src/graph/gsubgpos-graph.hh

/*
 * Copyright © 2022  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
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 * 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.
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 * Google Author(s): Garret Rieger
 */

#include "graph.hh"
#include "../hb-ot-layout-gsubgpos.hh"
#include "../OT/Layout/GSUB/ExtensionSubst.hh"
#include "gsubgpos-context.hh"
#include "pairpos-graph.hh"
#include "markbasepos-graph.hh"

#ifndef GRAPH_GSUBGPOS_GRAPH_HH
#define GRAPH_GSUBGPOS_GRAPH_HH

namespace graph {

struct Lookup;

template<typename T>
struct ExtensionFormat1 : public OT::ExtensionFormat1<T>
{
  void reset(unsigned type)
  {
    this->format = 1;
    this->extensionLookupType = type;
    this->extensionOffset = 0;
  }

  bool sanitize (graph_t::vertex_t& vertex) const
  {
    int64_t vertex_len = vertex.obj.tail - vertex.obj.head;
    return vertex_len >= OT::ExtensionFormat1<T>::static_size;
  }

  unsigned get_lookup_type () const
  {
    return this->extensionLookupType;
  }

  unsigned get_subtable_index (graph_t& graph, unsigned this_index) const
  {
    return graph.index_for_offset (this_index, &this->extensionOffset);
  }
};

struct Lookup : public OT::Lookup
{
  unsigned number_of_subtables () const
  {
    return subTable.len;
  }

  bool sanitize (graph_t::vertex_t& vertex) const
  {
    int64_t vertex_len = vertex.obj.tail - vertex.obj.head;
    if (vertex_len < OT::Lookup::min_size) return false;
    return vertex_len >= this->get_size ();
  }

  bool is_extension (hb_tag_t table_tag) const
  {
    return lookupType == extension_type (table_tag);
  }

  bool make_extension (gsubgpos_graph_context_t& c,
                       unsigned this_index)
  {
    unsigned type = lookupType;
    unsigned ext_type = extension_type (c.table_tag);
    if (!ext_type || is_extension (c.table_tag))
    {
      // NOOP
      return true;
    }

    DEBUG_MSG (SUBSET_REPACK, nullptr,
               "Promoting lookup type %u (obj %u) to extension.",
               type,
               this_index);

    for (unsigned i = 0; i < subTable.len; i++)
    {
      unsigned subtable_index = c.graph.index_for_offset (this_index, &subTable[i]);
      if (!make_subtable_extension (c,
                                    this_index,
                                    subtable_index))
        return false;
    }

    lookupType = ext_type;
    return true;
  }

  bool split_subtables_if_needed (gsubgpos_graph_context_t& c,
                                  unsigned this_index)
  {
    unsigned type = lookupType;
    bool is_ext = is_extension (c.table_tag);

    if (c.table_tag != HB_OT_TAG_GPOS)
      return true;

    if (!is_ext &&
        type != OT::Layout::GPOS_impl::PosLookupSubTable::Type::Pair &&
        type != OT::Layout::GPOS_impl::PosLookupSubTable::Type::MarkBase)
      return true;

    hb_vector_t<hb_pair_t<unsigned, hb_vector_t<unsigned>>> all_new_subtables;
    for (unsigned i = 0; i < subTable.len; i++)
    {
      unsigned subtable_index = c.graph.index_for_offset (this_index, &subTable[i]);
      unsigned parent_index = this_index;
      if (is_ext) {
        unsigned ext_subtable_index = subtable_index;
        parent_index = ext_subtable_index;
        ExtensionFormat1<OT::Layout::GSUB_impl::ExtensionSubst>* extension =
            (ExtensionFormat1<OT::Layout::GSUB_impl::ExtensionSubst>*)
            c.graph.object (ext_subtable_index).head;
        if (!extension || !extension->sanitize (c.graph.vertices_[ext_subtable_index]))
          continue;

        subtable_index = extension->get_subtable_index (c.graph, ext_subtable_index);
        type = extension->get_lookup_type ();
        if (type != OT::Layout::GPOS_impl::PosLookupSubTable::Type::Pair
            && type != OT::Layout::GPOS_impl::PosLookupSubTable::Type::MarkBase)
          continue;
      }

      hb_vector_t<unsigned> new_sub_tables;
      switch (type)
      {
      case 2:
        new_sub_tables = split_subtable<PairPos> (c, parent_index, subtable_index); break;
      case 4:
        new_sub_tables = split_subtable<MarkBasePos> (c, parent_index, subtable_index); break;
      default:
        break;
      }
      if (new_sub_tables.in_error ()) return false;
      if (!new_sub_tables) continue;
      hb_pair_t<unsigned, hb_vector_t<unsigned>>* entry = all_new_subtables.push ();
      entry->first = i;
      entry->second = std::move (new_sub_tables);
    }

