text: /*
   * Copyright © 1998-2004  David Turner and Werner Lemberg
   * Copyright © 2004,2007,2009,2010  Red Hat, Inc.
   * Copyright © 2011,2012  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): Owen Taylor, Behdad Esfahbod
   * Google Author(s): Behdad Esfahbod
   */
  
  #include "hb-buffer.hh"
  #include "hb-utf.hh"
  
  
  /**
   * SECTION: hb-buffer
   * @title: hb-buffer
   * @short_description: Input and output buffers
   * @include: hb.h
   *
   * Buffers serve dual role in HarfBuzz; they hold the input characters that are
   * passed to hb_shape(), and after shaping they hold the output glyphs.
   **/
  
  
  /**
   * hb_segment_properties_equal:
   * @a: first #hb_segment_properties_t to compare.
   * @b: second #hb_segment_properties_t to compare.
   *
   * Checks the equality of two #hb_segment_properties_t's.
   *
   * Return value:
   * %true if all properties of @a equal those of @b, false otherwise.
   *
   * Since: 0.9.7
   **/
  hb_bool_t
  hb_segment_properties_equal (const hb_segment_properties_t *a,
  			     const hb_segment_properties_t *b)
  {
    return a->direction == b->direction &&
  	 a->script    == b->script    &&
  	 a->language  == b->language  &&
  	 a->reserved1 == b->reserved1 &&
  	 a->reserved2 == b->reserved2;
  
  }
  
  /**
   * hb_segment_properties_hash:
   * @p: #hb_segment_properties_t to hash.
   *
   * Creates a hash representing @p.
   *
   * Return value:
   * A hash of @p.
   *
   * Since: 0.9.7
   **/
  unsigned int
  hb_segment_properties_hash (const hb_segment_properties_t *p)
  {
    return (unsigned int) p->direction ^
  	 (unsigned int) p->script ^
  	 (intptr_t) (p->language);
  }
  
  
  
  /* Here is how the buffer works internally:
   *
   * There are two info pointers: info and out_info.  They always have
   * the same allocated size, but different lengths.
   *
   * As an optimization, both info and out_info may point to the
   * same piece of memory, which is owned by info.  This remains the
   * case as long as out_len doesn't exceed i at any time.
   * In that case, swap_buffers() is no-op and the glyph operations operate
   * mostly in-place.
   *
   * As soon as out_info gets longer than info, out_info is moved over
   * to an alternate buffer (which we reuse the pos buffer for!), and its
   * current contents (out_len entries) are copied to the new place.
   * This should all remain transparent to the user.  swap_buffers() then
   * switches info and out_info.
   */
  
  
  
  /* Internal API */
  
  bool
  hb_buffer_t::enlarge (unsigned int size)
  {
    if (unlikely (!successful))
      return false;
    if (unlikely (size > max_len))
    {
      successful = false;
      return false;
    }
  
    unsigned int new_allocated = allocated;
    hb_glyph_position_t *new_pos = nullptr;
    hb_glyph_info_t *new_info = nullptr;
    bool separate_out = out_info != info;
  
    if (unlikely (hb_unsigned_mul_overflows (size, sizeof (info[0]))))
      goto done;
  
    while (size >= new_allocated)
      new_allocated += (new_allocated >> 1) + 32;
  
    static_assert ((sizeof (info[0]) == sizeof (pos[0])), "");
    if (unlikely (hb_unsigned_mul_overflows (new_allocated, sizeof (info[0]))))
      goto done;
  
    new_pos = (hb_glyph_position_t *) realloc (pos, new_allocated * sizeof (pos[0]));
    new_info = (hb_glyph_info_t *) realloc (info, new_allocated * sizeof (info[0]));
  
  done:
    if (unlikely (!new_pos || !new_info))
      successful = false;
  
    if (likely (new_pos))
      pos = new_pos;
  
    if (likely (new_info))
      info = new_info;
  
    out_info = separate_out ? (hb_glyph_info_t *) pos : info;
    if (likely (successful))
      allocated = new_allocated;
  
    return likely (successful);
  }
  
  bool
  hb_buffer_t::make_room_for (unsigned int num_in,
  			    unsigned int num_out)
  {
    if (unlikely (!ensure (out_len + num_out))) return false;
  
    if (out_info == info &&
        out_len + num_out > idx + num_in)
    {
      assert (have_output);
  
      out_info = (hb_glyph_info_t *) pos;
      memcpy (out_info, info, out_len * sizeof (out_info[0]));
    }
  
    return true;
  }
  
  bool
  hb_buffer_t::shift_forward (unsigned int count)
  {
    assert (have_output);
    if (unlikely (!ensure (len + count))) return false;
  
    memmove (info + idx + count, info + idx, (len - idx) * sizeof (info[0]));
    if (idx + count > len)
    {
      /* Under memory failure we might expose this area.  At least
       * clean it up.  Oh well...
       *
       * Ideally, we should at least set Default_Ignorable bits on
       * these, as well as consistent cluster values.  But the former
       * is layering violation... */
      memset (info + len, 0, (idx + count - len) * sizeof (info[0]));
    }
    len += count;
    idx += count;
  
    return true;
  }
  
  hb_buffer_t::scratch_buffer_t *
  hb_buffer_t::get_scratch_buffer (unsigned int *size)
  {
    have_output = false;
    have_positions = false;
  
    out_len = 0;
    out_info = info;
  
    assert ((uintptr_t) pos % sizeof (scratch_buffer_t) == 0);
    *size = allocated * sizeof (pos[0]) / sizeof (scratch_buffer_t);
    return (scratch_buffer_t *) (void *) pos;
  }
  
  
  
  /* HarfBuzz-Internal API */
  
  void
  hb_buffer_t::reset ()
  {
    if (unlikely (hb_object_is_immutable (this)))
      return;
  
    hb_unicode_funcs_destroy (unicode);
    unicode = hb_unicode_funcs_reference (hb_unicode_funcs_get_default ());
    flags = HB_BUFFER_FLAG_DEFAULT;
    replacement = HB_BUFFER_REPLACEMENT_CODEPOINT_DEFAULT;
    invisible = 0;
  
    clear ();
  }
  
  void
  hb_buffer_t::clear ()
  {
    if (unlikely (hb_object_is_immutable (this)))
      return;
  
    hb_segment_properties_t default_props = HB_SEGMENT_PROPERTIES_DEFAULT;
    props = default_props;
    scratch_flags = HB_BUFFER_SCRATCH_FLAG_DEFAULT;
  
    content_type = HB_BUFFER_CONTENT_TYPE_INVALID;
    successful = true;
    have_output = false;
    have_positions = false;
  
    idx = 0;
    len = 0;
    out_len = 0;
    out_info = info;
  
    serial = 0;
  
    memset (context, 0, sizeof context);
    memset (context_len, 0, sizeof context_len);
  
    deallocate_var_all ();
  }
  
  void
  hb_buffer_t::add (hb_codepoint_t  codepoint,
  		  unsigned int    cluster)
  {
    hb_glyph_info_t *glyph;
  
    if (unlikely (!ensure (len + 1))) return;
  
    glyph = &info[len];
  
    memset (glyph, 0, sizeof (*glyph));
    glyph->codepoint = codepoint;
    glyph->mask = 0;
    glyph->cluster = cluster;
  
    len++;
  }
  
  void
  hb_buffer_t::add_info (const hb_glyph_info_t &glyph_info)
  {
    if (unlikely (!ensure (len + 1))) return;
  
    info[len] = glyph_info;
  
    len++;
  }
  
  
  void
  hb_buffer_t::remove_output ()
  {
    if (unlikely (hb_object_is_immutable (this)))
      return;
  
