/*
 * 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_GSUB_TABLE_HH
#define HB_OT_LAYOUT_GSUB_TABLE_HH

#include "hb-ot-layout-gsubgpos-private.hh"


namespace OT {


struct SingleSubstFormat1
{
  inline bool is_inplace (hb_is_inplace_context_t *c) const
  {
    TRACE_IS_INPLACE (this);
    return TRACE_RETURN (true);
  }

  inline void closure (hb_closure_context_t *c) const
  {
    TRACE_CLOSURE (this);
    Coverage::Iter iter;
    for (iter.init (this+coverage); iter.more (); iter.next ()) {
      hb_codepoint_t glyph_id = iter.get_glyph ();
      if (c->glyphs->has (glyph_id))
	c->glyphs->add ((glyph_id + deltaGlyphID) & 0xFFFF);
    }
  }

  inline void collect_glyphs (hb_collect_glyphs_context_t *c) const
  {
    TRACE_COLLECT_GLYPHS (this);
    Coverage::Iter iter;
    for (iter.init (this+coverage); iter.more (); iter.next ()) {
      hb_codepoint_t glyph_id = iter.get_glyph ();
      c->input->add (glyph_id);
      c->output->add ((glyph_id + deltaGlyphID) & 0xFFFF);
    }
  }

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

  inline bool would_apply (hb_would_apply_context_t *c) const
  {
    TRACE_WOULD_APPLY (this);
    return TRACE_RETURN (c->len == 1 && (this+coverage).get_coverage (c->glyphs[0]) != NOT_COVERED);
  }

  inline bool apply (hb_apply_context_t *c) const
  {
    TRACE_APPLY (this);
    hb_codepoint_t glyph_id = c->buffer->cur().codepoint;
    unsigned int index = (this+coverage).get_coverage (glyph_id);
    if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);

    /* According to the Adobe Annotated OpenType Suite, result is always
     * limited to 16bit. */
    glyph_id = (glyph_id + deltaGlyphID) & 0xFFFF;
    c->replace_glyph (glyph_id);

    return TRACE_RETURN (true);
  }

  inline bool serialize (hb_serialize_context_t *c,
			 Supplier<GlyphID> &glyphs,
			 unsigned int num_glyphs,
			 int delta)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!c->extend_min (*this))) return TRACE_RETURN (false);
    if (unlikely (!coverage.serialize (c, this).serialize (c, glyphs, num_glyphs))) return TRACE_RETURN (false);
    deltaGlyphID.set (delta); /* TODO(serilaize) overflow? */
    return TRACE_RETURN (true);
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    return TRACE_RETURN (coverage.sanitize (c, this) && deltaGlyphID.sanitize (c));
  }

  protected:
  USHORT	format;			/* Format identifier--format = 1 */
  OffsetTo<Coverage>
		coverage;		/* Offset to Coverage table--from
					 * beginning of Substitution table */
  SHORT		deltaGlyphID;		/* Add to original GlyphID to get
					 * substitute GlyphID */
  public:
  DEFINE_SIZE_STATIC (6);
};

struct SingleSubstFormat2
{
  inline bool is_inplace (hb_is_inplace_context_t *c) const
  {
    TRACE_IS_INPLACE (this);
    return TRACE_RETURN (true);
  }

  inline void closure (hb_closure_context_t *c) const
  {
    TRACE_CLOSURE (this);
    Coverage::Iter iter;
    for (iter.init (this+coverage); iter.more (); iter.next ()) {
      if (c->glyphs->has (iter.get_glyph ()))
	c->glyphs->add (substitute[iter.get_coverage ()]);
    }
  }

  inline void collect_glyphs (hb_collect_glyphs_context_t *c) const
  {
    TRACE_COLLECT_GLYPHS (this);
    Coverage::Iter iter;
    for (iter.init (this+coverage); iter.more (); iter.next ()) {
      c->input->add (iter.get_glyph ());
      c->output->add (substitute[iter.get_coverage ()]);
    }
  }

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

  inline bool would_apply (hb_would_apply_context_t *c) const
  {
    TRACE_WOULD_APPLY (this);
    return TRACE_RETURN (c->len == 1 && (this+coverage).get_coverage (c->glyphs[0]) != NOT_COVERED);
  }

  inline bool apply (hb_apply_context_t *c) const
  {
    TRACE_APPLY (this);
    hb_codepoint_t glyph_id = c->buffer->cur().codepoint;
    unsigned int index = (this+coverage).get_coverage (glyph_id);
    if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);

    if (unlikely (index >= substitute.len)) return TRACE_RETURN (false);

    glyph_id = substitute[index];
    c->replace_glyph (glyph_id);

    return TRACE_RETURN (true);
  }

  inline bool serialize (hb_serialize_context_t *c,
			 Supplier<GlyphID> &glyphs,
			 Supplier<GlyphID> &substitutes,
			 unsigned int num_glyphs)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!c->extend_min (*this))) return TRACE_RETURN (false);
    if (unlikely (!substitute.serialize (c, substitutes, num_glyphs))) return TRACE_RETURN (false);
    if (unlikely (!coverage.serialize (c, this).serialize (c, glyphs, num_glyphs))) return TRACE_RETURN (false);
    return TRACE_RETURN (true);
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    return TRACE_RETURN (coverage.sanitize (c, this) && substitute.sanitize (c));
  }

  protected:
  USHORT	format;			/* Format identifier--format = 2 */
  OffsetTo<Coverage>
		coverage;		/* Offset to Coverage table--from
					 * beginning of Substitution table */
  ArrayOf<GlyphID>
		substitute;		/* Array of substitute
					 * GlyphIDs--ordered by Coverage Index */
  public:
  DEFINE_SIZE_ARRAY (6, substitute);
};

