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Diffstat (limited to 'gfx/harfbuzz/src/hb-null.hh')
| -rw-r--r-- | gfx/harfbuzz/src/hb-null.hh | 226 |
1 files changed, 226 insertions, 0 deletions
diff --git a/gfx/harfbuzz/src/hb-null.hh b/gfx/harfbuzz/src/hb-null.hh new file mode 100644 index 0000000000..3da2d75ef5 --- /dev/null +++ b/gfx/harfbuzz/src/hb-null.hh @@ -0,0 +1,226 @@ +/* + * Copyright © 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. + * + * Google Author(s): Behdad Esfahbod + */ + +#ifndef HB_NULL_HH +#define HB_NULL_HH + +#include "hb.hh" +#include "hb-meta.hh" + + +/* + * Static pools + */ + +/* Global nul-content Null pool. Enlarge as necessary. */ + +#define HB_NULL_POOL_SIZE 520 + +template <typename T, typename> +struct _hb_has_min_size : hb_false_type {}; +template <typename T> +struct _hb_has_min_size<T, hb_void_t<decltype (T::min_size)>> + : hb_true_type {}; +template <typename T> +using hb_has_min_size = _hb_has_min_size<T, void>; +#define hb_has_min_size(T) hb_has_min_size<T>::value + +template <typename T, typename> +struct _hb_has_null_size : hb_false_type {}; +template <typename T> +struct _hb_has_null_size<T, hb_void_t<decltype (T::null_size)>> + : hb_true_type {}; +template <typename T> +using hb_has_null_size = _hb_has_null_size<T, void>; +#define hb_has_null_size(T) hb_has_null_size<T>::value + +/* Use SFINAE to sniff whether T has min_size; in which case return the larger + * of sizeof(T) and T::null_size, otherwise return sizeof(T). + * + * The main purpose of this is to let structs communicate that they are not nullable, + * by defining min_size but *not* null_size. */ + +/* The hard way... + * https://stackoverflow.com/questions/7776448/sfinae-tried-with-bool-gives-compiler-error-template-argument-tvalue-invol + */ + +template <typename T, typename> +struct _hb_null_size : hb_integral_constant<unsigned, sizeof (T)> {}; +template <typename T> +struct _hb_null_size<T, hb_void_t<decltype (T::min_size)>> + : hb_integral_constant<unsigned, + (sizeof (T) > T::null_size ? sizeof (T) : T::null_size)> {}; +template <typename T> +using hb_null_size = _hb_null_size<T, void>; +#define hb_null_size(T) hb_null_size<T>::value + +/* These doesn't belong here, but since is copy/paste from above, put it here. */ + +/* hb_static_size (T) + * Returns T::static_size if T::min_size is defined, or sizeof (T) otherwise. */ + +template <typename T, typename> +struct _hb_static_size : hb_integral_constant<unsigned, sizeof (T)> {}; +template <typename T> +struct _hb_static_size<T, hb_void_t<decltype (T::min_size)>> : hb_integral_constant<unsigned, T::static_size> {}; +template <typename T> +using hb_static_size = _hb_static_size<T, void>; +#define hb_static_size(T) hb_static_size<T>::value + +template <typename T, typename> +struct _hb_min_size : hb_integral_constant<unsigned, sizeof (T)> {}; +template <typename T> +struct _hb_min_size<T, hb_void_t<decltype (T::min_size)>> : hb_integral_constant<unsigned, T::min_size> {}; +template <typename T> +using hb_min_size = _hb_min_size<T, void>; +#define hb_min_size(T) hb_min_size<T>::value + + +/* + * Null() + */ + +extern HB_INTERNAL +uint64_t const _hb_NullPool[(HB_NULL_POOL_SIZE + sizeof (uint64_t) - 1) / sizeof (uint64_t)]; + +/* Generic nul-content Null objects. */ +template <typename Type> +struct Null { + static Type const & get_null () + { + static_assert (hb_null_size (Type) <= HB_NULL_POOL_SIZE, "Increase HB_NULL_POOL_SIZE."); + return *reinterpret_cast<Type const *> (_hb_NullPool); + } +}; +template <typename QType> +struct NullHelper +{ + typedef hb_remove_const<hb_remove_reference<QType>> Type; + static const Type & get_null () { return Null<Type>::get_null (); } +}; +#define