    have_output = false;
    have_positions = false;
  
    out_len = 0;
    out_info = info;
  }
  
  void
  hb_buffer_t::clear_output ()
  {
    if (unlikely (hb_object_is_immutable (this)))
      return;
  
    have_output = true;
    have_positions = false;
  
    out_len = 0;
    out_info = info;
  }
  
  void
  hb_buffer_t::clear_positions ()
  {
    if (unlikely (hb_object_is_immutable (this)))
      return;
  
    have_output = false;
    have_positions = true;
  
    out_len = 0;
    out_info = info;
  
    memset (pos, 0, sizeof (pos[0]) * len);
  }
  
  void
  hb_buffer_t::swap_buffers ()
  {
    if (unlikely (!successful)) return;
  
    assert (have_output);
    have_output = false;
  
    if (out_info != info)
    {
      hb_glyph_info_t *tmp_string;
      tmp_string = info;
      info = out_info;
      out_info = tmp_string;
      pos = (hb_glyph_position_t *) out_info;
    }
  
    unsigned int tmp;
    tmp = len;
    len = out_len;
    out_len = tmp;
  
    idx = 0;
  }
  
  
  void
  hb_buffer_t::replace_glyphs (unsigned int num_in,
  			     unsigned int num_out,
  			     const uint32_t *glyph_data)
  {
    if (unlikely (!make_room_for (num_in, num_out))) return;
  
    assert (idx + num_in <= len);
  
    merge_clusters (idx, idx + num_in);
  
    hb_glyph_info_t orig_info = info[idx];
    hb_glyph_info_t *pinfo = &out_info[out_len];
    for (unsigned int i = 0; i < num_out; i++)
    {
      *pinfo = orig_info;
      pinfo->codepoint = glyph_data[i];
      pinfo++;
    }
  
    idx  += num_in;
    out_len += num_out;
  }
  
  bool
  hb_buffer_t::move_to (unsigned int i)
  {
    if (!have_output)
    {
      assert (i <= len);
      idx = i;
      return true;
    }
    if (unlikely (!successful))
      return false;
  
    assert (i <= out_len + (len - idx));
  
    if (out_len < i)
    {
      unsigned int count = i - out_len;
      if (unlikely (!make_room_for (count, count))) return false;
  
      memmove (out_info + out_len, info + idx, count * sizeof (out_info[0]));
      idx += count;
      out_len += count;
    }
    else if (out_len > i)
    {
      /* Tricky part: rewinding... */
      unsigned int count = out_len - i;
  
      /* This will blow in our face if memory allocation fails later
       * in this same lookup...
       *
       * We used to shift with extra 32 items, instead of the 0 below.
       * But that would leave empty slots in the buffer in case of allocation
       * failures.  Setting to zero for now to avoid other problems (see
       * comments in shift_forward().  This can cause O(N^2) behavior more
       * severely than adding 32 empty slots can... */
      if (unlikely (idx < count && !shift_forward (count + 0))) return false;
  
      assert (idx >= count);
  
      idx -= count;
      out_len -= count;
      memmove (info + idx, out_info + out_len, count * sizeof (out_info[0]));
    }
  
    return true;
  }
  
  
  void
  hb_buffer_t::set_masks (hb_mask_t    value,
  			hb_mask_t    mask,
  			unsigned int cluster_start,
  			unsigned int cluster_end)
  {
    hb_mask_t not_mask = ~mask;
    value &= mask;
  
    if (!mask)
      return;
  
    if (cluster_start == 0 && cluster_end == (unsigned int)-1) {
      unsigned int count = len;
      for (unsigned int i = 0; i < count; i++)
        info[i].mask = (info[i].mask & not_mask) | value;
      return;
    }
  
    unsigned int count = len;
    for (unsigned int i = 0; i < count; i++)
      if (cluster_start <= info[i].cluster && info[i].cluster < cluster_end)
        info[i].mask = (info[i].mask & not_mask) | value;
  }
  
  void
  hb_buffer_t::reverse_range (unsigned int start,
  			    unsigned int end)
  {
    unsigned int i, j;
  
    if (end - start < 2)
      return;
  
    for (i = start, j = end - 1; i < j; i++, j--) {
      hb_glyph_info_t t;
  
      t = info[i];
      info[i] = info[j];
      info[j] = t;
    }
  
    if (have_positions) {
      for (i = start, j = end - 1; i < j; i++, j--) {
        hb_glyph_position_t t;
  
        t = pos[i];
        pos[i] = pos[j];
        pos[j] = t;
      }
    }
  }
  
  void
  hb_buffer_t::reverse ()
  {
    if (unlikely (!len))
      return;
  
    reverse_range (0, len);
  }
  
  void
  hb_buffer_t::reverse_clusters ()
  {
    unsigned int i, start, count, last_cluster;
  
    if (unlikely (!len))
      return;
  
    reverse ();
  
    count = len;
    start = 0;
    last_cluster = info[0].cluster;
    for (i = 1; i < count; i++) {
      if (last_cluster != info[i].cluster) {
        reverse_range (start, i);
        start = i;
        last_cluster = info[i].cluster;
      }
    }
    reverse_range (start, i);
  }
  
  void
  hb_buffer_t::merge_clusters_impl (unsigned int start,
  				  unsigned int end)
  {
    if (cluster_level == HB_BUFFER_CLUSTER_LEVEL_CHARACTERS)
    {
      unsafe_to_break (start, end);
      return;
    }
  
    unsigned int cluster = info[start].cluster;
  
    for (unsigned int i = start + 1; i < end; i++)
      cluster = MIN<unsigned int> (cluster, info[i].cluster);
  
    /* Extend end */
    while (end < len && info[end - 1].cluster == info[end].cluster)
      end++;
  
    /* Extend start */
    while (idx < start && info[start - 1].cluster == info[start].cluster)
      start--;
  
    /* If we hit the start of buffer, continue in out-buffer. */
    if (idx == start)
      for (unsigned int i = out_len; i && out_info[i - 1].cluster == info[start].cluster; i--)
        set_cluster (out_info[i - 1], cluster);
  
    for (unsigned int i = start; i < end; i++)
      set_cluster (info[i], cluster);
  }
  void
  hb_buffer_t::merge_out_clusters (unsigned int start,
  				 unsigned int end)
  {
    if (cluster_level == HB_BUFFER_CLUSTER_LEVEL_CHARACTERS)
      return;
  
    if (unlikely (end - start < 2))
      return;
  
    unsigned int cluster = out_info[start].cluster;
  
    for (unsigned int i = start + 1; i < end; i++)
      cluster = MIN<unsigned int> (cluster, out_info[i].cluster);
  
    /* Extend start */
    while (start && out_info[start - 1].cluster == out_info[start].cluster)
      start--;
  
    /* Extend end */
    while (end < out_len && out_info[end - 1].cluster == out_info[end].cluster)
      end++;
  