struct SingleSubst
{
  inline bool serialize (hb_serialize_context_t *c,
			 Supplier<GlyphID> &glyphs,
			 Supplier<GlyphID> &substitutes,
			 unsigned int num_glyphs)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!c->extend_min (u.format))) return TRACE_RETURN (false);
    unsigned int format = 2;
    int delta;
    if (num_glyphs) {
      format = 1;
      /* TODO(serialize) check for wrap-around */
      delta = substitutes[0] - glyphs[0];
      for (unsigned int i = 1; i < num_glyphs; i++)
	if (delta != substitutes[i] - glyphs[i]) {
	  format = 2;
	  break;
	}
    }
    u.format.set (format);
    switch (u.format) {
    case 1: return TRACE_RETURN (u.format1.serialize (c, glyphs, num_glyphs, delta));
    case 2: return TRACE_RETURN (u.format2.serialize (c, glyphs, substitutes, num_glyphs));
    default:return TRACE_RETURN (false);
    }
  }

  template <typename context_t>
  inline typename context_t::return_t dispatch (context_t *c) const
  {
    TRACE_DISPATCH (this);
    switch (u.format) {
    case 1: return TRACE_RETURN (c->dispatch (u.format1));
    case 2: return TRACE_RETURN (c->dispatch (u.format2));
    default:return TRACE_RETURN (c->default_return_value ());
    }
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    if (!u.format.sanitize (c)) return TRACE_RETURN (false);
    switch (u.format) {
    case 1: return TRACE_RETURN (u.format1.sanitize (c));
    case 2: return TRACE_RETURN (u.format2.sanitize (c));
    default:return TRACE_RETURN (true);
    }
  }

  protected:
  union {
  USHORT		format;		/* Format identifier */
  SingleSubstFormat1	format1;
  SingleSubstFormat2	format2;
  } u;
};


struct Sequence
{
  inline bool is_inplace (hb_is_inplace_context_t *c) const
  {
    TRACE_IS_INPLACE (this);
    /* For len==0 we don't do anything, so it's harmless. */
    return TRACE_RETURN (substitute.len <= 1);
  }

  inline void closure (hb_closure_context_t *c) const
  {
    TRACE_CLOSURE (this);
    unsigned int count = substitute.len;
    for (unsigned int i = 0; i < count; i++)
      c->glyphs->add (substitute[i]);
  }

  inline void collect_glyphs (hb_collect_glyphs_context_t *c) const
  {
    TRACE_COLLECT_GLYPHS (this);
    unsigned int count = substitute.len;
    for (unsigned int i = 0; i < count; i++)
      c->output->add (substitute[i]);
  }

  inline bool apply (hb_apply_context_t *c) const
  {
    TRACE_APPLY (this);
    if (unlikely (!substitute.len)) return TRACE_RETURN (false);

    unsigned int klass = c->buffer->cur().glyph_props() &
			 HB_OT_LAYOUT_GLYPH_PROPS_LIGATURE ? HB_OT_LAYOUT_GLYPH_PROPS_BASE_GLYPH : 0;
    unsigned int count = substitute.len;
    if (count == 1) /* Special-case to make it in-place. */
    {
      c->replace_glyph (substitute.array[0]);
    }
    else
    {
      for (unsigned int i = 0; i < count; i++) {
	set_lig_props_for_component (c->buffer->cur(), i);
	c->output_glyph (substitute.array[i], klass);
      }
      c->buffer->skip_glyph ();
    }

    return TRACE_RETURN (true);
  }

  inline bool serialize (hb_serialize_context_t *c,
			 Supplier<GlyphID> &glyphs,
			 unsigned int num_glyphs)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!c->extend_min (*this))) return TRACE_RETURN (false);
    if (unlikely (!substitute.serialize (c, glyphs, num_glyphs))) return TRACE_RETURN (false);
    return TRACE_RETURN (true);
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    return TRACE_RETURN (substitute.sanitize (c));
  }

  protected:
  ArrayOf<GlyphID>
		substitute;		/* String of GlyphIDs to substitute */
  public:
  DEFINE_SIZE_ARRAY (2, substitute);
};

struct MultipleSubstFormat1
{
  inline bool is_inplace (hb_is_inplace_context_t *c) const
  {
    TRACE_IS_INPLACE (this);
    /* Some tools generate MultipleSubst with each substitute having length 1!
     * So, check them. */
    unsigned int count = sequence.len;
    for (unsigned int i = 0; i < count; i++)
	if (!(this+sequence[i]).is_inplace (c))
	  return TRACE_RETURN (false);
    return TRACE_RETURN (true);
  }

  inline void closure (hb_closure_context_t *c) const
  {
    TRACE_CLOSURE (this);
    Coverage::Iter iter;
    for (iter.init (this+coverage); iter.more (); iter.next ()) {
      if (c->glyphs->has (iter.get_glyph ()))
	(this+sequence[iter.get_coverage ()]).closure (c);
    }
  }

  inline void collect_glyphs (hb_collect_glyphs_context_t *c) const
  {
    TRACE_COLLECT_GLYPHS (this);
    (this+coverage).add_coverage (c->input);
    unsigned int count = sequence.len;
    for (unsigned int i = 0; i < count; i++)
	(this+sequence[i]).collect_glyphs (c);
  }

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

  inline bool would_apply (hb_would_apply_context_t *c) const
  {
    TRACE_WOULD_APPLY (this);
    return TRACE_RETURN (c->len == 1 && (this+coverage).get_coverage (c->glyphs[0]) != NOT_COVERED);
  }

  inline bool apply (hb_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_RETURN (false);

    return TRACE_RETURN ((this+sequence[index]).apply (c));
  }

  inline bool serialize (hb_serialize_context_t *c,
			 Supplier<GlyphID> &glyphs,
			 Supplier<unsigned int> &substitute_len_list,
			 unsigned int num_glyphs,
			 Supplier<GlyphID> &substitute_glyphs_list)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!c->extend_min (*this))) return TRACE_RETURN (false);
    if (unlikely (!sequence.serialize (c, num_glyphs))) return TRACE_RETURN (false);
    for (unsigned int i = 0; i < num_glyphs; i++)
      if (unlikely (!sequence[i].serialize (c, this).serialize (c,
								substitute_glyphs_list,
								substitute_len_list[i]))) return TRACE_RETURN (false);
    substitute_len_list.advance (num_glyphs);
    if (unlikely (!coverage.serialize (c, this).serialize (c, glyphs, num_glyphs))) return TRACE_RETURN (false);
    return TRACE_RETURN (true);
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    return TRACE_RETURN (coverage.sanitize (c, this) && sequence.sanitize (c, this));
  }

