Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 761 insertions, 0 deletions

diff --git a/gfx/harfbuzz/src/hb-serialize.hh b/gfx/harfbuzz/src/hb-serialize.hh
new file mode 100644
index 0000000000..d5573281f1
--- /dev/null
+++ b/gfx/harfbuzz/src/hb-serialize.hh
@@ -0,0 +1,761 @@
+/*
+ * Copyright © 2007,2008,2009,2010  Red Hat, Inc.
+ * Copyright © 2012,2018  Google, Inc.
+ * Copyright © 2019  Facebook, Inc.
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Red Hat Author(s): Behdad Esfahbod
+ * Google Author(s): Behdad Esfahbod
+ * Facebook Author(s): Behdad Esfahbod
+ */
+
+#ifndef HB_SERIALIZE_HH
+#define HB_SERIALIZE_HH
+
+#include "hb.hh"
+#include "hb-blob.hh"
+#include "hb-map.hh"
+#include "hb-pool.hh"
+
+#ifdef HB_EXPERIMENTAL_API
+#include "hb-subset-repacker.h"
+#endif
+
+/*
+ * Serialize
+ */
+
+enum hb_serialize_error_t {
+  HB_SERIALIZE_ERROR_NONE =            0x00000000u,
+  HB_SERIALIZE_ERROR_OTHER =           0x00000001u,
+  HB_SERIALIZE_ERROR_OFFSET_OVERFLOW = 0x00000002u,
+  HB_SERIALIZE_ERROR_OUT_OF_ROOM =     0x00000004u,
+  HB_SERIALIZE_ERROR_INT_OVERFLOW =    0x00000008u,
+  HB_SERIALIZE_ERROR_ARRAY_OVERFLOW =  0x00000010u
+};
+HB_MARK_AS_FLAG_T (hb_serialize_error_t);
+
+struct hb_serialize_context_t
+{
+  typedef unsigned objidx_t;
+
+  enum whence_t {
+     Head,	/* Relative to the current object head (default). */
+     Tail,	/* Relative to the current object tail after packed. */
+     Absolute	/* Absolute: from the start of the serialize buffer. */
+   };
+
+
+
+  struct object_t
+  {
+    void fini () {
+      real_links.fini ();
+      virtual_links.fini ();
+    }
+
+    object_t () = default;
+
+#ifdef HB_EXPERIMENTAL_API
+    object_t (const hb_object_t &o)
+    {
+      head = o.head;
+      tail = o.tail;
+      next = nullptr;
+      real_links.alloc (o.num_real_links);
+      for (unsigned i = 0 ; i < o.num_real_links; i++)
+        real_links.push (o.real_links[i]);
+
+      virtual_links.alloc (o.num_virtual_links);
+      for (unsigned i = 0; i < o.num_virtual_links; i++)
+        virtual_links.push (o.virtual_links[i]);
+    }
+#endif
+
+    friend void swap (object_t& a, object_t& b)
+    {
+      hb_swap (a.head, b.head);
+      hb_swap (a.tail, b.tail);
+      hb_swap (a.next, b.next);
+      hb_swap (a.real_links, b.real_links);
+      hb_swap (a.virtual_links, b.virtual_links);
+    }
+
+    bool operator == (const object_t &o) const
+    {
+      // Virtual links aren't considered for equality since they don't affect the functionality
+      // of the object.
+      return (tail - head == o.tail - o.head)
+	  && (real_links.length == o.real_links.length)
+	  && 0 == hb_memcmp (head, o.head, tail - head)
+	  && real_links.as_bytes () == o.real_links.as_bytes ();
+    }
+    uint32_t hash () const
+    {
+      // Virtual links aren't considered for equality since they don't affect the functionality
+      // of the object.