    /* If we hit the end of out-buffer, continue in buffer. */
    if (end == out_len)
      for (unsigned int i = idx; i < len && info[i].cluster == out_info[end - 1].cluster; i++)
        set_cluster (info[i], cluster);
  
    for (unsigned int i = start; i < end; i++)
      set_cluster (out_info[i], cluster);
  }
  void
  hb_buffer_t::delete_glyph ()
  {
    /* The logic here is duplicated in hb_ot_hide_default_ignorables(). */
  
    unsigned int cluster = info[idx].cluster;
    if (idx + 1 < len && cluster == info[idx + 1].cluster)
    {
      /* Cluster survives; do nothing. */
      goto done;
    }
  
    if (out_len)
    {
      /* Merge cluster backward. */
      if (cluster < out_info[out_len - 1].cluster)
      {
        unsigned int mask = info[idx].mask;
        unsigned int old_cluster = out_info[out_len - 1].cluster;
        for (unsigned i = out_len; i && out_info[i - 1].cluster == old_cluster; i--)
  	set_cluster (out_info[i - 1], cluster, mask);
      }
      goto done;
    }
  
    if (idx + 1 < len)
    {
      /* Merge cluster forward. */
      merge_clusters (idx, idx + 2);
      goto done;
    }
  
  done:
    skip_glyph ();
  }
  
  void
  hb_buffer_t::unsafe_to_break_impl (unsigned int start, unsigned int end)
  {
    unsigned int cluster = (unsigned int) -1;
    cluster = _unsafe_to_break_find_min_cluster (info, start, end, cluster);
    _unsafe_to_break_set_mask (info, start, end, cluster);
  }
  void
  hb_buffer_t::unsafe_to_break_from_outbuffer (unsigned int start, unsigned int end)
  {
    if (!have_output)
    {
      unsafe_to_break_impl (start, end);
      return;
    }
  
    assert (start <= out_len);
    assert (idx <= end);
  
    unsigned int cluster = (unsigned int) -1;
    cluster = _unsafe_to_break_find_min_cluster (out_info, start, out_len, cluster);
    cluster = _unsafe_to_break_find_min_cluster (info, idx, end, cluster);
    _unsafe_to_break_set_mask (out_info, start, out_len, cluster);
    _unsafe_to_break_set_mask (info, idx, end, cluster);
  }
  
  void
  hb_buffer_t::guess_segment_properties ()
  {
    assert (content_type == HB_BUFFER_CONTENT_TYPE_UNICODE ||
  	  (!len && content_type == HB_BUFFER_CONTENT_TYPE_INVALID));
  
    /* If script is set to INVALID, guess from buffer contents */
    if (props.script == HB_SCRIPT_INVALID) {
      for (unsigned int i = 0; i < len; i++) {
        hb_script_t script = unicode->script (info[i].codepoint);
        if (likely (script != HB_SCRIPT_COMMON &&
  		  script != HB_SCRIPT_INHERITED &&
  		  script != HB_SCRIPT_UNKNOWN)) {
          props.script = script;
          break;
        }
      }
    }
  
    /* If direction is set to INVALID, guess from script */
    if (props.direction == HB_DIRECTION_INVALID) {
      props.direction = hb_script_get_horizontal_direction (props.script);
      if (props.direction == HB_DIRECTION_INVALID)
        props.direction = HB_DIRECTION_LTR;
    }
  
    /* If language is not set, use default language from locale */
    if (props.language == HB_LANGUAGE_INVALID) {
      /* TODO get_default_for_script? using $LANGUAGE */
      props.language = hb_language_get_default ();
    }
  }
  
  
  /* Public API */
  
  DEFINE_NULL_INSTANCE (hb_buffer_t) =
  {
    HB_OBJECT_HEADER_STATIC,
  
    const_cast<hb_unicode_funcs_t *> (&_hb_Null_hb_unicode_funcs_t),
    HB_BUFFER_FLAG_DEFAULT,
    HB_BUFFER_CLUSTER_LEVEL_DEFAULT,
    HB_BUFFER_REPLACEMENT_CODEPOINT_DEFAULT,
    0, /* invisible */
    HB_BUFFER_SCRATCH_FLAG_DEFAULT,
    HB_BUFFER_MAX_LEN_DEFAULT,
    HB_BUFFER_MAX_OPS_DEFAULT,
  
    HB_BUFFER_CONTENT_TYPE_INVALID,
    HB_SEGMENT_PROPERTIES_DEFAULT,
    false, /* successful */
    true, /* have_output */
    true  /* have_positions */
  
    /* Zero is good enough for everything else. */
  };
  
  
  /**
   * hb_buffer_create: (Xconstructor)
   *
   * Creates a new #hb_buffer_t with all properties to defaults.
   *
   * Return value: (transfer full):
   * A newly allocated #hb_buffer_t with a reference count of 1. The initial
   * reference count should be released with hb_buffer_destroy() when you are done
   * using the #hb_buffer_t. This function never returns %NULL. If memory cannot
   * be allocated, a special #hb_buffer_t object will be returned on which
   * hb_buffer_allocation_successful() returns %false.
   *
   * Since: 0.9.2
   **/
  hb_buffer_t *
  hb_buffer_create ()
  {
    hb_buffer_t *buffer;
  
    if (!(buffer = hb_object_create<hb_buffer_t> ()))
      return hb_buffer_get_empty ();
  
    buffer->max_len = HB_BUFFER_MAX_LEN_DEFAULT;
    buffer->max_ops = HB_BUFFER_MAX_OPS_DEFAULT;
  
    buffer->reset ();
  
    return buffer;
  }
  
  /**
   * hb_buffer_get_empty:
   *
   *
   *
   * Return value: (transfer full):
   *
   * Since: 0.9.2
   **/
  hb_buffer_t *
  hb_buffer_get_empty ()
  {
    return const_cast<hb_buffer_t *> (&Null(hb_buffer_t));
  }
  
  /**
   * hb_buffer_reference: (skip)
   * @buffer: an #hb_buffer_t.
   *
   * Increases the reference count on @buffer by one. This prevents @buffer from
   * being destroyed until a matching call to hb_buffer_destroy() is made.
   *
   * Return value: (transfer full):
   * The referenced #hb_buffer_t.
   *
   * Since: 0.9.2
   **/
  hb_buffer_t *
  hb_buffer_reference (hb_buffer_t *buffer)
  {
    return hb_object_reference (buffer);
  }
  
  /**
   * hb_buffer_destroy: (skip)
   * @buffer: an #hb_buffer_t.
   *
   * Deallocate the @buffer.
   * Decreases the reference count on @buffer by one. If the result is zero, then
   * @buffer and all associated resources are freed. See hb_buffer_reference().
   *
   * Since: 0.9.2
   **/
  void
  hb_buffer_destroy (hb_buffer_t *buffer)
  {
    if (!hb_object_destroy (buffer)) return;
  
    hb_unicode_funcs_destroy (buffer->unicode);
  
    free (buffer->info);
    free (buffer->pos);
    if (buffer->message_destroy)
      buffer->message_destroy (buffer->message_data);
  
    free (buffer);
  }
  
  /**
   * hb_buffer_set_user_data: (skip)
   * @buffer: an #hb_buffer_t.
   * @key:
   * @data:
   * @destroy:
   * @replace:
   *
   *
   *
   * Return value:
   *
   * Since: 0.9.2
   **/
  hb_bool_t
  hb_buffer_set_user_data (hb_buffer_t        *buffer,
  			 hb_user_data_key_t *key,
  			 void *              data,
  			 hb_destroy_func_t   destroy,
  			 hb_bool_t           replace)
  {
    return hb_object_set_user_data (buffer, key, data, destroy, replace);
  }
  
  /**
   * hb_buffer_get_user_data: (skip)
   * @buffer: an #hb_buffer_t.
   * @key:
   *
   *
   *
   * Return value:
   *
   * Since: 0.9.2
   **/
  void *
  hb_buffer_get_user_data (hb_buffer_t        *buffer,
  			 hb_user_data_key_t *key)
  {
    return hb_object_get_user_data (buffer, key);
  }
  
  
  /**
   * hb_buffer_set_content_type:
   * @buffer: an #hb_buffer_t.
   * @content_type: the type of buffer contents to set
   *
   * Sets the type of @buffer contents, buffers are either empty, contain
   * characters (before shaping) or glyphs (the result of shaping).
   *
   * Since: 0.9.5
   **/
  void
  hb_buffer_set_content_type (hb_buffer_t              *buffer,
  			    hb_buffer_content_type_t  content_type)
  {
    buffer->content_type = content_type;
  }
  
