tor-browser

hb-buffer.cc (60701B)

---

/*
* 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 a dual role in HarfBuzz; before shaping, they hold
* the input characters that are passed to hb_shape(), and after
* shaping they hold the output glyphs.
*
* The input buffer is a sequence of Unicode codepoints, with
* associated attributes such as direction and script.  The output
* buffer is a sequence of glyphs, with associated attributes such
* as position and cluster.
**/


/**
* 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 * 31 +
  (unsigned int) p->script) * 31 +
 (intptr_t) (p->language);
}

/**
* hb_segment_properties_overlay:
* @p: #hb_segment_properties_t to fill in.
* @src: #hb_segment_properties_t to fill in from.
*
* Fills in missing fields of @p from @src in a considered manner.
*
* First, if @p does not have direction set, direction is copied from @src.
*
* Next, if @p and @src have the same direction (which can be unset), if @p
* does not have script set, script is copied from @src.
*
* Finally, if @p and @src have the same direction and script (which either
* can be unset), if @p does not have language set, language is copied from
* @src.
*
* Since: 3.3.0
**/
void
hb_segment_properties_overlay (hb_segment_properties_t *p,
		       const hb_segment_properties_t *src)
{
 if (unlikely (!p || !src))
   return;

 if (!p->direction)
   p->direction = src->direction;

 if (p->direction != src->direction)
   return;

 if (!p->script)
   p->script = src->script;

 if (p->script != src->script)
   return;

 if (!p->language)
   p->language = src->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, sync() is mostly 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.  sync() then
* switches info over to out_info and does housekeeping.
*/



/* Internal API */

bool
hb_buffer_t::enlarge (unsigned int size)
{
 if (unlikely (size > max_len))
 {
   successful = false;
   return false;
 }

 if (unlikely (!successful))
   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;

 unsigned new_bytes;
 if (unlikely (hb_unsigned_mul_overflows (new_allocated, sizeof (info[0]), &new_bytes)))
   goto done;

 static_assert (sizeof (info[0]) == sizeof (pos[0]), "");
 new_pos = (hb_glyph_position_t *) hb_realloc (pos, new_bytes);
 new_info = (hb_glyph_info_t *) hb_realloc (info, new_bytes);

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;
   hb_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;

 max_ops -= len - idx;
 if (unlikely (max_ops < 0))
 {
   successful = false;
   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... */
   hb_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::similar (const hb_buffer_t &src)
{
 hb_unicode_funcs_destroy (unicode);
 unicode = hb_unicode_funcs_reference (src.unicode);
 flags = src.flags;
 cluster_level = src.cluster_level;
 replacement = src.replacement;
 invisible = src.invisible;
 not_found = src.not_found;
 not_found_variation_selector = src.not_found_variation_selector;
}

void
hb_buffer_t::reset ()
{
 hb_unicode_funcs_destroy (unicode);
 unicode = hb_unicode_funcs_reference (hb_unicode_funcs_get_default ());
 flags = HB_BUFFER_FLAG_DEFAULT;
 cluster_level = HB_BUFFER_CLUSTER_LEVEL_DEFAULT;
 replacement = HB_BUFFER_REPLACEMENT_CODEPOINT_DEFAULT;
 invisible = 0;
 not_found = 0;
 not_found_variation_selector = HB_CODEPOINT_INVALID;

 clear ();
}

void
hb_buffer_t::clear ()
{
 content_type = HB_BUFFER_CONTENT_TYPE_INVALID;
 hb_segment_properties_t default_props = HB_SEGMENT_PROPERTIES_DEFAULT;
 props = default_props;

 successful = true;
 have_output = false;
 have_positions = false;

 idx = 0;
 len = 0;
 out_len = 0;
 out_info = info;

 hb_memset (context, 0, sizeof context);
 hb_memset (context_len, 0, sizeof context_len);

 deallocate_var_all ();
 serial = 0;
 random_state = 1;
 scratch_flags = HB_BUFFER_SCRATCH_FLAG_DEFAULT;
}