+      return hb_bytes_t (head, tail - head).hash () ^
+          real_links.as_bytes ().hash ();
+    }
+
+    struct link_t
+    {
+      unsigned width: 3;
+      unsigned is_signed: 1;
+      unsigned whence: 2;
+      unsigned bias : 26;
+      unsigned position;
+      objidx_t objidx;
+
+      link_t () = default;
+
+#ifdef HB_EXPERIMENTAL_API
+      link_t (const hb_link_t &o)
+      {
+        width = o.width;
+        is_signed = 0;
+        whence = 0;
+        position = o.position;
+        bias = 0;
+        objidx = o.objidx;
+      }
+#endif
+
+      HB_INTERNAL static int cmp (const void* a, const void* b)
+      {
+        int cmp = ((const link_t*)a)->position - ((const link_t*)b)->position;
+        if (cmp) return cmp;
+
+        return ((const link_t*)a)->objidx - ((const link_t*)b)->objidx;
+      }
+    };
+
+    char *head;
+    char *tail;
+    hb_vector_t<link_t> real_links;
+    hb_vector_t<link_t> virtual_links;
+    object_t *next;
+
+    auto all_links () const HB_AUTO_RETURN
+        (( hb_concat (this->real_links, this->virtual_links) ));
+    auto all_links_writer () HB_AUTO_RETURN
+        (( hb_concat (this->real_links.writer (), this->virtual_links.writer ()) ));
+  };
+
+  struct snapshot_t
+  {
+    char *head;
+    char *tail;
+    object_t *current; // Just for sanity check
+    unsigned num_real_links;
+    unsigned num_virtual_links;
+    hb_serialize_error_t errors;
+  };
+
+  snapshot_t snapshot ()
+  { return snapshot_t {
+      head, tail, current, current->real_links.length, current->virtual_links.length, errors }; }
+
+  hb_serialize_context_t (void *start_, unsigned int size) :
+    start ((char *) start_),
+    end (start + size),
+    current (nullptr)
+  { reset (); }
+  ~hb_serialize_context_t () { fini (); }
+
+  void fini ()
+  {
+    for (object_t *_ : ++hb_iter (packed)) _->fini ();
+    packed.fini ();
+    this->packed_map.fini ();
+
+    while (current)
+    {
+      auto *_ = current;
+      current = current->next;
+      _->fini ();
+    }
+  }
+
+  bool in_error () const { return bool (errors); }
+
+  bool successful () const { return !bool (errors); }
+
+  HB_NODISCARD bool ran_out_of_room () const { return errors & HB_SERIALIZE_ERROR_OUT_OF_ROOM; }
+  HB_NODISCARD bool offset_overflow () const { return errors & HB_SERIALIZE_ERROR_OFFSET_OVERFLOW; }
+  HB_NODISCARD bool only_offset_overflow () const { return errors == HB_SERIALIZE_ERROR_OFFSET_OVERFLOW; }
+  HB_NODISCARD bool only_overflow () const
+  {
+    return errors == HB_SERIALIZE_ERROR_OFFSET_OVERFLOW
+        || errors == HB_SERIALIZE_ERROR_INT_OVERFLOW
+        || errors == HB_SERIALIZE_ERROR_ARRAY_OVERFLOW;
+  }
+
+  void reset (void *start_, unsigned int size)
+  {
+    start = (char*) start_;
+    end = start + size;
+    reset ();
+    current = nullptr;
+  }
+
+  void reset ()
+  {
+    this->errors = HB_SERIALIZE_ERROR_NONE;
+    this->head = this->start;
+    this->tail = this->end;
+    this->zerocopy = nullptr;
+    this->debug_depth = 0;
+
+    fini ();
+    this->packed.push (nullptr);
+    this->packed_map.init ();
+  }
+
+  bool check_success (bool success,
+                      hb_serialize_error_t err_type = HB_SERIALIZE_ERROR_OTHER)
+  {
+    return successful ()
+        && (success || err (err_type));
+  }
+
+  template <typename T1, typename T2>
+  bool check_equal (T1 &&v1, T2 &&v2, hb_serialize_error_t err_type)
+  {
+    if ((long long) v1 != (long long) v2)
+    {
+      return err (err_type);
+    }
+    return true;
+  }
+
+  template <typename T1, typename T2>
+  bool check_assign (T1 &v1, T2 &&v2, hb_serialize_error_t err_type)
+  { return check_equal (v1 = v2, v2, err_type); }
+
+  template <typename T> bool propagate_error (T &&obj)
+  { return check_success (!hb_deref (obj).in_error ()); }
+
+  template <typename T1, typename... Ts> bool propagate_error (T1 &&o1, Ts&&... os)
+  { return propagate_error (std::forward<T1> (o1)) &&
+	   propagate_error (std::forward<Ts> (os)...); }
+
+  /* To be called around main operation. */
+  template <typename Type>
+  Type *start_serialize ()
+  {
+    DEBUG_MSG_LEVEL (SERIALIZE, this->start, 0, +1,
+		     "start [%p..%p] (%lu bytes)",
+		     this->start, this->end,
+		     (unsigned long) (this->end - this->start));
+
+    assert (!current);
+    return push<Type> ();
+  }
+  void end_serialize ()
+  {
+    DEBUG_MSG_LEVEL (SERIALIZE, this->start, 0, -1,
+		     "end [%p..%p] serialized %u bytes; %s",
+		     this->start, this->end,
+		     (unsigned) (this->head - this->start),
+		     successful () ? "successful" : "UNSUCCESSFUL");
+
+    propagate_error (packed, packed_map);
+
+    if (unlikely (!current)) return;
+    if (unlikely (in_error()))
+    {
+      // Offset overflows that occur before link resolution cannot be handled
+      // by repacking, so set a more general error.
