGATURE : 0;

  unsigned int lig_id = is_ligature ? _hb_allocate_lig_id (buffer) : 0;

  unsigned int last_lig_id = _hb_glyph_info_get_lig_id (&buffer->cur());

  unsigned int last_num_components = _hb_glyph_info_get_lig_num_comps (&buffer->cur());

  unsigned int components_so_far = last_num_components;

  if (is_ligature)

    _hb_glyph_info_set_lig_props_for_ligature (&buffer->cur(), lig_id, total_component_count);

    if (_hb_glyph_info_get_general_category (&buffer->cur()) == HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)

      _hb_glyph_info_set_general_category (&buffer->cur(), HB_UNICODE_GENERAL_CATEGORY_OTHER_LETTER);

  c->replace_glyph_with_ligature (lig_glyph, klass);

  for (unsigned int i = 1; i < count; i++)

    while (buffer->idx < match_positions[i] && buffer->successful)

      if (is_ligature)

	unsigned int this_comp = _hb_glyph_info_get_lig_comp (&buffer->cur());

	if (this_comp == 0)

	  this_comp = last_num_components;

	unsigned int new_lig_comp = components_so_far - last_num_components +

				    hb_min (this_comp, last_num_components);

	  _hb_glyph_info_set_lig_props_for_mark (&buffer->cur(), lig_id, new_lig_comp);

      (void) buffer->next_glyph ();

    last_lig_id = _hb_glyph_info_get_lig_id (&buffer->cur());

    last_num_components = _hb_glyph_info_get_lig_num_comps (&buffer->cur());

    components_so_far += last_num_components;

    /* Skip the base glyph */

    buffer->idx++;

  if (!is_mark_ligature && last_lig_id)

    /* Re-adjust components for any marks following. */

    for (unsigned i = buffer->idx; i < buffer->len; ++i)

      if (last_lig_id != _hb_glyph_info_get_lig_id (&buffer->info[i])) break;

      unsigned this_comp = _hb_glyph_info_get_lig_comp (&buffer->info[i]);

      if (!this_comp) break;

      unsigned new_lig_comp = components_so_far - last_num_components +

			      hb_min (this_comp, last_num_components);

      _hb_glyph_info_set_lig_props_for_mark (&buffer->info[i], lig_id, new_lig_comp);

  return_trace (true);

template <typename HBUINT>

#ifndef HB_OPTIMIZE_SIZE

HB_ALWAYS_INLINE

#endif

static bool match_backtrack (hb_ot_apply_context_t *c,

			     unsigned int count,

			     const HBUINT backtrack[],

			     match_func_t match_func,

			     const void *match_data,

			     unsigned int *match_start)

  TRACE_APPLY (nullptr);

  hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c->iter_context;

  skippy_iter.reset (c->buffer->backtrack_len ());

  skippy_iter.set_match_func (match_func, match_data);

  skippy_iter.set_glyph_data (backtrack);

  for (unsigned int i = 0; i < count; i++)

    unsigned unsafe_from;

    if (!skippy_iter.prev (&unsafe_from))

      *match_start = unsafe_from;

      return_trace (false);

  *match_start = skippy_iter.idx;

  return_trace (true);

template <typename HBUINT>

#ifndef HB_OPTIMIZE_SIZE

HB_ALWAYS_INLINE

#endif

static bool match_lookahead (hb_ot_apply_context_t *c,

			     unsigned int count,

			     const HBUINT lookahead[],

			     match_func_t match_func,

			     const void *match_data,

			     unsigned int start_index,

			     unsigned int *end_index)

  TRACE_APPLY (nullptr);

  hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c->iter_context;

  skippy_iter.reset (start_index - 1);

  skippy_iter.set_match_func (match_func, match_data);

  skippy_iter.set_glyph_data (lookahead);

  for (unsigned int i = 0; i < count; i++)

    unsigned unsafe_to;

    if (!skippy_iter.next (&unsafe_to))

      *end_index = unsafe_to;

      return_trace (false);

  *end_index = skippy_iter.idx + 1;

  return_trace (true);

struct LookupRecord

  bool serialize (hb_serialize_context_t *c,

		  const hb_map_t         *lookup_map) const

    TRACE_SERIALIZE (this);

    auto *out = c->embed (*this);

    if (unlikely (!out)) return_trace (false);

    return_trace (c->check_assign (out->lookupListIndex, lookup_map->get (lookupListIndex), HB_SERIALIZE_ERROR_INT_OVERFLOW));

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    return_trace (c->check_struct (this));

  HBUINT16	sequenceIndex;		/* Index into current glyph

					 * sequence--first glyph = 0 */

  HBUINT16	lookupListIndex;	/* Lookup to apply to that

					 * position--zero--based */

  public:

  DEFINE_SIZE_STATIC (4);

};

static unsigned serialize_lookuprecord_array (hb_serialize_context_t *c,

					      const hb_array_t<const LookupRecord> lookupRecords,

					      const hb_map_t *lookup_map)

  unsigned count = 0;

  for (const LookupRecord& r : lookupRecords)

    if (!lookup_map->has (r.lookupListIndex))

      continue;

    if (!r.serialize (c, lookup_map))

      return 0;

    count++;

  return count;

enum ContextFormat { SimpleContext = 1, ClassBasedContext = 2, CoverageBasedContext = 3 };

template <typename HBUINT>

static void context_closure_recurse_lookups (hb_closure_context_t *c,

					     unsigned inputCount, const HBUINT input[],

					     unsigned lookupCount,

					     const LookupRecord lookupRecord[] /* Array of LookupRecords--in design order */,

					     unsigned value,

					     ContextFormat context_format,

					     const void *data,

					     intersected_glyphs_func_t intersected_glyphs_func,

					     void *cache)

  hb_set_t covered_seq_indicies;

  hb_set_t pos_glyphs;

  for (unsigned int i = 0; i < lookupCount; i++)

    unsigned seqIndex = lookupRecord[i].sequenceIndex;

    if (seqIndex >= inputCount) continue;

    bool has_pos_glyphs = false;

    if (!covered_seq_indicies.has (seqIndex))

      has_pos_glyphs = true;

      pos_glyphs.clear ();

      if (seqIndex == 0)

        switch (context_format) {

        case ContextFormat::SimpleContext:

          pos_glyphs.add (value);

          break;

        case ContextFormat::ClassBasedContext:

          intersected_glyphs_func (&c->parent_active_glyphs (), data, value, &pos_glyphs, cache);

          break;

        case ContextFormat::CoverageBasedContext:

          pos_glyphs.set (c->parent_active_glyphs ());

          break;

      else

        const void *input_data = input;

        unsigned input_value = seqIndex - 1;

        if (context_format != ContextFormat::SimpleContext)

          input_data = data;

          input_value = input[seqIndex - 1];

        intersected_glyphs_func (c->glyphs, input_data, input_value, &pos_glyphs, cache);

    covered_seq_indicies.add (seqIndex);

    hb_set_t *cur_active_glyphs = c->push_cur_active_glyphs ();

    if (unlikely (!cur_active_glyphs))

      return;

    if (has_pos_glyphs) {

      *cur_active_glyphs = std::move (pos_glyphs);

    } else {

      *cur_active_glyphs = *c->glyphs;

    unsigned endIndex = inputCount;

    if (context_format == ContextFormat::CoverageBasedContext)

      endIndex += 1;

    c->recurse (lookupRecord[i].lookupListIndex, &covered_seq_indicies, seqIndex, endIndex);

    c->pop_cur_done_glyphs ();

template <typename context_t>

static inline void recurse_lookups (context_t *c,

                                    unsigned int lookupCount,

                                    const LookupRecord lookupRecord[] /* Array of LookupRecords--in design order */)

  for (unsigned int i = 0; i < lookupCount; i++)

    c->recurse (lookupRecord[i].lookupListIndex);

static inline void apply_lookup (hb_ot_apply_context_t *c,

				 unsigned int count, /* Including the first glyph */

				 unsigned int *match_positions, /* Including the first glyph */

				 unsigned int lookupCount,

				 const LookupRecord lookupRecord[], /* Array of LookupRecords--in design order */

				 unsigned int match_end)

  hb_buffer_t *buffer = c->buffer;

  int end;

  unsigned int *match_positions_input = match_positions;

  unsigned int match_positions_count = count;

  /* All positions are distance from beginning of *output* buffer.

   * Adjust. */

    unsigned int bl = buffer->backtrack_len ();

    end = bl + match_end - buffer->idx;

    int delta = bl - buffer->idx;

    /* Convert positions to new indexing. */

    for (unsigned int j = 0; j < count; j++)

      match_positions[j] += delta;

  for (unsigned int i = 0; i < lookupCount && buffer->successful; i++)

    unsigned int idx = lookupRecord[i].sequenceIndex;

    if (idx >= count)

      continue;

    unsigned int orig_len = buffer->backtrack_len () + buffer->lookahead_len ();

    /* This can happen if earlier recursed lookups deleted many entries. */

    if (unlikely (match_positions[idx] >= orig_len))

      continue;

    if (unlikely (!buffer->move_to (match_positions[idx])))

      break;

    if (unlikely (buffer->max_ops <= 0))

      break;

    if (HB_BUFFER_MESSAGE_MORE && c->buffer->messaging ())

      if (buffer->have_output)

        c->buffer->sync_so_far ();

      c->buffer->message (c->font,

			  "recursing to lookup %u at %u",

			  (unsigned) lookupRecord[i].lookupListIndex,

			  buffer->idx);

    if (!c->recurse (lookupRecord[i].lookupListIndex))

      continue;

    if (HB_BUFFER_MESSAGE_MORE && c->buffer->messaging ())

      if (buffer->have_output)

        c->buffer->sync_so_far ();

      c->buffer->message (c->font,

			  "recursed to lookup %u",

			  (unsigned) lookupRecord[i].lookupListIndex);

    unsigned int new_len = buffer->backtrack_len () + buffer->lookahead_len ();

    int delta = new_len - orig_len;

    if (!delta)

      continue;

    /* Recursed lookup changed buffer len.  Adjust.

     * TODO:

     * Right now, if buffer length increased by n, we assume n new glyphs

     * were added right after the current position, and if buffer length

     * was decreased by n, we assume n match positions after the current

     * one where removed.  The former (buffer length increased) case is

     * fine, but the decrease case can be improved in at least two ways,

     * both of which are significant:

     *   - If recursed-to lookup is MultipleSubst and buffer length

     *     decreased, then it's current match position that was deleted,

     *     NOT the one after it.

     *   - If buffer length was decreased by n, it does not necessarily

     *     mean that n match positions where removed, as there recursed-to

     *     lookup might had a different LookupFlag.  Here's a constructed

     *     case of that:

     *     https://github.com/harfbuzz/harfbuzz/discussions/3538

     * It should be possible to construct tests for both of these cases.

*/

    end += delta;

    if (end < int (match_positions[idx]))

      /* End might end up being smaller than match_positions[idx] if the recursed

       * lookup ended up removing many items.

       * Just never rewind end beyond start of current position, since that is

       * not possible in the recursed lookup.  Also adjust delta as such.

       * https://bugs.chromium.org/p/chromium/issues/detail?id=659496

       * https://github.com/harfbuzz/harfbuzz/issues/1611

*/

      delta += match_positions[idx] - end;

      end = match_positions[idx];

    unsigned int next = idx + 1; /* next now is the position after the recursed lookup. */

    if (delta > 0)

      if (unlikely (delta + count > HB_MAX_CONTEXT_LENGTH))

	break;

      if (unlikely (delta + count > match_positions_count))

        unsigned new_match_positions_count = hb_max (delta + count, hb_max(match_positions_count, 4u) * 1.5);

        if (match_positions == match_positions_input)

	  match_positions = (unsigned int *) hb_malloc (new_match_positions_count * sizeof (match_positions[0]));

	  if (unlikely (!match_positions))

	    break;

	  memcpy (match_positions, match_positions_input, count * sizeof (match_positions[0]));

	  match_positions_count = new_match_positions_count;

	else

	  unsigned int *new_match_positions = (unsigned int *) hb_realloc (match_positions, new_match_positions_count * sizeof (match_positions[0]));

	  if (unlikely (!new_match_positions))

	    break;

	  match_positions = new_match_positions;

	  match_positions_count = new_match_positions_count;

    else

      /* NOTE: delta is non-positive. */

      delta = hb_max (delta, (int) next - (int) count);

      next -= delta;

    /* Shift! */

    memmove (match_positions + next + delta, match_positions + next,

	     (count - next) * sizeof (match_positions[0]));

    next += delta;

    count += delta;

    /* Fill in new entries. */

    for (unsigned int j = idx + 1; j < next; j++)

      match_positions[j] = match_positions[j - 1] + 1;

    /* And fixup the rest. */

    for (; next < count; next++)

      match_positions[next] += delta;

  if (match_positions != match_positions_input)

    hb_free (match_positions);

  (void) buffer->move_to (end);

/* Contextual lookups */

struct ContextClosureLookupContext

  ContextClosureFuncs funcs;

  ContextFormat context_format;

  const void *intersects_data;

  void *intersects_cache;

  void *intersected_glyphs_cache;

};

struct ContextCollectGlyphsLookupContext

  ContextCollectGlyphsFuncs funcs;

  const void *collect_data;

};

struct ContextApplyLookupContext

  ContextApplyFuncs funcs;

  const void *match_data;

};

template <typename HBUINT>

static inline bool context_intersects (const hb_set_t *glyphs,

				       unsigned int inputCount, /* Including the first glyph (not matched) */

				       const HBUINT input[], /* Array of input values--start with second glyph */

				       ContextClosureLookupContext &lookup_context)

  return array_is_subset_of (glyphs,

			     inputCount ? inputCount - 1 : 0, input,

			     lookup_context.funcs.intersects,

			     lookup_context.intersects_data,

			     lookup_context.intersects_cache);

template <typename HBUINT>

static inline void context_closure_lookup (hb_closure_context_t *c,

					   unsigned int inputCount, /* Including the first glyph (not matched) */

					   const HBUINT input[], /* Array of input values--start with second glyph */

					   unsigned int lookupCount,

					   const LookupRecord lookupRecord[],

					   unsigned value, /* Index of first glyph in Coverage or Class value in ClassDef table */