void
hb_buffer_t::enter ()
{
 deallocate_var_all ();
 serial = 0;
 scratch_flags = HB_BUFFER_SCRATCH_FLAG_DEFAULT;
 unsigned mul;
 if (likely (!hb_unsigned_mul_overflows (len, HB_BUFFER_MAX_LEN_FACTOR, &mul)))
 {
   max_len = hb_max (mul, (unsigned) HB_BUFFER_MAX_LEN_MIN);
 }
 if (likely (!hb_unsigned_mul_overflows (len, HB_BUFFER_MAX_OPS_FACTOR, &mul)))
 {
   max_ops = hb_max (mul, (unsigned) HB_BUFFER_MAX_OPS_MIN);
 }
}
void
hb_buffer_t::leave ()
{
 max_len = HB_BUFFER_MAX_LEN_DEFAULT;
 max_ops = HB_BUFFER_MAX_OPS_DEFAULT;
 deallocate_var_all ();
 serial = 0;
}


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];

 hb_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::add_info_and_pos (const hb_glyph_info_t &glyph_info,
		       const hb_glyph_position_t &glyph_pos)
{
 if (unlikely (!ensure (len + 1))) return;

 info[len] = glyph_info;
 assert (have_positions);
 pos[len] = glyph_pos;

 len++;
}


void
hb_buffer_t::clear_output ()
{
 have_output = true;
 have_positions = false;

 idx = 0;
 out_len = 0;
 out_info = info;
}

void
hb_buffer_t::clear_positions ()
{
 have_output = false;
 have_positions = true;

 out_len = 0;
 out_info = info;

 hb_memset (pos, 0, sizeof (pos[0]) * len);
}

bool
hb_buffer_t::sync ()
{
 bool ret = false;

 assert (have_output);

 assert (idx <= len);

 if (unlikely (!successful || !next_glyphs (len - idx)))
   goto reset;

 if (out_info != info)
 {
   pos = (hb_glyph_position_t *) info;
   info = out_info;
 }
 len = out_len;
 ret = true;

reset:
 have_output = false;
 out_len = 0;
 out_info = info;
 idx = 0;

 return ret;
}

int
hb_buffer_t::sync_so_far ()
{
 bool had_output = have_output;
 unsigned out_i = out_len;
 unsigned i = idx;
 unsigned old_idx = idx;

 if (sync ())
   idx = out_i;
 else
   idx = i;

 if (had_output)
 {
   have_output = true;
   out_len = idx;
 }

 assert (idx <= len);

 return idx - old_idx;
}

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.
    * But that would leave empty slots in the buffer in case of allocation
    * failures.  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 - idx))) 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)
{
 if (!mask)
   return;

 hb_mask_t not_mask = ~mask;
 value &= mask;

 max_ops -= len;
 if (unlikely (max_ops < 0))
   successful = false;

 unsigned int count = len;

 if (cluster_start == 0 && cluster_end == (unsigned int) -1)
 {
   for (unsigned int i = 0; i < count; i++)
     info[i].mask = (info[i].mask & not_mask) | value;
   return;
 }

 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::merge_clusters_impl (unsigned int start,
			  unsigned int end)
{
 if (!HB_BUFFER_CLUSTER_LEVEL_IS_MONOTONE (cluster_level))
 {
   unsafe_to_break (start, end);
   return;
 }

 max_ops -= end - start;
 if (unlikely (max_ops < 0))
   successful = false;

 unsigned int cluster = info[start].cluster;

 for (unsigned int i = start + 1; i < end; i++)
   cluster = hb_min (cluster, info[i].cluster);

 /* Extend end */
 if (cluster != info[end - 1].cluster)
   while (end < len && info[end - 1].cluster == info[end].cluster)
     end++;