  protected:
  USHORT	format;			/* Format identifier--format = 1 */
  OffsetTo<Coverage>
		coverage;		/* Offset to Coverage table--from
					 * beginning of Substitution table */
  OffsetArrayOf<Sequence>
		sequence;		/* Array of Sequence tables
					 * ordered by Coverage Index */
  public:
  DEFINE_SIZE_ARRAY (6, sequence);
};

struct MultipleSubst
{
  inline bool serialize (hb_serialize_context_t *c,
			 Supplier<GlyphID> &glyphs,
			 Supplier<unsigned int> &substitute_len_list,
			 unsigned int num_glyphs,
			 Supplier<GlyphID> &substitute_glyphs_list)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!c->extend_min (u.format))) return TRACE_RETURN (false);
    unsigned int format = 1;
    u.format.set (format);
    switch (u.format) {
    case 1: return TRACE_RETURN (u.format1.serialize (c, glyphs, substitute_len_list, num_glyphs, substitute_glyphs_list));
    default:return TRACE_RETURN (false);
    }
  }

  template <typename context_t>
  inline typename context_t::return_t dispatch (context_t *c) const
  {
    TRACE_DISPATCH (this);
    switch (u.format) {
    case 1: return TRACE_RETURN (c->dispatch (u.format1));
    default:return TRACE_RETURN (c->default_return_value ());
    }
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    if (!u.format.sanitize (c)) return TRACE_RETURN (false);
    switch (u.format) {
    case 1: return TRACE_RETURN (u.format1.sanitize (c));
    default:return TRACE_RETURN (true);
    }
  }

  protected:
  union {
  USHORT		format;		/* Format identifier */
  MultipleSubstFormat1	format1;
  } u;
};


typedef ArrayOf<GlyphID> AlternateSet;	/* Array of alternate GlyphIDs--in
					 * arbitrary order */

struct AlternateSubstFormat1
{
  inline bool is_inplace (hb_is_inplace_context_t *c) const
  {
    TRACE_IS_INPLACE (this);
    return TRACE_RETURN (true);
  }

  inline void closure (hb_closure_context_t *c) const
  {
    TRACE_CLOSURE (this);
    Coverage::Iter iter;
    for (iter.init (this+coverage); iter.more (); iter.next ()) {
      if (c->glyphs->has (iter.get_glyph ())) {
	const AlternateSet &alt_set = this+alternateSet[iter.get_coverage ()];
	unsigned int count = alt_set.len;
	for (unsigned int i = 0; i < count; i++)
	  c->glyphs->add (alt_set[i]);
      }
    }
  }

  inline void collect_glyphs (hb_collect_glyphs_context_t *c) const
  {
    TRACE_COLLECT_GLYPHS (this);
    Coverage::Iter iter;
    for (iter.init (this+coverage); iter.more (); iter.next ()) {
      c->input->add (iter.get_glyph ());
      const AlternateSet &alt_set = this+alternateSet[iter.get_coverage ()];
      unsigned int count = alt_set.len;
      for (unsigned int i = 0; i < count; i++)
	c->output->add (alt_set[i]);
    }
  }

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

  inline bool would_apply (hb_would_apply_context_t *c) const
  {
    TRACE_WOULD_APPLY (this);
    return TRACE_RETURN (c->len == 1 && (this+coverage).get_coverage (c->glyphs[0]) != NOT_COVERED);
  }

  inline bool apply (hb_apply_context_t *c) const
  {
    TRACE_APPLY (this);
    hb_codepoint_t glyph_id = c->buffer->cur().codepoint;

    unsigned int index = (this+coverage).get_coverage (glyph_id);
    if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);

    const AlternateSet &alt_set = this+alternateSet[index];

    if (unlikely (!alt_set.len)) return TRACE_RETURN (false);

    hb_mask_t glyph_mask = c->buffer->cur().mask;
    hb_mask_t lookup_mask = c->lookup_mask;

    /* Note: This breaks badly if two features enabled this lookup together. */
    unsigned int shift = _hb_ctz (lookup_mask);
    unsigned int alt_index = ((lookup_mask & glyph_mask) >> shift);

    if (unlikely (alt_index > alt_set.len || alt_index == 0)) return TRACE_RETURN (false);

    glyph_id = alt_set[alt_index - 1];

    c->replace_glyph (glyph_id);

    return TRACE_RETURN (true);
  }

  inline bool serialize (hb_serialize_context_t *c,
			 Supplier<GlyphID> &glyphs,
			 Supplier<unsigned int> &alternate_len_list,
			 unsigned int num_glyphs,
			 Supplier<GlyphID> &alternate_glyphs_list)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!c->extend_min (*this))) return TRACE_RETURN (false);
    if (unlikely (!alternateSet.serialize (c, num_glyphs))) return TRACE_RETURN (false);
    for (unsigned int i = 0; i < num_glyphs; i++)
      if (unlikely (!alternateSet[i].serialize (c, this).serialize (c,
								    alternate_glyphs_list,
								    alternate_len_list[i]))) return TRACE_RETURN (false);
    alternate_len_list.advance (num_glyphs);
    if (unlikely (!coverage.serialize (c, this).serialize (c, glyphs, num_glyphs))) return TRACE_RETURN (false);
    return TRACE_RETURN (true);
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    return TRACE_RETURN (coverage.sanitize (c, this) && alternateSet.sanitize (c, this));
  }

  protected:
  USHORT	format;			/* Format identifier--format = 1 */
  OffsetTo<Coverage>
		coverage;		/* Offset to Coverage table--from
					 * beginning of Substitution table */
  OffsetArrayOf<AlternateSet>
		alternateSet;		/* Array of AlternateSet tables
					 * ordered by Coverage Index */
  public:
  DEFINE_SIZE_ARRAY (6, alternateSet);
};

struct AlternateSubst
{
  inline bool serialize (hb_serialize_context_t *c,
			 Supplier<GlyphID> &glyphs,
			 Supplier<unsigned int> &alternate_len_list,
			 unsigned int num_glyphs,
			 Supplier<GlyphID> &alternate_glyphs_list)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!c->extend_min (u.format))) return TRACE_RETURN (false);
    unsigned int format = 1;
    u.format.set (format);
    switch (u.format) {
    case 1: return TRACE_RETURN (u.format1.serialize (c, glyphs, alternate_len_list, num_glyphs, alternate_glyphs_list));
    default:return TRACE_RETURN (false);
    }
  }