  /**
   * hb_buffer_get_content_type:
   * @buffer: an #hb_buffer_t.
   *
   * see hb_buffer_set_content_type().
   *
   * Return value:
   * The type of @buffer contents.
   *
   * Since: 0.9.5
   **/
  hb_buffer_content_type_t
  hb_buffer_get_content_type (hb_buffer_t *buffer)
  {
    return buffer->content_type;
  }
  
  
  /**
   * hb_buffer_set_unicode_funcs:
   * @buffer: an #hb_buffer_t.
   * @unicode_funcs:
   *
   *
   *
   * Since: 0.9.2
   **/
  void
  hb_buffer_set_unicode_funcs (hb_buffer_t        *buffer,
  			     hb_unicode_funcs_t *unicode_funcs)
  {
    if (unlikely (hb_object_is_immutable (buffer)))
      return;
  
    if (!unicode_funcs)
      unicode_funcs = hb_unicode_funcs_get_default ();
  
    hb_unicode_funcs_reference (unicode_funcs);
    hb_unicode_funcs_destroy (buffer->unicode);
    buffer->unicode = unicode_funcs;
  }
  
  /**
   * hb_buffer_get_unicode_funcs:
   * @buffer: an #hb_buffer_t.
   *
   *
   *
   * Return value:
   *
   * Since: 0.9.2
   **/
  hb_unicode_funcs_t *
  hb_buffer_get_unicode_funcs (hb_buffer_t        *buffer)
  {
    return buffer->unicode;
  }
  
  /**
   * hb_buffer_set_direction:
   * @buffer: an #hb_buffer_t.
   * @direction: the #hb_direction_t of the @buffer
   *
   * Set the text flow direction of the buffer. No shaping can happen without
   * setting @buffer direction, and it controls the visual direction for the
   * output glyphs; for RTL direction the glyphs will be reversed. Many layout
   * features depend on the proper setting of the direction, for example,
   * reversing RTL text before shaping, then shaping with LTR direction is not
   * the same as keeping the text in logical order and shaping with RTL
   * direction.
   *
   * Since: 0.9.2
   **/
  void
  hb_buffer_set_direction (hb_buffer_t    *buffer,
  			 hb_direction_t  direction)
  
  {
    if (unlikely (hb_object_is_immutable (buffer)))
      return;
  
    buffer->props.direction = direction;
  }
  
  /**
   * hb_buffer_get_direction:
   * @buffer: an #hb_buffer_t.
   *
   * See hb_buffer_set_direction()
   *
   * Return value:
   * The direction of the @buffer.
   *
   * Since: 0.9.2
   **/
  hb_direction_t
  hb_buffer_get_direction (hb_buffer_t    *buffer)
  {
    return buffer->props.direction;
  }
  
  /**
   * hb_buffer_set_script:
   * @buffer: an #hb_buffer_t.
   * @script: an #hb_script_t to set.
   *
   * Sets the script of @buffer to @script.
   *
   * Script is crucial for choosing the proper shaping behaviour for scripts that
   * require it (e.g. Arabic) and the which OpenType features defined in the font
   * to be applied.
   *
   * You can pass one of the predefined #hb_script_t values, or use
   * hb_script_from_string() or hb_script_from_iso15924_tag() to get the
   * corresponding script from an ISO 15924 script tag.
   *
   * Since: 0.9.2
   **/
  void
  hb_buffer_set_script (hb_buffer_t *buffer,
  		      hb_script_t  script)
  {
    if (unlikely (hb_object_is_immutable (buffer)))
      return;
  
    buffer->props.script = script;
  }
  
  /**
   * hb_buffer_get_script:
   * @buffer: an #hb_buffer_t.
   *
   * See hb_buffer_set_script().
   *
   * Return value:
   * The #hb_script_t of the @buffer.
   *
   * Since: 0.9.2
   **/
  hb_script_t
  hb_buffer_get_script (hb_buffer_t *buffer)
  {
    return buffer->props.script;
  }
  
  /**
   * hb_buffer_set_language:
   * @buffer: an #hb_buffer_t.
   * @language: an hb_language_t to set.
   *
   * Sets the language of @buffer to @language.
   *
   * Languages are crucial for selecting which OpenType feature to apply to the
   * buffer which can result in applying language-specific behaviour. Languages
   * are orthogonal to the scripts, and though they are related, they are
   * different concepts and should not be confused with each other.
   *
   * Use hb_language_from_string() to convert from BCP 47 language tags to
   * #hb_language_t.
   *
   * Since: 0.9.2
   **/
  void
  hb_buffer_set_language (hb_buffer_t   *buffer,
  			hb_language_t  language)
  {
    if (unlikely (hb_object_is_immutable (buffer)))
      return;
  
    buffer->props.language = language;
  }
  
  /**
   * hb_buffer_get_language:
   * @buffer: an #hb_buffer_t.
   *
   * See hb_buffer_set_language().
   *
   * Return value: (transfer none):
   * The #hb_language_t of the buffer. Must not be freed by the caller.
   *
   * Since: 0.9.2
   **/
  hb_language_t
  hb_buffer_get_language (hb_buffer_t *buffer)
  {
    return buffer->props.language;
  }
  
  /**
   * hb_buffer_set_segment_properties:
   * @buffer: an #hb_buffer_t.
   * @props: an #hb_segment_properties_t to use.
   *
   * Sets the segment properties of the buffer, a shortcut for calling
   * hb_buffer_set_direction(), hb_buffer_set_script() and
   * hb_buffer_set_language() individually.
   *
   * Since: 0.9.7
   **/
  void
  hb_buffer_set_segment_properties (hb_buffer_t *buffer,
  				  const hb_segment_properties_t *props)
  {
    if (unlikely (hb_object_is_immutable (buffer)))
      return;
  
    buffer->props = *props;
  }
  
  /**
   * hb_buffer_get_segment_properties:
   * @buffer: an #hb_buffer_t.
   * @props: (out): the output #hb_segment_properties_t.
   *
   * Sets @props to the #hb_segment_properties_t of @buffer.
   *
   * Since: 0.9.7
   **/
  void
  hb_buffer_get_segment_properties (hb_buffer_t *buffer,
  				  hb_segment_properties_t *props)
  {
    *props = buffer->props;
  }
  
  
  /**
   * hb_buffer_set_flags:
   * @buffer: an #hb_buffer_t.
   * @flags: the buffer flags to set.
   *
   * Sets @buffer flags to @flags. See #hb_buffer_flags_t.
   *
   * Since: 0.9.7
   **/
  void
  hb_buffer_set_flags (hb_buffer_t       *buffer,
  		     hb_buffer_flags_t  flags)
  {
    if (unlikely (hb_object_is_immutable (buffer)))
      return;
  
    buffer->flags = flags;
  }
  
  /**
   * hb_buffer_get_flags:
   * @buffer: an #hb_buffer_t.
   *
   * See hb_buffer_set_flags().
   *
   * Return value:
   * The @buffer flags.
   *
   * Since: 0.9.7
   **/
  hb_buffer_flags_t
  hb_buffer_get_flags (hb_buffer_t *buffer)
  {
    return buffer->flags;
  }
  