					   ContextClosureLookupContext &lookup_context)

  if (context_intersects (c->glyphs,

			  inputCount, input,

			  lookup_context))

    context_closure_recurse_lookups (c,

				     inputCount, input,

				     lookupCount, lookupRecord,

				     value,

				     lookup_context.context_format,

				     lookup_context.intersects_data,

				     lookup_context.funcs.intersected_glyphs,

				     lookup_context.intersected_glyphs_cache);

template <typename HBUINT>

static inline void context_collect_glyphs_lookup (hb_collect_glyphs_context_t *c,

						  unsigned int inputCount, /* Including the first glyph (not matched) */

						  const HBUINT input[], /* Array of input values--start with second glyph */

						  unsigned int lookupCount,

						  const LookupRecord lookupRecord[],

						  ContextCollectGlyphsLookupContext &lookup_context)

  collect_array (c, c->input,

		 inputCount ? inputCount - 1 : 0, input,

		 lookup_context.funcs.collect, lookup_context.collect_data);

  recurse_lookups (c,

		   lookupCount, lookupRecord);

template <typename HBUINT>

static inline bool context_would_apply_lookup (hb_would_apply_context_t *c,

					       unsigned int inputCount, /* Including the first glyph (not matched) */

					       const HBUINT input[], /* Array of input values--start with second glyph */

					       unsigned int lookupCount HB_UNUSED,

					       const LookupRecord lookupRecord[] HB_UNUSED,

					       const ContextApplyLookupContext &lookup_context)

  return would_match_input (c,

			    inputCount, input,

			    lookup_context.funcs.match, lookup_context.match_data);

template <typename HBUINT>

HB_ALWAYS_INLINE

static bool context_apply_lookup (hb_ot_apply_context_t *c,

				  unsigned int inputCount, /* Including the first glyph (not matched) */

				  const HBUINT input[], /* Array of input values--start with second glyph */

				  unsigned int lookupCount,

				  const LookupRecord lookupRecord[],

				  const ContextApplyLookupContext &lookup_context)

  if (unlikely (inputCount > HB_MAX_CONTEXT_LENGTH)) return false;

  unsigned match_positions_stack[4];

  unsigned *match_positions = match_positions_stack;

  if (unlikely (inputCount > ARRAY_LENGTH (match_positions_stack)))

    match_positions = (unsigned *) hb_malloc (hb_max (inputCount, 1u) * sizeof (match_positions[0]));

    if (unlikely (!match_positions))

      return false;

  unsigned match_end = 0;

  bool ret = false;

  if (match_input (c,

		   inputCount, input,

		   lookup_context.funcs.match, lookup_context.match_data,

		   &match_end, match_positions))

    c->buffer->unsafe_to_break (c->buffer->idx, match_end);

    apply_lookup (c,

		  inputCount, match_positions,

		  lookupCount, lookupRecord,

		  match_end);

    ret = true;

  else

    c->buffer->unsafe_to_concat (c->buffer->idx, match_end);

    ret = false;

  if (unlikely (match_positions != match_positions_stack))

    hb_free (match_positions);

  return ret;

template <typename Types>

struct Rule

  template <typename T>

  friend struct RuleSet;

  bool intersects (const hb_set_t *glyphs, ContextClosureLookupContext &lookup_context) const

    return context_intersects (glyphs,

			       inputCount, inputZ.arrayZ,

			       lookup_context);

  void closure (hb_closure_context_t *c, unsigned value, ContextClosureLookupContext &lookup_context) const

    if (unlikely (c->lookup_limit_exceeded ())) return;

    const auto &lookupRecord = StructAfter<UnsizedArrayOf<LookupRecord>>

					   (inputZ.as_array ((inputCount ? inputCount - 1 : 0)));

    context_closure_lookup (c,

			    inputCount, inputZ.arrayZ,

			    lookupCount, lookupRecord.arrayZ,

			    value, lookup_context);

  void closure_lookups (hb_closure_lookups_context_t *c,

                        ContextClosureLookupContext &lookup_context) const

    if (unlikely (c->lookup_limit_exceeded ())) return;

    if (!intersects (c->glyphs, lookup_context)) return;

    const auto &lookupRecord = StructAfter<UnsizedArrayOf<LookupRecord>>

					   (inputZ.as_array (inputCount ? inputCount - 1 : 0));

    recurse_lookups (c, lookupCount, lookupRecord.arrayZ);

  void collect_glyphs (hb_collect_glyphs_context_t *c,

		       ContextCollectGlyphsLookupContext &lookup_context) const

    const auto &lookupRecord = StructAfter<UnsizedArrayOf<LookupRecord>>

					   (inputZ.as_array (inputCount ? inputCount - 1 : 0));

    context_collect_glyphs_lookup (c,

				   inputCount, inputZ.arrayZ,

				   lookupCount, lookupRecord.arrayZ,

				   lookup_context);

  bool would_apply (hb_would_apply_context_t *c,

		    const ContextApplyLookupContext &lookup_context) const

    const auto &lookupRecord = StructAfter<UnsizedArrayOf<LookupRecord>>

					   (inputZ.as_array (inputCount ? inputCount - 1 : 0));

    return context_would_apply_lookup (c,

				       inputCount, inputZ.arrayZ,

				       lookupCount, lookupRecord.arrayZ,

				       lookup_context);

  bool apply (hb_ot_apply_context_t *c,

	      const ContextApplyLookupContext &lookup_context) const

    TRACE_APPLY (this);

    const auto &lookupRecord = StructAfter<UnsizedArrayOf<LookupRecord>>

					   (inputZ.as_array (inputCount ? inputCount - 1 : 0));

    return_trace (context_apply_lookup (c, inputCount, inputZ.arrayZ, lookupCount, lookupRecord.arrayZ, lookup_context));

  bool serialize (hb_serialize_context_t *c,

		  const hb_map_t *input_mapping, /* old->new glyphid or class mapping */

		  const hb_map_t *lookup_map) const

    TRACE_SERIALIZE (this);

    auto *out = c->start_embed (this);

    if (unlikely (!c->extend_min (out))) return_trace (false);

    out->inputCount = inputCount;

    const auto input = inputZ.as_array (inputCount - 1);

    for (const auto org : input)

      HBUINT16 d;

      d = input_mapping->get (org);

      c->copy (d);

    const auto &lookupRecord = StructAfter<UnsizedArrayOf<LookupRecord>>

					   (inputZ.as_array ((inputCount ? inputCount - 1 : 0)));

    unsigned count = serialize_lookuprecord_array (c, lookupRecord.as_array (lookupCount), lookup_map);

    return_trace (c->check_assign (out->lookupCount, count, HB_SERIALIZE_ERROR_INT_OVERFLOW));

  bool subset (hb_subset_context_t *c,

	       const hb_map_t *lookup_map,

	       const hb_map_t *klass_map = nullptr) const

    TRACE_SUBSET (this);

    if (unlikely (!inputCount)) return_trace (false);

    const auto input = inputZ.as_array (inputCount - 1);

    const hb_map_t *mapping = klass_map == nullptr ? c->plan->glyph_map : klass_map;

    if (!hb_all (input, mapping)) return_trace (false);

    return_trace (serialize (c->serializer, mapping, lookup_map));

  public:

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    return_trace (c->check_struct (this) &&

		  hb_barrier () &&

		  c->check_range (inputZ.arrayZ,

				  inputZ.item_size * (inputCount ? inputCount - 1 : 0) +

				  LookupRecord::static_size * lookupCount));

  protected:

  HBUINT16	inputCount;		/* Total number of glyphs in input

					 * glyph sequence--includes the first

					 * glyph */

  HBUINT16	lookupCount;		/* Number of LookupRecords */

  UnsizedArrayOf<typename Types::HBUINT>

		inputZ;			/* Array of match inputs--start with

					 * second glyph */

/*UnsizedArrayOf<LookupRecord>

		lookupRecordX;*/	/* Array of LookupRecords--in

					 * design order */

  public:

  DEFINE_SIZE_ARRAY (4, inputZ);

};

template <typename Types>

struct RuleSet

  using Rule = OT::Rule<Types>;

  bool intersects (const hb_set_t *glyphs,

		   ContextClosureLookupContext &lookup_context) const

    return

    + hb_iter (rule)

    | hb_map (hb_add (this))

    | hb_map ([&] (const Rule &_) { return _.intersects (glyphs, lookup_context); })

    | hb_any

  void closure (hb_closure_context_t *c, unsigned value,

		ContextClosureLookupContext &lookup_context) const

    if (unlikely (c->lookup_limit_exceeded ())) return;

    return

    + hb_iter (rule)

    | hb_map (hb_add (this))

    | hb_apply ([&] (const Rule &_) { _.closure (c, value, lookup_context); })

  void closure_lookups (hb_closure_lookups_context_t *c,

                        ContextClosureLookupContext &lookup_context) const

    if (unlikely (c->lookup_limit_exceeded ())) return;

    + hb_iter (rule)

    | hb_map (hb_add (this))

    | hb_apply ([&] (const Rule &_) { _.closure_lookups (c, lookup_context); })

  void collect_glyphs (hb_collect_glyphs_context_t *c,

		       ContextCollectGlyphsLookupContext &lookup_context) const

    return

    + hb_iter (rule)

    | hb_map (hb_add (this))

    | hb_apply ([&] (const Rule &_) { _.collect_glyphs (c, lookup_context); })

  bool would_apply (hb_would_apply_context_t *c,

		    const ContextApplyLookupContext &lookup_context) const

    return

    + hb_iter (rule)

    | hb_map (hb_add (this))

    | hb_map ([&] (const Rule &_) { return _.would_apply (c, lookup_context); })

    | hb_any

  bool apply (hb_ot_apply_context_t *c,

	      const ContextApplyLookupContext &lookup_context) const

    TRACE_APPLY (this);

    unsigned num_rules = rule.len;

#ifndef HB_NO_OT_RULESETS_FAST_PATH

    if (HB_OPTIMIZE_SIZE_VAL || num_rules <= 4)

#endif

    slow:

      return_trace (

      + hb_iter (rule)

      | hb_map (hb_add (this))

      | hb_map ([&] (const Rule &_) { return _.apply (c, lookup_context); })

      | hb_any

    /* This version is optimized for speed by matching the first & second

     * components of the rule here, instead of calling into the matching code.

     * Replicated from LigatureSet::apply(). */

    hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c->iter_input;

    skippy_iter.reset (c->buffer->idx);

    skippy_iter.set_match_func (match_always, nullptr);

    skippy_iter.set_glyph_data ((HBUINT16 *) nullptr);

    unsigned unsafe_to = (unsigned) -1, unsafe_to1 = 0, unsafe_to2 = 0;

    hb_glyph_info_t *first = nullptr, *second = nullptr;

    bool matched = skippy_iter.next ();

    if (likely (matched))

      first = &c->buffer->info[skippy_iter.idx];

      unsafe_to = skippy_iter.idx + 1;

      if (skippy_iter.may_skip (c->buffer->info[skippy_iter.idx]))

	/* Can't use the fast path if eg. the next char is a default-ignorable

	 * or other skippable. */

        goto slow;

    else

      /* Failed to match a next glyph. Only try applying rules that have

       * no further input. */

      return_trace (

      + hb_iter (rule)

      | hb_map (hb_add (this))

      | hb_filter ([&] (const Rule &_) { return _.inputCount <= 1; })

      | hb_map ([&] (const Rule &_) { return _.apply (c, lookup_context); })

      | hb_any

    matched = skippy_iter.next ();

    if (likely (matched && !skippy_iter.may_skip (c->buffer->info[skippy_iter.idx])))

      second = &c->buffer->info[skippy_iter.idx];

      unsafe_to2 = skippy_iter.idx + 1;

    auto match_input = lookup_context.funcs.match;

    auto *input_data = lookup_context.match_data;

    for (unsigned int i = 0; i < num_rules; i++)

      const auto &r = this+rule.arrayZ[i];

      const auto &input = r.inputZ;

      if (r.inputCount <= 1 ||

	  (!match_input ||

	   match_input (*first, input.arrayZ[0], input_data)))

        if (!second ||

	    (r.inputCount <= 2 ||

	     (!match_input ||

	      match_input (*second, input.arrayZ[1], input_data)))

	  if (r.apply (c, lookup_context))

	    if (unsafe_to != (unsigned) -1)

	      c->buffer->unsafe_to_concat (c->buffer->idx, unsafe_to);

	    return_trace (true);

	else

	  unsafe_to = unsafe_to2;

      else

	if (unsafe_to == (unsigned) -1)

	  unsafe_to = unsafe_to1;

    if (likely (unsafe_to != (unsigned) -1))

      c->buffer->unsafe_to_concat (c->buffer->idx, unsafe_to);

    return_trace (false);

  bool subset (hb_subset_context_t *c,

	       const hb_map_t *lookup_map,

	       const hb_map_t *klass_map = nullptr) const

    TRACE_SUBSET (this);

    auto snap = c->serializer->snapshot ();

    auto *out = c->serializer->start_embed (*this);

    if (unlikely (!c->serializer->extend_min (out))) return_trace (false);

    for (const Offset16To<Rule>& _ : rule)

      if (!_) continue;

      auto o_snap = c->serializer->snapshot ();

      auto *o = out->rule.serialize_append (c->serializer);

      if (unlikely (!o)) continue;

      if (!o->serialize_subset (c, _, this, lookup_map, klass_map))

	out->rule.pop ();

	c->serializer->revert (o_snap);

    bool ret = bool (out->rule);

    if (!ret) c->serializer->revert (snap);

    return_trace (ret);

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    return_trace (rule.sanitize (c, this));

  protected:

  Array16OfOffset16To<Rule>

		rule;			/* Array of Rule tables

					 * ordered by preference */

  public:

  DEFINE_SIZE_ARRAY (2, rule);