  template <typename context_t>
  inline typename context_t::return_t dispatch (context_t *c) const
  {
    TRACE_DISPATCH (this);
    switch (u.format) {
    case 1: return TRACE_RETURN (c->dispatch (u.format1));
    default:return TRACE_RETURN (c->default_return_value ());
    }
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    if (!u.format.sanitize (c)) return TRACE_RETURN (false);
    switch (u.format) {
    case 1: return TRACE_RETURN (u.format1.sanitize (c));
    default:return TRACE_RETURN (true);
    }
  }

  protected:
  union {
  USHORT		format;		/* Format identifier */
  AlternateSubstFormat1	format1;
  } u;
};


struct Ligature
{
  inline void closure (hb_closure_context_t *c) const
  {
    TRACE_CLOSURE (this);
    unsigned int count = component.len;
    for (unsigned int i = 1; i < count; i++)
      if (!c->glyphs->has (component[i]))
        return;
    c->glyphs->add (ligGlyph);
  }

  inline void collect_glyphs (hb_collect_glyphs_context_t *c) const
  {
    TRACE_COLLECT_GLYPHS (this);
    unsigned int count = component.len;
    for (unsigned int i = 1; i < count; i++)
      c->input->add (component[i]);
    c->output->add (ligGlyph);
  }

  inline bool would_apply (hb_would_apply_context_t *c) const
  {
    TRACE_WOULD_APPLY (this);
    if (c->len != component.len)
      return TRACE_RETURN (false);

    for (unsigned int i = 1; i < c->len; i++)
      if (likely (c->glyphs[i] != component[i]))
	return TRACE_RETURN (false);

    return TRACE_RETURN (true);
  }

  inline bool apply (hb_apply_context_t *c) const
  {
    TRACE_APPLY (this);
    unsigned int count = component.len;
    if (unlikely (count < 1)) return TRACE_RETURN (false);

    unsigned int end_offset = 0;
    bool is_mark_ligature = false;
    unsigned int total_component_count = 0;

    if (likely (!match_input (c, count,
			      &component[1],
			      match_glyph,
			      NULL,
			      &end_offset,
			      &is_mark_ligature,
			      &total_component_count)))
      return TRACE_RETURN (false);

    /* Deal, we are forming the ligature. */
    c->buffer->merge_clusters (c->buffer->idx, c->buffer->idx + end_offset);

    ligate_input (c,
		  count,
		  &component[1],
		  match_glyph,
		  NULL,
		  ligGlyph,
		  is_mark_ligature,
		  total_component_count);

    return TRACE_RETURN (true);
  }

  inline bool serialize (hb_serialize_context_t *c,
			 GlyphID ligature,
			 Supplier<GlyphID> &components, /* Starting from second */
			 unsigned int num_components /* Including first component */)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!c->extend_min (*this))) return TRACE_RETURN (false);
    ligGlyph = ligature;
    if (unlikely (!component.serialize (c, components, num_components))) return TRACE_RETURN (false);
    return TRACE_RETURN (true);
  }

  public:
  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    return TRACE_RETURN (ligGlyph.sanitize (c) && component.sanitize (c));
  }

  protected:
  GlyphID	ligGlyph;		/* GlyphID of ligature to substitute */
  HeadlessArrayOf<GlyphID>
		component;		/* Array of component GlyphIDs--start
					 * with the second  component--ordered
					 * in writing direction */
  public:
  DEFINE_SIZE_ARRAY (4, component);
};

struct LigatureSet
{
  inline void closure (hb_closure_context_t *c) const
  {
    TRACE_CLOSURE (this);
    unsigned int num_ligs = ligature.len;
    for (unsigned int i = 0; i < num_ligs; i++)
      (this+ligature[i]).closure (c);
  }

  inline void collect_glyphs (hb_collect_glyphs_context_t *c) const
  {
    TRACE_COLLECT_GLYPHS (this);
    unsigned int num_ligs = ligature.len;
    for (unsigned int i = 0; i < num_ligs; i++)
      (this+ligature[i]).collect_glyphs (c);
  }

  inline bool would_apply (hb_would_apply_context_t *c) const
  {
    TRACE_WOULD_APPLY (this);
    unsigned int num_ligs = ligature.len;
    for (unsigned int i = 0; i < num_ligs; i++)
    {
      const Ligature &lig = this+ligature[i];
      if (lig.would_apply (c))
        return TRACE_RETURN (true);
    }
    return TRACE_RETURN (false);
  }

  inline bool apply (hb_apply_context_t *c) const
  {
    TRACE_APPLY (this);
    unsigned int num_ligs = ligature.len;
    for (unsigned int i = 0; i < num_ligs; i++)
    {
      const Ligature &lig = this+ligature[i];
      if (lig.apply (c)) return TRACE_RETURN (true);
    }

    return TRACE_RETURN (false);
  }

  inline bool serialize (hb_serialize_context_t *c,
			 Supplier<GlyphID> &ligatures,
			 Supplier<unsigned int> &component_count_list,
			 unsigned int num_ligatures,
			 Supplier<GlyphID> &component_list /* Starting from second for each ligature */)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!c->extend_min (*this))) return TRACE_RETURN (false);
    if (unlikely (!ligature.serialize (c, num_ligatures))) return TRACE_RETURN (false);
    for (unsigned int i = 0; i < num_ligatures; i++)
      if (unlikely (!ligature[i].serialize (c, this).serialize (c,
								ligatures[i],
								component_list,
								component_count_list[i]))) return TRACE_RETURN (false);
    ligatures.advance (num_ligatures);
    component_count_list.advance (num_ligatures);
    return TRACE_RETURN (true);
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    return TRACE_RETURN (ligature.sanitize (c, this));
  }

  protected:
  OffsetArrayOf<Ligature>
		ligature;		/* Array LigatureSet tables
					 * ordered by preference */
  public:
  DEFINE_SIZE_ARRAY (2, ligature);
};

struct LigatureSubstFormat1
{
  inline bool is_inplace (hb_is_inplace_context_t *c) const
  {
    TRACE_IS_INPLACE (this);
    return TRACE_RETURN (false);
  }

  inline void closure (hb_closure_context_t *c) const
  {
    TRACE_CLOSURE (this);
    Coverage::Iter iter;
    for (iter.init (this+coverage); iter.more (); iter.next ()) {
      if (c->glyphs->has (iter.get_glyph ()))
	(this+ligatureSet[iter.get_coverage ()]).closure (c);
    }
  }

  inline void collect_glyphs (hb_collect_glyphs_context_t *c) const
  {
    TRACE_COLLECT_GLYPHS (this);
    Coverage::Iter iter;
    for (iter.init (this+coverage); iter.more (); iter.next ()) {
      c->input->add (iter.get_glyph ());
      (this+ligatureSet[iter.get_coverage ()]).collect_glyphs (c);
    }
  }