  /**
   * hb_buffer_set_cluster_level:
   * @buffer: an #hb_buffer_t.
   * @cluster_level:
   *
   *
   *
   * Since: 0.9.42
   **/
  void
  hb_buffer_set_cluster_level (hb_buffer_t       *buffer,
  		     hb_buffer_cluster_level_t  cluster_level)
  {
    if (unlikely (hb_object_is_immutable (buffer)))
      return;
  
    buffer->cluster_level = cluster_level;
  }
  
  /**
   * hb_buffer_get_cluster_level:
   * @buffer: an #hb_buffer_t.
   *
   *
   *
   * Return value:
   *
   * Since: 0.9.42
   **/
  hb_buffer_cluster_level_t
  hb_buffer_get_cluster_level (hb_buffer_t *buffer)
  {
    return buffer->cluster_level;
  }
  
  
  /**
   * hb_buffer_set_replacement_codepoint:
   * @buffer: an #hb_buffer_t.
   * @replacement: the replacement #hb_codepoint_t
   *
   * Sets the #hb_codepoint_t that replaces invalid entries for a given encoding
   * when adding text to @buffer.
   *
   * Default is %HB_BUFFER_REPLACEMENT_CODEPOINT_DEFAULT.
   *
   * Since: 0.9.31
   **/
  void
  hb_buffer_set_replacement_codepoint (hb_buffer_t    *buffer,
  				     hb_codepoint_t  replacement)
  {
    if (unlikely (hb_object_is_immutable (buffer)))
      return;
  
    buffer->replacement = replacement;
  }
  
  /**
   * hb_buffer_get_replacement_codepoint:
   * @buffer: an #hb_buffer_t.
   *
   * See hb_buffer_set_replacement_codepoint().
   *
   * Return value:
   * The @buffer replacement #hb_codepoint_t.
   *
   * Since: 0.9.31
   **/
  hb_codepoint_t
  hb_buffer_get_replacement_codepoint (hb_buffer_t    *buffer)
  {
    return buffer->replacement;
  }
  
  
  /**
   * hb_buffer_set_invisible_glyph:
   * @buffer: an #hb_buffer_t.
   * @invisible: the invisible #hb_codepoint_t
   *
   * Sets the #hb_codepoint_t that replaces invisible characters in
   * the shaping result.  If set to zero (default), the glyph for the
   * U+0020 SPACE character is used.  Otherwise, this value is used
   * verbatim.
   *
   * Since: 2.0.0
   **/
  void
  hb_buffer_set_invisible_glyph (hb_buffer_t    *buffer,
  			       hb_codepoint_t  invisible)
  {
    if (unlikely (hb_object_is_immutable (buffer)))
      return;
  
    buffer->invisible = invisible;
  }
  
  /**
   * hb_buffer_get_invisible_glyph:
   * @buffer: an #hb_buffer_t.
   *
   * See hb_buffer_set_invisible_glyph().
   *
   * Return value:
   * The @buffer invisible #hb_codepoint_t.
   *
   * Since: 2.0.0
   **/
  hb_codepoint_t
  hb_buffer_get_invisible_glyph (hb_buffer_t    *buffer)
  {
    return buffer->invisible;
  }
  
  
  /**
   * hb_buffer_reset:
   * @buffer: an #hb_buffer_t.
   *
   * Resets the buffer to its initial status, as if it was just newly created
   * with hb_buffer_create().
   *
   * Since: 0.9.2
   **/
  void
  hb_buffer_reset (hb_buffer_t *buffer)
  {
    buffer->reset ();
  }
  
  /**
   * hb_buffer_clear_contents:
   * @buffer: an #hb_buffer_t.
   *
   * Similar to hb_buffer_reset(), but does not clear the Unicode functions and
   * the replacement code point.
   *
   * Since: 0.9.11
   **/
  void
  hb_buffer_clear_contents (hb_buffer_t *buffer)
  {
    buffer->clear ();
  }
  
  /**
   * hb_buffer_pre_allocate:
   * @buffer: an #hb_buffer_t.
   * @size: number of items to pre allocate.
   *
   * Pre allocates memory for @buffer to fit at least @size number of items.
   *
   * Return value:
   * %true if @buffer memory allocation succeeded, %false otherwise.
   *
   * Since: 0.9.2
   **/
  hb_bool_t
  hb_buffer_pre_allocate (hb_buffer_t *buffer, unsigned int size)
  {
    return buffer->ensure (size);
  }
  
  /**
   * hb_buffer_allocation_successful:
   * @buffer: an #hb_buffer_t.
   *
   * Check if allocating memory for the buffer succeeded.
   *
   * Return value:
   * %true if @buffer memory allocation succeeded, %false otherwise.
   *
   * Since: 0.9.2
   **/
  hb_bool_t
  hb_buffer_allocation_successful (hb_buffer_t  *buffer)
  {
    return buffer->successful;
  }
  
  /**
   * hb_buffer_add:
   * @buffer: an #hb_buffer_t.
   * @codepoint: a Unicode code point.
   * @cluster: the cluster value of @codepoint.
   *
   * Appends a character with the Unicode value of @codepoint to @buffer, and
   * gives it the initial cluster value of @cluster. Clusters can be any thing
   * the client wants, they are usually used to refer to the index of the
   * character in the input text stream and are output in
   * #hb_glyph_info_t.cluster field.
   *
   * This function does not check the validity of @codepoint, it is up to the
   * caller to ensure it is a valid Unicode code point.
   *
   * Since: 0.9.7
   **/
  void
  hb_buffer_add (hb_buffer_t    *buffer,
  	       hb_codepoint_t  codepoint,
  	       unsigned int    cluster)
  {
    buffer->add (codepoint, cluster);
    buffer->clear_context (1);
  }
  
  /**
   * hb_buffer_set_length:
   * @buffer: an #hb_buffer_t.
   * @length: the new length of @buffer.
   *
   * Similar to hb_buffer_pre_allocate(), but clears any new items added at the
   * end.
   *
   * Return value:
   * %true if @buffer memory allocation succeeded, %false otherwise.
   *
   * Since: 0.9.2
   **/
  hb_bool_t
  hb_buffer_set_length (hb_buffer_t  *buffer,
  		      unsigned int  length)
  {
    if (unlikely (hb_object_is_immutable (buffer)))
      return length == 0;
  
    if (!buffer->ensure (length))
      return false;
  
    /* Wipe the new space */
    if (length > buffer->len) {
      memset (buffer->info + buffer->len, 0, sizeof (buffer->info[0]) * (length - buffer->len));
      if (buffer->have_positions)
        memset (buffer->pos + buffer->len, 0, sizeof (buffer->pos[0]) * (length - buffer->len));
    }
  
    buffer->len = length;
  
    if (!length)
    {
      buffer->content_type = HB_BUFFER_CONTENT_TYPE_INVALID;
      buffer->clear_context (0);
    }
    buffer->clear_context (1);
  
    return true;
  }
  
  /**
   * hb_buffer_get_length:
   * @buffer: an #hb_buffer_t.
   *
   * Returns the number of items in the buffer.
   *
   * Return value:
   * The @buffer length.
   * The value valid as long as buffer has not been modified.
   *
   * Since: 0.9.2
   **/
  unsigned int
  hb_buffer_get_length (hb_buffer_t *buffer)
  {
    return buffer->len;
  }
  