 /* Extend start */
 if (cluster != info[start].cluster)
   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 && info[start].cluster != cluster)
   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 (!HB_BUFFER_CLUSTER_LEVEL_IS_MONOTONE (cluster_level))
   return;

 if (unlikely (end - start < 2))
   return;

 max_ops -= end - start;
 if (unlikely (max_ops < 0))
   successful = false;

 unsigned int cluster = out_info[start].cluster;

 for (unsigned int i = start + 1; i < end; i++)
   cluster = hb_min (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) ||
     (out_len && cluster == out_info[out_len - 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::delete_glyphs_inplace (bool (*filter) (const hb_glyph_info_t *info))
{
 /* Merge clusters and delete filtered glyphs.
  * NOTE! We can't use out-buffer as we have positioning data. */
 unsigned int j = 0;
 unsigned int count = len;
 for (unsigned int i = 0; i < count; i++)
 {
   if (filter (&info[i]))
   {
     /* Merge clusters.
      * Same logic as delete_glyph(), but for in-place removal. */

     unsigned int cluster = info[i].cluster;
     if (i + 1 < count && cluster == info[i + 1].cluster)
continue; /* Cluster survives; do nothing. */

     if (j)
     {
/* Merge cluster backward. */
if (cluster < info[j - 1].cluster)
{
  unsigned int mask = info[i].mask;
  unsigned int old_cluster = info[j - 1].cluster;
  for (unsigned k = j; k && info[k - 1].cluster == old_cluster; k--)
    set_cluster (info[k - 1], cluster, mask);
}
continue;
     }

     if (i + 1 < count)
merge_clusters (i, i + 2); /* Merge cluster forward. */

     continue;
   }

   if (j != i)
   {
     info[j] = info[i];
     pos[j] = pos[i];
   }
   j++;
 }
 len = j;
}

void
hb_buffer_t::guess_segment_properties ()
{
 assert_unicode ();

 /* 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 */
 0, /* not_found */
 HB_CODEPOINT_INVALID, /* not_found_variation_selector */


 HB_BUFFER_CONTENT_TYPE_INVALID,
 HB_SEGMENT_PROPERTIES_DEFAULT,

 false, /* successful */
 false, /* have_output */
 true  /* have_positions */

 /* Zero is good enough for everything else. */
};


/**
* hb_buffer_create:
*
* 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_create_similar:
* @src: An #hb_buffer_t
*
* Creates a new #hb_buffer_t, similar to hb_buffer_create(). The only
* difference is that the buffer is configured similarly to @src.
*
* Return value: (transfer full):
* A newly allocated #hb_buffer_t, similar to hb_buffer_create().
*
* Since: 3.3.0
**/
hb_buffer_t *
hb_buffer_create_similar (const hb_buffer_t *src)
{
 hb_buffer_t *buffer = hb_buffer_create ();

 buffer->similar (*src);

 return buffer;
}

/**
* 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)
{
 if (unlikely (hb_object_is_immutable (buffer)))
   return;

 buffer->reset ();
}

/**
* hb_buffer_get_empty:
*
* Fetches an empty #hb_buffer_t.
*
* Return value: (transfer full): The empty buffer
*
* 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);

 hb_free (buffer->info);
 hb_free (buffer->pos);
#ifndef HB_NO_BUFFER_MESSAGE
 if (buffer->message_destroy)
   buffer->message_destroy (buffer->message_data);
#endif