};

template <typename Types>

struct ContextFormat1_4

  using RuleSet = OT::RuleSet<Types>;

  bool intersects (const hb_set_t *glyphs) const

    struct ContextClosureLookupContext lookup_context = {

      {intersects_glyph, intersected_glyph},

      ContextFormat::SimpleContext,

      nullptr

};

    return

    + hb_zip (this+coverage, ruleSet)

    | hb_filter (*glyphs, hb_first)

    | hb_map (hb_second)

    | hb_map (hb_add (this))

    | hb_map ([&] (const RuleSet &_) { return _.intersects (glyphs, lookup_context); })

    | hb_any

  bool may_have_non_1to1 () const

  { return true; }

  void closure (hb_closure_context_t *c) const

    hb_set_t* cur_active_glyphs = c->push_cur_active_glyphs ();

    if (unlikely (!cur_active_glyphs)) return;

    get_coverage ().intersect_set (c->previous_parent_active_glyphs (), *cur_active_glyphs);

    struct ContextClosureLookupContext lookup_context = {

      {intersects_glyph, intersected_glyph},

      ContextFormat::SimpleContext,

      nullptr

};

    + hb_zip (this+coverage, hb_range ((unsigned) ruleSet.len))

    | hb_filter ([&] (hb_codepoint_t _) {

      return c->previous_parent_active_glyphs ().has (_);

    }, hb_first)

    | hb_map ([&](const hb_pair_t<hb_codepoint_t, unsigned> _) { return hb_pair_t<unsigned, const RuleSet&> (_.first, this+ruleSet[_.second]); })

    | hb_apply ([&] (const hb_pair_t<unsigned, const RuleSet&>& _) { _.second.closure (c, _.first, lookup_context); })

    c->pop_cur_done_glyphs ();

  void closure_lookups (hb_closure_lookups_context_t *c) const

    struct ContextClosureLookupContext lookup_context = {

      {intersects_glyph, nullptr},

      ContextFormat::SimpleContext,

      nullptr

};

    + hb_zip (this+coverage, ruleSet)

    | hb_filter (*c->glyphs, hb_first)

    | hb_map (hb_second)

    | hb_map (hb_add (this))

    | hb_apply ([&] (const RuleSet &_) { _.closure_lookups (c, lookup_context); })

  void collect_variation_indices (hb_collect_variation_indices_context_t *c) const {}

  void collect_glyphs (hb_collect_glyphs_context_t *c) const

    (this+coverage).collect_coverage (c->input);

    struct ContextCollectGlyphsLookupContext lookup_context = {

      {collect_glyph},

      nullptr

};

    + hb_iter (ruleSet)

    | hb_map (hb_add (this))

    | hb_apply ([&] (const RuleSet &_) { _.collect_glyphs (c, lookup_context); })

  bool would_apply (hb_would_apply_context_t *c) const

    const RuleSet &rule_set = this+ruleSet[(this+coverage).get_coverage (c->glyphs[0])];

    struct ContextApplyLookupContext lookup_context = {

      {match_glyph},

      nullptr

};

    return rule_set.would_apply (c, lookup_context);

  const Coverage &get_coverage () const { return this+coverage; }

  bool apply (hb_ot_apply_context_t *c) const

    TRACE_APPLY (this);

    unsigned int index = (this+coverage).get_coverage (c->buffer->cur().codepoint);

    if (likely (index == NOT_COVERED))

      return_trace (false);

    const RuleSet &rule_set = this+ruleSet[index];

    struct ContextApplyLookupContext lookup_context = {

      {match_glyph},

      nullptr

};

    return_trace (rule_set.apply (c, lookup_context));

  bool subset (hb_subset_context_t *c) const

    TRACE_SUBSET (this);

    const hb_set_t &glyphset = *c->plan->glyphset_gsub ();

    const hb_map_t &glyph_map = *c->plan->glyph_map;

    auto *out = c->serializer->start_embed (*this);

    if (unlikely (!c->serializer->extend_min (out))) return_trace (false);

    out->format = format;

    const hb_map_t *lookup_map = c->table_tag == HB_OT_TAG_GSUB ? &c->plan->gsub_lookups : &c->plan->gpos_lookups;

    hb_sorted_vector_t<hb_codepoint_t> new_coverage;

    + hb_zip (this+coverage, ruleSet)

    | hb_filter (glyphset, hb_first)

    | hb_filter (subset_offset_array (c, out->ruleSet, this, lookup_map), hb_second)

    | hb_map (hb_first)

    | hb_map (glyph_map)

    | hb_sink (new_coverage)

    out->coverage.serialize_serialize (c->serializer, new_coverage.iter ());

    return_trace (bool (new_coverage));

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    return_trace (coverage.sanitize (c, this) && ruleSet.sanitize (c, this));

  protected:

  HBUINT16	format;			/* Format identifier--format = 1 */

  typename Types::template OffsetTo<Coverage>

		coverage;		/* Offset to Coverage table--from

					 * beginning of table */

  Array16Of<typename Types::template OffsetTo<RuleSet>>

		ruleSet;		/* Array of RuleSet tables

					 * ordered by Coverage Index */

  public:

  DEFINE_SIZE_ARRAY (2 + 2 * Types::size, ruleSet);

};

template <typename Types>

struct ContextFormat2_5

  using RuleSet = OT::RuleSet<SmallTypes>;

  bool intersects (const hb_set_t *glyphs) const

    if (!(this+coverage).intersects (glyphs))

      return false;

    const ClassDef &class_def = this+classDef;

    hb_map_t cache;

    struct ContextClosureLookupContext lookup_context = {

      {intersects_class, nullptr},

      ContextFormat::ClassBasedContext,

      &class_def,

      &cache

};

    hb_set_t retained_coverage_glyphs;

    (this+coverage).intersect_set (*glyphs, retained_coverage_glyphs);

    hb_set_t coverage_glyph_classes;

    class_def.intersected_classes (&retained_coverage_glyphs, &coverage_glyph_classes);

    return

    + hb_iter (ruleSet)

    | hb_map (hb_add (this))

    | hb_enumerate

    | hb_map ([&] (const hb_pair_t<unsigned, const RuleSet &> p)

	      { return class_def.intersects_class (glyphs, p.first) &&

		       coverage_glyph_classes.has (p.first) &&

		       p.second.intersects (glyphs, lookup_context); })

    | hb_any

  bool may_have_non_1to1 () const

  { return true; }

  void closure (hb_closure_context_t *c) const

    if (!(this+coverage).intersects (c->glyphs))

      return;

    hb_set_t* cur_active_glyphs = c->push_cur_active_glyphs ();

    if (unlikely (!cur_active_glyphs)) return;

    get_coverage ().intersect_set (c->previous_parent_active_glyphs (),

				   *cur_active_glyphs);

    const ClassDef &class_def = this+classDef;

    hb_map_t cache;

    intersected_class_cache_t intersected_cache;

    struct ContextClosureLookupContext lookup_context = {

      {intersects_class, intersected_class_glyphs},

      ContextFormat::ClassBasedContext,

      &class_def,

      &cache,

      &intersected_cache

};

    + hb_enumerate (ruleSet)

    | hb_filter ([&] (unsigned _)

    { return class_def.intersects_class (&c->parent_active_glyphs (), _); },

		 hb_first)

    | hb_apply ([&] (const hb_pair_t<unsigned, const typename Types::template OffsetTo<RuleSet>&> _)

                  const RuleSet& rule_set = this+_.second;

                  rule_set.closure (c, _.first, lookup_context);

})

    c->pop_cur_done_glyphs ();

  void closure_lookups (hb_closure_lookups_context_t *c) const

    if (!(this+coverage).intersects (c->glyphs))

      return;

    const ClassDef &class_def = this+classDef;

    hb_map_t cache;

    struct ContextClosureLookupContext lookup_context = {

      {intersects_class, nullptr},

      ContextFormat::ClassBasedContext,

      &class_def,

      &cache

};

    + hb_iter (ruleSet)

    | hb_map (hb_add (this))

    | hb_enumerate

    | hb_filter ([&] (const hb_pair_t<unsigned, const RuleSet &> p)

    { return class_def.intersects_class (c->glyphs, p.first); })

    | hb_map (hb_second)

    | hb_apply ([&] (const RuleSet & _)

    { _.closure_lookups (c, lookup_context); });

  void collect_variation_indices (hb_collect_variation_indices_context_t *c) const {}

  void collect_glyphs (hb_collect_glyphs_context_t *c) const

    (this+coverage).collect_coverage (c->input);

    const ClassDef &class_def = this+classDef;

    struct ContextCollectGlyphsLookupContext lookup_context = {

      {collect_class},

      &class_def

};

    + hb_iter (ruleSet)

    | hb_map (hb_add (this))

    | hb_apply ([&] (const RuleSet &_) { _.collect_glyphs (c, lookup_context); })

  bool would_apply (hb_would_apply_context_t *c) const

    const ClassDef &class_def = this+classDef;

    unsigned int index = class_def.get_class (c->glyphs[0]);

    const RuleSet &rule_set = this+ruleSet[index];

    struct ContextApplyLookupContext lookup_context = {

      {match_class},

      &class_def

};

    return rule_set.would_apply (c, lookup_context);

  const Coverage &get_coverage () const { return this+coverage; }

  unsigned cache_cost () const

    unsigned c = (this+classDef).cost () * ruleSet.len;

    return c >= 4 ? c : 0;

  bool cache_func (hb_ot_apply_context_t *c, bool enter) const

    if (enter)

      if (!HB_BUFFER_TRY_ALLOCATE_VAR (c->buffer, syllable))

	return false;

      auto &info = c->buffer->info;

      unsigned count = c->buffer->len;

      for (unsigned i = 0; i < count; i++)

	info[i].syllable() = 255;

      c->new_syllables = 255;

      return true;

    else

      c->new_syllables = (unsigned) -1;

      HB_BUFFER_DEALLOCATE_VAR (c->buffer, syllable);

      return true;

  bool apply_cached (hb_ot_apply_context_t *c) const { return _apply (c, true); }

  bool apply (hb_ot_apply_context_t *c) const { return _apply (c, false); }

  bool _apply (hb_ot_apply_context_t *c, bool cached) const

    TRACE_APPLY (this);

    unsigned int index = (this+coverage).get_coverage (c->buffer->cur().codepoint);

    if (likely (index == NOT_COVERED)) return_trace (false);

    const ClassDef &class_def = this+classDef;

    struct ContextApplyLookupContext lookup_context = {

      {cached ? match_class_cached : match_class},

      &class_def

};

    if (cached && c->buffer->cur().syllable() < 255)

      index = c->buffer->cur().syllable ();

    else

      index = class_def.get_class (c->buffer->cur().codepoint);

    const RuleSet &rule_set = this+ruleSet[index];

    return_trace (rule_set.apply (c, lookup_context));

  bool subset (hb_subset_context_t *c) const

    TRACE_SUBSET (this);

    auto *out = c->serializer->start_embed (*this);

    if (unlikely (!c->serializer->extend_min (out))) return_trace (false);

    out->format = format;

    if (unlikely (!out->coverage.serialize_subset (c, coverage, this)))

      return_trace (false);

    hb_map_t klass_map;

    out->classDef.serialize_subset (c, classDef, this, &klass_map);

    const hb_set_t* glyphset = c->plan->glyphset_gsub ();

    hb_set_t retained_coverage_glyphs;

    (this+coverage).intersect_set (*glyphset, retained_coverage_glyphs);

    hb_set_t coverage_glyph_classes;

    (this+classDef).intersected_classes (&retained_coverage_glyphs, &coverage_glyph_classes);

    const hb_map_t *lookup_map = c->table_tag == HB_OT_TAG_GSUB ? &c->plan->gsub_lookups : &c->plan->gpos_lookups;

    bool ret = true;

    int non_zero_index = -1, index = 0;

    auto snapshot = c->serializer->snapshot();

    for (const auto& _ : + hb_enumerate (ruleSet)

			 | hb_filter (klass_map, hb_first))

      auto *o = out->ruleSet.serialize_append (c->serializer);

      if (unlikely (!o))

	ret = false;

	break;

      if (coverage_glyph_classes.has (_.first) &&

	  o->serialize_subset (c, _.second, this, lookup_map, &klass_map)) {

	non_zero_index = index;

        snapshot = c->serializer->snapshot();

      index++;

    if (!ret || non_zero_index == -1) return_trace (false);

    //prune empty trailing ruleSets

    --index;

    while (index > non_zero_index)

      out->ruleSet.pop ();

      index--;

    c->serializer->revert (snapshot);

    return_trace (bool (out->ruleSet));

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    return_trace (coverage.sanitize (c, this) && classDef.sanitize (c, this) && ruleSet.sanitize (c, this));

  protected:

  HBUINT16	format;			/* Format identifier--format = 2 */

  typename Types::template OffsetTo<Coverage>

		coverage;		/* Offset to Coverage table--from

					 * beginning of table */

  typename Types::template OffsetTo<ClassDef>

		classDef;		/* Offset to glyph ClassDef table--from

					 * beginning of table */

  Array16Of<typename Types::template OffsetTo<RuleSet>>

		ruleSet;		/* Array of RuleSet tables

					 * ordered by class */

  public:

  DEFINE_SIZE_ARRAY (4 + 2 * Types::size, ruleSet);