+      if (offset_overflow ()) err (HB_SERIALIZE_ERROR_OTHER);
+      return;
+    }
+
+    assert (!current->next);
+
+    /* Only "pack" if there exist other objects... Otherwise, don't bother.
+     * Saves a move. */
+    if (packed.length <= 1)
+      return;
+
+    pop_pack (false);
+
+    resolve_links ();
+  }
+
+  template <typename Type = void>
+  Type *push ()
+  {
+    if (unlikely (in_error ())) return start_embed<Type> ();
+
+    object_t *obj = object_pool.alloc ();
+    if (unlikely (!obj))
+      check_success (false);
+    else
+    {
+      obj->head = head;
+      obj->tail = tail;
+      obj->next = current;
+      current = obj;
+    }
+    return start_embed<Type> ();
+  }
+  void pop_discard ()
+  {
+    object_t *obj = current;
+    if (unlikely (!obj)) return;
+    if (unlikely (in_error() && !only_overflow ())) return;
+
+    current = current->next;
+    revert (zerocopy ? zerocopy : obj->head, obj->tail);
+    zerocopy = nullptr;
+    obj->fini ();
+    object_pool.release (obj);
+  }
+
+  /* Set share to false when an object is unlikely shareable with others
+   * so not worth an attempt, or a contiguous table is serialized as
+   * multiple consecutive objects in the reverse order so can't be shared.
+   */
+  objidx_t pop_pack (bool share=true)
+  {
+    object_t *obj = current;
+    if (unlikely (!obj)) return 0;
+    if (unlikely (in_error())) return 0;
+
+    current = current->next;
+    obj->tail = head;
+    obj->next = nullptr;
+    assert (obj->head <= obj->tail);
+    unsigned len = obj->tail - obj->head;
+    head = zerocopy ? zerocopy : obj->head; /* Rewind head. */
+    bool was_zerocopy = zerocopy;
+    zerocopy = nullptr;
+
+    if (!len)
+    {
+      assert (!obj->real_links.length);
+      assert (!obj->virtual_links.length);
+      return 0;
+    }
+
+    objidx_t objidx;
+    uint32_t hash = 0;
+    if (share)
+    {
+      hash = hb_hash (obj);
+      objidx = packed_map.get_with_hash (obj, hash);
+      if (objidx)
+      {
+        merge_virtual_links (obj, objidx);
+	obj->fini ();
+	return objidx;
+      }
+    }
+
+    tail -= len;
+    if (was_zerocopy)
+      assert (tail == obj->head);
+    else
+      memmove (tail, obj->head, len);
+
+    obj->head = tail;
+    obj->tail = tail + len;
+
+    packed.push (obj);
+
+    if (unlikely (!propagate_error (packed)))
+    {
+      /* Obj wasn't successfully added to packed, so clean it up otherwise its
+       * links will be leaked. When we use constructor/destructors properly, we
+       * can remove these. */
+      obj->fini ();
+      return 0;
+    }
+
+    objidx = packed.length - 1;
+
+    if (share) packed_map.set_with_hash (obj, hash, objidx);
+    propagate_error (packed_map);
+
+    return objidx;
+  }
+
+  void revert (snapshot_t snap)
+  {
+    // Overflows that happened after the snapshot will be erased by the revert.
