src/hb-machinery.hh - third_party/harfbuzz - Git at Google

 /*
  * Copyright © 2007,2008,2009,2010  Red Hat, Inc.
  * Copyright © 2012,2018  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
  * 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
  */

 #ifndef HB_MACHINERY_HH
 #define HB_MACHINERY_HH

 #include "hb.hh"
 #include "hb-blob.hh"

 #include "hb-dispatch.hh"
 #include "hb-sanitize.hh"


 /*
  * Casts
  */

 /* StructAtOffset<T>(P,Ofs) returns the struct T& that is placed at memory
  * location pointed to by P plus Ofs bytes. */
 template<typename Type>
 static inline const Type& StructAtOffset(const void *P, unsigned int offset)
 { return * reinterpret_cast<const Type*> ((const char *) P + offset); }
 template<typename Type>
 static inline Type& StructAtOffset(void *P, unsigned int offset)
 { return * reinterpret_cast<Type*> ((char *) P + offset); }
 template<typename Type>
 static inline const Type& StructAtOffsetUnaligned(const void *P, unsigned int offset)
 {
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wcast-align"
   return * reinterpret_cast<const Type*> ((const char *) P + offset);
 #pragma GCC diagnostic pop
 }
 template<typename Type>
 static inline Type& StructAtOffsetUnaligned(void *P, unsigned int offset)
 {
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wcast-align"
   return * reinterpret_cast<Type*> ((char *) P + offset);
 #pragma GCC diagnostic pop
 }

 /* StructAfter<T>(X) returns the struct T& that is placed after X.
  * Works with X of variable size also.  X must implement get_size() */
 template<typename Type, typename TObject>
 static inline const Type& StructAfter(const TObject &X)
 { return StructAtOffset<Type>(&X, X.get_size()); }
 template<typename Type, typename TObject>
 static inline Type& StructAfter(TObject &X)
 { return StructAtOffset<Type>(&X, X.get_size()); }


 /*
  * Size checking
  */

 /* Size signifying variable-sized array */
 #ifndef HB_VAR_ARRAY
 #define HB_VAR_ARRAY 1
 #endif

 /* Check _assertion in a method environment */
 #define _DEFINE_INSTANCE_ASSERTION1(_line, _assertion) \
   void _instance_assertion_on_line_##_line () const \
   { static_assert ((_assertion), ""); }
 # define _DEFINE_INSTANCE_ASSERTION0(_line, _assertion) _DEFINE_INSTANCE_ASSERTION1 (_line, _assertion)
 # define DEFINE_INSTANCE_ASSERTION(_assertion) _DEFINE_INSTANCE_ASSERTION0 (__LINE__, _assertion)

 /* Check that _code compiles in a method environment */
 #define _DEFINE_COMPILES_ASSERTION1(_line, _code) \
   void _compiles_assertion_on_line_##_line () const \
   { _code; }
 # define _DEFINE_COMPILES_ASSERTION0(_line, _code) _DEFINE_COMPILES_ASSERTION1 (_line, _code)
 # define DEFINE_COMPILES_ASSERTION(_code) _DEFINE_COMPILES_ASSERTION0 (__LINE__, _code)


 #define DEFINE_SIZE_STATIC(size) \
   DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size)) \
   unsigned int get_size () const { return (size); } \
   static constexpr unsigned null_size = (size); \
   static constexpr unsigned min_size = (size); \
   static constexpr unsigned static_size = (size)

 #define DEFINE_SIZE_UNION(size, _member) \
   DEFINE_COMPILES_ASSERTION ((void) this->u._member.static_size) \
   DEFINE_INSTANCE_ASSERTION (sizeof(this->u._member) == (size)) \
   static constexpr unsigned null_size = (size); \
   static constexpr unsigned min_size = (size)

 #define DEFINE_SIZE_MIN(size) \
   DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
   static constexpr unsigned null_size = (size); \
   static constexpr unsigned min_size = (size)

 #define DEFINE_SIZE_UNBOUNDED(size) \
   DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
   static constexpr unsigned min_size = (size)

 #define DEFINE_SIZE_ARRAY(size, array) \
   DEFINE_COMPILES_ASSERTION ((void) (array)[0].static_size) \
   DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size) + (HB_VAR_ARRAY+0) * sizeof ((array)[0])) \
   static constexpr unsigned null_size = (size); \
   static constexpr unsigned min_size = (size)