};

struct ContextFormat3

  using RuleSet = OT::RuleSet<SmallTypes>;

  bool intersects (const hb_set_t *glyphs) const

    if (!(this+coverageZ[0]).intersects (glyphs))

      return false;

    struct ContextClosureLookupContext lookup_context = {

      {intersects_coverage, nullptr},

      ContextFormat::CoverageBasedContext,

      this

};

    return context_intersects (glyphs,

			       glyphCount, (const HBUINT16 *) (coverageZ.arrayZ + 1),

			       lookup_context);

  bool may_have_non_1to1 () const

  { return true; }

  void closure (hb_closure_context_t *c) const

    if (!(this+coverageZ[0]).intersects (c->glyphs))

      return;

    hb_set_t* cur_active_glyphs = c->push_cur_active_glyphs ();

    if (unlikely (!cur_active_glyphs)) return;

    get_coverage ().intersect_set (c->previous_parent_active_glyphs (),

				   *cur_active_glyphs);

    const LookupRecord *lookupRecord = &StructAfter<LookupRecord> (coverageZ.as_array (glyphCount));

    struct ContextClosureLookupContext lookup_context = {

      {intersects_coverage, intersected_coverage_glyphs},

      ContextFormat::CoverageBasedContext,

      this

};

    context_closure_lookup (c,

			    glyphCount, (const HBUINT16 *) (coverageZ.arrayZ + 1),

			    lookupCount, lookupRecord,

			    0, lookup_context);

    c->pop_cur_done_glyphs ();

  void closure_lookups (hb_closure_lookups_context_t *c) const

    if (!intersects (c->glyphs))

      return;

    const LookupRecord *lookupRecord = &StructAfter<LookupRecord> (coverageZ.as_array (glyphCount));

    recurse_lookups (c, lookupCount, lookupRecord);

  void collect_variation_indices (hb_collect_variation_indices_context_t *c) const {}

  void collect_glyphs (hb_collect_glyphs_context_t *c) const

    (this+coverageZ[0]).collect_coverage (c->input);

    const LookupRecord *lookupRecord = &StructAfter<LookupRecord> (coverageZ.as_array (glyphCount));

    struct ContextCollectGlyphsLookupContext lookup_context = {

      {collect_coverage},

      this

};

    context_collect_glyphs_lookup (c,

				   glyphCount, (const HBUINT16 *) (coverageZ.arrayZ + 1),

				   lookupCount, lookupRecord,

				   lookup_context);

  bool would_apply (hb_would_apply_context_t *c) const

    const LookupRecord *lookupRecord = &StructAfter<LookupRecord> (coverageZ.as_array (glyphCount));

    struct ContextApplyLookupContext lookup_context = {

      {match_coverage},

      this

};

    return context_would_apply_lookup (c,

				       glyphCount, (const HBUINT16 *) (coverageZ.arrayZ + 1),

				       lookupCount, lookupRecord,

				       lookup_context);

  const Coverage &get_coverage () const { return this+coverageZ[0]; }

  bool apply (hb_ot_apply_context_t *c) const

    TRACE_APPLY (this);

    unsigned int index = (this+coverageZ[0]).get_coverage (c->buffer->cur().codepoint);

    if (likely (index == NOT_COVERED)) return_trace (false);

    const LookupRecord *lookupRecord = &StructAfter<LookupRecord> (coverageZ.as_array (glyphCount));

    struct ContextApplyLookupContext lookup_context = {

      {match_coverage},

      this

};

    return_trace (context_apply_lookup (c, glyphCount, (const HBUINT16 *) (coverageZ.arrayZ + 1), lookupCount, lookupRecord, lookup_context));

  bool subset (hb_subset_context_t *c) const

    TRACE_SUBSET (this);

    auto *out = c->serializer->start_embed (this);

    if (unlikely (!c->serializer->extend_min (out))) return_trace (false);

    out->format = format;

    out->glyphCount = glyphCount;

    auto coverages = coverageZ.as_array (glyphCount);

    for (const Offset16To<Coverage>& offset : coverages)

      /* TODO(subset) This looks like should not be necessary to write this way. */

      auto *o = c->serializer->allocate_size<Offset16To<Coverage>> (Offset16To<Coverage>::static_size);

      if (unlikely (!o)) return_trace (false);

      if (!o->serialize_subset (c, offset, this)) return_trace (false);

    const auto& lookupRecord = StructAfter<UnsizedArrayOf<LookupRecord>> (coverageZ.as_array (glyphCount));

    const hb_map_t *lookup_map = c->table_tag == HB_OT_TAG_GSUB ? &c->plan->gsub_lookups : &c->plan->gpos_lookups;

    unsigned count = serialize_lookuprecord_array (c->serializer, lookupRecord.as_array (lookupCount), lookup_map);

    return_trace (c->serializer->check_assign (out->lookupCount, count, HB_SERIALIZE_ERROR_INT_OVERFLOW));

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    if (unlikely (!c->check_struct (this))) return_trace (false);

    hb_barrier ();

    unsigned int count = glyphCount;

    if (unlikely (!count)) return_trace (false); /* We want to access coverageZ[0] freely. */

    if (unlikely (!c->check_array (coverageZ.arrayZ, count))) return_trace (false);

    for (unsigned int i = 0; i < count; i++)

      if (unlikely (!coverageZ[i].sanitize (c, this))) return_trace (false);

    const LookupRecord *lookupRecord = &StructAfter<LookupRecord> (coverageZ.as_array (glyphCount));

    return_trace (likely (c->check_array (lookupRecord, lookupCount)));

  protected:

  HBUINT16	format;			/* Format identifier--format = 3 */

  HBUINT16	glyphCount;		/* Number of glyphs in the input glyph

					 * sequence */

  HBUINT16	lookupCount;		/* Number of LookupRecords */

  UnsizedArrayOf<Offset16To<Coverage>>

		coverageZ;		/* Array of offsets to Coverage

					 * table in glyph sequence order */

/*UnsizedArrayOf<LookupRecord>

		lookupRecordX;*/	/* Array of LookupRecords--in

					 * design order */

  public:

  DEFINE_SIZE_ARRAY (6, coverageZ);

};

struct Context

  template <typename context_t, typename ...Ts>

  typename context_t::return_t dispatch (context_t *c, Ts&&... ds) const

    if (unlikely (!c->may_dispatch (this, &u.format))) return c->no_dispatch_return_value ();

    TRACE_DISPATCH (this, u.format);

    switch (u.format) {

    case 1: hb_barrier (); return_trace (c->dispatch (u.format1, std::forward<Ts> (ds)...));

    case 2: hb_barrier (); return_trace (c->dispatch (u.format2, std::forward<Ts> (ds)...));

    case 3: hb_barrier (); return_trace (c->dispatch (u.format3, std::forward<Ts> (ds)...));

#ifndef HB_NO_BEYOND_64K

    case 4: hb_barrier (); return_trace (c->dispatch (u.format4, std::forward<Ts> (ds)...));

    case 5: hb_barrier (); return_trace (c->dispatch (u.format5, std::forward<Ts> (ds)...));

#endif

    default:return_trace (c->default_return_value ());

  protected:

  union {

  HBUINT16			format;		/* Format identifier */

  ContextFormat1_4<SmallTypes>	format1;

  ContextFormat2_5<SmallTypes>	format2;

  ContextFormat3		format3;

#ifndef HB_NO_BEYOND_64K

  ContextFormat1_4<MediumTypes>	format4;

  ContextFormat2_5<MediumTypes>	format5;

#endif

  } u;

};

/* Chaining Contextual lookups */

struct ChainContextClosureLookupContext

  ContextClosureFuncs funcs;

  ContextFormat context_format;

  const void *intersects_data[3];

  void *intersects_cache[3];

  void *intersected_glyphs_cache;

};

struct ChainContextCollectGlyphsLookupContext

  ContextCollectGlyphsFuncs funcs;

  const void *collect_data[3];

};

struct ChainContextApplyLookupContext

  ChainContextApplyFuncs funcs;

  const void *match_data[3];

};

template <typename HBUINT>

static inline bool chain_context_intersects (const hb_set_t *glyphs,

					     unsigned int backtrackCount,

					     const HBUINT backtrack[],

					     unsigned int inputCount, /* Including the first glyph (not matched) */

					     const HBUINT input[], /* Array of input values--start with second glyph */

					     unsigned int lookaheadCount,

					     const HBUINT lookahead[],

					     ChainContextClosureLookupContext &lookup_context)

  return array_is_subset_of (glyphs,

			     backtrackCount, backtrack,

			     lookup_context.funcs.intersects,

			     lookup_context.intersects_data[0],

			     lookup_context.intersects_cache[0])

      && array_is_subset_of (glyphs,

			     inputCount ? inputCount - 1 : 0, input,

			     lookup_context.funcs.intersects,

			     lookup_context.intersects_data[1],

			     lookup_context.intersects_cache[1])

      && array_is_subset_of (glyphs,

			     lookaheadCount, lookahead,

			     lookup_context.funcs.intersects,

			     lookup_context.intersects_data[2],

			     lookup_context.intersects_cache[2]);

template <typename HBUINT>

static inline void chain_context_closure_lookup (hb_closure_context_t *c,

						 unsigned int backtrackCount,

						 const HBUINT backtrack[],

						 unsigned int inputCount, /* Including the first glyph (not matched) */

						 const HBUINT input[], /* Array of input values--start with second glyph */

						 unsigned int lookaheadCount,

						 const HBUINT lookahead[],

						 unsigned int lookupCount,

						 const LookupRecord lookupRecord[],

						 unsigned value,

						 ChainContextClosureLookupContext &lookup_context)

  if (chain_context_intersects (c->glyphs,

				backtrackCount, backtrack,

				inputCount, input,

				lookaheadCount, lookahead,

				lookup_context))

    context_closure_recurse_lookups (c,

		     inputCount, input,

		     lookupCount, lookupRecord,

		     value,

		     lookup_context.context_format,

		     lookup_context.intersects_data[1],

		     lookup_context.funcs.intersected_glyphs,

		     lookup_context.intersected_glyphs_cache);

template <typename HBUINT>

static inline void chain_context_collect_glyphs_lookup (hb_collect_glyphs_context_t *c,

							unsigned int backtrackCount,

							const HBUINT backtrack[],

							unsigned int inputCount, /* Including the first glyph (not matched) */

							const HBUINT input[], /* Array of input values--start with second glyph */

							unsigned int lookaheadCount,

							const HBUINT lookahead[],

							unsigned int lookupCount,

							const LookupRecord lookupRecord[],

							ChainContextCollectGlyphsLookupContext &lookup_context)

  collect_array (c, c->before,

		 backtrackCount, backtrack,

		 lookup_context.funcs.collect, lookup_context.collect_data[0]);

  collect_array (c, c->input,

		 inputCount ? inputCount - 1 : 0, input,

		 lookup_context.funcs.collect, lookup_context.collect_data[1]);

  collect_array (c, c->after,

		 lookaheadCount, lookahead,

		 lookup_context.funcs.collect, lookup_context.collect_data[2]);

  recurse_lookups (c,

		   lookupCount, lookupRecord);

template <typename HBUINT>

static inline bool chain_context_would_apply_lookup (hb_would_apply_context_t *c,

						     unsigned int backtrackCount,

						     const HBUINT backtrack[] HB_UNUSED,

						     unsigned int inputCount, /* Including the first glyph (not matched) */

						     const HBUINT input[], /* Array of input values--start with second glyph */

						     unsigned int lookaheadCount,

						     const HBUINT lookahead[] HB_UNUSED,

						     unsigned int lookupCount HB_UNUSED,

						     const LookupRecord lookupRecord[] HB_UNUSED,

						     const ChainContextApplyLookupContext &lookup_context)

  return (c->zero_context ? !backtrackCount && !lookaheadCount : true)

      && would_match_input (c,

			    inputCount, input,

			    lookup_context.funcs.match[1], lookup_context.match_data[1]);

template <typename HBUINT>

HB_ALWAYS_INLINE

static bool chain_context_apply_lookup (hb_ot_apply_context_t *c,

					unsigned int backtrackCount,

					const HBUINT backtrack[],

					unsigned int inputCount, /* Including the first glyph (not matched) */

					const HBUINT input[], /* Array of input values--start with second glyph */

					unsigned int lookaheadCount,

					const HBUINT lookahead[],

					unsigned int lookupCount,

					const LookupRecord lookupRecord[],

					const ChainContextApplyLookupContext &lookup_context)

  if (unlikely (inputCount > HB_MAX_CONTEXT_LENGTH)) return false;

  unsigned match_positions_stack[4];

  unsigned *match_positions = match_positions_stack;

  if (unlikely (inputCount > ARRAY_LENGTH (match_positions_stack)))

    match_positions = (unsigned *) hb_malloc (hb_max (inputCount, 1u) * sizeof (match_positions[0]));

    if (unlikely (!match_positions))

      return false;

  unsigned start_index = c->buffer->out_len;

  unsigned end_index = c->buffer->idx;

  unsigned match_end = 0;

  bool ret = true;

  if (!(match_input (c,

		     inputCount, input,

		     lookup_context.funcs.match[1], lookup_context.match_data[1],

		     &match_end, match_positions) && (end_index = match_end)

       && match_lookahead (c,

			   lookaheadCount, lookahead,

			   lookup_context.funcs.match[2], lookup_context.match_data[2],

			   match_end, &end_index)))

    c->buffer->unsafe_to_concat (c->buffer->idx, end_index);

    ret = false;

    goto done;

  if (!match_backtrack (c,

			backtrackCount, backtrack,

			lookup_context.funcs.match[0], lookup_context.match_data[0],

			&start_index))

    c->buffer->unsafe_to_concat_from_outbuffer (start_index, end_index);

    ret = false;

    goto done;

  c->buffer->unsafe_to_break_from_outbuffer (start_index, end_index);

  apply_lookup (c,

		inputCount, match_positions,

		lookupCount, lookupRecord,

		match_end);

  done:

  if (unlikely (match_positions != match_positions_stack))

    hb_free (match_positions);

  return ret;

template <typename Types>

struct ChainRule

  template <typename T>

  friend struct ChainRuleSet;

  bool intersects (const hb_set_t *glyphs, ChainContextClosureLookupContext &lookup_context) const

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    return chain_context_intersects (glyphs,

				     backtrack.len, backtrack.arrayZ,

				     input.lenP1, input.arrayZ,

				     lookahead.len, lookahead.arrayZ,

				     lookup_context);

  void closure (hb_closure_context_t *c, unsigned value,

		ChainContextClosureLookupContext &lookup_context) const

    if (unlikely (c->lookup_limit_exceeded ())) return;

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    chain_context_closure_lookup (c,

				  backtrack.len, backtrack.arrayZ,

				  input.lenP1, input.arrayZ,

				  lookahead.len, lookahead.arrayZ,

				  lookup.len, lookup.arrayZ,

				  value,

				  lookup_context);

  void closure_lookups (hb_closure_lookups_context_t *c,

                        ChainContextClosureLookupContext &lookup_context) const

    if (unlikely (c->lookup_limit_exceeded ())) return;

    if (!intersects (c->glyphs, lookup_context)) return;

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    recurse_lookups (c, lookup.len, lookup.arrayZ);

  void collect_glyphs (hb_collect_glyphs_context_t *c,

		       ChainContextCollectGlyphsLookupContext &lookup_context) const

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    chain_context_collect_glyphs_lookup (c,

					 backtrack.len, backtrack.arrayZ,

					 input.lenP1, input.arrayZ,

					 lookahead.len, lookahead.arrayZ,

					 lookup.len, lookup.arrayZ,

					 lookup_context);

  bool would_apply (hb_would_apply_context_t *c,

		    const ChainContextApplyLookupContext &lookup_context) const

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    return chain_context_would_apply_lookup (c,

					     backtrack.len, backtrack.arrayZ,

					     input.lenP1, input.arrayZ,

					     lookahead.len, lookahead.arrayZ, lookup.len,

					     lookup.arrayZ, lookup_context);

  bool apply (hb_ot_apply_context_t *c,

	      const ChainContextApplyLookupContext &lookup_context) const

    TRACE_APPLY (this);