  /**
   * hb_buffer_get_glyph_infos:
   * @buffer: an #hb_buffer_t.
   * @length: (out): output array length.
   *
   * Returns @buffer glyph information array.  Returned pointer
   * is valid as long as @buffer contents are not modified.
   *
   * Return value: (transfer none) (array length=length):
   * The @buffer glyph information array.
   * The value valid as long as buffer has not been modified.
   *
   * Since: 0.9.2
   **/
  hb_glyph_info_t *
  hb_buffer_get_glyph_infos (hb_buffer_t  *buffer,
                             unsigned int *length)
  {
    if (length)
      *length = buffer->len;
  
    return (hb_glyph_info_t *) buffer->info;
  }
  
  /**
   * hb_buffer_get_glyph_positions:
   * @buffer: an #hb_buffer_t.
   * @length: (out): output length.
   *
   * Returns @buffer glyph position array.  Returned pointer
   * is valid as long as @buffer contents are not modified.
   *
   * Return value: (transfer none) (array length=length):
   * The @buffer glyph position array.
   * The value valid as long as buffer has not been modified.
   *
   * Since: 0.9.2
   **/
  hb_glyph_position_t *
  hb_buffer_get_glyph_positions (hb_buffer_t  *buffer,
                                 unsigned int *length)
  {
    if (!buffer->have_positions)
      buffer->clear_positions ();
  
    if (length)
      *length = buffer->len;
  
    return (hb_glyph_position_t *) buffer->pos;
  }
  
  /**
   * hb_glyph_info_get_glyph_flags:
   * @info: a #hb_glyph_info_t.
   *
   * Returns glyph flags encoded within a #hb_glyph_info_t.
   *
   * Return value:
   * The #hb_glyph_flags_t encoded within @info.
   *
   * Since: 1.5.0
   **/
  hb_glyph_flags_t
  (hb_glyph_info_get_glyph_flags) (const hb_glyph_info_t *info)
  {
    return hb_glyph_info_get_glyph_flags (info);
  }
  
  /**
   * hb_buffer_reverse:
   * @buffer: an #hb_buffer_t.
   *
   * Reverses buffer contents.
   *
   * Since: 0.9.2
   **/
  void
  hb_buffer_reverse (hb_buffer_t *buffer)
  {
    buffer->reverse ();
  }
  
  /**
   * hb_buffer_reverse_range:
   * @buffer: an #hb_buffer_t.
   * @start: start index.
   * @end: end index.
   *
   * Reverses buffer contents between start to end.
   *
   * Since: 0.9.41
   **/
  void
  hb_buffer_reverse_range (hb_buffer_t *buffer,
  			 unsigned int start, unsigned int end)
  {
    buffer->reverse_range (start, end);
  }
  
  /**
   * hb_buffer_reverse_clusters:
   * @buffer: an #hb_buffer_t.
   *
   * Reverses buffer clusters.  That is, the buffer contents are
   * reversed, then each cluster (consecutive items having the
   * same cluster number) are reversed again.
   *
   * Since: 0.9.2
   **/
  void
  hb_buffer_reverse_clusters (hb_buffer_t *buffer)
  {
    buffer->reverse_clusters ();
  }
  
  /**
   * hb_buffer_guess_segment_properties:
   * @buffer: an #hb_buffer_t.
   *
   * Sets unset buffer segment properties based on buffer Unicode
   * contents.  If buffer is not empty, it must have content type
   * %HB_BUFFER_CONTENT_TYPE_UNICODE.
   *
   * If buffer script is not set (ie. is %HB_SCRIPT_INVALID), it
   * will be set to the Unicode script of the first character in
   * the buffer that has a script other than %HB_SCRIPT_COMMON,
   * %HB_SCRIPT_INHERITED, and %HB_SCRIPT_UNKNOWN.
   *
   * Next, if buffer direction is not set (ie. is %HB_DIRECTION_INVALID),
   * it will be set to the natural horizontal direction of the
   * buffer script as returned by hb_script_get_horizontal_direction().
   * If hb_script_get_horizontal_direction() returns %HB_DIRECTION_INVALID,
   * then %HB_DIRECTION_LTR is used.
   *
   * Finally, if buffer language is not set (ie. is %HB_LANGUAGE_INVALID),
   * it will be set to the process's default language as returned by
   * hb_language_get_default().  This may change in the future by
   * taking buffer script into consideration when choosing a language.
   * Note that hb_language_get_default() is NOT threadsafe the first time
   * it is called.  See documentation for that function for details.
   *
   * Since: 0.9.7
   **/
  void
  hb_buffer_guess_segment_properties (hb_buffer_t *buffer)
  {
    buffer->guess_segment_properties ();
  }
  
  template <typename utf_t>
  static inline void
  hb_buffer_add_utf (hb_buffer_t  *buffer,
  		   const typename utf_t::codepoint_t *text,
  		   int           text_length,
  		   unsigned int  item_offset,
  		   int           item_length)
  {
    typedef typename utf_t::codepoint_t T;
    const hb_codepoint_t replacement = buffer->replacement;
  
    assert (buffer->content_type == HB_BUFFER_CONTENT_TYPE_UNICODE ||
  	  (!buffer->len && buffer->content_type == HB_BUFFER_CONTENT_TYPE_INVALID));
  
    if (unlikely (hb_object_is_immutable (buffer)))
      return;
  
    if (text_length == -1)
      text_length = utf_t::strlen (text);
  
    if (item_length == -1)
      item_length = text_length - item_offset;
  
    buffer->ensure (buffer->len + item_length * sizeof (T) / 4);
  
    /* If buffer is empty and pre-context provided, install it.
     * This check is written this way, to make sure people can
     * provide pre-context in one add_utf() call, then provide
     * text in a follow-up call.  See:
     *
     * https://bugzilla.mozilla.org/show_bug.cgi?id=801410#c13
     */
    if (!buffer->len && item_offset > 0)
    {
      /* Add pre-context */
      buffer->clear_context (0);
      const T *prev = text + item_offset;
      const T *start = text;
      while (start < prev && buffer->context_len[0] < buffer->CONTEXT_LENGTH)
      {
        hb_codepoint_t u;
        prev = utf_t::prev (prev, start, &u, replacement);
        buffer->context[0][buffer->context_len[0]++] = u;
      }
    }
  
    const T *next = text + item_offset;
    const T *end = next + item_length;
    while (next < end)
    {
      hb_codepoint_t u;
      const T *old_next = next;
      next = utf_t::next (next, end, &u, replacement);
      buffer->add (u, old_next - (const T *) text);
    }
  
    /* Add post-context */
    buffer->clear_context (1);
    end = text + text_length;
    while (next < end && buffer->context_len[1] < buffer->CONTEXT_LENGTH)
    {
      hb_codepoint_t u;
      next = utf_t::next (next, end, &u, replacement);
      buffer->context[1][buffer->context_len[1]++] = u;
    }
  
    buffer->content_type = HB_BUFFER_CONTENT_TYPE_UNICODE;
  }
  
  /**
   * hb_buffer_add_utf8:
   * @buffer: an #hb_buffer_t.
   * @text: (array length=text_length) (element-type uint8_t): an array of UTF-8
   *               characters to append.
   * @text_length: the length of the @text, or -1 if it is %NULL terminated.
   * @item_offset: the offset of the first character to add to the @buffer.
   * @item_length: the number of characters to add to the @buffer, or -1 for the
   *               end of @text (assuming it is %NULL terminated).
   *
   * See hb_buffer_add_codepoints().
   *
   * Replaces invalid UTF-8 characters with the @buffer replacement code point,
   * see hb_buffer_set_replacement_codepoint().
   *
   * Since: 0.9.2
   **/
  void
  hb_buffer_add_utf8 (hb_buffer_t  *buffer,
  		    const char   *text,
  		    int           text_length,
  		    unsigned int  item_offset,
  		    int           item_length)
  {
    hb_buffer_add_utf<hb_utf8_t> (buffer, (const uint8_t *) text, text_length, item_offset, item_length);
  }
  