+    if (unlikely (in_error () && !only_overflow ())) return;
+    assert (snap.current == current);
+    current->real_links.shrink (snap.num_real_links);
+    current->virtual_links.shrink (snap.num_virtual_links);
+    errors = snap.errors;
+    revert (snap.head, snap.tail);
+  }
+
+  void revert (char *snap_head,
+	       char *snap_tail)
+  {
+    if (unlikely (in_error ())) return;
+    assert (snap_head <= head);
+    assert (tail <= snap_tail);
+    head = snap_head;
+    tail = snap_tail;
+    discard_stale_objects ();
+  }
+
+  void discard_stale_objects ()
+  {
+    if (unlikely (in_error ())) return;
+    while (packed.length > 1 &&
+	   packed.tail ()->head < tail)
+    {
+      packed_map.del (packed.tail ());
+      assert (!packed.tail ()->next);
+      packed.tail ()->fini ();
+      packed.pop ();
+    }
+    if (packed.length > 1)
+      assert (packed.tail ()->head == tail);
+  }
+
+  // Adds a virtual link from the current object to objidx. A virtual link is not associated with
+  // an actual offset field. They are solely used to enforce ordering constraints between objects.
+  // Adding a virtual link from object a to object b will ensure that object b is always packed after
+  // object a in the final serialized order.
+  //
+  // This is useful in certain situations where there needs to be a specific ordering in the
+  // final serialization. Such as when platform bugs require certain orderings, or to provide
+  //  guidance to the repacker for better offset overflow resolution.
+  void add_virtual_link (objidx_t objidx)
+  {
+    if (unlikely (in_error ())) return;
+
+    if (!objidx)
+      return;
+
+    assert (current);
+
+    auto& link = *current->virtual_links.push ();
+    if (current->virtual_links.in_error ())
+      err (HB_SERIALIZE_ERROR_OTHER);
+
+    link.width = 0;
+    link.objidx = objidx;
+    link.is_signed = 0;
+    link.whence = 0;
+    link.position = 0;
+    link.bias = 0;
+  }
+
+  template <typename T>
+  void add_link (T &ofs, objidx_t objidx,
+		 whence_t whence = Head,
+		 unsigned bias = 0)
+  {
+    if (unlikely (in_error ())) return;
+
+    if (!objidx)
+      return;
+
+    assert (current);
+    assert (current->head <= (const char *) &ofs);
+
+    auto& link = *current->real_links.push ();
+    if (current->real_links.in_error ())
+      err (HB_SERIALIZE_ERROR_OTHER);
+
+    link.width = sizeof (T);
+    link.objidx = objidx;
+    if (unlikely (!sizeof (T)))
+    {
+      // This link is not associated with an actual offset and exists merely to enforce
+      // an ordering constraint.
+      link.is_signed = 0;
+      link.whence = 0;
+      link.position = 0;
+      link.bias = 0;
+      return;
+    }
+
+    link.is_signed = std::is_signed<hb_unwrap_type (T)>::value;
+    link.whence = (unsigned) whence;
+    link.position = (const char *) &ofs - current->head;
+    link.bias = bias;
+  }
+
+  unsigned to_bias (const void *base) const
+  {
+    if (unlikely (in_error ())) return 0;
+    if (!base) return 0;
+    assert (current);
+    assert (current->head <= (const char *) base);
+    return (const char *) base - current->head;
+  }
+
+  void resolve_links ()
+  {
+    if (unlikely (in_error ())) return;
+
+    assert (!current);
+    assert (packed.length > 1);
+
+    for (const object_t* parent : ++hb_iter (packed))