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    return_trace (chain_context_apply_lookup (c,

					      backtrack.len, backtrack.arrayZ,

					      input.lenP1, input.arrayZ,

					      lookahead.len, lookahead.arrayZ, lookup.len,

					      lookup.arrayZ, lookup_context));

  template<typename Iterator,

	   hb_requires (hb_is_iterator (Iterator))>

  void serialize_array (hb_serialize_context_t *c,

			HBUINT16 len,

			Iterator it) const

    c->copy (len);

    for (const auto g : it)

      c->copy ((HBUINT16) g);

  bool serialize (hb_serialize_context_t *c,

		  const hb_map_t *lookup_map,

		  const hb_map_t *backtrack_map,

		  const hb_map_t *input_map = nullptr,

		  const hb_map_t *lookahead_map = nullptr) const

    TRACE_SERIALIZE (this);

    const hb_map_t *mapping = backtrack_map;

    serialize_array (c, backtrack.len, + backtrack.iter ()

				       | hb_map (mapping));

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    if (input_map) mapping = input_map;

    serialize_array (c, input.lenP1, + input.iter ()

				     | hb_map (mapping));

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    if (lookahead_map) mapping = lookahead_map;

    serialize_array (c, lookahead.len, + lookahead.iter ()

				       | hb_map (mapping));

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    HBUINT16* lookupCount = c->embed (&(lookup.len));

    if (!lookupCount) return_trace (false);

    unsigned count = serialize_lookuprecord_array (c, lookup.as_array (), lookup_map);

    return_trace (c->check_assign (*lookupCount, count, HB_SERIALIZE_ERROR_INT_OVERFLOW));

  bool subset (hb_subset_context_t *c,

	       const hb_map_t *lookup_map,

	       const hb_map_t *backtrack_map = nullptr,

	       const hb_map_t *input_map = nullptr,

	       const hb_map_t *lookahead_map = nullptr) const

    TRACE_SUBSET (this);

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    if (!backtrack_map)

      const hb_set_t &glyphset = *c->plan->glyphset_gsub ();

      if (!hb_all (backtrack, glyphset) ||

	  !hb_all (input, glyphset) ||

	  !hb_all (lookahead, glyphset))

	return_trace (false);

      serialize (c->serializer, lookup_map, c->plan->glyph_map);

    else

      if (!hb_all (backtrack, backtrack_map) ||

	  !hb_all (input, input_map) ||

	  !hb_all (lookahead, lookahead_map))

	return_trace (false);

      serialize (c->serializer, lookup_map, backtrack_map, input_map, lookahead_map);

    return_trace (true);

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    /* Hyper-optimized sanitized because this is really hot. */

    if (unlikely (!backtrack.len.sanitize (c))) return_trace (false);

    hb_barrier ();

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    if (unlikely (!input.lenP1.sanitize (c))) return_trace (false);

    hb_barrier ();

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    if (unlikely (!lookahead.len.sanitize (c))) return_trace (false);

    hb_barrier ();

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    return_trace (likely (lookup.sanitize (c)));

  protected:

  Array16Of<typename Types::HBUINT>

		backtrack;		/* Array of backtracking values

					 * (to be matched before the input

					 * sequence) */

  HeadlessArray16Of<typename Types::HBUINT>

		inputX;			/* Array of input values (start with

					 * second glyph) */

  Array16Of<typename Types::HBUINT>

		lookaheadX;		/* Array of lookahead values's (to be

					 * matched after the input sequence) */

  Array16Of<LookupRecord>

		lookupX;		/* Array of LookupRecords--in

					 * design order) */

  public:

  DEFINE_SIZE_MIN (8);

};

template <typename Types>

struct ChainRuleSet

  using ChainRule = OT::ChainRule<Types>;

  bool intersects (const hb_set_t *glyphs, ChainContextClosureLookupContext &lookup_context) const

    return

    + hb_iter (rule)

    | hb_map (hb_add (this))

    | hb_map ([&] (const ChainRule &_) { return _.intersects (glyphs, lookup_context); })

    | hb_any

  void closure (hb_closure_context_t *c, unsigned value, ChainContextClosureLookupContext &lookup_context) const

    if (unlikely (c->lookup_limit_exceeded ())) return;

    return

    + hb_iter (rule)

    | hb_map (hb_add (this))

    | hb_apply ([&] (const ChainRule &_) { _.closure (c, value, lookup_context); })

  void closure_lookups (hb_closure_lookups_context_t *c,

                        ChainContextClosureLookupContext &lookup_context) const

    if (unlikely (c->lookup_limit_exceeded ())) return;

    + hb_iter (rule)

    | hb_map (hb_add (this))

    | hb_apply ([&] (const ChainRule &_) { _.closure_lookups (c, lookup_context); })

  void collect_glyphs (hb_collect_glyphs_context_t *c, ChainContextCollectGlyphsLookupContext &lookup_context) const

    return

    + hb_iter (rule)

    | hb_map (hb_add (this))

    | hb_apply ([&] (const ChainRule &_) { _.collect_glyphs (c, lookup_context); })

  bool would_apply (hb_would_apply_context_t *c,

		    const ChainContextApplyLookupContext &lookup_context) const

    return

    + hb_iter (rule)

    | hb_map (hb_add (this))

    | hb_map ([&] (const ChainRule &_) { return _.would_apply (c, lookup_context); })

    | hb_any

  bool apply (hb_ot_apply_context_t *c,

	      const ChainContextApplyLookupContext &lookup_context) const

    TRACE_APPLY (this);

    unsigned num_rules = rule.len;

#ifndef HB_NO_OT_RULESETS_FAST_PATH

    if (HB_OPTIMIZE_SIZE_VAL || num_rules <= 4)

#endif

    slow:

      return_trace (

      + hb_iter (rule)

      | hb_map (hb_add (this))

      | hb_map ([&] (const ChainRule &_) { return _.apply (c, lookup_context); })

      | hb_any

    /* This version is optimized for speed by matching the first & second

     * components of the rule here, instead of calling into the matching code.

     * Replicated from LigatureSet::apply(). */

    /* If the input skippy has non-auto joiners behavior (as in Indic shapers),

     * skip this fast path, as we don't distinguish between input & lookahead

     * matching in the fast path.

     * https://github.com/harfbuzz/harfbuzz/issues/4813

*/

    if (!c->auto_zwnj || !c->auto_zwj)

      goto slow;

    hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c->iter_input;

    skippy_iter.reset (c->buffer->idx);

    skippy_iter.set_match_func (match_always, nullptr);

    skippy_iter.set_glyph_data ((HBUINT16 *) nullptr);

    unsigned unsafe_to = (unsigned) -1, unsafe_to1 = 0, unsafe_to2 = 0;

    hb_glyph_info_t *first = nullptr, *second = nullptr;

    bool matched = skippy_iter.next ();

    if (likely (matched))

      first = &c->buffer->info[skippy_iter.idx];

      unsafe_to1 = skippy_iter.idx + 1;

      if (skippy_iter.may_skip (c->buffer->info[skippy_iter.idx]))

	/* Can't use the fast path if eg. the next char is a default-ignorable

	 * or other skippable. */

        goto slow;

    else

      /* Failed to match a next glyph. Only try applying rules that have

       * no further input and lookahead. */

      return_trace (

      + hb_iter (rule)

      | hb_map (hb_add (this))

      | hb_filter ([&] (const ChainRule &_)

		     const auto &input = StructAfter<decltype (_.inputX)> (_.backtrack);

		     const auto &lookahead = StructAfter<decltype (_.lookaheadX)> (input);

		     return input.lenP1 <= 1 && lookahead.len == 0;

})

      | hb_map ([&] (const ChainRule &_) { return _.apply (c, lookup_context); })

      | hb_any

    matched = skippy_iter.next ();

    if (likely (matched && !skippy_iter.may_skip (c->buffer->info[skippy_iter.idx])))

      second = &c->buffer->info[skippy_iter.idx];

      unsafe_to2 = skippy_iter.idx + 1;

    auto match_input = lookup_context.funcs.match[1];

    auto match_lookahead = lookup_context.funcs.match[2];

    auto *input_data = lookup_context.match_data[1];

    auto *lookahead_data = lookup_context.match_data[2];

    for (unsigned int i = 0; i < num_rules; i++)

      const auto &r = this+rule.arrayZ[i];

      const auto &input = StructAfter<decltype (r.inputX)> (r.backtrack);

      const auto &lookahead = StructAfter<decltype (r.lookaheadX)> (input);

      unsigned lenP1 = hb_max ((unsigned) input.lenP1, 1u);

      if (lenP1 > 1 ?

	   (!match_input ||

	    match_input (*first, input.arrayZ[0], input_data))

	   (!lookahead.len || !match_lookahead ||

	    match_lookahead (*first, lookahead.arrayZ[0], lookahead_data)))

        if (!second ||

	    (lenP1 > 2 ?

	     (!match_input ||

	      match_input (*second, input.arrayZ[1], input_data))

	     (lookahead.len <= 2 - lenP1 || !match_lookahead ||

	      match_lookahead (*second, lookahead.arrayZ[2 - lenP1], lookahead_data))))

	  if (r.apply (c, lookup_context))

	    if (unsafe_to != (unsigned) -1)

	      c->buffer->unsafe_to_concat (c->buffer->idx, unsafe_to);

	    return_trace (true);

	else

	  unsafe_to = unsafe_to2;

      else

	if (unsafe_to == (unsigned) -1)

	  unsafe_to = unsafe_to1;

    if (likely (unsafe_to != (unsigned) -1))

      c->buffer->unsafe_to_concat (c->buffer->idx, unsafe_to);

    return_trace (false);

  bool subset (hb_subset_context_t *c,

	       const hb_map_t *lookup_map,

	       const hb_map_t *backtrack_klass_map = nullptr,

	       const hb_map_t *input_klass_map = nullptr,

	       const hb_map_t *lookahead_klass_map = nullptr) const

    TRACE_SUBSET (this);

    auto snap = c->serializer->snapshot ();

    auto *out = c->serializer->start_embed (*this);

    if (unlikely (!c->serializer->extend_min (out))) return_trace (false);

    for (const Offset16To<ChainRule>& _ : rule)

      if (!_) continue;

      auto o_snap = c->serializer->snapshot ();

      auto *o = out->rule.serialize_append (c->serializer);

      if (unlikely (!o)) continue;

      if (!o->serialize_subset (c, _, this,

				lookup_map,

				backtrack_klass_map,

				input_klass_map,

				lookahead_klass_map))

	out->rule.pop ();

	c->serializer->revert (o_snap);

    bool ret = bool (out->rule);

    if (!ret) c->serializer->revert (snap);

    return_trace (ret);

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    return_trace (rule.sanitize (c, this));

  protected:

  Array16OfOffset16To<ChainRule>

		rule;			/* Array of ChainRule tables

					 * ordered by preference */

  public:

  DEFINE_SIZE_ARRAY (2, rule);

};

template <typename Types>

struct ChainContextFormat1_4

  using ChainRuleSet = OT::ChainRuleSet<Types>;

  bool intersects (const hb_set_t *glyphs) const

    struct ChainContextClosureLookupContext lookup_context = {

      {intersects_glyph, intersected_glyph},

      ContextFormat::SimpleContext,

      {nullptr, nullptr, nullptr}

};

    return

    + hb_zip (this+coverage, ruleSet)

    | hb_filter (*glyphs, hb_first)

    | hb_map (hb_second)

    | hb_map (hb_add (this))

    | hb_map ([&] (const ChainRuleSet &_) { return _.intersects (glyphs, lookup_context); })

    | hb_any

  bool may_have_non_1to1 () const

  { return true; }

  void closure (hb_closure_context_t *c) const

    hb_set_t* cur_active_glyphs = c->push_cur_active_glyphs ();

    if (unlikely (!cur_active_glyphs)) return;

    get_coverage ().intersect_set (c->previous_parent_active_glyphs (),

				   *cur_active_glyphs);

    struct ChainContextClosureLookupContext lookup_context = {

      {intersects_glyph, intersected_glyph},

      ContextFormat::SimpleContext,

      {nullptr, nullptr, nullptr}

};

    + hb_zip (this+coverage, hb_range ((unsigned) ruleSet.len))

    | hb_filter ([&] (hb_codepoint_t _) {

      return c->previous_parent_active_glyphs ().has (_);

    }, hb_first)

    | hb_map ([&](const hb_pair_t<hb_codepoint_t, unsigned> _) { return hb_pair_t<unsigned, const ChainRuleSet&> (_.first, this+ruleSet[_.second]); })

    | hb_apply ([&] (const hb_pair_t<unsigned, const ChainRuleSet&>& _) { _.second.closure (c, _.first, lookup_context); })

    c->pop_cur_done_glyphs ();

  void closure_lookups (hb_closure_lookups_context_t *c) const

    struct ChainContextClosureLookupContext lookup_context = {

      {intersects_glyph, nullptr},

      ContextFormat::SimpleContext,

      {nullptr, nullptr, nullptr}

};

    + hb_zip (this+coverage, ruleSet)

    | hb_filter (*c->glyphs, hb_first)

    | hb_map (hb_second)

    | hb_map (hb_add (this))

    | hb_apply ([&] (const ChainRuleSet &_) { _.closure_lookups (c, lookup_context); })

  void collect_variation_indices (hb_collect_variation_indices_context_t *c) const {}

  void collect_glyphs (hb_collect_glyphs_context_t *c) const

    (this+coverage).collect_coverage (c->input);

    struct ChainContextCollectGlyphsLookupContext lookup_context = {

      {collect_glyph},

      {nullptr, nullptr, nullptr}

};