 #define DEFINE_SIZE_ARRAY_SIZED(size, array) \
   unsigned int get_size () const { return (size - (array).min_size + (array).get_size ()); } \
   DEFINE_SIZE_ARRAY(size, array)


 /*
  * Lazy loaders.
  *
  * The lazy-loaders are thread-safe pointer-like objects that create their
  * instead on-demand.  They also support access to a "data" object that is
  * necessary for creating their instance.  The data object, if specified,
  * is accessed via pointer math, located at a location before the position
  * of the loader itself.  This avoids having to store a pointer to data
  * for every lazy-loader.  Multiple lazy-loaders can access the same data.
  */

 template <typename Data, unsigned int WheresData>
 struct hb_data_wrapper_t
 {
   static_assert (WheresData > 0, "");

   Data * get_data () const
   { return *(((Data **) (void *) this) - WheresData); }

   bool is_inert () const { return !get_data (); }

   template <typename Stored, typename Subclass>
   Stored * call_create () const { return Subclass::create (get_data ()); }
 };
 template <>
 struct hb_data_wrapper_t<void, 0>
 {
   bool is_inert () const { return false; }

   template <typename Stored, typename Funcs>
   Stored * call_create () const { return Funcs::create (); }
 };

 template <typename T1, typename T2> struct hb_non_void_t { typedef T1 value; };
 template <typename T2> struct hb_non_void_t<void, T2> { typedef T2 value; };

 template <typename Returned,
 	  typename Subclass = void,
 	  typename Data = void,
 	  unsigned int WheresData = 0,
 	  typename Stored = Returned>
 struct hb_lazy_loader_t : hb_data_wrapper_t<Data, WheresData>
 {
   typedef typename hb_non_void_t<Subclass,
 				 hb_lazy_loader_t<Returned,Subclass,Data,WheresData,Stored>
 				>::value Funcs;

   hb_lazy_loader_t () = default;
   hb_lazy_loader_t (const hb_lazy_loader_t &other) = delete;

   void init0 () {} /* Init, when memory is already set to 0. No-op for us. */
   void init ()  { instance.set_relaxed (nullptr); }
   void fini ()  { do_destroy (instance.get_acquire ()); init (); }

   void free_instance ()
   {
   retry:
     Stored *p = instance.get_acquire ();
     if (unlikely (p && !cmpexch (p, nullptr)))
       goto retry;
     do_destroy (p);
   }

   static void do_destroy (Stored *p)
   {
     if (p && p != const_cast<Stored *> (Funcs::get_null ()))
       Funcs::destroy (p);
   }

   const Returned * operator -> () const { return get (); }
   template <typename U = Returned, hb_enable_if (!hb_is_same (U, void))>
   const U & operator * () const  { return *get (); }
   explicit operator bool () const
   { return get_stored () != Funcs::get_null (); }
   template <typename C> operator const C * () const { return get (); }

   Stored * get_stored () const
   {
   retry:
     Stored *p = this->instance.get_acquire ();
     if (unlikely (!p))
     {
       if (unlikely (this->is_inert ()))
 	return const_cast<Stored *> (Funcs::get_null ());

       p = this->template call_create<Stored, Funcs> ();
       if (unlikely (!p))
 	p = const_cast<Stored *> (Funcs::get_null ());

       if (unlikely (!cmpexch (nullptr, p)))
       {
 	do_destroy (p);
 	goto retry;
       }
     }
     return p;
   }
   Stored * get_stored_relaxed () const
   {
     return this->instance.get_relaxed ();
   }

   bool cmpexch (Stored *current, Stored *value) const
   {
     /* This function can only be safely called directly if no
      * other thread is accessing. */
     return this->instance.cmpexch (current, value);
   }

   const Returned * get () const { return Funcs::convert (get_stored ()); }
   const Returned * get_relaxed () const { return Funcs::convert (get_stored_relaxed ()); }
   Returned * get_unconst () const { return const_cast<Returned *> (Funcs::convert (get_stored ())); }

   /* To be possibly overloaded by subclasses. */
   static Returned* convert (Stored *p) { return p; }

   /* By default null/init/fini the object. */
   static const Stored* get_null () { return &Null (Stored); }
   static Stored *create (Data *data)
   {
     Stored *p = (Stored *) hb_calloc (1, sizeof (Stored));
     if (likely (p))
       p = new (p) Stored (data);
     return p;
   }
   static Stored *create ()
   {
     Stored *p = (Stored *) hb_calloc (1, sizeof (Stored));
     if (likely (p))
       p = new (p) Stored ();
     return p;
   }
   static void destroy (Stored *p)
   {
     p->~Stored ();
     hb_free (p);
   }

   private:
   /* Must only have one pointer. */
   hb_atomic_ptr_t<Stored *> instance;
 };