    if (all_new_subtables) {
      return add_sub_tables (c, this_index, type, all_new_subtables);
    }

    return true;
  }

  template<typename T>
  hb_vector_t<unsigned> split_subtable (gsubgpos_graph_context_t& c,
                                        unsigned parent_idx,
                                        unsigned objidx)
  {
    T* sub_table = (T*) c.graph.object (objidx).head;
    if (!sub_table || !sub_table->sanitize (c.graph.vertices_[objidx]))
      return hb_vector_t<unsigned> ();

    return sub_table->split_subtables (c, parent_idx, objidx);
  }

  bool add_sub_tables (gsubgpos_graph_context_t& c,
                       unsigned this_index,
                       unsigned type,
                       hb_vector_t<hb_pair_t<unsigned, hb_vector_t<unsigned>>>& subtable_ids)
  {
    bool is_ext = is_extension (c.table_tag);
    auto& v = c.graph.vertices_[this_index];
    fix_existing_subtable_links (c, this_index, subtable_ids);

    unsigned new_subtable_count = 0;
    for (const auto& p : subtable_ids)
      new_subtable_count += p.second.length;

    size_t new_size = v.table_size ()
                      + new_subtable_count * OT::Offset16::static_size;
    char* buffer = (char*) hb_calloc (1, new_size);
    if (!buffer) return false;
    if (!c.add_buffer (buffer))
    {
      hb_free (buffer);
     return false;
    }
    hb_memcpy (buffer, v.obj.head, v.table_size());

    v.obj.head = buffer;
    v.obj.tail = buffer + new_size;

    Lookup* new_lookup = (Lookup*) buffer;

    unsigned shift = 0;
    new_lookup->subTable.len = subTable.len + new_subtable_count;
    for (const auto& p : subtable_ids)
    {
      unsigned offset_index = p.first + shift + 1;
      shift += p.second.length;

      for (unsigned subtable_id : p.second)
      {
        if (is_ext)
        {
          unsigned ext_id = create_extension_subtable (c, subtable_id, type);
          c.graph.vertices_[subtable_id].add_parent (ext_id);
          subtable_id = ext_id;
        }

        auto* link = v.obj.real_links.push ();
        link->width = 2;
        link->objidx = subtable_id;
        link->position = (char*) &new_lookup->subTable[offset_index++] -
                         (char*) new_lookup;
        c.graph.vertices_[subtable_id].add_parent (this_index);
      }
    }

    // Repacker sort order depends on link order, which we've messed up so resort it.
    v.obj.real_links.qsort ();

    // The head location of the lookup has changed, invalidating the lookups map entry
    // in the context. Update the map.
    c.lookups.set (this_index, new_lookup);
    return true;
  }

  void fix_existing_subtable_links (gsubgpos_graph_context_t& c,
                                    unsigned this_index,
                                    hb_vector_t<hb_pair_t<unsigned, hb_vector_t<unsigned>>>& subtable_ids)
  {
    auto& v = c.graph.vertices_[this_index];
    Lookup* lookup = (Lookup*) v.obj.head;

    unsigned shift = 0;
    for (const auto& p : subtable_ids)
    {
      unsigned insert_index = p.first + shift;
      unsigned pos_offset = p.second.length * OT::Offset16::static_size;
      unsigned insert_offset = (char*) &lookup->subTable[insert_index] - (char*) lookup;
      shift += p.second.length;

      for (auto& l : v.obj.all_links_writer ())
      {
        if (l.position > insert_offset) l.position += pos_offset;
      }
    }
  }

  unsigned create_extension_subtable (gsubgpos_graph_context_t& c,
                                      unsigned subtable_index,
                                      unsigned type)
  {
    unsigned extension_size = OT::ExtensionFormat1<OT::Layout::GSUB_impl::ExtensionSubst>::static_size;

    unsigned ext_index = c.create_node (extension_size);
    if (ext_index == (unsigned) -1)
      return -1;

    auto& ext_vertex = c.graph.vertices_[ext_index];
    ExtensionFormat1<OT::Layout::GSUB_impl::ExtensionSubst>* extension =
        (ExtensionFormat1<OT::Layout::GSUB_impl::ExtensionSubst>*) ext_vertex.obj.head;
    extension->reset (type);