    + hb_iter (ruleSet)

    | hb_map (hb_add (this))

    | hb_apply ([&] (const ChainRuleSet &_) { _.collect_glyphs (c, lookup_context); })

  bool would_apply (hb_would_apply_context_t *c) const

    const ChainRuleSet &rule_set = this+ruleSet[(this+coverage).get_coverage (c->glyphs[0])];

    struct ChainContextApplyLookupContext lookup_context = {

      {{match_glyph, match_glyph, match_glyph}},

      {nullptr, nullptr, nullptr}

};

    return rule_set.would_apply (c, lookup_context);

  const Coverage &get_coverage () const { return this+coverage; }

  bool apply (hb_ot_apply_context_t *c) const

    TRACE_APPLY (this);

    unsigned int index = (this+coverage).get_coverage (c->buffer->cur().codepoint);

    if (likely (index == NOT_COVERED)) return_trace (false);

    const ChainRuleSet &rule_set = this+ruleSet[index];

    struct ChainContextApplyLookupContext lookup_context = {

      {{match_glyph, match_glyph, match_glyph}},

      {nullptr, nullptr, nullptr}

};

    return_trace (rule_set.apply (c, lookup_context));

  bool subset (hb_subset_context_t *c) const

    TRACE_SUBSET (this);

    const hb_set_t &glyphset = *c->plan->glyphset_gsub ();

    const hb_map_t &glyph_map = *c->plan->glyph_map;

    auto *out = c->serializer->start_embed (*this);

    if (unlikely (!c->serializer->extend_min (out))) return_trace (false);

    out->format = format;

    const hb_map_t *lookup_map = c->table_tag == HB_OT_TAG_GSUB ? &c->plan->gsub_lookups : &c->plan->gpos_lookups;

    hb_sorted_vector_t<hb_codepoint_t> new_coverage;

    + hb_zip (this+coverage, ruleSet)

    | hb_filter (glyphset, hb_first)

    | hb_filter (subset_offset_array (c, out->ruleSet, this, lookup_map), hb_second)

    | hb_map (hb_first)

    | hb_map (glyph_map)

    | hb_sink (new_coverage)

    out->coverage.serialize_serialize (c->serializer, new_coverage.iter ());

    return_trace (bool (new_coverage));

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    return_trace (coverage.sanitize (c, this) && ruleSet.sanitize (c, this));

  protected:

  HBUINT16	format;			/* Format identifier--format = 1 */

  typename Types::template OffsetTo<Coverage>

		coverage;		/* Offset to Coverage table--from

					 * beginning of table */

  Array16Of<typename Types::template OffsetTo<ChainRuleSet>>

		ruleSet;		/* Array of ChainRuleSet tables

					 * ordered by Coverage Index */

  public:

  DEFINE_SIZE_ARRAY (2 + 2 * Types::size, ruleSet);

};

template <typename Types>

struct ChainContextFormat2_5

  using ChainRuleSet = OT::ChainRuleSet<SmallTypes>;

  bool intersects (const hb_set_t *glyphs) const

    if (!(this+coverage).intersects (glyphs))

      return false;

    const ClassDef &backtrack_class_def = this+backtrackClassDef;

    const ClassDef &input_class_def = this+inputClassDef;

    const ClassDef &lookahead_class_def = this+lookaheadClassDef;

    hb_map_t caches[3] = {};

    struct ChainContextClosureLookupContext lookup_context = {

      {intersects_class, nullptr},

      ContextFormat::ClassBasedContext,

      {&backtrack_class_def,

       &input_class_def,

       &lookahead_class_def},

      {&caches[0], &caches[1], &caches[2]}

};

    hb_set_t retained_coverage_glyphs;

    (this+coverage).intersect_set (*glyphs, retained_coverage_glyphs);

    hb_set_t coverage_glyph_classes;

    input_class_def.intersected_classes (&retained_coverage_glyphs, &coverage_glyph_classes);

    return

    + hb_iter (ruleSet)

    | hb_map (hb_add (this))

    | hb_enumerate

    | hb_map ([&] (const hb_pair_t<unsigned, const ChainRuleSet &> p)

	      { return input_class_def.intersects_class (glyphs, p.first) &&

		       coverage_glyph_classes.has (p.first) &&

		       p.second.intersects (glyphs, lookup_context); })

    | hb_any

  bool may_have_non_1to1 () const

  { return true; }

  void closure (hb_closure_context_t *c) const

    if (!(this+coverage).intersects (c->glyphs))

      return;

    hb_set_t* cur_active_glyphs = c->push_cur_active_glyphs ();

    if (unlikely (!cur_active_glyphs)) return;

    get_coverage ().intersect_set (c->previous_parent_active_glyphs (),

				   *cur_active_glyphs);

    const ClassDef &backtrack_class_def = this+backtrackClassDef;

    const ClassDef &input_class_def = this+inputClassDef;

    const ClassDef &lookahead_class_def = this+lookaheadClassDef;

    hb_map_t caches[3] = {};

    intersected_class_cache_t intersected_cache;

    struct ChainContextClosureLookupContext lookup_context = {

      {intersects_class, intersected_class_glyphs},

      ContextFormat::ClassBasedContext,

      {&backtrack_class_def,

       &input_class_def,

       &lookahead_class_def},

      {&caches[0], &caches[1], &caches[2]},

      &intersected_cache

};

    + hb_enumerate (ruleSet)

    | hb_filter ([&] (unsigned _)

    { return input_class_def.intersects_class (&c->parent_active_glyphs (), _); },

		 hb_first)

    | hb_apply ([&] (const hb_pair_t<unsigned, const typename Types::template OffsetTo<ChainRuleSet>&> _)

                  const ChainRuleSet& chainrule_set = this+_.second;

                  chainrule_set.closure (c, _.first, lookup_context);

})

    c->pop_cur_done_glyphs ();

  void closure_lookups (hb_closure_lookups_context_t *c) const

    if (!(this+coverage).intersects (c->glyphs))

      return;

    const ClassDef &backtrack_class_def = this+backtrackClassDef;

    const ClassDef &input_class_def = this+inputClassDef;

    const ClassDef &lookahead_class_def = this+lookaheadClassDef;

    hb_map_t caches[3] = {};

    struct ChainContextClosureLookupContext lookup_context = {

      {intersects_class, nullptr},

      ContextFormat::ClassBasedContext,

      {&backtrack_class_def,

       &input_class_def,

       &lookahead_class_def},

      {&caches[0], &caches[1], &caches[2]}

};

    + hb_iter (ruleSet)

    | hb_map (hb_add (this))

    | hb_enumerate

    | hb_filter([&] (unsigned klass)

    { return input_class_def.intersects_class (c->glyphs, klass); }, hb_first)

    | hb_map (hb_second)

    | hb_apply ([&] (const ChainRuleSet &_)

    { _.closure_lookups (c, lookup_context); })

  void collect_variation_indices (hb_collect_variation_indices_context_t *c) const {}

  void collect_glyphs (hb_collect_glyphs_context_t *c) const

    (this+coverage).collect_coverage (c->input);

    const ClassDef &backtrack_class_def = this+backtrackClassDef;

    const ClassDef &input_class_def = this+inputClassDef;

    const ClassDef &lookahead_class_def = this+lookaheadClassDef;

    struct ChainContextCollectGlyphsLookupContext lookup_context = {

      {collect_class},

      {&backtrack_class_def,

       &input_class_def,

       &lookahead_class_def}

};

    + hb_iter (ruleSet)

    | hb_map (hb_add (this))

    | hb_apply ([&] (const ChainRuleSet &_) { _.collect_glyphs (c, lookup_context); })

  bool would_apply (hb_would_apply_context_t *c) const

    const ClassDef &backtrack_class_def = this+backtrackClassDef;

    const ClassDef &input_class_def = this+inputClassDef;

    const ClassDef &lookahead_class_def = this+lookaheadClassDef;

    unsigned int index = input_class_def.get_class (c->glyphs[0]);

    const ChainRuleSet &rule_set = this+ruleSet[index];

    struct ChainContextApplyLookupContext lookup_context = {

      {{match_class, match_class, match_class}},

      {&backtrack_class_def,

       &input_class_def,

       &lookahead_class_def}

};

    return rule_set.would_apply (c, lookup_context);

  const Coverage &get_coverage () const { return this+coverage; }

  unsigned cache_cost () const

    unsigned c = (this+lookaheadClassDef).cost () * ruleSet.len;

    return c >= 4 ? c : 0;

  bool cache_func (hb_ot_apply_context_t *c, bool enter) const

    if (enter)

      if (!HB_BUFFER_TRY_ALLOCATE_VAR (c->buffer, syllable))

	return false;

      auto &info = c->buffer->info;

      unsigned count = c->buffer->len;

      for (unsigned i = 0; i < count; i++)

	info[i].syllable() = 255;

      c->new_syllables = 255;

      return true;

    else

      c->new_syllables = (unsigned) -1;

      HB_BUFFER_DEALLOCATE_VAR (c->buffer, syllable);

      return true;

  bool apply_cached (hb_ot_apply_context_t *c) const { return _apply (c, true); }

  bool apply (hb_ot_apply_context_t *c) const { return _apply (c, false); }

  bool _apply (hb_ot_apply_context_t *c, bool cached) const

    TRACE_APPLY (this);

    unsigned int index = (this+coverage).get_coverage (c->buffer->cur().codepoint);

    if (likely (index == NOT_COVERED)) return_trace (false);

    const ClassDef &backtrack_class_def = this+backtrackClassDef;

    const ClassDef &input_class_def = this+inputClassDef;

    const ClassDef &lookahead_class_def = this+lookaheadClassDef;

    /* match_class_caches1 is slightly faster. Use it for lookahead,

     * which is typically longer. */

    struct ChainContextApplyLookupContext lookup_context = {

      {{cached && &backtrack_class_def == &lookahead_class_def ? match_class_cached1 : match_class,

        cached ? match_class_cached2 : match_class,

        cached ? match_class_cached1 : match_class}},

      {&backtrack_class_def,

       &input_class_def,

       &lookahead_class_def}

};

    // Note: Corresponds to match_class_cached2

    if (cached && ((c->buffer->cur().syllable() & 0xF0) >> 4) < 15)

      index = (c->buffer->cur().syllable () & 0xF0) >> 4;

    else

      index = input_class_def.get_class (c->buffer->cur().codepoint);

    const ChainRuleSet &rule_set = this+ruleSet[index];

    return_trace (rule_set.apply (c, lookup_context));

  bool subset (hb_subset_context_t *c) const

    TRACE_SUBSET (this);

    auto *out = c->serializer->start_embed (*this);

    if (unlikely (!c->serializer->extend_min (out))) return_trace (false);

    out->format = format;

    out->coverage.serialize_subset (c, coverage, this);

    hb_map_t backtrack_klass_map;

    hb_map_t input_klass_map;

    hb_map_t lookahead_klass_map;

    out->backtrackClassDef.serialize_subset (c, backtrackClassDef, this, &backtrack_klass_map);

    // TODO: subset inputClassDef based on glyphs survived in Coverage subsetting

    out->inputClassDef.serialize_subset (c, inputClassDef, this, &input_klass_map);

    out->lookaheadClassDef.serialize_subset (c, lookaheadClassDef, this, &lookahead_klass_map);

    if (unlikely (!c->serializer->propagate_error (backtrack_klass_map,

						   input_klass_map,

						   lookahead_klass_map)))

      return_trace (false);

    const hb_set_t* glyphset = c->plan->glyphset_gsub ();

    hb_set_t retained_coverage_glyphs;

    (this+coverage).intersect_set (*glyphset, retained_coverage_glyphs);

    hb_set_t coverage_glyph_classes;

    (this+inputClassDef).intersected_classes (&retained_coverage_glyphs, &coverage_glyph_classes);

    int non_zero_index = -1, index = 0;

    bool ret = true;

    const hb_map_t *lookup_map = c->table_tag == HB_OT_TAG_GSUB ? &c->plan->gsub_lookups : &c->plan->gpos_lookups;

    auto last_non_zero = c->serializer->snapshot ();

    for (const auto& _ : + hb_enumerate (ruleSet)

			 | hb_filter (input_klass_map, hb_first))

      auto *o = out->ruleSet.serialize_append (c->serializer);

      if (unlikely (!o))

	ret = false;

	break;

      if (coverage_glyph_classes.has (_.first) &&

          o->serialize_subset (c, _.second, this,

			       lookup_map,

			       &backtrack_klass_map,

			       &input_klass_map,

			       &lookahead_klass_map))

        last_non_zero = c->serializer->snapshot ();

	non_zero_index = index;

      index++;

    if (!ret || non_zero_index == -1) return_trace (false);

    // prune empty trailing ruleSets

    if (index > non_zero_index) {

      c->serializer->revert (last_non_zero);

      out->ruleSet.len = non_zero_index + 1;

    return_trace (bool (out->ruleSet));

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    return_trace (coverage.sanitize (c, this) &&

		  backtrackClassDef.sanitize (c, this) &&

		  inputClassDef.sanitize (c, this) &&

		  lookaheadClassDef.sanitize (c, this) &&

		  ruleSet.sanitize (c, this));

  protected:

  HBUINT16	format;			/* Format identifier--format = 2 */

  typename Types::template OffsetTo<Coverage>

		coverage;		/* Offset to Coverage table--from

					 * beginning of table */

  typename Types::template OffsetTo<ClassDef>

		backtrackClassDef;	/* Offset to glyph ClassDef table

					 * containing backtrack sequence

					 * data--from beginning of table */

  typename Types::template OffsetTo<ClassDef>

		inputClassDef;		/* Offset to glyph ClassDef

					 * table containing input sequence

					 * data--from beginning of table */

  typename Types::template OffsetTo<ClassDef>

		lookaheadClassDef;	/* Offset to glyph ClassDef table

					 * containing lookahead sequence

					 * data--from beginning of table */

  Array16Of<typename Types::template OffsetTo<ChainRuleSet>>

		ruleSet;		/* Array of ChainRuleSet tables

					 * ordered by class */

  public:

  DEFINE_SIZE_ARRAY (4 + 4 * Types::size, ruleSet);

};

struct ChainContextFormat3

  using RuleSet = OT::RuleSet<SmallTypes>;

  bool intersects (const hb_set_t *glyphs) const

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    if (!(this+input[0]).intersects (glyphs))

      return false;

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    struct ChainContextClosureLookupContext lookup_context = {

