/*
 * Copyright © 2017  Google, Inc.
 *
 *  This is part of HarfBuzz, a text shaping library.
 *
 * Permission is hereby granted, without written agreement and without
 * license or royalty fees, to use, copy, modify, and distribute this
 * software and its documentation for any purpose, provided that the
 * above copyright notice and the following two paragraphs appear in
 * all copies of this software.
 *
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 *
 * Google Author(s): Behdad Esfahbod
 */

#ifndef HB_AAT_LAYOUT_COMMON_HH
#define HB_AAT_LAYOUT_COMMON_HH

#include "hb-aat-layout.hh"
#include "hb-open-type.hh"


namespace AAT {

using namespace OT;


/*
 * Lookup Table
 */

template <typename T> struct Lookup;

template <typename T>
struct LookupFormat0
{
  friend struct Lookup<T>;

  private:
  const T* get_value (hb_codepoint_t glyph_id, unsigned int num_glyphs) const
  {
    if (unlikely (glyph_id >= num_glyphs)) return nullptr;
    return &arrayZ[glyph_id];
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (arrayZ.sanitize (c, c->get_num_glyphs ()));
  }
  bool sanitize (hb_sanitize_context_t *c, const void *base) const
  {
    TRACE_SANITIZE (this);
    return_trace (arrayZ.sanitize (c, c->get_num_glyphs (), base));
  }

  protected:
  HBUINT16      format;         /* Format identifier--format = 0 */
  UnsizedArrayOf<T>
                arrayZ;         /* Array of lookup values, indexed by glyph index. */
  public:
  DEFINE_SIZE_UNBOUNDED (2);
};


template <typename T>
struct LookupSegmentSingle
{
  static constexpr unsigned TerminationWordCount = 2u;

  int cmp (hb_codepoint_t g) const
  { return g < first ? -1 : g <= last ? 0 : +1 ; }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && value.sanitize (c));
  }
  bool sanitize (hb_sanitize_context_t *c, const void *base) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && value.sanitize (c, base));
  }

  GlyphID       last;           /* Last GlyphID in this segment */
  GlyphID       first;          /* First GlyphID in this segment */
  T             value;          /* The lookup value (only one) */
  public:
  DEFINE_SIZE_STATIC (4 + T::static_size);
};

template <typename T>
struct LookupFormat2
{
  friend struct Lookup<T>;

  private:
  const T* get_value (hb_codepoint_t glyph_id) const
  {
    const LookupSegmentSingle<T> *v = segments.bsearch (glyph_id);
    return v ? &v->value : nullptr;
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (segments.sanitize (c));
  }
  bool sanitize (hb_sanitize_context_t *c, const void *base) const
  {
    TRACE_SANITIZE (this);
    return_trace (segments.sanitize (c, base));
  }

  protected:
  HBUINT16      format;         /* Format identifier--format = 2 */
  VarSizedBinSearchArrayOf<LookupSegmentSingle<T> >
                segments;       /* The actual segments. These must already be sorted,
                                 * according to the first word in each one (the last
                                 * glyph in each segment). */
  public:
  DEFINE_SIZE_ARRAY (8, segments);
};

template <typename T>
struct LookupSegmentArray
{
  static constexpr unsigned TerminationWordCount = 2u;

  const T* get_value (hb_codepoint_t glyph_id, const void *base) const
  {
    return first <= glyph_id && glyph_id <= last ? &(base+valuesZ)[glyph_id - first] : nullptr;
  }

  int cmp (hb_codepoint_t g) const
  { return g < first ? -1 : g <= last ? 0 : +1; }

  bool sanitize (hb_sanitize_context_t *c, const void *base) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) &&
                  first <= last &&
                  valuesZ.sanitize (c, base, last - first + 1));
  }
  template <typename T2>
  bool sanitize (hb_sanitize_context_t *c, const void *base, T2 user_data) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) &&
                  first <= last &&
                  valuesZ.sanitize (c, base, last - first + 1, user_data));
  }