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

  inline bool would_apply (hb_would_apply_context_t *c) const
  {
    TRACE_WOULD_APPLY (this);
    unsigned int index = (this+coverage).get_coverage (c->glyphs[0]);
    if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);

    const LigatureSet &lig_set = this+ligatureSet[index];
    return TRACE_RETURN (lig_set.would_apply (c));
  }

  inline bool apply (hb_apply_context_t *c) const
  {
    TRACE_APPLY (this);
    hb_codepoint_t glyph_id = c->buffer->cur().codepoint;

    unsigned int index = (this+coverage).get_coverage (glyph_id);
    if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);

    const LigatureSet &lig_set = this+ligatureSet[index];
    return TRACE_RETURN (lig_set.apply (c));
  }

  inline bool serialize (hb_serialize_context_t *c,
			 Supplier<GlyphID> &first_glyphs,
			 Supplier<unsigned int> &ligature_per_first_glyph_count_list,
			 unsigned int num_first_glyphs,
			 Supplier<GlyphID> &ligatures_list,
			 Supplier<unsigned int> &component_count_list,
			 Supplier<GlyphID> &component_list /* Starting from second for each ligature */)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!c->extend_min (*this))) return TRACE_RETURN (false);
    if (unlikely (!ligatureSet.serialize (c, num_first_glyphs))) return TRACE_RETURN (false);
    for (unsigned int i = 0; i < num_first_glyphs; i++)
      if (unlikely (!ligatureSet[i].serialize (c, this).serialize (c,
								   ligatures_list,
								   component_count_list,
								   ligature_per_first_glyph_count_list[i],
								   component_list))) return TRACE_RETURN (false);
    ligature_per_first_glyph_count_list.advance (num_first_glyphs);
    if (unlikely (!coverage.serialize (c, this).serialize (c, first_glyphs, num_first_glyphs))) return TRACE_RETURN (false);
    return TRACE_RETURN (true);
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    return TRACE_RETURN (coverage.sanitize (c, this) && ligatureSet.sanitize (c, this));
  }

  protected:
  USHORT	format;			/* Format identifier--format = 1 */
  OffsetTo<Coverage>
		coverage;		/* Offset to Coverage table--from
					 * beginning of Substitution table */
  OffsetArrayOf<LigatureSet>
		ligatureSet;		/* Array LigatureSet tables
					 * ordered by Coverage Index */
  public:
  DEFINE_SIZE_ARRAY (6, ligatureSet);
};

struct LigatureSubst
{
  inline bool serialize (hb_serialize_context_t *c,
			 Supplier<GlyphID> &first_glyphs,
			 Supplier<unsigned int> &ligature_per_first_glyph_count_list,
			 unsigned int num_first_glyphs,
			 Supplier<GlyphID> &ligatures_list,
			 Supplier<unsigned int> &component_count_list,
			 Supplier<GlyphID> &component_list /* Starting from second for each ligature */)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!c->extend_min (u.format))) return TRACE_RETURN (false);
    unsigned int format = 1;
    u.format.set (format);
    switch (u.format) {
    case 1: return TRACE_RETURN (u.format1.serialize (c, first_glyphs, ligature_per_first_glyph_count_list, num_first_glyphs,
						      ligatures_list, component_count_list, component_list));
    default:return TRACE_RETURN (false);
    }
  }

  template <typename context_t>
  inline typename context_t::return_t dispatch (context_t *c) const
  {
    TRACE_DISPATCH (this);
    switch (u.format) {
    case 1: return TRACE_RETURN (c->dispatch (u.format1));
    default:return TRACE_RETURN (c->default_return_value ());
    }
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    if (!u.format.sanitize (c)) return TRACE_RETURN (false);
    switch (u.format) {
    case 1: return TRACE_RETURN (u.format1.sanitize (c));
    default:return TRACE_RETURN (true);
    }
  }

  protected:
  union {
  USHORT		format;		/* Format identifier */
  LigatureSubstFormat1	format1;
  } u;
};


struct ContextSubst : Context {};

struct ChainContextSubst : ChainContext {};

struct ExtensionSubst : Extension<ExtensionSubst>
{
  typedef struct SubstLookupSubTable LookupSubTable;

  inline bool is_reverse (void) const;
};


struct ReverseChainSingleSubstFormat1
{
  inline bool is_inplace (hb_is_inplace_context_t *c) const
  {
    TRACE_IS_INPLACE (this);
    return TRACE_RETURN (true);
  }

  inline void closure (hb_closure_context_t *c) const
  {
    TRACE_CLOSURE (this);
    const OffsetArrayOf<Coverage> &lookahead = StructAfter<OffsetArrayOf<Coverage> > (backtrack);

    unsigned int count;

    count = backtrack.len;
    for (unsigned int i = 0; i < count; i++)
      if (!(this+backtrack[i]).intersects (c->glyphs))
        return;

    count = lookahead.len;
    for (unsigned int i = 0; i < count; i++)
      if (!(this+lookahead[i]).intersects (c->glyphs))
        return;

    const ArrayOf<GlyphID> &substitute = StructAfter<ArrayOf<GlyphID> > (lookahead);
    Coverage::Iter iter;
    for (iter.init (this+coverage); iter.more (); iter.next ()) {
      if (c->glyphs->has (iter.get_glyph ()))
	c->glyphs->add (substitute[iter.get_coverage ()]);
    }
  }

  inline void collect_glyphs (hb_collect_glyphs_context_t *c) const
  {
    TRACE_COLLECT_GLYPHS (this);

    const OffsetArrayOf<Coverage> &lookahead = StructAfter<OffsetArrayOf<Coverage> > (backtrack);

    unsigned int count;