 hb_free (buffer);
}

/**
* hb_buffer_set_user_data: (skip)
* @buffer: An #hb_buffer_t
* @key: The user-data key
* @data: A pointer to the user data
* @destroy: (nullable): A callback to call when @data is not needed anymore
* @replace: Whether to replace an existing data with the same key
*
* Attaches a user-data key/data pair to the specified buffer.
*
* Return value: `true` if success, `false` otherwise
*
* 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: The user-data key to query
*
* Fetches the user data associated with the specified key,
* attached to the specified buffer.
*
* Return value: (transfer none): A pointer to the user data
*
* Since: 0.9.2
**/
void *
hb_buffer_get_user_data (const 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 contain glyphs (the result of shaping).
*
* You rarely need to call this function, since a number of other
* functions transition the content type for you. Namely:
*
* - A newly created buffer starts with content type
*   %HB_BUFFER_CONTENT_TYPE_INVALID. Calling hb_buffer_reset(),
*   hb_buffer_clear_contents(), as well as calling hb_buffer_set_length()
*   with an argument of zero all set the buffer content type to invalid
*   as well.
*
* - Calling hb_buffer_add_utf8(), hb_buffer_add_utf16(),
*   hb_buffer_add_utf32(), hb_buffer_add_codepoints() and
*   hb_buffer_add_latin1() expect that buffer is either empty and
*   have a content type of invalid, or that buffer content type is
*   %HB_BUFFER_CONTENT_TYPE_UNICODE, and they also set the content
*   type to Unicode if they added anything to an empty buffer.
*
* - Finally hb_shape() and hb_shape_full() expect that the buffer
*   is either empty and have content type of invalid, or that buffer
*   content type is %HB_BUFFER_CONTENT_TYPE_UNICODE, and upon
*   success they set the buffer content type to
*   %HB_BUFFER_CONTENT_TYPE_GLYPHS.
*
* The above transitions are designed such that one can use a buffer
* in a loop of "reset : add-text : shape" without needing to ever
* modify the content type manually.
*
* 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
*
* Fetches the type of @buffer contents. Buffers are either empty, contain
* characters (before shaping), or contain glyphs (the result of shaping).
*
* Return value:
* The type of @buffer contents
*
* Since: 0.9.5
**/
hb_buffer_content_type_t
hb_buffer_get_content_type (const hb_buffer_t *buffer)
{
 return buffer->content_type;
}


/**
* hb_buffer_set_unicode_funcs:
* @buffer: An #hb_buffer_t
* @unicode_funcs: The Unicode-functions structure
*
* Sets the Unicode-functions structure of a buffer to
* @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
*
* Fetches the Unicode-functions structure of a buffer.
*
* Return value: The Unicode-functions structure
*
* Since: 0.9.2
**/
hb_unicode_funcs_t *
hb_buffer_get_unicode_funcs (const 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 (const 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
*
* Fetches the script of @buffer.
*
* Return value:
* The #hb_script_t of the @buffer
*
* Since: 0.9.2
**/
hb_script_t
hb_buffer_get_script (const 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 (const 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 (const 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
*
* Fetches the #hb_buffer_flags_t of @buffer.
*
* Return value:
* The @buffer flags
*
* Since: 0.9.7
**/
hb_buffer_flags_t
hb_buffer_get_flags (const hb_buffer_t *buffer)
{
 return buffer->flags;
}

/**
* hb_buffer_set_cluster_level:
* @buffer: An #hb_buffer_t
* @cluster_level: The cluster level to set on the buffer
*
* Sets the cluster level of a buffer. The #hb_buffer_cluster_level_t
* dictates one aspect of how HarfBuzz will treat non-base characters
* during shaping.
*
* 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
*
* Fetches the cluster level of a buffer. The #hb_buffer_cluster_level_t
* dictates one aspect of how HarfBuzz will treat non-base characters
* during shaping.
*
* Return value: The cluster level of @buffer
*
* Since: 0.9.42
**/
hb_buffer_cluster_level_t
hb_buffer_get_cluster_level (const 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
*
* Fetches the #hb_codepoint_t that replaces invalid entries for a given encoding
* when adding text to @buffer.
*
* Return value:
* The @buffer replacement #hb_codepoint_t
*
* Since: 0.9.31
**/
hb_codepoint_t
hb_buffer_get_replacement_codepoint (const 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 (const hb_buffer_t *buffer)
{
 return buffer->invisible;
}