  GlyphID       last;           /* Last GlyphID in this segment */
  GlyphID       first;          /* First GlyphID in this segment */
  NNOffsetTo<UnsizedArrayOf<T> >
                valuesZ;        /* A 16-bit offset from the start of
                                 * the table to the data. */
  public:
  DEFINE_SIZE_STATIC (6);
};

template <typename T>
struct LookupFormat4
{
  friend struct Lookup<T>;

  private:
  const T* get_value (hb_codepoint_t glyph_id) const
  {
    const LookupSegmentArray<T> *v = segments.bsearch (glyph_id);
    return v ? v->get_value (glyph_id, this) : nullptr;
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (segments.sanitize (c, this));
  }
  bool sanitize (hb_sanitize_context_t *c, const void *base) const
  {
    TRACE_SANITIZE (this);
    return_trace (segments.sanitize (c, this, base));
  }

  protected:
  HBUINT16      format;         /* Format identifier--format = 4 */
  VarSizedBinSearchArrayOf<LookupSegmentArray<T> >
                segments;       /* The actual segments. These must already be sorted,
                                 * according to the first word in each one (the last
                                 * glyph in each segment). */
  public:
  DEFINE_SIZE_ARRAY (8, segments);
};

template <typename T>
struct LookupSingle
{
  static constexpr unsigned TerminationWordCount = 1u;

  int cmp (hb_codepoint_t g) const { return glyph.cmp (g); }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && value.sanitize (c));
  }
  bool sanitize (hb_sanitize_context_t *c, const void *base) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && value.sanitize (c, base));
  }

  GlyphID       glyph;          /* Last GlyphID */
  T             value;          /* The lookup value (only one) */
  public:
  DEFINE_SIZE_STATIC (2 + T::static_size);
};

template <typename T>
struct LookupFormat6
{
  friend struct Lookup<T>;

  private:
  const T* get_value (hb_codepoint_t glyph_id) const
  {
    const LookupSingle<T> *v = entries.bsearch (glyph_id);
    return v ? &v->value : nullptr;
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (entries.sanitize (c));
  }
  bool sanitize (hb_sanitize_context_t *c, const void *base) const
  {
    TRACE_SANITIZE (this);
    return_trace (entries.sanitize (c, base));
  }

  protected:
  HBUINT16      format;         /* Format identifier--format = 6 */
  VarSizedBinSearchArrayOf<LookupSingle<T> >
                entries;        /* The actual entries, sorted by glyph index. */
  public:
  DEFINE_SIZE_ARRAY (8, entries);
};

template <typename T>
struct LookupFormat8
{
  friend struct Lookup<T>;

  private:
  const T* get_value (hb_codepoint_t glyph_id) const
  {
    return firstGlyph <= glyph_id && glyph_id - firstGlyph < glyphCount ?
           &valueArrayZ[glyph_id - firstGlyph] : nullptr;
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && valueArrayZ.sanitize (c, glyphCount));
  }
  bool sanitize (hb_sanitize_context_t *c, const void *base) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && valueArrayZ.sanitize (c, glyphCount, base));
  }

  protected:
  HBUINT16      format;         /* Format identifier--format = 8 */
  GlyphID       firstGlyph;     /* First glyph index included in the trimmed array. */
  HBUINT16      glyphCount;     /* Total number of glyphs (equivalent to the last
                                 * glyph minus the value of firstGlyph plus 1). */
  UnsizedArrayOf<T>
                valueArrayZ;    /* The lookup values (indexed by the glyph index
                                 * minus the value of firstGlyph). */
  public:
  DEFINE_SIZE_ARRAY (6, valueArrayZ);
};

template <typename T>
struct LookupFormat10
{
  friend struct Lookup<T>;

  private:
  const typename T::type get_value_or_null (hb_codepoint_t glyph_id) const
  {
    if (!(firstGlyph <= glyph_id && glyph_id - firstGlyph < glyphCount))
      return Null(T);

    const HBUINT8 *p = &valueArrayZ[(glyph_id - firstGlyph) * valueSize];

    unsigned int v = 0;
    unsigned int count = valueSize;
    for (unsigned int i = 0; i < count; i++)
      v = (v << 8) | *p++;

    return v;
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) &&
                  valueSize <= 4 &&
                  valueArrayZ.sanitize (c, glyphCount * valueSize));
  }

  protected:
  HBUINT16      format;         /* Format identifier--format = 8 */
  HBUINT16      valueSize;      /* Byte size of each value. */
  GlyphID       firstGlyph;     /* First glyph index included in the trimmed array. */
  HBUINT16      glyphCount;     /* Total number of glyphs (equivalent to the last
                                 * glyph minus the value of firstGlyph plus 1). */
  UnsizedArrayOf<HBUINT8>
                valueArrayZ;    /* The lookup values (indexed by the glyph index
                                 * minus the value of firstGlyph). */
  public:
  DEFINE_SIZE_ARRAY (8, valueArrayZ);
};