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

    count = backtrack.len;
    for (unsigned int i = 0; i < count; i++)
      (this+backtrack[i]).add_coverage (c->before);

    count = lookahead.len;
    for (unsigned int i = 0; i < count; i++)
      (this+lookahead[i]).add_coverage (c->after);

    const ArrayOf<GlyphID> &substitute = StructAfter<ArrayOf<GlyphID> > (lookahead);
    count = substitute.len;
    for (unsigned int i = 0; i < count; i++)
      c->output->add (substitute[i]);
  }

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

  inline bool would_apply (hb_would_apply_context_t *c) const
  {
    TRACE_WOULD_APPLY (this);
    return TRACE_RETURN (c->len == 1 && (this+coverage).get_coverage (c->glyphs[0]) != NOT_COVERED);
  }

  inline bool apply (hb_apply_context_t *c) const
  {
    TRACE_APPLY (this);
    if (unlikely (c->nesting_level_left != MAX_NESTING_LEVEL))
      return TRACE_RETURN (false); /* No chaining to this type */

    unsigned int index = (this+coverage).get_coverage (c->buffer->cur().codepoint);
    if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);

    const OffsetArrayOf<Coverage> &lookahead = StructAfter<OffsetArrayOf<Coverage> > (backtrack);
    const ArrayOf<GlyphID> &substitute = StructAfter<ArrayOf<GlyphID> > (lookahead);

    if (match_backtrack (c,
			 backtrack.len, (USHORT *) backtrack.array,
			 match_coverage, this) &&
        match_lookahead (c,
			 lookahead.len, (USHORT *) lookahead.array,
			 match_coverage, this,
			 1))
    {
      c->replace_glyph_inplace (substitute[index]);
      c->buffer->idx--; /* Reverse! */
      return TRACE_RETURN (true);
    }

    return TRACE_RETURN (false);
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    if (!(coverage.sanitize (c, this) && backtrack.sanitize (c, this)))
      return TRACE_RETURN (false);
    OffsetArrayOf<Coverage> &lookahead = StructAfter<OffsetArrayOf<Coverage> > (backtrack);
    if (!lookahead.sanitize (c, this))
      return TRACE_RETURN (false);
    ArrayOf<GlyphID> &substitute = StructAfter<ArrayOf<GlyphID> > (lookahead);
    return TRACE_RETURN (substitute.sanitize (c));
  }

  protected:
  USHORT	format;			/* Format identifier--format = 1 */
  OffsetTo<Coverage>
		coverage;		/* Offset to Coverage table--from
					 * beginning of table */
  OffsetArrayOf<Coverage>
		backtrack;		/* Array of coverage tables
					 * in backtracking sequence, in  glyph
					 * sequence order */
  OffsetArrayOf<Coverage>
		lookaheadX;		/* Array of coverage tables
					 * in lookahead sequence, in glyph
					 * sequence order */
  ArrayOf<GlyphID>
		substituteX;		/* Array of substitute
					 * GlyphIDs--ordered by Coverage Index */
  public:
  DEFINE_SIZE_MIN (10);
};

struct ReverseChainSingleSubst
{
  template <typename context_t>
  inline typename context_t::return_t dispatch (context_t *c) const
  {
    TRACE_DISPATCH (this);
    switch (u.format) {
    case 1: return TRACE_RETURN (c->dispatch (u.format1));
    default:return TRACE_RETURN (c->default_return_value ());
    }
  }

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    if (!u.format.sanitize (c)) return TRACE_RETURN (false);
    switch (u.format) {
    case 1: return TRACE_RETURN (u.format1.sanitize (c));
    default:return TRACE_RETURN (true);
    }
  }

  protected:
  union {
  USHORT				format;		/* Format identifier */
  ReverseChainSingleSubstFormat1	format1;
  } u;
};


/*
 * SubstLookup
 */

struct SubstLookupSubTable
{
  friend struct SubstLookup;

  enum Type {
    Single		= 1,
    Multiple		= 2,
    Alternate		= 3,
    Ligature		= 4,
    Context		= 5,
    ChainContext	= 6,
    Extension		= 7,
    ReverseChainSingle	= 8
  };

  template <typename context_t>
  inline typename context_t::return_t dispatch (context_t *c, unsigned int lookup_type) const
  {
    TRACE_DISPATCH (this);
    switch (lookup_type) {
    case Single:		return TRACE_RETURN (u.single.dispatch (c));
    case Multiple:		return TRACE_RETURN (u.multiple.dispatch (c));
    case Alternate:		return TRACE_RETURN (u.alternate.dispatch (c));
    case Ligature:		return TRACE_RETURN (u.ligature.dispatch (c));
    case Context:		return TRACE_RETURN (u.context.dispatch (c));
    case ChainContext:		return TRACE_RETURN (u.chainContext.dispatch (c));
    case Extension:		return TRACE_RETURN (u.extension.dispatch (c));
    case ReverseChainSingle:	return TRACE_RETURN (u.reverseChainContextSingle.dispatch (c));
    default:			return TRACE_RETURN (c->default_return_value ());
    }
  }

  inline bool sanitize (hb_sanitize_context_t *c, unsigned int lookup_type) {
    TRACE_SANITIZE (this);
    if (!u.header.sub_format.sanitize (c))
      return TRACE_RETURN (false);
    switch (lookup_type) {
    case Single:		return TRACE_RETURN (u.single.sanitize (c));
    case Multiple:		return TRACE_RETURN (u.multiple.sanitize (c));
    case Alternate:		return TRACE_RETURN (u.alternate.sanitize (c));
    case Ligature:		return TRACE_RETURN (u.ligature.sanitize (c));
    case Context:		return TRACE_RETURN (u.context.sanitize (c));
    case ChainContext:		return TRACE_RETURN (u.chainContext.sanitize (c));
    case Extension:		return TRACE_RETURN (u.extension.sanitize (c));
    case ReverseChainSingle:	return TRACE_RETURN (u.reverseChainContextSingle.sanitize (c));
    default:			return TRACE_RETURN (true);
    }
  }