      {intersects_coverage, nullptr},

      ContextFormat::CoverageBasedContext,

      {this, this, this}

};

    return chain_context_intersects (glyphs,

				     backtrack.len, (const HBUINT16 *) backtrack.arrayZ,

				     input.len, (const HBUINT16 *) input.arrayZ + 1,

				     lookahead.len, (const HBUINT16 *) lookahead.arrayZ,

				     lookup_context);

  bool may_have_non_1to1 () const

  { return true; }

  void closure (hb_closure_context_t *c) const

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    if (!(this+input[0]).intersects (c->glyphs))

      return;

    hb_set_t* cur_active_glyphs = c->push_cur_active_glyphs ();

    if (unlikely (!cur_active_glyphs))

      return;

    get_coverage ().intersect_set (c->previous_parent_active_glyphs (),

				   *cur_active_glyphs);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    struct ChainContextClosureLookupContext lookup_context = {

      {intersects_coverage, intersected_coverage_glyphs},

      ContextFormat::CoverageBasedContext,

      {this, this, this}

};

    chain_context_closure_lookup (c,

				  backtrack.len, (const HBUINT16 *) backtrack.arrayZ,

				  input.len, (const HBUINT16 *) input.arrayZ + 1,

				  lookahead.len, (const HBUINT16 *) lookahead.arrayZ,

				  lookup.len, lookup.arrayZ,

				  0, lookup_context);

    c->pop_cur_done_glyphs ();

  void closure_lookups (hb_closure_lookups_context_t *c) const

    if (!intersects (c->glyphs))

      return;

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    recurse_lookups (c, lookup.len, lookup.arrayZ);

  void collect_variation_indices (hb_collect_variation_indices_context_t *c) const {}

  void collect_glyphs (hb_collect_glyphs_context_t *c) const

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    (this+input[0]).collect_coverage (c->input);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    struct ChainContextCollectGlyphsLookupContext lookup_context = {

      {collect_coverage},

      {this, this, this}

};

    chain_context_collect_glyphs_lookup (c,

					 backtrack.len, (const HBUINT16 *) backtrack.arrayZ,

					 input.len, (const HBUINT16 *) input.arrayZ + 1,

					 lookahead.len, (const HBUINT16 *) lookahead.arrayZ,

					 lookup.len, lookup.arrayZ,

					 lookup_context);

  bool would_apply (hb_would_apply_context_t *c) const

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    struct ChainContextApplyLookupContext lookup_context = {

      {{match_coverage, match_coverage, match_coverage}},

      {this, this, this}

};

    return chain_context_would_apply_lookup (c,

					     backtrack.len, (const HBUINT16 *) backtrack.arrayZ,

					     input.len, (const HBUINT16 *) input.arrayZ + 1,

					     lookahead.len, (const HBUINT16 *) lookahead.arrayZ,

					     lookup.len, lookup.arrayZ, lookup_context);

  const Coverage &get_coverage () const

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    return this+input[0];

  bool apply (hb_ot_apply_context_t *c) const

    TRACE_APPLY (this);

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    unsigned int index = (this+input[0]).get_coverage (c->buffer->cur().codepoint);

    if (likely (index == NOT_COVERED)) return_trace (false);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    struct ChainContextApplyLookupContext lookup_context = {

      {{match_coverage, match_coverage, match_coverage}},

      {this, this, this}

};

    return_trace (chain_context_apply_lookup (c,

					      backtrack.len, (const HBUINT16 *) backtrack.arrayZ,

					      input.len, (const HBUINT16 *) input.arrayZ + 1,

					      lookahead.len, (const HBUINT16 *) lookahead.arrayZ,

					      lookup.len, lookup.arrayZ, lookup_context));

  template<typename Iterator,

	   hb_requires (hb_is_iterator (Iterator))>

  bool serialize_coverage_offsets (hb_subset_context_t *c, Iterator it, const void* base) const

    TRACE_SERIALIZE (this);

    auto *out = c->serializer->start_embed<Array16OfOffset16To<Coverage>> ();

    if (unlikely (!c->serializer->allocate_size<HBUINT16> (HBUINT16::static_size)))

      return_trace (false);

    for (auto& offset : it) {

      auto *o = out->serialize_append (c->serializer);

      if (unlikely (!o) || !o->serialize_subset (c, offset, base))

        return_trace (false);

    return_trace (true);

  bool subset (hb_subset_context_t *c) const

    TRACE_SUBSET (this);

    if (unlikely (!c->serializer->embed (this->format))) return_trace (false);

    if (!serialize_coverage_offsets (c, backtrack.iter (), this))

      return_trace (false);

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    if (!serialize_coverage_offsets (c, input.iter (), this))

      return_trace (false);

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    if (!serialize_coverage_offsets (c, lookahead.iter (), this))

      return_trace (false);

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    const hb_map_t *lookup_map = c->table_tag == HB_OT_TAG_GSUB ? &c->plan->gsub_lookups : &c->plan->gpos_lookups;

    HBUINT16 *lookupCount = c->serializer->copy<HBUINT16> (lookup.len);

    if (!lookupCount) return_trace (false);

    unsigned count = serialize_lookuprecord_array (c->serializer, lookup.as_array (), lookup_map);

    return_trace (c->serializer->check_assign (*lookupCount, count, HB_SERIALIZE_ERROR_INT_OVERFLOW));

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    if (unlikely (!backtrack.sanitize (c, this))) return_trace (false);

    hb_barrier ();

    const auto &input = StructAfter<decltype (inputX)> (backtrack);

    if (unlikely (!input.sanitize (c, this))) return_trace (false);

    hb_barrier ();

    if (unlikely (!input.len)) return_trace (false); /* To be consistent with Context. */

    const auto &lookahead = StructAfter<decltype (lookaheadX)> (input);

    if (unlikely (!lookahead.sanitize (c, this))) return_trace (false);

    hb_barrier ();

    const auto &lookup = StructAfter<decltype (lookupX)> (lookahead);

    return_trace (likely (lookup.sanitize (c)));

  protected:

  HBUINT16	format;			/* Format identifier--format = 3 */

  Array16OfOffset16To<Coverage>

		backtrack;		/* Array of coverage tables

					 * in backtracking sequence, in  glyph

					 * sequence order */

  Array16OfOffset16To<Coverage>

		inputX		;	/* Array of coverage

					 * tables in input sequence, in glyph

					 * sequence order */

  Array16OfOffset16To<Coverage>

		lookaheadX;		/* Array of coverage tables

					 * in lookahead sequence, in glyph

					 * sequence order */

  Array16Of<LookupRecord>

		lookupX;		/* Array of LookupRecords--in

					 * design order) */

  public:

  DEFINE_SIZE_MIN (10);

};

struct ChainContext

  template <typename context_t, typename ...Ts>

  typename context_t::return_t dispatch (context_t *c, Ts&&... ds) const

    if (unlikely (!c->may_dispatch (this, &u.format))) return c->no_dispatch_return_value ();

    TRACE_DISPATCH (this, u.format);

    switch (u.format) {

    case 1: hb_barrier (); return_trace (c->dispatch (u.format1, std::forward<Ts> (ds)...));

    case 2: hb_barrier (); return_trace (c->dispatch (u.format2, std::forward<Ts> (ds)...));

    case 3: hb_barrier (); return_trace (c->dispatch (u.format3, std::forward<Ts> (ds)...));

#ifndef HB_NO_BEYOND_64K

    case 4: hb_barrier (); return_trace (c->dispatch (u.format4, std::forward<Ts> (ds)...));

    case 5: hb_barrier (); return_trace (c->dispatch (u.format5, std::forward<Ts> (ds)...));

#endif

    default:return_trace (c->default_return_value ());

  protected:

  union {

  HBUINT16				format;	/* Format identifier */

  ChainContextFormat1_4<SmallTypes>	format1;

  ChainContextFormat2_5<SmallTypes>	format2;

  ChainContextFormat3			format3;

#ifndef HB_NO_BEYOND_64K

  ChainContextFormat1_4<MediumTypes>	format4;

  ChainContextFormat2_5<MediumTypes>	format5;

#endif

  } u;

};

template <typename T>

struct ExtensionFormat1

  unsigned int get_type () const { return extensionLookupType; }

  template <typename X>

  const X& get_subtable () const

  { return this + reinterpret_cast<const Offset32To<typename T::SubTable> &> (extensionOffset); }

  template <typename context_t, typename ...Ts>

  typename context_t::return_t dispatch (context_t *c, Ts&&... ds) const

    if (unlikely (!c->may_dispatch (this, this))) return c->no_dispatch_return_value ();

    TRACE_DISPATCH (this, format);

    return_trace (get_subtable<typename T::SubTable> ().dispatch (c, get_type (), std::forward<Ts> (ds)...));

  void collect_variation_indices (hb_collect_variation_indices_context_t *c) const

  { dispatch (c); }

  /* This is called from may_dispatch() above with hb_sanitize_context_t. */

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    return_trace (c->check_struct (this) &&

		  hb_barrier () &&

		  extensionLookupType != T::SubTable::Extension);

  bool subset (hb_subset_context_t *c) const

    TRACE_SUBSET (this);

    auto *out = c->serializer->start_embed (this);

    if (unlikely (!c->serializer->extend_min (out))) return_trace (false);

    out->format = format;

    out->extensionLookupType = extensionLookupType;

    const auto& src_offset =

        reinterpret_cast<const Offset32To<typename T::SubTable> &> (extensionOffset);

    auto& dest_offset =

        reinterpret_cast<Offset32To<typename T::SubTable> &> (out->extensionOffset);

    return_trace (dest_offset.serialize_subset (c, src_offset, this, get_type ()));

  protected:

  HBUINT16	format;			/* Format identifier. Set to 1. */

  HBUINT16	extensionLookupType;	/* Lookup type of subtable referenced

					 * by ExtensionOffset (i.e. the

					 * extension subtable). */

  Offset32	extensionOffset;	/* Offset to the extension subtable,

					 * of lookup type subtable. */

  public:

  DEFINE_SIZE_STATIC (8);

};

template <typename T>

struct Extension

  unsigned int get_type () const

    switch (u.format) {

    case 1: hb_barrier (); return u.format1.get_type ();

    default:return 0;

  template <typename X>

  const X& get_subtable () const

    switch (u.format) {

    case 1: hb_barrier (); return u.format1.template get_subtable<typename T::SubTable> ();

    default:return Null (typename T::SubTable);

  // Specialization of dispatch for subset. dispatch() normally just

  // dispatches to the sub table this points too, but for subset

  // we need to run subset on this subtable too.

  template <typename ...Ts>

  typename hb_subset_context_t::return_t dispatch (hb_subset_context_t *c, Ts&&... ds) const

    switch (u.format) {

    case 1: hb_barrier (); return u.format1.subset (c);

    default: return c->default_return_value ();

  template <typename context_t, typename ...Ts>

  typename context_t::return_t dispatch (context_t *c, Ts&&... ds) const

    if (unlikely (!c->may_dispatch (this, &u.format))) return c->no_dispatch_return_value ();

    TRACE_DISPATCH (this, u.format);

    switch (u.format) {

    case 1: hb_barrier (); return_trace (u.format1.dispatch (c, std::forward<Ts> (ds)...));

    default:return_trace (c->default_return_value ());

  protected:

  union {

  HBUINT16		format;		/* Format identifier */

  ExtensionFormat1<T>	format1;

  } u;

};

/*

 * GSUB/GPOS Common

*/

struct hb_ot_layout_lookup_accelerator_t

  template <typename TLookup>

  static hb_ot_layout_lookup_accelerator_t *create (const TLookup &lookup)

    unsigned count = lookup.get_subtable_count ();

    unsigned size = sizeof (hb_ot_layout_lookup_accelerator_t) -

		    HB_VAR_ARRAY * sizeof (hb_accelerate_subtables_context_t::hb_applicable_t) +

		    count * sizeof (hb_accelerate_subtables_context_t::hb_applicable_t);

    /* The following is a calloc because when we are collecting subtables,

     * some of them might be invalid and hence not collect; as a result,

     * we might not fill in all the count entries of the subtables array.

     * Zeroing it allows the set digest to gatekeep it without having to

     * initialize it further. */

    auto *thiz = (hb_ot_layout_lookup_accelerator_t *) hb_calloc (1, size);

    if (unlikely (!thiz))

      return nullptr;

    hb_accelerate_subtables_context_t c_accelerate_subtables (thiz->subtables);

    lookup.dispatch (&c_accelerate_subtables);

    thiz->digest.init ();

    for (auto& subtable : hb_iter (thiz->subtables, count))

      thiz->digest.union_ (subtable.digest);

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

    thiz->cache_user_idx = c_accelerate_subtables.cache_user_idx;

    for (unsigned i = 0; i < count; i++)

      if (i != thiz->cache_user_idx)

	thiz->subtables[i].apply_cached_func = thiz->subtables[i].apply_func;

#endif

    return thiz;

  bool may_have (hb_codepoint_t g) const

  { return digest.may_have (g); }

#ifndef HB_OPTIMIZE_SIZE

  HB_ALWAYS_INLINE

#endif

  bool apply (hb_ot_apply_context_t *c, unsigned subtables_count, bool use_cache) const

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

    if (use_cache)

      return

      + hb_iter (hb_iter (subtables, subtables_count))

      | hb_map ([&c] (const hb_accelerate_subtables_context_t::hb_applicable_t &_) { return _.apply_cached (c); })

      | hb_any

    else

#endif

      return

      + hb_iter (hb_iter (subtables, subtables_count))

      | hb_map ([&c] (const hb_accelerate_subtables_context_t::hb_applicable_t &_) { return _.apply (c); })

      | hb_any

    return false;

  bool cache_enter (hb_ot_apply_context_t *c) const

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

    return cache_user_idx != (unsigned) -1 &&

	   subtables[cache_user_idx].cache_enter (c);

#else

    return false;

#endif

  void cache_leave (hb_ot_apply_context_t *c) const

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

    subtables[cache_user_idx].cache_leave (c);

#endif

  hb_set_digest_t digest;

  private:

#ifndef HB_NO_OT_LAYOUT_LOOKUP_CACHE

  unsigned cache_user_idx = (unsigned) -1;

#endif

  hb_accelerate_subtables_context_t::hb_applicable_t subtables[HB_VAR_ARRAY];

};

template <typename Types>

struct GSUBGPOSVersion1_2

  friend struct GSUBGPOS;

  protected:

  FixedVersion<>version;	/* Version of the GSUB/GPOS table--initially set

				 * to 0x00010000u */

  typename Types:: template OffsetTo<ScriptList>

		scriptList;	/* ScriptList table */

  typename Types::template OffsetTo<FeatureList>

		featureList;	/* FeatureList table */

  typename Types::template OffsetTo<LookupList<Types>>

		lookupList;	/* LookupList table */

  Offset32To<FeatureVariations>

		featureVars;	/* Offset to Feature Variations

				   table--from beginning of table

				 * (may be NULL).  Introduced

				 * in version 0x00010001. */

  public:

  DEFINE_SIZE_MIN (4 + 3 * Types::size);

  unsigned int get_size () const

    return min_size +

	   (version.to_int () >= 0x00010001u ? featureVars.static_size : 0);

  const typename Types::template OffsetTo<LookupList<Types>>* get_lookup_list_offset () const

    return &lookupList;

  template <typename TLookup>

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    typedef List16OfOffsetTo<TLookup, typename Types::HBUINT> TLookupList;

    if (unlikely (!(scriptList.sanitize (c, this) &&

		    featureList.sanitize (c, this) &&

		    reinterpret_cast<const typename Types::template OffsetTo<TLookupList> &> (lookupList).sanitize (c, this))))

      return_trace (false);

#ifndef HB_NO_VAR

    if (unlikely (!(version.to_int () < 0x00010001u || featureVars.sanitize (c, this))))

      return_trace (false);

#endif

    return_trace (true);

  template <typename TLookup>

  bool subset (hb_subset_layout_context_t *c) const

    TRACE_SUBSET (this);

    auto *out = c->subset_context->serializer->start_embed (this);

    if (unlikely (!c->subset_context->serializer->extend_min (out))) return_trace (false);

    out->version = version;

    typedef LookupOffsetList<TLookup, typename Types::HBUINT> TLookupList;

    reinterpret_cast<typename Types::template OffsetTo<TLookupList> &> (out->lookupList)

	.serialize_subset (c->subset_context,

			   reinterpret_cast<const typename Types::template OffsetTo<TLookupList> &> (lookupList),

			   this,

c);

    reinterpret_cast<typename Types::template OffsetTo<RecordListOfFeature> &> (out->featureList)

	.serialize_subset (c->subset_context,

			   reinterpret_cast<const typename Types::template OffsetTo<RecordListOfFeature> &> (featureList),

			   this,

c);

    out->scriptList.serialize_subset (c->subset_context,

				      scriptList,

				      this,

c);

#ifndef HB_NO_VAR

    if (version.to_int () >= 0x00010001u)

      auto snapshot = c->subset_context->serializer->snapshot ();

      if (!c->subset_context->serializer->extend_min (&out->featureVars))

        return_trace (false);

      // if all axes are pinned all feature vars are dropped.

      bool ret = !c->subset_context->plan->all_axes_pinned

                 && out->featureVars.serialize_subset (c->subset_context, featureVars, this, c);

      if (!ret && version.major == 1)

        c->subset_context->serializer->revert (snapshot);

	out->version.major = 1;

	out->version.minor = 0;

#endif

    return_trace (true);

};

struct GSUBGPOS

  unsigned int get_size () const

    switch (u.version.major) {

    case 1: hb_barrier (); return u.version1.get_size ();

#ifndef HB_NO_BEYOND_64K

    case 2: hb_barrier (); return u.version2.get_size ();

#endif

    default: return u.version.static_size;

  template <typename TLookup>

  bool sanitize (hb_sanitize_context_t *c) const

    TRACE_SANITIZE (this);

    if (unlikely (!u.version.sanitize (c))) return_trace (false);

    hb_barrier ();

    switch (u.version.major) {

    case 1: hb_barrier (); return_trace (u.version1.sanitize<TLookup> (c));

#ifndef HB_NO_BEYOND_64K

    case 2: hb_barrier (); return_trace (u.version2.sanitize<TLookup> (c));

#endif

    default: return_trace (true);

  template <typename TLookup>

  bool subset (hb_subset_layout_context_t *c) const

    switch (u.version.major) {

    case 1: hb_barrier (); return u.version1.subset<TLookup> (c);

#ifndef HB_NO_BEYOND_64K

    case 2: hb_barrier (); return u.version2.subset<TLookup> (c);

#endif

    default: return false;

  const ScriptList &get_script_list () const

    switch (u.version.major) {

    case 1: hb_barrier (); return this+u.version1.scriptList;

#ifndef HB_NO_BEYOND_64K

    case 2: hb_barrier (); return this+u.version2.scriptList;

#endif

    default: return Null (ScriptList);

  const FeatureList &get_feature_list () const

    switch (u.version.major) {

    case 1: hb_barrier (); return this+u.version1.featureList;

#ifndef HB_NO_BEYOND_64K

    case 2: hb_barrier (); return this+u.version2.featureList;

#endif

    default: return Null (FeatureList);

  unsigned int get_lookup_count () const

    switch (u.version.major) {

    case 1: hb_barrier (); return (this+u.version1.lookupList).len;

#ifndef HB_NO_BEYOND_64K

    case 2: hb_barrier (); return (this+u.version2.lookupList).len;

#endif

    default: return 0;

  const Lookup& get_lookup (unsigned int i) const

    switch (u.version.major) {

    case 1: hb_barrier (); return (this+u.version1.lookupList)[i];

#ifndef HB_NO_BEYOND_64K

    case 2: hb_barrier (); return (this+u.version2.lookupList)[i];

#endif

    default: return Null (Lookup);

  const FeatureVariations &get_feature_variations () const

    switch (u.version.major) {

    case 1: hb_barrier (); return (u.version.to_int () >= 0x00010001u && hb_barrier () ? this+u.version1.featureVars : Null (FeatureVariations));

#ifndef HB_NO_BEYOND_64K

    case 2: hb_barrier (); return this+u.version2.featureVars;

#endif

    default: return Null (FeatureVariations);

  bool has_data () const { return u.version.to_int (); }

  unsigned int get_script_count () const

  { return get_script_list ().len; }

  const Tag& get_script_tag (unsigned int i) const

  { return get_script_list ().get_tag (i); }

  unsigned int get_script_tags (unsigned int start_offset,

				unsigned int *script_count /* IN/OUT */,

				hb_tag_t     *script_tags /* OUT */) const

  { return get_script_list ().get_tags (start_offset, script_count, script_tags); }

  const Script& get_script (unsigned int i) const

  { return get_script_list ()[i]; }

  bool find_script_index (hb_tag_t tag, unsigned int *index) const

  { return get_script_list ().find_index (tag, index); }

  unsigned int get_feature_count () const

  { return get_feature_list ().len; }

  hb_tag_t get_feature_tag (unsigned int i) const

  { return i == Index::NOT_FOUND_INDEX ? HB_TAG_NONE : get_feature_list ().get_tag (i); }

  unsigned int get_feature_tags (unsigned int start_offset,

				 unsigned int *feature_count /* IN/OUT */,

				 hb_tag_t     *feature_tags /* OUT */) const

  { return get_feature_list ().get_tags (start_offset, feature_count, feature_tags); }

  const Feature& get_feature (unsigned int i) const

  { return get_feature_list ()[i]; }

  bool find_feature_index (hb_tag_t tag, unsigned int *index) const

  { return get_feature_list ().find_index (tag, index); }

  bool find_variations_index (const int *coords, unsigned int num_coords,

			      unsigned int *index,

			      ItemVarStoreInstancer *instancer) const

#ifdef HB_NO_VAR

    *index = FeatureVariations::NOT_FOUND_INDEX;

    return false;

#endif

    return get_feature_variations ().find_index (coords, num_coords, index, instancer);

  const Feature& get_feature_variation (unsigned int feature_index,

					unsigned int variations_index) const

#ifndef HB_NO_VAR

    if (FeatureVariations::NOT_FOUND_INDEX != variations_index &&

	u.version.to_int () >= 0x00010001u)

      const Feature *feature = get_feature_variations ().find_substitute (variations_index,

									  feature_index);

      if (feature)

	return *feature;

#endif

    return get_feature (feature_index);

  void feature_variation_collect_lookups (const hb_set_t *feature_indexes,

					  const hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> *feature_record_cond_idx_map,

					  hb_set_t       *lookup_indexes /* OUT */) const

#ifndef HB_NO_VAR

    get_feature_variations ().collect_lookups (feature_indexes, feature_record_cond_idx_map, lookup_indexes);

#endif

#ifndef HB_NO_VAR

  void collect_feature_substitutes_with_variations (hb_collect_feature_substitutes_with_var_context_t *c) const

  { get_feature_variations ().collect_feature_substitutes_with_variations (c); }

#endif

  template <typename TLookup>

  void closure_lookups (hb_face_t      *face,

			const hb_set_t *glyphs,

			hb_set_t       *lookup_indexes /* IN/OUT */) const

    hb_set_t visited_lookups, inactive_lookups;

    hb_closure_lookups_context_t c (face, glyphs, &visited_lookups, &inactive_lookups);

    c.set_recurse_func (TLookup::template dispatch_recurse_func<hb_closure_lookups_context_t>);

    for (unsigned lookup_index : *lookup_indexes)

      reinterpret_cast<const TLookup &> (get_lookup (lookup_index)).closure_lookups (&c, lookup_index);

    hb_set_union (lookup_indexes, &visited_lookups);

    hb_set_subtract (lookup_indexes, &inactive_lookups);

  void prune_langsys (const hb_map_t *duplicate_feature_map,

                      const hb_set_t *layout_scripts,

                      hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *script_langsys_map,

                      hb_set_t       *new_feature_indexes /* OUT */) const

    hb_prune_langsys_context_t c (this, script_langsys_map, duplicate_feature_map, new_feature_indexes);

    unsigned count = get_script_count ();

    for (unsigned script_index = 0; script_index < count; script_index++)

      const Tag& tag = get_script_tag (script_index);

      if (!layout_scripts->has (tag)) continue;

      const Script& s = get_script (script_index);

      s.prune_langsys (&c, script_index);

  void prune_features (const hb_map_t *lookup_indices, /* IN */

		       const hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> *feature_record_cond_idx_map, /* IN */

		       const hb_hashmap_t<unsigned, const Feature*> *feature_substitutes_map, /* IN */

		       hb_set_t       *feature_indices /* IN/OUT */) const

#ifndef HB_NO_VAR

    // This is the set of feature indices which have alternate versions defined

    // if the FeatureVariation's table and the alternate version(s) intersect the

    // set of lookup indices.

    hb_set_t alternate_feature_indices;

    get_feature_variations ().closure_features (lookup_indices, feature_record_cond_idx_map, &alternate_feature_indices);

    if (unlikely (alternate_feature_indices.in_error()))

      feature_indices->err ();

      return;

#endif

    for (unsigned i : hb_iter (feature_indices))

      hb_tag_t tag =  get_feature_tag (i);

      if (tag == HB_TAG ('p', 'r', 'e', 'f'))

        // Note: Never ever drop feature 'pref', even if it's empty.

        // HarfBuzz chooses shaper for Khmer based on presence of this

        // feature.	See thread at:

	// http://lists.freedesktop.org/archives/harfbuzz/2012-November/002660.html

        continue;

      const Feature *f = &(get_feature (i));

      const Feature** p = nullptr;

      if (feature_substitutes_map->has (i, &p))

        f = *p;

      if (!f->featureParams.is_null () &&

          tag == HB_TAG ('s', 'i', 'z', 'e'))

        continue;

      if (!f->intersects_lookup_indexes (lookup_indices)

#ifndef HB_NO_VAR

          && !alternate_feature_indices.has (i)

#endif

	feature_indices->del (i);

  void collect_name_ids (const hb_map_t *feature_index_map,

                         hb_set_t *nameids_to_retain /* OUT */) const

    unsigned count = get_feature_count ();

    for (unsigned i = 0 ; i < count; i++)

      if (!feature_index_map->has (i)) continue;

      hb_tag_t tag = get_feature_tag (i);

      get_feature (i).collect_name_ids (tag, nameids_to_retain);

  template <typename T>

  struct accelerator_t

    accelerator_t (hb_face_t *face)

      hb_sanitize_context_t sc;

      sc.lazy_some_gpos = true;

      this->table = sc.reference_table<T> (face);

      if (unlikely (this->table->is_blocklisted (this->table.get_blob (), face)))

	hb_blob_destroy (this->table.get_blob ());

	this->table = hb_blob_get_empty ();

      this->lookup_count = table->get_lookup_count ();

      this->accels = (hb_atomic_ptr_t<hb_ot_layout_lookup_accelerator_t> *) hb_calloc (this->lookup_count, sizeof (*accels));

      if (unlikely (!this->accels))

	this->lookup_count = 0;

	this->table.destroy ();

	this->table = hb_blob_get_empty ();

    ~accelerator_t ()

      for (unsigned int i = 0; i < this->lookup_count; i++)

	hb_free (this->accels[i]);

      hb_free (this->accels);

      this->table.destroy ();

    hb_blob_t *get_blob () const { return table.get_blob (); }

    hb_ot_layout_lookup_accelerator_t *get_accel (unsigned lookup_index) const

      if (unlikely (lookup_index >= lookup_count)) return nullptr;

    retry:

      auto *accel = accels[lookup_index].get_acquire ();

      if (unlikely (!accel))

	accel = hb_ot_layout_lookup_accelerator_t::create (table->get_lookup (lookup_index));

	if (unlikely (!accel))

	  return nullptr;

	if (unlikely (!accels[lookup_index].cmpexch (nullptr, accel)))

	  hb_free (accel);

	  goto retry;

      return accel;

    hb_blob_ptr_t<T> table;

    unsigned int lookup_count;

    hb_atomic_ptr_t<hb_ot_layout_lookup_accelerator_t> *accels;

};

  protected:

  union {

  FixedVersion<>			version;	/* Version identifier */

  GSUBGPOSVersion1_2<SmallTypes>	version1;

#ifndef HB_NO_BEYOND_64K

  GSUBGPOSVersion1_2<MediumTypes>	version2;

#endif

  } u;

  public:

  DEFINE_SIZE_MIN (4);

};

} /* namespace OT */

#endif /* HB_OT_LAYOUT_GSUBGPOS_HH */