/**
* hb_buffer_set_not_found_glyph:
* @buffer: An #hb_buffer_t
* @not_found: the not-found #hb_codepoint_t
*
* Sets the #hb_codepoint_t that replaces characters not found in
* the font during shaping.
*
* The not-found glyph defaults to zero, sometimes known as the
* ".notdef" glyph.  This API allows for differentiating the two.
*
* Since: 3.1.0
**/
void
hb_buffer_set_not_found_glyph (hb_buffer_t    *buffer,
		       hb_codepoint_t  not_found)
{
 if (unlikely (hb_object_is_immutable (buffer)))
   return;

 buffer->not_found = not_found;
}

/**
* hb_buffer_get_not_found_glyph:
* @buffer: An #hb_buffer_t
*
* See hb_buffer_set_not_found_glyph().
*
* Return value:
* The @buffer not-found #hb_codepoint_t
*
* Since: 3.1.0
**/
hb_codepoint_t
hb_buffer_get_not_found_glyph (const hb_buffer_t *buffer)
{
 return buffer->not_found;
}

/**
* hb_buffer_set_not_found_variation_selector_glyph:
* @buffer: An #hb_buffer_t
* @not_found_variation_selector: the not-found-variation-selector #hb_codepoint_t
*
* Sets the #hb_codepoint_t that replaces variation-selector characters not resolved
* in the font during shaping.
*
* The not-found-variation-selector glyph defaults to #HB_CODEPOINT_INVALID,
* in which case an unresolved variation-selector will be removed from the glyph
* string during shaping. This API allows for changing that and retaining a glyph,
* such that the situation can be detected by the client and handled accordingly
* (e.g. by using a different font).
*
* Since: 10.0.0
**/
void
hb_buffer_set_not_found_variation_selector_glyph (hb_buffer_t    *buffer,
					  hb_codepoint_t  not_found_variation_selector)
{
 buffer->not_found_variation_selector = not_found_variation_selector;
}

/**
* hb_buffer_get_not_found_variation_selector_glyph:
* @buffer: An #hb_buffer_t
*
* See hb_buffer_set_not_found_variation_selector_glyph().
*
* Return value:
* The @buffer not-found-variation-selector #hb_codepoint_t
*
* Since: 10.0.0
**/
hb_codepoint_t
hb_buffer_get_not_found_variation_selector_glyph (const hb_buffer_t *buffer)
{
 return buffer->not_found_variation_selector;
}

/**
* hb_buffer_set_random_state:
* @buffer: An #hb_buffer_t
* @state: the new random state
*
* Sets the random state of the buffer. The state changes
* every time a glyph uses randomness (eg. the `rand`
* OpenType feature). This function together with
* hb_buffer_get_random_state() allow for transferring
* the current random state to a subsequent buffer, to
* get better randomness distribution.
*
* Defaults to 1 and when buffer contents are cleared.
* A value of 0 disables randomness during shaping.
*
* Since: 8.4.0
**/
void
hb_buffer_set_random_state (hb_buffer_t    *buffer,
		    unsigned        state)
{
 if (unlikely (hb_object_is_immutable (buffer)))
   return;

 buffer->random_state = state;
}

/**
* hb_buffer_get_random_state:
* @buffer: An #hb_buffer_t
*
* See hb_buffer_set_random_state().
*
* Return value:
* The @buffer random state
*
* Since: 8.4.0
**/
unsigned
hb_buffer_get_random_state (const hb_buffer_t *buffer)
{
 return buffer->random_state;
}

/**
* 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)
{
 if (unlikely (hb_object_is_immutable (buffer)))
   return;

 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 (unlikely (!buffer->ensure (length)))
   return false;

 /* Wipe the new space */
 if (length > buffer->len) {
   hb_memset (buffer->info + buffer->len, 0, sizeof (buffer->info[0]) * (length - buffer->len));
   if (buffer->have_positions)
     hb_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 (const hb_buffer_t *buffer)
{
 return buffer->len;
}