template <typename T>
struct Lookup
{
  const T* get_value (hb_codepoint_t glyph_id, unsigned int num_glyphs) const
  {
    switch (u.format) {
    case 0: return u.format0.get_value (glyph_id, num_glyphs);
    case 2: return u.format2.get_value (glyph_id);
    case 4: return u.format4.get_value (glyph_id);
    case 6: return u.format6.get_value (glyph_id);
    case 8: return u.format8.get_value (glyph_id);
    default:return nullptr;
    }
  }

  const typename T::type get_value_or_null (hb_codepoint_t glyph_id, unsigned int num_glyphs) const
  {
    switch (u.format) {
      /* Format 10 cannot return a pointer. */
      case 10: return u.format10.get_value_or_null (glyph_id);
      default:
      const T *v = get_value (glyph_id, num_glyphs);
      return v ? *v : Null(T);
    }
  }

  typename T::type get_class (hb_codepoint_t glyph_id,
                              unsigned int num_glyphs,
                              unsigned int outOfRange) const
  {
    const T *v = get_value (glyph_id, num_glyphs);
    return v ? *v : outOfRange;
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    if (!u.format.sanitize (c)) return_trace (false);
    switch (u.format) {
    case 0: return_trace (u.format0.sanitize (c));
    case 2: return_trace (u.format2.sanitize (c));
    case 4: return_trace (u.format4.sanitize (c));
    case 6: return_trace (u.format6.sanitize (c));
    case 8: return_trace (u.format8.sanitize (c));
    case 10: return_trace (u.format10.sanitize (c));
    default:return_trace (true);
    }
  }
  bool sanitize (hb_sanitize_context_t *c, const void *base) const
  {
    TRACE_SANITIZE (this);
    if (!u.format.sanitize (c)) return_trace (false);
    switch (u.format) {
    case 0: return_trace (u.format0.sanitize (c, base));
    case 2: return_trace (u.format2.sanitize (c, base));
    case 4: return_trace (u.format4.sanitize (c, base));
    case 6: return_trace (u.format6.sanitize (c, base));
    case 8: return_trace (u.format8.sanitize (c, base));
    case 10: return_trace (false); /* We don't support format10 here currently. */
    default:return_trace (true);
    }
  }

  protected:
  union {
  HBUINT16              format;         /* Format identifier */
  LookupFormat0<T>      format0;
  LookupFormat2<T>      format2;
  LookupFormat4<T>      format4;
  LookupFormat6<T>      format6;
  LookupFormat8<T>      format8;
  LookupFormat10<T>     format10;
  } u;
  public:
  DEFINE_SIZE_UNION (2, format);
};
/* Lookup 0 has unbounded size (dependant on num_glyphs).  So we need to defined
 * special NULL objects for Lookup<> objects, but since it's template our macros
 * don't work.  So we have to hand-code them here.  UGLY. */
} /* Close namespace. */
/* Ugly hand-coded null objects for template Lookup<> :(. */
extern HB_INTERNAL const unsigned char _hb_Null_AAT_Lookup[2];
template <>
/*static*/ inline const AAT::Lookup<OT::HBUINT16>& Null<AAT::Lookup<OT::HBUINT16> > ()
{ return *reinterpret_cast<const AAT::Lookup<OT::HBUINT16> *> (_hb_Null_AAT_Lookup); }
template <>
/*static*/ inline const AAT::Lookup<OT::HBUINT32>& Null<AAT::Lookup<OT::HBUINT32> > ()
{ return *reinterpret_cast<const AAT::Lookup<OT::HBUINT32> *> (_hb_Null_AAT_Lookup); }
template <>
/*static*/ inline const AAT::Lookup<OT::Offset<OT::HBUINT16, false> >& Null<AAT::Lookup<OT::Offset<OT::HBUINT16, false> > > ()
{ return *reinterpret_cast<const AAT::Lookup<OT::Offset<OT::HBUINT16, false> > *> (_hb_Null_AAT_Lookup); }
namespace AAT {

enum { DELETED_GLYPH = 0xFFFF };

