rel_ptr.h

#ifndef REL_PTR_H
#define REL_PTR_H

#include <atomic>
#include <exception>
#include <libpmemobj.h>
#include <stdint.h>

using namespace std;
/* relative pointer */
template<typename T>
class rel_ptr
{
#ifdef BZ_DEBUG
public:
#endif // BZ_DEBUG

	/* base address initialized in the start */
  static unsigned char *base_address;
  static PMEMoid base_oid;
  /* offset from the base address */
  uint64_t off;
public:
	/* constructors */
	rel_ptr() : off(0) {}
        rel_ptr(const T *abs_ptr)
            : off((unsigned char *)abs_ptr - base_address) {}
        explicit rel_ptr(uint64_t rel_addr) : off(rel_addr) {}
        template <typename U>
        rel_ptr(rel_ptr<U> rptr)
            : off((unsigned char *)rptr.abs() - base_address) {}
        rel_ptr(PMEMoid oid)
            : off((unsigned char *)pmemobj_direct(oid) - base_address) {}

        /* return coresponding PMEMoid */
	PMEMoid oid() { return { base_oid.pool_uuid_lo, base_oid.off + off }; }

	/* basic pointer usage */
	T& operator *() {
		if (!off)
                  throw "NULL_PTR_ERROR";
                return *(T*)(base_address + off);
	}
	T* operator ->() {
		if (!off)
                  throw "NULL_PTR_ERROR";
                return (T*)(base_address + off); 
	}

	/* return absolute or relative address */
        uint64_t *abs() { return (uint64_t *)(base_address + off); }
        uint64_t rel() { return off; }

	/* comparison */
	bool operator ==(const rel_ptr<T>& rptr) { return off == rptr.off; }
	bool operator <(const rel_ptr<T>& rptr) { return off < rptr.off; }
	bool operator >(const rel_ptr<T>& rptr) { return off > rptr.off; }
	bool operator !=(const rel_ptr<T> & rptr) { return off != rptr.off; }

	bool is_null() { return !off; }
	void set_null() { off = 0; }
        static void set_base(PMEMoid o) {
          base_oid = o;
          base_address = (unsigned char *)pmemobj_direct(o);
        }
        static rel_ptr<T> null() { return rel_ptr<T>(); }
};

template <typename T> unsigned char *rel_ptr<T>::base_address(nullptr);
template<typename T>
PMEMoid rel_ptr<T>::base_oid(OID_NULL);

#endif // !REL_PTR_H