+      for (const object_t::link_t &link : parent->real_links)
+      {
+	const object_t* child = packed[link.objidx];
+	if (unlikely (!child)) { err (HB_SERIALIZE_ERROR_OTHER); return; }
+	unsigned offset = 0;
+	switch ((whence_t) link.whence) {
+	case Head:     offset = child->head - parent->head; break;
+	case Tail:     offset = child->head - parent->tail; break;
+	case Absolute: offset = (head - start) + (child->head - tail); break;
+	}
+
+	assert (offset >= link.bias);
+	offset -= link.bias;
+	if (link.is_signed)
+	{
+	  assert (link.width == 2 || link.width == 4);
+	  if (link.width == 4)
+	    assign_offset<int32_t> (parent, link, offset);
+	  else
+	    assign_offset<int16_t> (parent, link, offset);
+	}
+	else
+	{
+	  assert (link.width == 2 || link.width == 3 || link.width == 4);
+	  if (link.width == 4)
+	    assign_offset<uint32_t> (parent, link, offset);
+	  else if (link.width == 3)
+	    assign_offset<uint32_t, 3> (parent, link, offset);
+	  else
+	    assign_offset<uint16_t> (parent, link, offset);
+	}
+      }
+  }
+
+  unsigned int length () const
+  {
+    if (unlikely (!current)) return 0;
+    return this->head - current->head;
+  }
+
+  void align (unsigned int alignment)
+  {
+    unsigned int l = length () % alignment;
+    if (l)
+      allocate_size<void> (alignment - l);
+  }
+
+  template <typename Type = void>
+  Type *start_embed (const Type *obj HB_UNUSED = nullptr) const
+  { return reinterpret_cast<Type *> (this->head); }
+  template <typename Type>
+  Type *start_embed (const Type &obj) const
+  { return start_embed (std::addressof (obj)); }
+
+  bool err (hb_serialize_error_t err_type)
+  {
+    return !bool ((errors = (errors | err_type)));
+  }
+
+  bool start_zerocopy (size_t size)
+  {
+    if (unlikely (in_error ())) return false;
+
+    if (unlikely (size > INT_MAX || this->tail - this->head < ptrdiff_t (size)))
+    {
+      err (HB_SERIALIZE_ERROR_OUT_OF_ROOM);
+      return false;
+    }
+
+    assert (!this->zerocopy);
+    this->zerocopy = this->head;
+
+    assert (this->current->head == this->head);
+    this->current->head = this->current->tail = this->head = this->tail - size;
+    return true;
+  }
+
+  template <typename Type>
+  Type *allocate_size (size_t size, bool clear = true)
+  {
+    if (unlikely (in_error ())) return nullptr;
+
+    if (unlikely (size > INT_MAX || this->tail - this->head < ptrdiff_t (size)))
+    {
+      err (HB_SERIALIZE_ERROR_OUT_OF_ROOM);
+      return nullptr;
+    }
+    if (clear)
+      hb_memset (this->head, 0, size);
+    char *ret = this->head;
+    this->head += size;
+    return reinterpret_cast<Type *> (ret);
+  }
+
+  template <typename Type>
+  Type *allocate_min ()
+  { return this->allocate_size<Type> (Type::min_size); }
+
+  template <typename Type>
+  Type *embed (const Type *obj)
+  {
+    unsigned int size = obj->get_size ();
+    Type *ret = this->allocate_size<Type> (size, false);
+    if (unlikely (!ret)) return nullptr;
+    hb_memcpy (ret, obj, size);
+    return ret;
+  }
+  template <typename Type>
+  Type *embed (const Type &obj)
+  { return embed (std::addressof (obj)); }
+
+  template <typename Type, typename ...Ts> auto
+  _copy (const Type &src, hb_priority<1>, Ts&&... ds) HB_RETURN
+  (Type *, src.copy (this, std::forward<Ts> (ds)...))