/*
 * (Extended) State Table
 */

template <typename T>
struct Entry
{
  bool sanitize (hb_sanitize_context_t *c, unsigned int count) const
  {
    TRACE_SANITIZE (this);
    /* Note, we don't recurse-sanitize data because we don't access it.
     * That said, in our DEFINE_SIZE_STATIC we access T::static_size,
     * which ensures that data has a simple sanitize(). To be determined
     * if I need to remove that as well.
     *
     * HOWEVER! Because we are a template, our DEFINE_SIZE_STATIC
     * assertion wouldn't be checked, hence the line below. */
    static_assert (T::static_size, "");

    return_trace (c->check_struct (this));
  }

  public:
  HBUINT16      newState;       /* Byte offset from beginning of state table
                                 * to the new state. Really?!?! Or just state
                                 * number?  The latter in morx for sure. */
  HBUINT16      flags;          /* Table specific. */
  T             data;           /* Optional offsets to per-glyph tables. */
  public:
  DEFINE_SIZE_STATIC (4 + T::static_size);
};

template <>
struct Entry<void>
{
  bool sanitize (hb_sanitize_context_t *c, unsigned int count /*XXX Unused?*/) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  public:
  HBUINT16      newState;       /* Byte offset from beginning of state table to the new state. */
  HBUINT16      flags;          /* Table specific. */
  public:
  DEFINE_SIZE_STATIC (4);
};

template <typename Types, typename Extra>
struct StateTable
{
  typedef typename Types::HBUINT HBUINT;
  typedef typename Types::HBUSHORT HBUSHORT;
  typedef typename Types::ClassTypeNarrow ClassType;

  enum State
  {
    STATE_START_OF_TEXT = 0,
    STATE_START_OF_LINE = 1,
  };
  enum Class
  {
    CLASS_END_OF_TEXT = 0,
    CLASS_OUT_OF_BOUNDS = 1,
    CLASS_DELETED_GLYPH = 2,
    CLASS_END_OF_LINE = 3,
  };

  int new_state (unsigned int newState) const
  { return Types::extended ? newState : ((int) newState - (int) stateArrayTable) / (int) nClasses; }

  unsigned int get_class (hb_codepoint_t glyph_id, unsigned int num_glyphs) const
  {
    if (unlikely (glyph_id == DELETED_GLYPH)) return CLASS_DELETED_GLYPH;
    return (this+classTable).get_class (glyph_id, num_glyphs, 1);
  }

  const Entry<Extra> *get_entries () const
  { return (this+entryTable).arrayZ; }

  const Entry<Extra> &get_entry (int state, unsigned int klass) const
  {
    if (unlikely (klass >= nClasses))
      klass = StateTable<Types, Entry<Extra> >::CLASS_OUT_OF_BOUNDS;

    const HBUSHORT *states = (this+stateArrayTable).arrayZ;
    const Entry<Extra> *entries = (this+entryTable).arrayZ;

    unsigned int entry = states[state * nClasses + klass];
    DEBUG_MSG (APPLY, nullptr, "e%u", entry);

    return entries[entry];
  }

  bool sanitize (hb_sanitize_context_t *c,
                 unsigned int *num_entries_out = nullptr) const
  {
    TRACE_SANITIZE (this);
    if (unlikely (!(c->check_struct (this) &&
                    nClasses >= 4 /* Ensure pre-defined classes fit.  */ &&
                    classTable.sanitize (c, this)))) return_trace (false);

    const HBUSHORT *states = (this+stateArrayTable).arrayZ;
    const Entry<Extra> *entries = (this+entryTable).arrayZ;

    unsigned int num_classes = nClasses;
    if (unlikely (hb_unsigned_mul_overflows (num_classes, states[0].static_size)))
      return_trace (false);
    unsigned int row_stride = num_classes * states[0].static_size;

    /* Apple 'kern' table has this peculiarity:
     *
     * "Because the stateTableOffset in the state table header is (strictly
     * speaking) redundant, some 'kern' tables use it to record an initial
     * state where that should not be StartOfText. To determine if this is
     * done, calculate what the stateTableOffset should be. If it's different
     * from the actual stateTableOffset, use it as the initial state."
     *
     * We implement this by calling the initial state zero, but allow *negative*
     * states if the start state indeed was not the first state.  Since the code
     * is shared, this will also apply to 'mort' table.  The 'kerx' / 'morx'
     * tables are not affected since those address states by index, not offset.
     */

    int min_state = 0;
    int max_state = 0;
    unsigned int num_entries = 0;

    int state_pos = 0;
    int state_neg = 0;
    unsigned int entry = 0;
    while (min_state < state_neg || state_pos <= max_state)
    {
      if (min_state < state_neg)
      {
        /* Negative states. */
        if (unlikely (hb_unsigned_mul_overflows (min_state, num_classes)))
          return_trace (false);
        if (unlikely (!c->check_range (&states[min_state * num_classes],
                                       -min_state,
                                       row_stride)))
          return_trace (false);
        if ((c->max_ops -= state_neg - min_state) <= 0)
          return_trace (false);
        { /* Sweep new states. */
          const HBUSHORT *stop = &states[min_state * num_classes];
          if (unlikely (stop > states))
            return_trace (false);
          for (const HBUSHORT *p = states; stop < p; p--)
            num_entries = MAX<unsigned int> (num_entries, *(p - 1) + 1);
          state_neg = min_state;
        }
      }

