Reduce storage by sharing face amongst lazy_loaders

src/hb-machinery-private.hh

@@ -590,93 +590,106 @@ struct BEInt<Type, 4>
  * Lazy struct and blob loaders.
  */
 
-template <typename Subclass,
+template <unsigned int WheresFace,
+	  typename Subclass,
 	  typename Returned,
 	  typename Stored = Returned>
 struct hb_base_lazy_loader_t
 {
+  static_assert (WheresFace > 0, "");
+
   /* https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern */
   inline const Subclass* thiz (void) const { return static_cast<const Subclass *> (this); }
+  inline Subclass* thiz (void) { return static_cast<Subclass *> (this); }
 
-  inline void init (hb_face_t *face_)
+  inline void init (void)
   {
-    face = face_;
     instance = nullptr;
   }
-
-  inline const Returned * operator-> (void) const
+  inline void fini (void)
   {
-    return thiz ()->get ();
+    if (instance)
+      thiz ()->destroy (instance);
   }
 
-  protected:
-  hb_face_t *face;
-  mutable Stored *instance;
-};
-
-template <typename T>
-struct hb_lazy_loader_t : hb_base_lazy_loader_t<hb_lazy_loader_t<T>, T>
-{
-  inline void fini (void)
+  inline const Returned * operator-> (void) const
   {
-    if (this->instance && this->instance != &Null(T))
-    {
-      this->instance->fini();
-      free (this->instance);
-    }
+    return thiz ()->get ();
   }
 
-  inline const T* get (void) const
+  inline Stored * get_stored (void) const
   {
   retry:
-    T *p = (T *) hb_atomic_ptr_get (&this->instance);
+    Stored *p = (Stored *) hb_atomic_ptr_get (&this->instance);
     if (unlikely (!p))
     {
-      p = (T *) calloc (1, sizeof (T));
-      if (unlikely (!p))
-        p = const_cast<T *> (&Null(T));
-      else
-	p->init (this->face);
-      if (unlikely (!hb_atomic_ptr_cmpexch (const_cast<T **>(&this->instance), nullptr, p)))
+      hb_face_t *face = *(((hb_face_t **) this) - WheresFace);
+      p = thiz ()->create (face);
+      if (unlikely (!hb_atomic_ptr_cmpexch (const_cast<Stored **>(&this->instance), nullptr, p)))
       {
-	if (p != &Null(T))
-	  p->fini ();
+        thiz ()->destroy (p);
 	goto retry;
       }
     }
     return p;
   }
+
+  inline const Returned * get (void) const
+  {
+    return thiz ()->convert (get_stored ());
+  }
+
+  static inline const Returned* convert (const Stored *p)
+  {
+    return p;
+  }
+
+  private:
+  /* Must only have one pointer. */
+  mutable Stored *instance;
 };
 
-template <typename T>
-struct hb_table_lazy_loader_t : hb_base_lazy_loader_t<hb_table_lazy_loader_t<T>, T, hb_blob_t>
+template <unsigned int WheresFace, typename T>
+struct hb_lazy_loader_t : hb_base_lazy_loader_t<WheresFace, hb_lazy_loader_t<WheresFace, T>, T>
 {
-  inline void fini (void)
+  static inline T *create (hb_face_t *face)
   {
-    hb_blob_destroy (this->instance);
+    T *p = (T *) calloc (1, sizeof (T));
+    if (unlikely (!p))
+      p = const_cast<T *> (&Null(T));
+    else
+      p->init (face);
+    return p;
   }
-
-  inline hb_blob_t* get_blob (void) const
+  static inline void destroy (T *p)
   {
-  retry:
-    hb_blob_t *b = (hb_blob_t *) hb_atomic_ptr_get (&this->instance);
-    if (unlikely (!b))
+    if (p != &Null(T))
     {
-      b = hb_sanitize_context_t ().reference_table<T> (this->face);
-      if (!hb_atomic_ptr_cmpexch (&this->instance, nullptr, b))
-      {
-	hb_blob_destroy (b);
-	goto retry;
-      }
-      this->instance = b;
+      p->fini();
+      free (p);
     }
-    return b;
   }
+};
 
