/* * 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 … template <typename T, typename> struct _hb_has_min_size : hb_false_type { … }; _hb_has_min_size<T, hb_void_t<decltype(T::min_size)>>; hb_has_min_size; #define hb_has_min_size(T) … template <typename T, typename> struct _hb_has_null_size : hb_false_type { … }; _hb_has_null_size<T, hb_void_t<decltype(T::null_size)>>; hb_has_null_size; #define hb_has_null_size(T) … /* 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)> { … }; _hb_null_size<T, hb_void_t<decltype(T::min_size)>>; hb_null_size; #define hb_null_size(T) … /* 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)> { … }; _hb_static_size<T, hb_void_t<decltype(T::static_size)>>; hb_static_size; #define hb_static_size(T) … template <typename T, typename> struct _hb_min_size : hb_integral_constant<unsigned, sizeof (T)> { … }; _hb_min_size<T, hb_void_t<decltype(T::min_size)>>; hb_min_size; #define hb_min_size(T) … /* * 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 { … }; template <typename QType> struct NullHelper { … }; #define Null(Type) … /* Specializations for arbitrary-content Null objects expressed in bytes. */ #define DECLARE_NULL_NAMESPACE_BYTES(Namespace, Type) … #define DECLARE_NULL_NAMESPACE_BYTES_TEMPLATE1(Namespace, Type, Size) … #define DEFINE_NULL_NAMESPACE_BYTES(Namespace, Type) … /* Specializations for arbitrary-content Null objects expressed as struct initializer. */ #define DECLARE_NULL_INSTANCE(Type) … #define DEFINE_NULL_INSTANCE(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 () { … } template <typename QType> struct CrapHelper { … }; #define Crap(Type) … template <typename Type> struct CrapOrNullHelper { … }; CrapOrNullHelper<const Type>; #define CrapOrNull(Type) … /* * hb_nonnull_ptr_t */ template <typename P> struct hb_nonnull_ptr_t { … }; #endif /* HB_NULL_HH */
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