      if (state_pos <= max_state)
      {
        /* Positive states. */
        if (unlikely (!c->check_range (states,
                                       max_state + 1,
                                       row_stride)))
          return_trace (false);
        if ((c->max_ops -= max_state - state_pos + 1) <= 0)
          return_trace (false);
        { /* Sweep new states. */
          if (unlikely (hb_unsigned_mul_overflows ((max_state + 1), num_classes)))
            return_trace (false);
          const HBUSHORT *stop = &states[(max_state + 1) * num_classes];
          if (unlikely (stop < states))
            return_trace (false);
          for (const HBUSHORT *p = &states[state_pos * num_classes]; p < stop; p++)
            num_entries = MAX<unsigned int> (num_entries, *p + 1);
          state_pos = max_state + 1;
        }
      }

      if (unlikely (!c->check_array (entries, num_entries)))
        return_trace (false);
      if ((c->max_ops -= num_entries - entry) <= 0)
        return_trace (false);
      { /* Sweep new entries. */
        const Entry<Extra> *stop = &entries[num_entries];
        for (const Entry<Extra> *p = &entries[entry]; p < stop; p++)
        {
          int newState = new_state (p->newState);
          min_state = MIN (min_state, newState);
          max_state = MAX (max_state, newState);
        }
        entry = num_entries;
      }
    }

    if (num_entries_out)
      *num_entries_out = num_entries;

    return_trace (true);
  }

  protected:
  HBUINT        nClasses;       /* Number of classes, which is the number of indices
                                 * in a single line in the state array. */
  NNOffsetTo<ClassType, HBUINT>
                classTable;     /* Offset to the class table. */
  NNOffsetTo<UnsizedArrayOf<HBUSHORT>, HBUINT>
                stateArrayTable;/* Offset to the state array. */
  NNOffsetTo<UnsizedArrayOf<Entry<Extra> >, HBUINT>
                entryTable;     /* Offset to the entry array. */

  public:
  DEFINE_SIZE_STATIC (4 * sizeof (HBUINT));
};

template <typename HBUCHAR>
struct ClassTable
{
  unsigned int get_class (hb_codepoint_t glyph_id, unsigned int outOfRange) const
  {
    unsigned int i = glyph_id - firstGlyph;
    return i >= classArray.len ? outOfRange : classArray.arrayZ[i];
  }
  unsigned int get_class (hb_codepoint_t glyph_id,
                          unsigned int num_glyphs HB_UNUSED,
                          unsigned int outOfRange) const
  {
    return get_class (glyph_id, outOfRange);
  }
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && classArray.sanitize (c));
  }
  protected:
  GlyphID               firstGlyph;     /* First glyph index included in the trimmed array. */
  ArrayOf<HBUCHAR>      classArray;     /* The class codes (indexed by glyph index minus
                                         * firstGlyph). */
  public:
  DEFINE_SIZE_ARRAY (4, classArray);
};

struct ObsoleteTypes
{
  static constexpr bool extended = false;
  typedef HBUINT16 HBUINT;
  typedef HBUINT8 HBUSHORT;
  typedef ClassTable<HBUINT8> ClassTypeNarrow;
  typedef ClassTable<HBUINT16> ClassTypeWide;

  template <typename T>
  static unsigned int offsetToIndex (unsigned int offset,
                                     const void *base,
                                     const T *array)
  {
    return (offset - ((const char *) array - (const char *) base)) / sizeof (T);
  }
  template <typename T>
  static unsigned int byteOffsetToIndex (unsigned int offset,
                                         const void *base,
                                         const T *array)
  {
    return offsetToIndex (offset, base, array);
  }
  template <typename T>
  static unsigned int wordOffsetToIndex (unsigned int offset,
                                         const void *base,
                                         const T *array)
  {
    return offsetToIndex (2 * offset, base, array);
  }
};
struct ExtendedTypes
{
  static constexpr bool extended = true;
  typedef HBUINT32 HBUINT;
  typedef HBUINT16 HBUSHORT;
  typedef Lookup<HBUINT16> ClassTypeNarrow;
  typedef Lookup<HBUINT16> ClassTypeWide;