-  inline const T* get (void) const
+template <unsigned int WheresFace, typename T>
+struct hb_table_lazy_loader_t : hb_base_lazy_loader_t<WheresFace, hb_table_lazy_loader_t<WheresFace, T>, T, hb_blob_t>
+{
+  static inline hb_blob_t *create (hb_face_t *face)
+  {
+    return hb_sanitize_context_t ().reference_table<T> (face);
+  }
+  static inline void destroy (hb_blob_t *p)
+  {
+    hb_blob_destroy (p);
+  }
+  static inline const T* convert (const hb_blob_t *blob)
+  {
+    return blob->as<T> ();
+  }
+
+  inline hb_blob_t* get_blob (void) const
   {
-    hb_blob_t *b = get_blob ();
-    return b->as<T> ();
+    return this->get_stored ();
   }
 };
 

src/hb-ot-font.cc

@@ -44,10 +44,12 @@ struct hb_ot_font_t
   OT::cmap::accelerator_t cmap;
   OT::hmtx::accelerator_t h_metrics;
   OT::vmtx::accelerator_t v_metrics;
-  hb_lazy_loader_t<OT::glyf::accelerator_t> glyf;
-  hb_lazy_loader_t<OT::CBDT::accelerator_t> cbdt;
-  hb_lazy_loader_t<OT::post::accelerator_t> post;
-  hb_lazy_loader_t<OT::kern::accelerator_t> kern;
+
+  hb_face_t *face; /* MUST be before the lazy loaders. */
+  hb_lazy_loader_t<1, OT::glyf::accelerator_t> glyf;
+  hb_lazy_loader_t<2, OT::CBDT::accelerator_t> cbdt;
+  hb_lazy_loader_t<3, OT::post::accelerator_t> post;
+  hb_lazy_loader_t<4, OT::kern::accelerator_t> kern;
 };
 
 
@@ -62,10 +64,11 @@ _hb_ot_font_create (hb_face_t *face)
   ot_font->cmap.init (face);
   ot_font->h_metrics.init (face);
   ot_font->v_metrics.init (face, ot_font->h_metrics.ascender - ot_font->h_metrics.descender); /* TODO Can we do this lazily? */
-  ot_font->glyf.init (face);
-  ot_font->cbdt.init (face);
-  ot_font->post.init (face);
-  ot_font->kern.init (face);
+  ot_font->face = face;
+  ot_font->glyf.init ();
+  ot_font->cbdt.init ();
+  ot_font->post.init ();
+  ot_font->kern.init ();
 
   return ot_font;
 }

src/hb-ot-layout-private.hh

@@ -172,11 +172,12 @@ struct hb_ot_layout_t
   const struct OT::GPOS *gpos;
 
   /* TODO Move the following out of this struct. */
-  hb_table_lazy_loader_t<struct OT::BASE> base;
-  hb_table_lazy_loader_t<struct OT::MATH> math;
-  hb_table_lazy_loader_t<struct OT::fvar> fvar;
-  hb_table_lazy_loader_t<struct OT::avar> avar;
-  hb_table_lazy_loader_t<struct AAT::morx> morx;
+  hb_face_t *face; /* MUST be before the lazy loaders. */
+  hb_table_lazy_loader_t<1, struct OT::BASE> base;
+  hb_table_lazy_loader_t<2, struct OT::MATH> math;
+  hb_table_lazy_loader_t<3, struct OT::fvar> fvar;
+  hb_table_lazy_loader_t<4, struct OT::avar> avar;
+  hb_table_lazy_loader_t<5, struct AAT::morx> morx;
 
   unsigned int gsub_lookup_count;
   unsigned int gpos_lookup_count;

src/hb-ot-layout.cc

@@ -63,10 +63,11 @@ _hb_ot_layout_create (hb_face_t *face)
   layout->gpos_blob = hb_sanitize_context_t ().reference_table<OT::GPOS> (face);
   layout->gpos = layout->gpos_blob->as<OT::GPOS> ();
 
-  layout->math.init (face);
-  layout->fvar.init (face);
-  layout->avar.init (face);
-  layout->morx.init (face);
+  layout->face = face;
+  layout->math.init ();
+  layout->fvar.init ();
+  layout->avar.init ();
+  layout->morx.init ();
 
   {
     /*