From f2a0e691624a8479170623154e131a9c65c04563 Mon Sep 17 00:00:00 2001
From: Garret Rieger <grieger@google.com>
Date: Thu, 21 Jul 2022 18:36:20 +0000
Subject: [PATCH] [repacker] size buffer correctly.

---
 src/graph/gsubgpos-graph.hh | 74 ++++++++++++++++++++++---------------
 src/hb-repacker.hh          | 24 ++++++++++--
 2 files changed, 66 insertions(+), 32 deletions(-)

diff --git a/src/graph/gsubgpos-graph.hh b/src/graph/gsubgpos-graph.hh
index 3a3b4c333..27a1e5cb6 100644
--- a/src/graph/gsubgpos-graph.hh
+++ b/src/graph/gsubgpos-graph.hh
@@ -33,8 +33,15 @@
 
 namespace graph {
 
+struct Lookup;
+
 struct GSTAR : public OT::GSUBGPOS
 {
+  static GSTAR* graph_to_gstar (graph_t& graph)
+  {
+    return (GSTAR*) graph.root ().obj.head;
+  }
+
   const void* get_lookup_list_field_offset () const
   {
     switch (u.version.major) {
@@ -46,18 +53,38 @@ struct GSTAR : public OT::GSUBGPOS
     }
   }
 
+  void find_lookups (graph_t& graph,
+                     hb_hashmap_t<unsigned, Lookup*>& lookups /* OUT */)
+  {
+    // TODO: template on types, based on gstar version.
+    unsigned lookup_list_idx = graph.index_for_offset (graph.root_idx (),
+                                                       get_lookup_list_field_offset());
+
+    const OT::LookupList<SmallTypes>* lookupList =
+        (const OT::LookupList<SmallTypes>*) graph.object (lookup_list_idx).head;
+
+    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;
+      lookups.set (lookup_idx, lookup);
+    }
+}
+
+
+
 };
 
 struct Lookup : public OT::Lookup
 {
-  unsigned extension_type (hb_tag_t table_tag)
+  unsigned number_of_subtables () const
   {
-    switch (table_tag)
-    {
-    case HB_OT_TAG_GPOS: return 9;
-    case HB_OT_TAG_GSUB: return 7;
-    default: return 0;
-    }
+    return subTable.len;
+  }
+
+  bool is_extension (hb_tag_t table_tag) const
+  {
+    return lookupType == extension_type (table_tag);
   }
 
   bool make_extension (hb_tag_t table_tag,
@@ -66,9 +93,9 @@ struct Lookup : public OT::Lookup
                        hb_vector_t<char>& buffer)
   {
     // TODO: use a context_t?
-    unsigned ext_type = extension_type (table_tag);
     unsigned type = lookupType;
-    if (!ext_type || type == ext_type)
+    unsigned ext_type = extension_type (table_tag);
+    if (!ext_type || is_extension (table_tag))
     {
       // NOOP
       printf("Already extension (obj %u).\n", this_index);
@@ -151,29 +178,18 @@ struct Lookup : public OT::Lookup
 
     return true;
   }
-};
 
-static inline void
-find_lookups (graph_t& graph,
-              hb_hashmap_t<unsigned, Lookup*>& lookups /* OUT */)
-{
-  // TODO: move this into GSTAR?
-  // TODO: template on types, based on gstar version.
-  const GSTAR* gstar = (const GSTAR*) graph.root ().obj.head;
-
-  unsigned lookup_list_idx = graph.index_for_offset (graph.root_idx (),
-                                                     gstar->get_lookup_list_field_offset());
-
-  const OT::LookupList<SmallTypes>* lookupList =
-      (const OT::LookupList<SmallTypes>*) graph.object (lookup_list_idx).head;
-
-  for (unsigned i = 0; i < lookupList->len; i++)
+ private:
+  unsigned extension_type (hb_tag_t table_tag) const
   {
-    unsigned lookup_idx = graph.index_for_offset (lookup_list_idx, &(lookupList->arrayZ[i]));
-    Lookup* lookup = (Lookup*) graph.object (lookup_idx).head;
-    lookups.set (lookup_idx, lookup);
+    switch (table_tag)
+    {
+    case HB_OT_TAG_GPOS: return 9;
+    case HB_OT_TAG_GSUB: return 7;
+    default: return 0;
+    }
   }
-}
+};
 
 }
 
diff --git a/src/hb-repacker.hh b/src/hb-repacker.hh
index 041b5260d..545da7ac2 100644
--- a/src/hb-repacker.hh
+++ b/src/hb-repacker.hh
@@ -43,12 +43,32 @@ using graph::graph_t;
  * docs/repacker.md
  */
 
+static inline
+unsigned _num_non_ext_subtables (hb_tag_t table_tag,
+                                 const hb_hashmap_t<unsigned, graph::Lookup*>& lookups)
+{
+  unsigned count = 0;
+  for (auto l : lookups.values ())
+  {
+    if (l->is_extension (table_tag)) continue;
+    count += l->number_of_subtables ();
+  }
+  return count;
+}
+
+
 static inline
 bool _make_extensions (hb_tag_t table_tag, graph_t& sorted_graph, hb_vector_t<char>& buffer)
 {
   // TODO: Move this into graph or gsubgpos graph?
+  graph::GSTAR* gstar = graph::GSTAR::graph_to_gstar (sorted_graph);
   hb_hashmap_t<unsigned, graph::Lookup*> lookups;
-  find_lookups (sorted_graph, lookups);
+  gstar->find_lookups (sorted_graph, lookups);
+
+  unsigned extension_size = OT::ExtensionFormat1<OT::Layout::GSUB_impl::ExtensionSubst>::static_size;
+  if (!buffer.alloc (_num_non_ext_subtables (table_tag, lookups) * extension_size))
+    return false;
+
 
   for (auto p : lookups.iter ())
   {
@@ -187,8 +207,6 @@ hb_resolve_overflows (const T& packed,
   }
 
   hb_vector_t<char> extension_buffer;
-  if (!extension_buffer.alloc(100000)) // TODO: cleanup
-    return nullptr;
   if ((table_tag == HB_OT_TAG_GPOS
        ||  table_tag == HB_OT_TAG_GSUB)
       && will_overflow)