  protected:
  union {
  struct {
    USHORT			sub_format;
  } header;
  SingleSubst			single;
  MultipleSubst			multiple;
  AlternateSubst		alternate;
  LigatureSubst			ligature;
  ContextSubst			context;
  ChainContextSubst		chainContext;
  ExtensionSubst		extension;
  ReverseChainSingleSubst	reverseChainContextSingle;
  } u;
  public:
  DEFINE_SIZE_UNION (2, header.sub_format);
};


struct SubstLookup : Lookup
{
  inline const SubstLookupSubTable& get_subtable (unsigned int i) const
  { return this+CastR<OffsetArrayOf<SubstLookupSubTable> > (subTable)[i]; }

  inline static bool lookup_type_is_reverse (unsigned int lookup_type)
  { return lookup_type == SubstLookupSubTable::ReverseChainSingle; }

  inline bool is_reverse (void) const
  {
    unsigned int type = get_type ();
    if (unlikely (type == SubstLookupSubTable::Extension))
      return CastR<ExtensionSubst> (get_subtable(0)).is_reverse ();
    return lookup_type_is_reverse (type);
  }

  inline hb_is_inplace_context_t::return_t is_inplace (hb_is_inplace_context_t *c) const
  {
    TRACE_IS_INPLACE (this);
    c->set_recurse_func (dispatch_recurse_func<hb_is_inplace_context_t>);
    return TRACE_RETURN (dispatch (c));
  }

  inline hb_closure_context_t::return_t closure (hb_closure_context_t *c) const
  {
    TRACE_CLOSURE (this);
    c->set_recurse_func (dispatch_recurse_func<hb_closure_context_t>);
    return TRACE_RETURN (dispatch (c));
  }

  inline hb_collect_glyphs_context_t::return_t collect_glyphs_lookup (hb_collect_glyphs_context_t *c) const
  {
    TRACE_COLLECT_GLYPHS (this);
    c->set_recurse_func (dispatch_recurse_func<hb_collect_glyphs_context_t>);
    return TRACE_RETURN (dispatch (c));
  }

  template <typename set_t>
  inline void add_coverage (set_t *glyphs) const
  {
    hb_get_coverage_context_t c;
    const Coverage *last = NULL;
    unsigned int count = get_subtable_count ();
    for (unsigned int i = 0; i < count; i++) {
      const Coverage *coverage = &get_subtable (i).dispatch (&c, get_type ());
      if (coverage != last) {
        coverage->add_coverage (glyphs);
        last = coverage;
      }
    }
  }

  inline bool would_apply (hb_would_apply_context_t *c, const hb_set_digest_t *digest) const
  {
    TRACE_WOULD_APPLY (this);
    if (unlikely (!c->len))  return TRACE_RETURN (false);
    if (!digest->may_have (c->glyphs[0]))  return TRACE_RETURN (false);
      return TRACE_RETURN (dispatch (c));
  }

  inline bool apply_once (hb_apply_context_t *c) const
  {
    TRACE_APPLY (this);
    if (!c->check_glyph_property (&c->buffer->cur(), c->lookup_props))
      return TRACE_RETURN (false);
    return TRACE_RETURN (dispatch (c));
  }

  static bool apply_recurse_func (hb_apply_context_t *c, unsigned int lookup_index);
  inline bool apply_string (hb_apply_context_t *c,
			    unsigned int start,
			    unsigned int end,
			    const hb_set_digest_t *digest) const
  {
    bool inplace = end != (unsigned int) -1;
    bool ret = false;
    end = MIN (end, c->buffer->len);

    if (unlikely (start >= end || !c->lookup_mask))
      return false;

    c->set_recurse_func (apply_recurse_func);
    c->set_lookup (*this);

    if (likely (!is_reverse ()))
    {
      /* in/out forward substitution */
      c->buffer->idx = start;
      if (inplace)
        c->buffer->out_len = start;

      while (c->buffer->idx < end)
      {
	if (digest->may_have (c->buffer->cur().codepoint) &&
	    (c->buffer->cur().mask & c->lookup_mask) &&
	    apply_once (c))
	  ret = true;
	else
	  c->buffer->next_glyph ();
      }
    }
    else
    {
      /* in-place backward substitution */
      c->buffer->remove_output ();
      c->buffer->idx = end - 1;
      do
      {
	if (digest->may_have (c->buffer->cur().codepoint) &&
	    (c->buffer->cur().mask & c->lookup_mask) &&
	    apply_once (c))
	  ret = true;
	else
	  c->buffer->idx--;
      }
      while ((int) c->buffer->idx >= (int) start);
    }

    return ret;
  }

  inline SubstLookupSubTable& serialize_subtable (hb_serialize_context_t *c,
						  unsigned int i)
  { return CastR<OffsetArrayOf<SubstLookupSubTable> > (subTable)[i].serialize (c, this); }

  inline bool serialize_single (hb_serialize_context_t *c,
				uint32_t lookup_props,
			        Supplier<GlyphID> &glyphs,
			        Supplier<GlyphID> &substitutes,
			        unsigned int num_glyphs)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!Lookup::serialize (c, SubstLookupSubTable::Single, lookup_props, 1))) return TRACE_RETURN (false);
    return TRACE_RETURN (serialize_subtable (c, 0).u.single.serialize (c, glyphs, substitutes, num_glyphs));
  }

  inline bool serialize_multiple (hb_serialize_context_t *c,
				  uint32_t lookup_props,
				  Supplier<GlyphID> &glyphs,
				  Supplier<unsigned int> &substitute_len_list,
				  unsigned int num_glyphs,
				  Supplier<GlyphID> &substitute_glyphs_list)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!Lookup::serialize (c, SubstLookupSubTable::Multiple, lookup_props, 1))) return TRACE_RETURN (false);
    return TRACE_RETURN (serialize_subtable (c, 0).u.multiple.serialize (c, glyphs, substitute_len_list, num_glyphs,
									 substitute_glyphs_list));
  }

