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/*
* 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"
/*
* Static pools
*/
/* Global nul-content Null pool. Enlarge as necessary. */
#define HB_NULL_POOL_SIZE 1024
extern HB_INTERNAL
hb_vector_size_impl_t const _hb_NullPool[(HB_NULL_POOL_SIZE + sizeof (hb_vector_size_impl_t) - 1) / sizeof (hb_vector_size_impl_t)];
/* Generic nul-content Null objects. */
template <typename Type>
static inline Type const & Null (void) {
static_assert (sizeof (Type) <= HB_NULL_POOL_SIZE, "Increase HB_NULL_POOL_SIZE.");
return *reinterpret_cast<Type const *> (_hb_NullPool);
}
#define Null(Type) Null<Type>()
/* 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[Namespace::Type::min_size]; \
template <> \
/*static*/ inline const Namespace::Type& Null<Namespace::Type> (void) { \
return *reinterpret_cast<const Namespace::Type *> (_hb_Null_##Namespace##_##Type); \
} \
namespace Namespace { \
static_assert (true, "Just so we take semicolon after.")
#define DEFINE_NULL_NAMESPACE_BYTES(Namespace, Type) \
const unsigned char _hb_Null_##Namespace##_##Type[Namespace::Type::min_size]
/* Specializations for arbitrary-content Null objects expressed as struct initializer. */
#define DECLARE_NULL_INSTANCE(Type) \
extern HB_INTERNAL const Type _hb_Null_##Type; \
template <> \
/*static*/ inline const Type& Null<Type> (void) { \
return _hb_Null_##Type; \
} \
static_assert (true, "Just so we take 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*/ hb_vector_size_impl_t _hb_CrapPool[(HB_NULL_POOL_SIZE + sizeof (hb_vector_size_impl_t) - 1) / sizeof (hb_vector_size_impl_t)];
/* CRAP pool: Common Region for Access Protection. */
template <typename Type>
static inline Type& Crap (void) {
static_assert (sizeof (Type) <= HB_NULL_POOL_SIZE, "Increase HB_NULL_POOL_SIZE.");
Type *obj = reinterpret_cast<Type *> (_hb_CrapPool);
*obj = Null(Type);
return *obj;
}
#define Crap(Type) Crap<Type>()
template <typename Type>
struct CrapOrNull {
static inline Type & get (void) { return Crap(Type); }
};
template <typename Type>
struct CrapOrNull<const Type> {
static inline Type const & get (void) { return Null(Type); }
};
#define CrapOrNull(Type) CrapOrNull<Type>::get ()
#endif /* HB_NULL_HH */
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