Null(Type) NullHelper<Type>::get_null () + +/* Specializations for arbitrary-content Null objects expressed in bytes. */ +#define DECLARE_NULL_NAMESPACE_BYTES(Namespace, Type) \ + } /* Close namespace. */ \ + extern HB_INTERNAL const unsigned char _hb_Null_##Namespace##_##Type[hb_null_size (Namespace::Type)]; \ + template <> \ + struct Null<Namespace::Type> { \ + static Namespace::Type const & get_null () { \ + return *reinterpret_cast<const Namespace::Type *> (_hb_Null_##Namespace##_##Type); \ + } \ + }; \ + namespace Namespace { \ + static_assert (true, "") /* Require semicolon after. */ +#define DECLARE_NULL_NAMESPACE_BYTES_TEMPLATE1(Namespace, Type, Size) \ + } /* Close namespace. */ \ + extern HB_INTERNAL const unsigned char _hb_Null_##Namespace##_##Type[Size]; \ + template <typename Spec> \ + struct Null<Namespace::Type<Spec>> { \ + static Namespace::Type<Spec> const & get_null () { \ + return *reinterpret_cast<const Namespace::Type<Spec> *> (_hb_Null_##Namespace##_##Type); \ + } \ + }; \ + namespace Namespace { \ + static_assert (true, "") /* Require semicolon after. */ +#define DEFINE_NULL_NAMESPACE_BYTES(Namespace, Type) \ + const unsigned char _hb_Null_##Namespace##_##Type[sizeof (_hb_Null_##Namespace##_##Type)] + +/* Specializations for arbitrary-content Null objects expressed as struct initializer. */ +#define DECLARE_NULL_INSTANCE(Type) \ + extern HB_INTERNAL const Type _hb_Null_##Type; \ + template <> \ + struct Null<Type> { \ + static Type const & get_null () { \ + return _hb_Null_##Type; \ + } \ + }; \ + static_assert (true, "") /* Require semicolon after. */ +#define DEFINE_NULL_INSTANCE(Type) \ + const Type _hb_Null_##Type + +/* Global writable pool. Enlarge as necessary. */ + +/* To be fully correct, CrapPool must be thread_local. However, we do not rely on CrapPool + * for correct operation. It only exist to catch and divert program logic bugs instead of + * causing bad memory access. So, races there are not actually introducing incorrectness + * in the code. Has ~12kb binary size overhead to have it, also clang build fails with it. */ +extern HB_INTERNAL +/*thread_local*/ uint64_t _hb_CrapPool[(HB_NULL_POOL_SIZE + sizeof (uint64_t) - 1) / sizeof (uint64_t)]; + +/* CRAP pool: Common Region for Access Protection. */ +template <typename Type> +static inline Type& Crap () { + static_assert (hb_null_size (Type) <= HB_NULL_POOL_SIZE, "Increase HB_NULL_POOL_SIZE."); + Type *obj = reinterpret_cast<Type *> (_hb_CrapPool); + memcpy (obj, &Null (Type), sizeof (*obj)); + return *obj; +} +template <typename QType> +struct CrapHelper +{ + typedef hb_remove_const<hb_remove_reference<QType>> Type; + static Type & get_crap () { return Crap<Type> (); } +}; +#define Crap(Type) CrapHelper<Type>::get_crap () + +template <typename Type> +struct CrapOrNullHelper { + static Type & get () { return Crap (Type); } +}; +template <typename Type> +struct CrapOrNullHelper<const Type> { + static const Type & get () { return Null (Type); } +}; +#define CrapOrNull(Type) CrapOrNullHelper<Type>::get () + + +/* + * hb_nonnull_ptr_t + */ + +template <typename P> +struct hb_nonnull_ptr_t +{ + typedef hb_remove_pointer<P> T; + + hb_nonnull_ptr_t (T *v_ = nullptr) : v (v_) {} + T * operator = (T *v_) { return v = v_; } + T * operator -> () const { return get (); } + T & operator * () const { return *get (); } + T ** operator & () const { return &v; } + /* Only auto-cast to const types. */ + template <typename C> operator const C * () const { return get (); } + operator const char * () const { return (const char *) get (); } + T * get () const { return v ? v : const_cast<T *> (&Null (T)); } + T * get_raw () const { return v; } + + private: + T *v; +}; + + +#endif /* HB_NULL_HH */ |