 /* Specializations. */

 template <typename T, unsigned int WheresFace>
 struct hb_face_lazy_loader_t : hb_lazy_loader_t<T,
 						hb_face_lazy_loader_t<T, WheresFace>,
 						hb_face_t, WheresFace>
 {
   // Hack; have them here for API parity with hb_table_lazy_loader_t
   hb_blob_t *get_blob () { return this->get ()->get_blob (); }
 };

 template <typename T, unsigned int WheresFace, bool core=false>
 struct hb_table_lazy_loader_t : hb_lazy_loader_t<T,
 						 hb_table_lazy_loader_t<T, WheresFace, core>,
 						 hb_face_t, WheresFace,
 						 hb_blob_t>
 {
   static hb_blob_t *create (hb_face_t *face)
   {
     hb_sanitize_context_t c;
     if (core)
       c.set_num_glyphs (0); // So we don't recurse ad infinitum, or doesn't need num_glyphs
     return c.reference_table<T> (face);
   }
   static void destroy (hb_blob_t *p) { hb_blob_destroy (p); }

   static const hb_blob_t *get_null ()
   { return hb_blob_get_empty (); }

   static const T* convert (const hb_blob_t *blob)
   { return blob->as<T> (); }

   hb_blob_t* get_blob () const { return this->get_stored (); }
 };

 #define HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T(Type) \
   template <typename Subclass> \
   struct hb_##Type##_funcs_lazy_loader_t : hb_lazy_loader_t<hb_##Type##_funcs_t, Subclass> \
   { \
     static void destroy (hb_##Type##_funcs_t *p) \
     { hb_##Type##_funcs_destroy (p); } \
     static const hb_##Type##_funcs_t *get_null () \
     { return hb_##Type##_funcs_get_empty (); } \
   }

 HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (font);
 HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (unicode);
 HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (draw);
 HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (paint);

 #undef HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T


 #endif /* HB_MACHINERY_HH */
	/*
	* Copyright © 2007,2008,2009,2010 Red Hat, Inc.
	* Copyright © 2012,2018 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
	* 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
	*/

	#ifndef HB_MACHINERY_HH
	#define HB_MACHINERY_HH

	#include "hb.hh"
	#include "hb-blob.hh"

	#include "hb-dispatch.hh"
	#include "hb-sanitize.hh"


	/*
	* Casts
	*/

	/* StructAtOffset<T>(P,Ofs) returns the struct T& that is placed at memory
	* location pointed to by P plus Ofs bytes. */
	template<typename Type>
	static inline const Type& StructAtOffset(const void *P, unsigned int offset)
	{ return * reinterpret_cast<const Type> ((const char ) P + offset); }
	template<typename Type>
	static inline Type& StructAtOffset(void *P, unsigned int offset)
	{ return * reinterpret_cast<Type> ((char ) P + offset); }
	template<typename Type>
	static inline const Type& StructAtOffsetUnaligned(const void *P, unsigned int offset)
	{
	#pragma GCC diagnostic push
	#pragma GCC diagnostic ignored "-Wcast-align"
	return * reinterpret_cast<const Type> ((const char ) P + offset);
	#pragma GCC diagnostic pop
	}
	template<typename Type>
	static inline Type& StructAtOffsetUnaligned(void *P, unsigned int offset)
	{
	#pragma GCC diagnostic push
	#pragma GCC diagnostic ignored "-Wcast-align"
	return * reinterpret_cast<Type> ((char ) P + offset);
	#pragma GCC diagnostic pop
	}

	/* StructAfter<T>(X) returns the struct T& that is placed after X.
	* Works with X of variable size also. X must implement get_size() */
	template<typename Type, typename TObject>
	static inline const Type& StructAfter(const TObject &X)
	{ return StructAtOffset<Type>(&X, X.get_size()); }
	template<typename Type, typename TObject>
	static inline Type& StructAfter(TObject &X)
	{ return StructAtOffset<Type>(&X, X.get_size()); }


	/*
	* Size checking
	*/

	/* Size signifying variable-sized array */
	#ifndef HB_VAR_ARRAY
	#define HB_VAR_ARRAY 1
	#endif