  template <typename T>
  static unsigned int offsetToIndex (unsigned int offset,
                                     const void *base HB_UNUSED,
                                     const T *array HB_UNUSED)
  {
    return offset;
  }
  template <typename T>
  static unsigned int byteOffsetToIndex (unsigned int offset,
                                         const void *base HB_UNUSED,
                                         const T *array HB_UNUSED)
  {
    return offset / 2;
  }
  template <typename T>
  static unsigned int wordOffsetToIndex (unsigned int offset,
                                         const void *base HB_UNUSED,
                                         const T *array HB_UNUSED)
  {
    return offset;
  }
};

template <typename Types, typename EntryData>
struct StateTableDriver
{
  StateTableDriver (const StateTable<Types, EntryData> &machine_,
                    hb_buffer_t *buffer_,
                    hb_face_t *face_) :
              machine (machine_),
              buffer (buffer_),
              num_glyphs (face_->get_num_glyphs ()) {}

  template <typename context_t>
  void drive (context_t *c)
  {
    if (!c->in_place)
      buffer->clear_output ();

    int state = StateTable<Types, EntryData>::STATE_START_OF_TEXT;
    for (buffer->idx = 0; buffer->successful;)
    {
      unsigned int klass = buffer->idx < buffer->len ?
                           machine.get_class (buffer->info[buffer->idx].codepoint, num_glyphs) :
                           (unsigned) StateTable<Types, EntryData>::CLASS_END_OF_TEXT;
      DEBUG_MSG (APPLY, nullptr, "c%u at %u", klass, buffer->idx);
      const Entry<EntryData> &entry = machine.get_entry (state, klass);

      /* Unsafe-to-break before this if not in state 0, as things might
       * go differently if we start from state 0 here.
       *
       * Ugh.  The indexing here is ugly... */
      if (state && buffer->backtrack_len () && buffer->idx < buffer->len)
      {
        /* If there's no action and we're just epsilon-transitioning to state 0,
         * safe to break. */
        if (c->is_actionable (this, entry) ||
            !(entry.newState == StateTable<Types, EntryData>::STATE_START_OF_TEXT &&
              entry.flags == context_t::DontAdvance))
          buffer->unsafe_to_break_from_outbuffer (buffer->backtrack_len () - 1, buffer->idx + 1);
      }

      /* Unsafe-to-break if end-of-text would kick in here. */
      if (buffer->idx + 2 <= buffer->len)
      {
        const Entry<EntryData> &end_entry = machine.get_entry (state, StateTable<Types, EntryData>::CLASS_END_OF_TEXT);
        if (c->is_actionable (this, end_entry))
          buffer->unsafe_to_break (buffer->idx, buffer->idx + 2);
      }

      c->transition (this, entry);

      state = machine.new_state (entry.newState);
      DEBUG_MSG (APPLY, nullptr, "s%d", state);

      if (buffer->idx == buffer->len)
        break;

      if (!(entry.flags & context_t::DontAdvance) || buffer->max_ops-- <= 0)
        buffer->next_glyph ();
    }

    if (!c->in_place)
    {
      for (; buffer->successful && buffer->idx < buffer->len;)
        buffer->next_glyph ();
      buffer->swap_buffers ();
    }
  }

  public:
  const StateTable<Types, EntryData> &machine;
  hb_buffer_t *buffer;
  unsigned int num_glyphs;
};


struct ankr;

struct hb_aat_apply_context_t :
       hb_dispatch_context_t<hb_aat_apply_context_t, bool, HB_DEBUG_APPLY>
{
  const char *get_name () { return "APPLY"; }
  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; }

  const hb_ot_shape_plan_t *plan;
  hb_font_t *font;
  hb_face_t *face;
  hb_buffer_t *buffer;
  hb_sanitize_context_t sanitizer;
  const ankr *ankr_table;

  /* Unused. For debug tracing only. */
  unsigned int lookup_index;
  unsigned int debug_depth;

  HB_INTERNAL hb_aat_apply_context_t (const hb_ot_shape_plan_t *plan_,
                                      hb_font_t *font_,
                                      hb_buffer_t *buffer_,
                                      hb_blob_t *blob = const_cast<hb_blob_t *> (&Null(hb_blob_t)));

  HB_INTERNAL ~hb_aat_apply_context_t ();

  HB_INTERNAL void set_ankr_table (const AAT::ankr *ankr_table_);

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


} /* namespace AAT */


#endif /* HB_AAT_LAYOUT_COMMON_HH */