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tptr: add pointer tagging templates ()

This commit is contained in:
Jakob Rath 2023-12-19 17:58:32 +01:00 committed by GitHub
parent fcc7b25c19
commit 4c9f705cd1
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@ -21,6 +21,7 @@ Revision History:
#include <cstdint>
#include "util/machine.h"
#include "util/debug.h"
#define TAG_SHIFT PTR_ALIGNMENT
#define ALIGNMENT_VALUE (1 << PTR_ALIGNMENT)
@ -42,4 +43,22 @@ Revision History:
#define UNBOXINT(PTR) static_cast<int>(reinterpret_cast<uintptr_t>(PTR) >> PTR_ALIGNMENT)
template <typename U, typename T>
U unbox(T* ptr) {
return static_cast<U>(reinterpret_cast<std::uintptr_t>(ptr) >> PTR_ALIGNMENT);
}
template <typename T>
unsigned get_tag(T* ptr) {
return reinterpret_cast<std::uintptr_t>(ptr) & TAG_MASK;
}
template <typename T, typename U>
T* box(U val, std::uintptr_t tag = 0) {
static_assert( sizeof(T*) >= sizeof(U) + PTR_ALIGNMENT );
SASSERT_EQ(tag & PTR_MASK, 0);
T* ptr = reinterpret_cast<T*>((static_cast<std::uintptr_t>(val) << PTR_ALIGNMENT) | tag);
SASSERT_EQ(val, unbox<U>(ptr)); // roundtrip of conversion integer -> pointer -> integer is not actually guaranteed by the C++ standard (but seems fine in practice, as indicated by previous usage of BOXINT/UNBOXINT)
SASSERT_EQ(tag, get_tag(ptr));
return ptr;
}