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/*++
Copyright (c) 2006 Microsoft Corporation

Module Name:

    tptr.h

Abstract:

    Support for tagged pointers and other low level pointer manipulation macros.

Author:

    Leonardo de Moura (leonardo) 2006-09-13.

Revision History:

--*/

#pragma once

#include 
#include "util/machine.h"
#include "util/debug.h"

#define TAG_SHIFT        PTR_ALIGNMENT
#define ALIGNMENT_VALUE  (1 << PTR_ALIGNMENT)
#define TAG_MASK         (ALIGNMENT_VALUE - 1)
#define PTR_MASK         (~TAG_MASK)  

#define ALIGN(T, PTR) reinterpret_cast(((reinterpret_cast(PTR) >> PTR_ALIGNMENT) + \
                         static_cast((reinterpret_cast(PTR) & TAG_MASK) != 0)) << PTR_ALIGNMENT)

#define UNTAG(T, PTR) reinterpret_cast(reinterpret_cast(PTR) & PTR_MASK)

#define TAG(T, PTR, TAG_VAL) reinterpret_cast(reinterpret_cast(PTR) | static_cast(TAG_VAL))

#define GET_TAG(PTR) (reinterpret_cast(PTR) & TAG_MASK)

#define BOXINT(T, VAL) reinterpret_cast(static_cast(VAL) << PTR_ALIGNMENT)

#define BOXTAGINT(T, VAL, TAG_VAL) reinterpret_cast((static_cast(VAL) << PTR_ALIGNMENT) | static_cast(TAG_VAL))

#define UNBOXINT(PTR) static_cast(reinterpret_cast(PTR) >> PTR_ALIGNMENT)

template 
U unbox(T* ptr) {
    return static_cast(reinterpret_cast(ptr) >> PTR_ALIGNMENT);
}

template 
unsigned get_tag(T* ptr) {
    return reinterpret_cast(ptr) & TAG_MASK;
}

template 
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((static_cast(val) << PTR_ALIGNMENT) | tag);
    SASSERT_EQ(val, unbox(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;
}