/**
* hb_buffer_get_glyph_infos:
* @buffer: An #hb_buffer_t
* @length: (out): The 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): The output length
*
* Returns @buffer glyph position array.  Returned pointer
* is valid as long as @buffer contents are not modified.
*
* If buffer did not have positions before, the positions will be
* initialized to zeros, unless this function is called from
* within a buffer message callback (see hb_buffer_set_message_func()),
* in which case `NULL` is returned.
*
* 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 (length)
   *length = buffer->len;

 if (!buffer->have_positions)
 {
   if (unlikely (buffer->message_depth))
     return nullptr;

   buffer->clear_positions ();
 }

 return (hb_glyph_position_t *) buffer->pos;
}

/**
* hb_buffer_has_positions:
* @buffer: an #hb_buffer_t.
*
* Returns whether @buffer has glyph position data.
* A buffer gains position data when hb_buffer_get_glyph_positions() is called on it,
* and cleared of position data when hb_buffer_clear_contents() is called.
*
* Return value:
* `true` if the @buffer has position array, `false` otherwise.
*
* Since: 2.7.3
**/
HB_EXTERN hb_bool_t
hb_buffer_has_positions (hb_buffer_t  *buffer)
{
 return buffer->have_positions;
}

/**
* 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 and @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;

 buffer->assert_unicode ();

 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;

 if (unlikely (item_length < 0 ||
	item_length > INT_MAX / 8 ||
	!buffer->ensure (buffer->len + item_length * sizeof (T) / 4)))
   return;

 /* 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 scalar values.  In contrast,
* hb_buffer_add_utf32() can be used that takes similar input but performs
* sanity-check on the input.
*
* 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 @UINT_MAX (or ((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,
	  const 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 + (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;

 if (!orig_len)
   buffer->content_type = source->content_type;
 if (!buffer->have_positions && source->have_positions)
   buffer->clear_positions ();

 hb_segment_properties_overlay (&buffer->props, &source->props);

 hb_memcpy (buffer->info + orig_len, source->info + start, (end - start) * sizeof (buffer->info[0]));
 if (buffer->have_positions)
   hb_memcpy (buffer->pos + orig_len, source->pos + start, (end - start) * sizeof (buffer->pos[0]));

 if (source->content_type == HB_BUFFER_CONTENT_TYPE_UNICODE)
 {
   /* See similar logic in add_utf. */

   /* pre-context */
   if (!orig_len && start + source->context_len[0] > 0)
   {
     buffer->clear_context (0);
     while (start > 0 && buffer->context_len[0] < buffer->CONTEXT_LENGTH)
buffer->context[0][buffer->context_len[0]++] = source->info[--start].codepoint;
     for (auto i = 0u; i < source->context_len[0] && buffer->context_len[0] < buffer->CONTEXT_LENGTH; i++)
buffer->context[0][buffer->context_len[0]++] = source->context[0][i];
   }

   /* post-context */
   buffer->clear_context (1);
   while (end < source->len && buffer->context_len[1] < buffer->CONTEXT_LENGTH)
     buffer->context[1][buffer->context_len[1]++] = source->info[end++].codepoint;
   for (auto i = 0u; i < source->context_len[1] && buffer->context_len[1] < buffer->CONTEXT_LENGTH; i++)
     buffer->context[1][buffer->context_len[1]++] = source->context[1][i];
 }
}


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);

 buffer->assert_glyphs ();

 bool backward = HB_DIRECTION_IS_BACKWARD (buffer->props.direction);

 foreach_cluster (buffer, 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_codepoint_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.
*/

#ifndef HB_NO_BUFFER_MESSAGE
/**
* hb_buffer_set_message_func:
* @buffer: An #hb_buffer_t
* @func: (closure user_data) (destroy destroy) (scope notified): Callback function
* @user_data: (nullable): Data to pass to @func
* @destroy: (nullable): The function to call when @user_data is not needed anymore
*
* Sets the implementation function for #hb_buffer_message_func_t.
*
* 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 (unlikely (hb_object_is_immutable (buffer)))
 {
   if (destroy)
     destroy (user_data);
   return;
 }

 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)
{
 assert (!have_output || (out_info == info && out_len == idx));

 message_depth++;

 char buf[100];
 vsnprintf (buf, sizeof (buf), fmt, ap);
 bool ret = (bool) this->message_func (this, font, buf, this->message_data);

 message_depth--;

 return ret;
}
#endif