+
+  template <typename Type> auto
+  _copy (const Type &src, hb_priority<0>) -> decltype (&(hb_declval<Type> () = src))
+  {
+    Type *ret = this->allocate_size<Type> (sizeof (Type));
+    if (unlikely (!ret)) return nullptr;
+    *ret = src;
+    return ret;
+  }
+
+  /* Like embed, but active: calls obj.operator=() or obj.copy() to transfer data
+   * instead of hb_memcpy(). */
+  template <typename Type, typename ...Ts>
+  Type *copy (const Type &src, Ts&&... ds)
+  { return _copy (src, hb_prioritize, std::forward<Ts> (ds)...); }
+  template <typename Type, typename ...Ts>
+  Type *copy (const Type *src, Ts&&... ds)
+  { return copy (*src, std::forward<Ts> (ds)...); }
+
+  template<typename Iterator,
+	   hb_requires (hb_is_iterator (Iterator)),
+	   typename ...Ts>
+  void copy_all (Iterator it, Ts&&... ds)
+  { for (decltype (*it) _ : it) copy (_, std::forward<Ts> (ds)...); }
+
+  template <typename Type>
+  hb_serialize_context_t& operator << (const Type &obj) & { embed (obj); return *this; }
+
+  template <typename Type>
+  Type *extend_size (Type *obj, size_t size, bool clear = true)
+  {
+    if (unlikely (in_error ())) return nullptr;
+
+    assert (this->start <= (char *) obj);
+    assert ((char *) obj <= this->head);
+    assert ((size_t) (this->head - (char *) obj) <= size);
+    if (unlikely (((char *) obj + size < (char *) obj) ||
+		  !this->allocate_size<Type> (((char *) obj) + size - this->head, clear))) return nullptr;
+    return reinterpret_cast<Type *> (obj);
+  }
+  template <typename Type>
+  Type *extend_size (Type &obj, size_t size, bool clear = true)
+  { return extend_size (std::addressof (obj), size, clear); }
+
+  template <typename Type>
+  Type *extend_min (Type *obj) { return extend_size (obj, obj->min_size); }
+  template <typename Type>
+  Type *extend_min (Type &obj) { return extend_min (std::addressof (obj)); }
+
+  template <typename Type, typename ...Ts>
+  Type *extend (Type *obj, Ts&&... ds)
+  { return extend_size (obj, obj->get_size (std::forward<Ts> (ds)...)); }
+  template <typename Type, typename ...Ts>
+  Type *extend (Type &obj, Ts&&... ds)
+  { return extend (std::addressof (obj), std::forward<Ts> (ds)...); }
+
+  /* Output routines. */
+  hb_bytes_t copy_bytes () const
+  {
+    assert (successful ());
+    /* Copy both items from head side and tail side... */
+    unsigned int len = (this->head - this->start)
+		     + (this->end  - this->tail);
+
+    // If len is zero don't hb_malloc as the memory won't get properly
+    // cleaned up later.
+    if (!len) return hb_bytes_t ();
+
+    char *p = (char *) hb_malloc (len);
+    if (unlikely (!p)) return hb_bytes_t ();
+
+    hb_memcpy (p, this->start, this->head - this->start);
+    hb_memcpy (p + (this->head - this->start), this->tail, this->end - this->tail);
+    return hb_bytes_t (p, len);
+  }
+  template <typename Type>
+  Type *copy () const
+  { return reinterpret_cast<Type *> ((char *) copy_bytes ().arrayZ); }
+  hb_blob_t *copy_blob () const
+  {
+    hb_bytes_t b = copy_bytes ();
+    return hb_blob_create (b.arrayZ, b.length,
+			   HB_MEMORY_MODE_WRITABLE,
+			   (char *) b.arrayZ, hb_free);
+  }
+
+  const hb_vector_t<object_t *>& object_graph() const
+  { return packed; }
+
+  private:
+  template <typename T, unsigned Size = sizeof (T)>
+  void assign_offset (const object_t* parent, const object_t::link_t &link, unsigned offset)
+  {
+    auto &off = * ((BEInt<T, Size> *) (parent->head + link.position));
+    assert (0 == off);
+    check_assign (off, offset, HB_SERIALIZE_ERROR_OFFSET_OVERFLOW);
+  }
+
+  public:
+  char *start, *head, *tail, *end, *zerocopy;
+  unsigned int debug_depth;
+  hb_serialize_error_t errors;
+
+  private:
+
+  void merge_virtual_links (const object_t* from, objidx_t to_idx) {
+    object_t* to = packed[to_idx];
+    for (const auto& l : from->virtual_links) {
+      to->virtual_links.push (l);
+    }
+  }
+
+  /* Object memory pool. */
+  hb_pool_t<object_t> object_pool;
+
+  /* Stack of currently under construction objects. */
+  object_t *current;
+
+  /* Stack of packed objects.  Object 0 is always nil object. */
+  hb_vector_t<object_t *> packed;
+
+  /* Map view of packed objects. */
+  hb_hashmap_t<const object_t *, objidx_t> packed_map;
+};
+
+#endif /* HB_SERIALIZE_HH */