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Use Type::null_size for our structs in Null(), sizeof() for other types

This commit is contained in:
Behdad Esfahbod 2018-11-22 01:10:22 -05:00
parent 7dd945a876
commit f2b91d6510
1 changed files with 15 additions and 2 deletions
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17
src/hb-null.hh
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@ -38,13 +38,26 @@
#define HB_NULL_POOL_SIZE 1024
/* Use SFINAE to sniff whether T has min_size; in which case return T::null_size,
* otherwise return sizeof(T). */
template <typename T, bool b>
struct _hb_null_size
{ enum { value = sizeof (T) }; };
template <typename T>
struct _hb_null_size<T, T::min_size ? false : false>
{ enum { value = T::null_size }; };
template <typename T>
struct hb_null_size
{ enum { value = _hb_null_size<T, false>::value }; };
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.");
static_assert (hb_null_size<Type>::value <= HB_NULL_POOL_SIZE, "Increase HB_NULL_POOL_SIZE.");
return *reinterpret_cast<Type const *> (_hb_NullPool);
}
#define Null(Type) Null<typename hb_remove_const<typename hb_remove_reference<Type>::value>::value>()
@ -85,7 +98,7 @@ extern HB_INTERNAL
/* 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.");
static_assert (hb_null_size<Type>::value <= HB_NULL_POOL_SIZE, "Increase HB_NULL_POOL_SIZE.");
Type *obj = reinterpret_cast<Type *> (_hb_CrapPool);
memcpy (obj, &Null(Type), sizeof (*obj));
return *obj;