Merge pull request #2163 from harfbuzz/absolute-link

added add_link_abs()

src/hb-open-type.hh

@@ -338,11 +338,15 @@ struct OffsetTo : Offset<OffsetType, has_null>
   }
 
   /* TODO: Somehow merge this with previous function into a serialize_dispatch(). */
+  /* Workaround clang bug: https://bugs.llvm.org/show_bug.cgi?id=23029
+   * Can't compile: whence = hb_serialize_context_t::Head followed by Ts&&...
+   */
   template <typename ...Ts>
   bool serialize_copy (hb_serialize_context_t *c,
 		       const OffsetTo& src,
 		       const void *src_base,
 		       const void *dst_base,
+		       hb_serialize_context_t::whence_t whence,
 		       Ts&&... ds)
   {
     *this = 0;
@@ -353,11 +357,17 @@ struct OffsetTo : Offset<OffsetType, has_null>
 
     bool ret = c->copy (src_base+src, hb_forward<Ts> (ds)...);
 
-    c->add_link (*this, c->pop_pack (), dst_base);
+    c->add_link (*this, c->pop_pack (), dst_base, whence);
 
     return ret;
   }
 
+  bool serialize_copy (hb_serialize_context_t *c,
+		       const OffsetTo& src,
+		       const void *src_base,
+		       const void *dst_base)
+  { return serialize_copy (c, src, src_base, dst_base, hb_serialize_context_t::Head); }
+
   bool sanitize_shallow (hb_sanitize_context_t *c, const void *base) const
   {
     TRACE_SANITIZE (this);

src/hb-ot-name-table.hh

@@ -98,13 +98,12 @@ struct NameRecord
   }
 
   NameRecord* copy (hb_serialize_context_t *c,
-		    const void *src_base,
-		    const void *dst_base) const
+		    const void *src_base) const
   {
     TRACE_SERIALIZE (this);
     auto *out = c->embed (this);
     if (unlikely (!out)) return_trace (nullptr);
-    out->offset.serialize_copy (c, offset, src_base, dst_base, length);
+    out->offset.serialize_copy (c, offset, src_base, nullptr, hb_serialize_context_t::Tail, length);
     return_trace (out);
   }
 
@@ -216,13 +215,6 @@ struct name
     this->format = 0;
     this->count = it.len ();
 
-    auto snap = c->snapshot ();
-    this->nameRecordZ.serialize (c, this->count);
-    if (unlikely (!c->check_assign (this->stringOffset, c->length ()))) return_trace (false);
-    c->revert (snap);
-
-    const void *dst_string_pool = &(this + this->stringOffset);
-
     NameRecord *name_records = (NameRecord *) calloc (it.len (), NameRecord::static_size);
     hb_array_t<NameRecord> records (name_records, it.len ());
 
@@ -234,12 +226,12 @@ struct name
 
     records.qsort ();
 
-    c->copy_all (records, src_string_pool, dst_string_pool);
+    c->copy_all (records, src_string_pool);
     free (records.arrayZ);
 
     if (unlikely (c->ran_out_of_room)) return_trace (false);
 
-    assert (this->stringOffset == c->length ());
+    this->stringOffset = c->length ();
 
     return_trace (true);
   }

src/hb-serialize.hh

@@ -50,6 +50,12 @@ struct hb_serialize_context_t
     char *head, *tail;
   };
 
+  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 : range_t
   {
     void fini () { links.fini (); }
@@ -70,7 +76,9 @@ struct hb_serialize_context_t
     struct link_t
     {
       bool is_wide: 1;
-      unsigned position : 31;
+      bool is_signed: 1;
+      unsigned whence: 2;
+      unsigned position: 28;
       unsigned bias;
       objidx_t objidx;
     };
@@ -269,7 +277,9 @@ struct hb_serialize_context_t
   }
 
   template <typename T>
-  void add_link (T &ofs, objidx_t objidx, const void *base = nullptr)
+  void add_link (T &ofs, objidx_t objidx,
+		 const void *base = nullptr,
+		 whence_t whence = Head)
   {
     static_assert (sizeof (T) == 2 || sizeof (T) == 4, "");
 
@@ -279,15 +289,24 @@ struct hb_serialize_context_t
     assert (current);
     assert (current->head <= (const char *) &ofs);
 
-    if (!base)
-      base = current->head;
-    else
-      assert (current->head <= (const char *) base);
-
     auto& link = *current->links.push ();
+
     link.is_wide = sizeof (T) == 4;
+    link.is_signed = hb_is_signed (hb_unwrap_type (T));
+    link.whence = (unsigned)whence;
     link.position = (const char *) &ofs - current->head;
-    link.bias = (const char *) base - current->head;
+    if (whence == Head)
+    {
+      if (base == nullptr)
+	link.bias = 0;
+      else
+      {
+	assert (current->head <= (const char *)base);
+	link.bias = (const char *) base - current->head;
+      }
+    }
+    else
+      link.bias = 0;
     link.objidx = objidx;
   }
 
@@ -302,20 +321,28 @@ struct hb_serialize_context_t
       for (const object_t::link_t &link : parent->links)
       {
 	const object_t* child = packed[link.objidx];
-	assert (link.bias <= (size_t) (parent->tail - parent->head));
-	unsigned offset = (child->head - parent->head) - link.bias;
+	if (unlikely (!child)) { err_other_error(); return; }
+	unsigned offset;
+	switch ((whence_t)link.whence) {
+	case Head:     offset = (child->head - parent->head) - link.bias; break;
+	case Tail:     offset = child->head - parent->tail; break;
+	case Absolute: offset = (head - start) + (child->head - tail); break;
+	default: assert (0);
+	}
 
-	if (link.is_wide)
+	if (link.is_signed)
 	{
-	  auto &off = * ((BEInt<uint32_t, 4> *) (parent->head + link.position));
-	  assert (0 == off);
-	  check_assign (off, offset);
+	  if (link.is_wide)
+	    assign_offset<int32_t> (parent, link, offset);
+	  else
+	    assign_offset<int16_t> (parent, link, offset);
 	}
 	else
 	{
-	  auto &off = * ((BEInt<uint16_t, 2> *) (parent->head + link.position));
-	  assert (0 == off);
-	  check_assign (off, offset);
+	  if (link.is_wide)
+	    assign_offset<uint32_t> (parent, link, offset);
+	  else
+	    assign_offset<uint16_t> (parent, link, offset);
 	}
       }
   }
@@ -456,6 +483,15 @@ struct hb_serialize_context_t
 			   (char *) b.arrayZ, free);
   }
 
+  private:
+  template <typename T>
+  void assign_offset (const object_t* parent, const object_t::link_t &link, unsigned offset)
+  {
+    auto &off = * ((BEInt<T, sizeof (T)> *) (parent->head + link.position));
+    assert (0 == off);
+    check_assign (off, offset);
+  }
+
   public: /* TODO Make private. */
   char *start, *head, *tail, *end;
   unsigned int debug_depth;