  /**
   * hb_buffer_add_utf16:
   * @buffer: an #hb_buffer_t.
   * @text: (array length=text_length): an array of UTF-16 characters to append.
   * @text_length: the length of the @text, or -1 if it is %NULL terminated.
   * @item_offset: the offset of the first character to add to the @buffer.
   * @item_length: the number of characters to add to the @buffer, or -1 for the
   *               end of @text (assuming it is %NULL terminated).
   *
   * See hb_buffer_add_codepoints().
   *
   * Replaces invalid UTF-16 characters with the @buffer replacement code point,
   * see hb_buffer_set_replacement_codepoint().
   *
   * Since: 0.9.2
   **/
  void
  hb_buffer_add_utf16 (hb_buffer_t    *buffer,
  		     const uint16_t *text,
  		     int             text_length,
  		     unsigned int    item_offset,
  		     int             item_length)
  {
    hb_buffer_add_utf<hb_utf16_t> (buffer, text, text_length, item_offset, item_length);
  }
  
  /**
   * hb_buffer_add_utf32:
   * @buffer: an #hb_buffer_t.
   * @text: (array length=text_length): an array of UTF-32 characters to append.
   * @text_length: the length of the @text, or -1 if it is %NULL terminated.
   * @item_offset: the offset of the first character to add to the @buffer.
   * @item_length: the number of characters to add to the @buffer, or -1 for the
   *               end of @text (assuming it is %NULL terminated).
   *
   * See hb_buffer_add_codepoints().
   *
   * Replaces invalid UTF-32 characters with the @buffer replacement code point,
   * see hb_buffer_set_replacement_codepoint().
   *
   * Since: 0.9.2
   **/
  void
  hb_buffer_add_utf32 (hb_buffer_t    *buffer,
  		     const uint32_t *text,
  		     int             text_length,
  		     unsigned int    item_offset,
  		     int             item_length)
  {
    hb_buffer_add_utf<hb_utf32_t> (buffer, text, text_length, item_offset, item_length);
  }
  
  /**
   * hb_buffer_add_latin1:
   * @buffer: an #hb_buffer_t.
   * @text: (array length=text_length) (element-type uint8_t): an array of UTF-8
   *               characters to append.
   * @text_length: the length of the @text, or -1 if it is %NULL terminated.
   * @item_offset: the offset of the first character to add to the @buffer.
   * @item_length: the number of characters to add to the @buffer, or -1 for the
   *               end of @text (assuming it is %NULL terminated).
   *
   * Similar to hb_buffer_add_codepoints(), but allows only access to first 256
   * Unicode code points that can fit in 8-bit strings.
   *
   * <note>Has nothing to do with non-Unicode Latin-1 encoding.</note>
   *
   * Since: 0.9.39
   **/
  void
  hb_buffer_add_latin1 (hb_buffer_t   *buffer,
  		      const uint8_t *text,
  		      int            text_length,
  		      unsigned int   item_offset,
  		      int            item_length)
  {
    hb_buffer_add_utf<hb_latin1_t> (buffer, text, text_length, item_offset, item_length);
  }
  
  /**
   * hb_buffer_add_codepoints:
   * @buffer: a #hb_buffer_t to append characters to.
   * @text: (array length=text_length): an array of Unicode code points to append.
   * @text_length: the length of the @text, or -1 if it is %NULL terminated.
   * @item_offset: the offset of the first code point to add to the @buffer.
   * @item_length: the number of code points to add to the @buffer, or -1 for the
   *               end of @text (assuming it is %NULL terminated).
   *
   * Appends characters from @text array to @buffer. The @item_offset is the
   * position of the first character from @text that will be appended, and
   * @item_length is the number of character. When shaping part of a larger text
   * (e.g. a run of text from a paragraph), instead of passing just the substring
   * corresponding to the run, it is preferable to pass the whole
   * paragraph and specify the run start and length as @item_offset and
   * @item_length, respectively, to give HarfBuzz the full context to be able,
   * for example, to do cross-run Arabic shaping or properly handle combining
   * marks at stat of run.
   *
   * This function does not check the validity of @text, it is up to the caller
   * to ensure it contains a valid Unicode code points.
   *
   * Since: 0.9.31
   **/
  void
  hb_buffer_add_codepoints (hb_buffer_t          *buffer,
  			  const hb_codepoint_t *text,
  			  int                   text_length,
  			  unsigned int          item_offset,
  			  int                   item_length)
  {
    hb_buffer_add_utf<hb_utf32_novalidate_t> (buffer, text, text_length, item_offset, item_length);
  }
  
  
  /**
   * hb_buffer_append:
   * @buffer: an #hb_buffer_t.
   * @source: source #hb_buffer_t.
   * @start: start index into source buffer to copy.  Use 0 to copy from start of buffer.
   * @end: end index into source buffer to copy.  Use (unsigned int) -1 to copy to end of buffer.
   *
   * Append (part of) contents of another buffer to this buffer.
   *
   * Since: 1.5.0
   **/
  HB_EXTERN void
  hb_buffer_append (hb_buffer_t *buffer,
  		  hb_buffer_t *source,
  		  unsigned int start,
  		  unsigned int end)
  {
    assert (!buffer->have_output && !source->have_output);
    assert (buffer->have_positions == source->have_positions ||
  	  !buffer->len || !source->len);
    assert (buffer->content_type == source->content_type ||
  	  !buffer->len || !source->len);
  
    if (end > source->len)
      end = source->len;
    if (start > end)
      start = end;
    if (start == end)
      return;
  
    if (!buffer->len)
      buffer->content_type = source->content_type;
    if (!buffer->have_positions && source->have_positions)
      buffer->clear_positions ();
  
    if (buffer->len + (end - start) < buffer->len) /* Overflows. */
    {
      buffer->successful = false;
      return;
    }
  
    unsigned int orig_len = buffer->len;
    hb_buffer_set_length (buffer, buffer->len + (end - start));
    if (unlikely (!buffer->successful))
      return;
  
    memcpy (buffer->info + orig_len, source->info + start, (end - start) * sizeof (buffer->info[0]));
    if (buffer->have_positions)
      memcpy (buffer->pos + orig_len, source->pos + start, (end - start) * sizeof (buffer->pos[0]));
  }
  
  
  static int
  compare_info_codepoint (const hb_glyph_info_t *pa,
  			const hb_glyph_info_t *pb)
  {
    return (int) pb->codepoint - (int) pa->codepoint;
  }
  
  static inline void
  normalize_glyphs_cluster (hb_buffer_t *buffer,
  			  unsigned int start,
  			  unsigned int end,
  			  bool backward)
  {
    hb_glyph_position_t *pos = buffer->pos;
  
    /* Total cluster advance */
    hb_position_t total_x_advance = 0, total_y_advance = 0;
    for (unsigned int i = start; i < end; i++)
    {
      total_x_advance += pos[i].x_advance;
      total_y_advance += pos[i].y_advance;
    }
  
    hb_position_t x_advance = 0, y_advance = 0;
    for (unsigned int i = start; i < end; i++)
    {
      pos[i].x_offset += x_advance;
      pos[i].y_offset += y_advance;
  
      x_advance += pos[i].x_advance;
      y_advance += pos[i].y_advance;
  
      pos[i].x_advance = 0;
      pos[i].y_advance = 0;
    }
  
    if (backward)
    {
      /* Transfer all cluster advance to the last glyph. */
      pos[end - 1].x_advance = total_x_advance;
      pos[end - 1].y_advance = total_y_advance;
  
      hb_stable_sort (buffer->info + start, end - start - 1, compare_info_codepoint, buffer->pos + start);
    } else {
      /* Transfer all cluster advance to the first glyph. */
      pos[start].x_advance += total_x_advance;
      pos[start].y_advance += total_y_advance;
      for (unsigned int i = start + 1; i < end; i++) {
        pos[i].x_offset -= total_x_advance;
        pos[i].y_offset -= total_y_advance;
      }
      hb_stable_sort (buffer->info + start + 1, end - start - 1, compare_info_codepoint, buffer->pos + start + 1);
    }
  }
  