	/* Check _assertion in a method environment */
	#define _DEFINE_INSTANCE_ASSERTION1(_line, _assertion) \
	void _instance_assertion_on_line_##_line () const \
	{ static_assert ((_assertion), ""); }
	# define _DEFINE_INSTANCE_ASSERTION0(_line, _assertion) _DEFINE_INSTANCE_ASSERTION1 (_line, _assertion)
	# define DEFINE_INSTANCE_ASSERTION(_assertion) _DEFINE_INSTANCE_ASSERTION0 (__LINE__, _assertion)

	/* Check that _code compiles in a method environment */
	#define _DEFINE_COMPILES_ASSERTION1(_line, _code) \
	void _compiles_assertion_on_line_##_line () const \
	{ _code; }
	# define _DEFINE_COMPILES_ASSERTION0(_line, _code) _DEFINE_COMPILES_ASSERTION1 (_line, _code)
	# define DEFINE_COMPILES_ASSERTION(_code) _DEFINE_COMPILES_ASSERTION0 (__LINE__, _code)


	#define DEFINE_SIZE_STATIC(size) \
	DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size)) \
	unsigned int get_size () const { return (size); } \
	static constexpr unsigned null_size = (size); \
	static constexpr unsigned min_size = (size); \
	static constexpr unsigned static_size = (size)

	#define DEFINE_SIZE_UNION(size, _member) \
	DEFINE_COMPILES_ASSERTION ((void) this->u._member.static_size) \
	DEFINE_INSTANCE_ASSERTION (sizeof(this->u._member) == (size)) \
	static constexpr unsigned null_size = (size); \
	static constexpr unsigned min_size = (size)

	#define DEFINE_SIZE_MIN(size) \
	DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
	static constexpr unsigned null_size = (size); \
	static constexpr unsigned min_size = (size)

	#define DEFINE_SIZE_UNBOUNDED(size) \
	DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
	static constexpr unsigned min_size = (size)

	#define DEFINE_SIZE_ARRAY(size, array) \
	DEFINE_COMPILES_ASSERTION ((void) (array)[0].static_size) \
	DEFINE_INSTANCE_ASSERTION (sizeof (this) == (size) + (HB_VAR_ARRAY+0) sizeof ((array)[0])) \
	static constexpr unsigned null_size = (size); \
	static constexpr unsigned min_size = (size)

	#define DEFINE_SIZE_ARRAY_SIZED(size, array) \
	unsigned int get_size () const { return (size - (array).min_size + (array).get_size ()); } \
	DEFINE_SIZE_ARRAY(size, array)



	/*
	* Lazy loaders.
	*
	* The lazy-loaders are thread-safe pointer-like objects that create their
	* instead on-demand. They also support access to a "data" object that is
	* necessary for creating their instance. The data object, if specified,
	* is accessed via pointer math, located at a location before the position
	* of the loader itself. This avoids having to store a pointer to data
	* for every lazy-loader. Multiple lazy-loaders can access the same data.
	*/

	template <typename Data, unsigned int WheresData>
	struct hb_data_wrapper_t
	{
	static_assert (WheresData > 0, "");

	Data * get_data () const
	{ return (((Data ) (void ) this) - WheresData); }

	bool is_inert () const { return !get_data (); }

	template <typename Stored, typename Subclass>
	Stored * call_create () const { return Subclass::create (get_data ()); }
	};
	template <>
	struct hb_data_wrapper_t<void, 0>
	{
	bool is_inert () const { return false; }

	template <typename Stored, typename Funcs>
	Stored * call_create () const { return Funcs::create (); }
	};

	template <typename T1, typename T2> struct hb_non_void_t { typedef T1 value; };
	template <typename T2> struct hb_non_void_t<void, T2> { typedef T2 value; };

	template <typename Returned,
	typename Subclass = void,
	typename Data = void,
	unsigned int WheresData = 0,
	typename Stored = Returned>
	struct hb_lazy_loader_t : hb_data_wrapper_t<Data, WheresData>
	{
	typedef typename hb_non_void_t<Subclass,
	hb_lazy_loader_t<Returned,Subclass,Data,WheresData,Stored>
	>::value Funcs;

	hb_lazy_loader_t () = default;
	hb_lazy_loader_t (const hb_lazy_loader_t &other) = delete;

	void init0 () {} /* Init, when memory is already set to 0. No-op for us. */
	void init () { instance.set_relaxed (nullptr); }
	void fini () { do_destroy (instance.get_acquire ()); init (); }

	void free_instance ()
	{
	retry:
	Stored *p = instance.get_acquire ();
	if (unlikely (p && !cmpexch (p, nullptr)))
	goto retry;
	do_destroy (p);
	}

	static void do_destroy (Stored *p)
	{
	if (p && p != const_cast<Stored *> (Funcs::get_null ()))
	Funcs::destroy (p);
	}

	const Returned * operator -> () const { return get (); }
	template <typename U = Returned, hb_enable_if (!hb_is_same (U, void))>
	const U & operator * () const { return *get (); }
	explicit operator bool () const
	{ return get_stored () != Funcs::get_null (); }
	template <typename C> operator const C * () const { return get (); }