  inline bool serialize_alternate (hb_serialize_context_t *c,
				   uint32_t lookup_props,
				   Supplier<GlyphID> &glyphs,
				   Supplier<unsigned int> &alternate_len_list,
				   unsigned int num_glyphs,
				   Supplier<GlyphID> &alternate_glyphs_list)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!Lookup::serialize (c, SubstLookupSubTable::Alternate, lookup_props, 1))) return TRACE_RETURN (false);
    return TRACE_RETURN (serialize_subtable (c, 0).u.alternate.serialize (c, glyphs, alternate_len_list, num_glyphs,
									  alternate_glyphs_list));
  }

  inline bool serialize_ligature (hb_serialize_context_t *c,
				  uint32_t lookup_props,
				  Supplier<GlyphID> &first_glyphs,
				  Supplier<unsigned int> &ligature_per_first_glyph_count_list,
				  unsigned int num_first_glyphs,
				  Supplier<GlyphID> &ligatures_list,
				  Supplier<unsigned int> &component_count_list,
				  Supplier<GlyphID> &component_list /* Starting from second for each ligature */)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (!Lookup::serialize (c, SubstLookupSubTable::Ligature, lookup_props, 1))) return TRACE_RETURN (false);
    return TRACE_RETURN (serialize_subtable (c, 0).u.ligature.serialize (c, first_glyphs, ligature_per_first_glyph_count_list, num_first_glyphs,
									 ligatures_list, component_count_list, component_list));
  }

  template <typename context_t>
  static inline typename context_t::return_t dispatch_recurse_func (context_t *c, unsigned int lookup_index);

  template <typename context_t>
  inline typename context_t::return_t dispatch (context_t *c) const
  {
    TRACE_DISPATCH (this);
    unsigned int lookup_type = get_type ();
    unsigned int count = get_subtable_count ();
    for (unsigned int i = 0; i < count; i++) {
      typename context_t::return_t r = get_subtable (i).dispatch (c, lookup_type);
      if (c->stop_sublookup_iteration (r))
        return TRACE_RETURN (r);
    }
    return TRACE_RETURN (c->default_return_value ());
  }

  inline bool sanitize (hb_sanitize_context_t *c)
  {
    TRACE_SANITIZE (this);
    if (unlikely (!Lookup::sanitize (c))) return TRACE_RETURN (false);
    OffsetArrayOf<SubstLookupSubTable> &list = CastR<OffsetArrayOf<SubstLookupSubTable> > (subTable);
    if (unlikely (!list.sanitize (c, this, get_type ()))) return TRACE_RETURN (false);

    if (unlikely (get_type () == SubstLookupSubTable::Extension))
    {
      /* The spec says all subtables of an Extension lookup should
       * have the same type.  This is specially important if one has
       * a reverse type! */
      unsigned int type = get_subtable (0).u.extension.get_type ();
      unsigned int count = get_subtable_count ();
      for (unsigned int i = 1; i < count; i++)
        if (get_subtable (i).u.extension.get_type () != type)
	  return TRACE_RETURN (false);
    }
    return TRACE_RETURN (true);
  }
};

typedef OffsetListOf<SubstLookup> SubstLookupList;

/*
 * GSUB -- The Glyph Substitution Table
 */

struct GSUB : GSUBGPOS
{
  static const hb_tag_t Tag	= HB_OT_TAG_GSUB;

  inline const SubstLookup& get_lookup (unsigned int i) const
  { return CastR<SubstLookup> (GSUBGPOS::get_lookup (i)); }

  static inline void substitute_start (hb_font_t *font, hb_buffer_t *buffer);
  static inline void substitute_finish (hb_font_t *font, hb_buffer_t *buffer);

  inline bool sanitize (hb_sanitize_context_t *c) {
    TRACE_SANITIZE (this);
    if (unlikely (!GSUBGPOS::sanitize (c))) return TRACE_RETURN (false);
    OffsetTo<SubstLookupList> &list = CastR<OffsetTo<SubstLookupList> > (lookupList);
    return TRACE_RETURN (list.sanitize (c, this));
  }
  public:
  DEFINE_SIZE_STATIC (10);
};


void
GSUB::substitute_start (hb_font_t *font, hb_buffer_t *buffer)
{
  HB_BUFFER_ALLOCATE_VAR (buffer, glyph_props);
  HB_BUFFER_ALLOCATE_VAR (buffer, lig_props);
  HB_BUFFER_ALLOCATE_VAR (buffer, syllable);

  const GDEF &gdef = *hb_ot_layout_from_face (font->face)->gdef;
  unsigned int count = buffer->len;
  for (unsigned int i = 0; i < count; i++) {
    buffer->info[i].lig_props() = buffer->info[i].syllable() = 0;
    buffer->info[i].glyph_props() = gdef.get_glyph_props (buffer->info[i].codepoint);
  }
}

void
GSUB::substitute_finish (hb_font_t *font HB_UNUSED, hb_buffer_t *buffer HB_UNUSED)
{
}


/* Out-of-class implementation for methods recursing */

inline bool ExtensionSubst::is_reverse (void) const
{
  unsigned int type = get_type ();
  if (unlikely (type == SubstLookupSubTable::Extension))
    return CastR<ExtensionSubst> (get_subtable<SubstLookupSubTable>()).is_reverse ();
  return SubstLookup::lookup_type_is_reverse (type);
}

template <typename context_t>
inline typename context_t::return_t SubstLookup::dispatch_recurse_func (context_t *c, unsigned int lookup_index)
{
  const GSUB &gsub = *(hb_ot_layout_from_face (c->face)->gsub);
  const SubstLookup &l = gsub.get_lookup (lookup_index);
  return l.dispatch (c);
}

inline bool SubstLookup::apply_recurse_func (hb_apply_context_t *c, unsigned int lookup_index)
{
  const GSUB &gsub = *(hb_ot_layout_from_face (c->face)->gsub);
  const SubstLookup &l = gsub.get_lookup (lookup_index);
  unsigned int saved_lookup_props = c->lookup_props;
  c->set_lookup (l);
  bool ret = l.apply_once (c);
  c->lookup_props = saved_lookup_props;
  return ret;
}


} /* namespace OT */


#endif /* HB_OT_LAYOUT_GSUB_TABLE_HH */