  /**
   * hb_buffer_normalize_glyphs:
   * @buffer: an #hb_buffer_t.
   *
   * Reorders a glyph buffer to have canonical in-cluster glyph order / position.
   * The resulting clusters should behave identical to pre-reordering clusters.
   *
   * <note>This has nothing to do with Unicode normalization.</note>
   *
   * Since: 0.9.2
   **/
  void
  hb_buffer_normalize_glyphs (hb_buffer_t *buffer)
  {
    assert (buffer->have_positions);
    assert (buffer->content_type == HB_BUFFER_CONTENT_TYPE_GLYPHS ||
  	  (!buffer->len && buffer->content_type == HB_BUFFER_CONTENT_TYPE_INVALID));
  
    bool backward = HB_DIRECTION_IS_BACKWARD (buffer->props.direction);
  
    unsigned int count = buffer->len;
    if (unlikely (!count)) return;
    hb_glyph_info_t *info = buffer->info;
  
    unsigned int start = 0;
    unsigned int end;
    for (end = start + 1; end < count; end++)
      if (info[start].cluster != info[end].cluster) {
        normalize_glyphs_cluster (buffer, start, end, backward);
        start = end;
      }
    normalize_glyphs_cluster (buffer, start, end, backward);
  }
  
  void
  hb_buffer_t::sort (unsigned int start, unsigned int end, int(*compar)(const hb_glyph_info_t *, const hb_glyph_info_t *))
  {
    assert (!have_positions);
    for (unsigned int i = start + 1; i < end; i++)
    {
      unsigned int j = i;
      while (j > start && compar (&info[j - 1], &info[i]) > 0)
        j--;
      if (i == j)
        continue;
      /* Move item i to occupy place for item j, shift what's in between. */
      merge_clusters (j, i + 1);
      {
        hb_glyph_info_t t = info[i];
        memmove (&info[j + 1], &info[j], (i - j) * sizeof (hb_glyph_info_t));
        info[j] = t;
      }
    }
  }
  
  
  /*
   * Comparing buffers.
   */
  
  /**
   * hb_buffer_diff:
   * @buffer: a buffer.
   * @reference: other buffer to compare to.
   * @dottedcircle_glyph: glyph id of U+25CC DOTTED CIRCLE, or (hb_codepont_t) -1.
   * @position_fuzz: allowed absolute difference in position values.
   *
   * If dottedcircle_glyph is (hb_codepoint_t) -1 then %HB_BUFFER_DIFF_FLAG_DOTTED_CIRCLE_PRESENT
   * and %HB_BUFFER_DIFF_FLAG_NOTDEF_PRESENT are never returned.  This should be used by most
   * callers if just comparing two buffers is needed.
   *
   * Since: 1.5.0
   **/
  hb_buffer_diff_flags_t
  hb_buffer_diff (hb_buffer_t *buffer,
  		hb_buffer_t *reference,
  		hb_codepoint_t dottedcircle_glyph,
  		unsigned int position_fuzz)
  {
    if (buffer->content_type != reference->content_type && buffer->len && reference->len)
      return HB_BUFFER_DIFF_FLAG_CONTENT_TYPE_MISMATCH;
  
    hb_buffer_diff_flags_t result = HB_BUFFER_DIFF_FLAG_EQUAL;
    bool contains = dottedcircle_glyph != (hb_codepoint_t) -1;
  
    unsigned int count = reference->len;
  
    if (buffer->len != count)
    {
      /*
       * we can't compare glyph-by-glyph, but we do want to know if there
       * are .notdef or dottedcircle glyphs present in the reference buffer
       */
      const hb_glyph_info_t *info = reference->info;
      unsigned int i;
      for (i = 0; i < count; i++)
      {
        if (contains && info[i].codepoint == dottedcircle_glyph)
          result |= HB_BUFFER_DIFF_FLAG_DOTTED_CIRCLE_PRESENT;
        if (contains && info[i].codepoint == 0)
          result |= HB_BUFFER_DIFF_FLAG_NOTDEF_PRESENT;
      }
      result |= HB_BUFFER_DIFF_FLAG_LENGTH_MISMATCH;
      return hb_buffer_diff_flags_t (result);
    }
  
    if (!count)
      return hb_buffer_diff_flags_t (result);
  
    const hb_glyph_info_t *buf_info = buffer->info;
    const hb_glyph_info_t *ref_info = reference->info;
    for (unsigned int i = 0; i < count; i++)
    {
      if (buf_info->codepoint != ref_info->codepoint)
        result |= HB_BUFFER_DIFF_FLAG_CODEPOINT_MISMATCH;
      if (buf_info->cluster != ref_info->cluster)
        result |= HB_BUFFER_DIFF_FLAG_CLUSTER_MISMATCH;
      if ((buf_info->mask & ~ref_info->mask & HB_GLYPH_FLAG_DEFINED))
        result |= HB_BUFFER_DIFF_FLAG_GLYPH_FLAGS_MISMATCH;
      if (contains && ref_info->codepoint == dottedcircle_glyph)
        result |= HB_BUFFER_DIFF_FLAG_DOTTED_CIRCLE_PRESENT;
      if (contains && ref_info->codepoint == 0)
        result |= HB_BUFFER_DIFF_FLAG_NOTDEF_PRESENT;
      buf_info++;
      ref_info++;
    }
  
    if (buffer->content_type == HB_BUFFER_CONTENT_TYPE_GLYPHS)
    {
      assert (buffer->have_positions);
      const hb_glyph_position_t *buf_pos = buffer->pos;
      const hb_glyph_position_t *ref_pos = reference->pos;
      for (unsigned int i = 0; i < count; i++)
      {
        if ((unsigned int) abs (buf_pos->x_advance - ref_pos->x_advance) > position_fuzz ||
            (unsigned int) abs (buf_pos->y_advance - ref_pos->y_advance) > position_fuzz ||
            (unsigned int) abs (buf_pos->x_offset - ref_pos->x_offset) > position_fuzz ||
            (unsigned int) abs (buf_pos->y_offset - ref_pos->y_offset) > position_fuzz)
        {
          result |= HB_BUFFER_DIFF_FLAG_POSITION_MISMATCH;
          break;
        }
        buf_pos++;
        ref_pos++;
      }
    }
  
    return result;
  }
  
  
  /*
   * Debugging.
   */
  
  /**
   * hb_buffer_set_message_func:
   * @buffer: an #hb_buffer_t.
   * @func: (closure user_data) (destroy destroy) (scope notified):
   * @user_data:
   * @destroy:
   *
   *
   *
   * Since: 1.1.3
   **/
  void
  hb_buffer_set_message_func (hb_buffer_t *buffer,
  			    hb_buffer_message_func_t func,
  			    void *user_data, hb_destroy_func_t destroy)
  {
    if (buffer->message_destroy)
      buffer->message_destroy (buffer->message_data);
  
    if (func) {
      buffer->message_func = func;
      buffer->message_data = user_data;
      buffer->message_destroy = destroy;
    } else {
      buffer->message_func = nullptr;
      buffer->message_data = nullptr;
      buffer->message_destroy = nullptr;
    }
  }
  
  bool
  hb_buffer_t::message_impl (hb_font_t *font, const char *fmt, va_list ap)
  {
    char buf[100];
    vsnprintf (buf, sizeof (buf),  fmt, ap);
    return (bool) this->message_func (this, font, buf, this->message_data);
  }
  