    // Make extension point at the subtable.
    auto* l = ext_vertex.obj.real_links.push ();

    l->width = 4;
    l->objidx = subtable_index;
    l->position = 4;

    return ext_index;
  }

  bool make_subtable_extension (gsubgpos_graph_context_t& c,
                                unsigned lookup_index,
                                unsigned subtable_index)
  {
    unsigned type = lookupType;
    unsigned ext_index = -1;
    unsigned* existing_ext_index = nullptr;
    if (c.subtable_to_extension.has(subtable_index, &existing_ext_index)) {
      ext_index = *existing_ext_index;
    } else {
      ext_index = create_extension_subtable(c, subtable_index, type);
      c.subtable_to_extension.set(subtable_index, ext_index);
    }

    if (ext_index == (unsigned) -1)
      return false;

    auto& subtable_vertex = c.graph.vertices_[subtable_index];
    auto& lookup_vertex = c.graph.vertices_[lookup_index];
    for (auto& l : lookup_vertex.obj.real_links.writer ())
    {
      if (l.objidx == subtable_index) {
        // Change lookup to point at the extension.
        l.objidx = ext_index;
        if (existing_ext_index)
          subtable_vertex.remove_parent(lookup_index);
      }
    }

    // Make extension point at the subtable.
    auto& ext_vertex = c.graph.vertices_[ext_index];
    ext_vertex.add_parent (lookup_index);
    if (!existing_ext_index)
      subtable_vertex.remap_parent (lookup_index, ext_index);

    return true;
  }

 private:
  unsigned extension_type (hb_tag_t table_tag) const
  {
    switch (table_tag)
    {
    case HB_OT_TAG_GPOS: return 9;
    case HB_OT_TAG_GSUB: return 7;
    default: return 0;
    }
  }
};

template <typename T>
struct LookupList : public OT::LookupList<T>
{
  bool sanitize (const graph_t::vertex_t& vertex) const
  {
    int64_t vertex_len = vertex.obj.tail - vertex.obj.head;
    if (vertex_len < OT::LookupList<T>::min_size) return false;
    return vertex_len >= OT::LookupList<T>::item_size * this->len;
  }
};

struct GSTAR : public OT::GSUBGPOS
{
  static GSTAR* graph_to_gstar (graph_t& graph)
  {
    const auto& r = graph.root ();

    GSTAR* gstar = (GSTAR*) r.obj.head;
    if (!gstar || !gstar->sanitize (r))
      return nullptr;

    return gstar;
  }

  const void* get_lookup_list_field_offset () const
  {
    switch (u.version.major) {
    case 1: return u.version1.get_lookup_list_offset ();
#ifndef HB_NO_BEYOND_64K
    case 2: return u.version2.get_lookup_list_offset ();
#endif
    default: return 0;
    }
  }

  bool sanitize (const graph_t::vertex_t& vertex)
  {
    int64_t len = vertex.obj.tail - vertex.obj.head;
    if (len < OT::GSUBGPOS::min_size) return false;
    return len >= get_size ();
  }

  void find_lookups (graph_t& graph,
                     hb_hashmap_t<unsigned, Lookup*>& lookups /* OUT */)
  {
    switch (u.version.major) {
      case 1: find_lookups<SmallTypes> (graph, lookups); break;
#ifndef HB_NO_BEYOND_64K
      case 2: find_lookups<MediumTypes> (graph, lookups); break;
#endif
    }
  }

  unsigned get_lookup_list_index (graph_t& graph)
  {
    return graph.index_for_offset (graph.root_idx (),
                                   get_lookup_list_field_offset());
  }

  template<typename Types>
  void find_lookups (graph_t& graph,
                     hb_hashmap_t<unsigned, Lookup*>& lookups /* OUT */)
  {
    unsigned lookup_list_idx = get_lookup_list_index (graph);
    const LookupList<Types>* lookupList =
        (const LookupList<Types>*) graph.object (lookup_list_idx).head;
    if (!lookupList || !lookupList->sanitize (graph.vertices_[lookup_list_idx]))
      return;

    for (unsigned i = 0; i < lookupList->len; i++)
    {
      unsigned lookup_idx = graph.index_for_offset (lookup_list_idx, &(lookupList->arrayZ[i]));
      Lookup* lookup = (Lookup*) graph.object (lookup_idx).head;
      if (!lookup || !lookup->sanitize (graph.vertices_[lookup_idx])) continue;
      lookups.set (lookup_idx, lookup);
    }
  }
};


}

#endif  /* GRAPH_GSUBGPOS_GRAPH_HH */