	Stored * get_stored () const
	{
	retry:
	Stored *p = this->instance.get_acquire ();
	if (unlikely (!p))
	{
	if (unlikely (this->is_inert ()))
	return const_cast<Stored *> (Funcs::get_null ());

	p = this->template call_create<Stored, Funcs> ();
	if (unlikely (!p))
	p = const_cast<Stored *> (Funcs::get_null ());

	if (unlikely (!cmpexch (nullptr, p)))
	{
	do_destroy (p);
	goto retry;
	}
	}
	return p;
	}
	Stored * get_stored_relaxed () const
	{
	return this->instance.get_relaxed ();
	}

	bool cmpexch (Stored current, Stored value) const
	{
	/* This function can only be safely called directly if no
	* other thread is accessing. */
	return this->instance.cmpexch (current, value);
	}

	const Returned * get () const { return Funcs::convert (get_stored ()); }
	const Returned * get_relaxed () const { return Funcs::convert (get_stored_relaxed ()); }
	Returned * get_unconst () const { return const_cast<Returned *> (Funcs::convert (get_stored ())); }

	/* To be possibly overloaded by subclasses. */
	static Returned* convert (Stored *p) { return p; }

	/* By default null/init/fini the object. */
	static const Stored* get_null () { return &Null (Stored); }
	static Stored create (Data data)
	{
	Stored p = (Stored ) hb_calloc (1, sizeof (Stored));
	if (likely (p))
	p = new (p) Stored (data);
	return p;
	}
	static Stored *create ()
	{
	Stored p = (Stored ) hb_calloc (1, sizeof (Stored));
	if (likely (p))
	p = new (p) Stored ();
	return p;
	}
	static void destroy (Stored *p)
	{
	p->~Stored ();
	hb_free (p);
	}

	private:
	/* Must only have one pointer. */
	hb_atomic_ptr_t<Stored *> instance;
	};

	/* Specializations. */

	template <typename T, unsigned int WheresFace>
	struct hb_face_lazy_loader_t : hb_lazy_loader_t<T,
	hb_face_lazy_loader_t<T, WheresFace>,
	hb_face_t, WheresFace>
	{
	// Hack; have them here for API parity with hb_table_lazy_loader_t
	hb_blob_t *get_blob () { return this->get ()->get_blob (); }
	};

	template <typename T, unsigned int WheresFace, bool core=false>
	struct hb_table_lazy_loader_t : hb_lazy_loader_t<T,
	hb_table_lazy_loader_t<T, WheresFace, core>,
	hb_face_t, WheresFace,
	hb_blob_t>
	{
	static hb_blob_t create (hb_face_t face)
	{
	hb_sanitize_context_t c;
	if (core)
	c.set_num_glyphs (0); // So we don't recurse ad infinitum, or doesn't need num_glyphs
	return c.reference_table<T> (face);
	}
	static void destroy (hb_blob_t *p) { hb_blob_destroy (p); }

	static const hb_blob_t *get_null ()
	{ return hb_blob_get_empty (); }

	static const T* convert (const hb_blob_t *blob)
	{ return blob->as<T> (); }

	hb_blob_t* get_blob () const { return this->get_stored (); }
	};

	#define HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T(Type) \
	template <typename Subclass> \
	struct hb_##Type##_funcs_lazy_loader_t : hb_lazy_loader_t<hb_##Type##_funcs_t, Subclass> \
	{ \
	static void destroy (hb_##Type##_funcs_t *p) \
	{ hb_##Type##_funcs_destroy (p); } \
	static const hb_##Type##_funcs_t *get_null () \
	{ return hb_##Type##_funcs_get_empty (); } \
	}

	HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (font);
	HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (unicode);
	HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (draw);
	HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (paint);

	#undef HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T


	#endif /* HB_MACHINERY_HH */