#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
#define pg_attribute_aligned(a) __attribute__((aligned(a)))
#define pg_attribute_packed() __attribute__((packed))
#endif

typedef unsigned short uint16;
typedef uint16 OffsetNumber;

typedef struct BlockIdData
{
	uint16		bi_hi;
	uint16		bi_lo;
} BlockIdData;


typedef struct ItemPointerData
{
	BlockIdData ip_blkid;
	OffsetNumber ip_posid;
}
/* If compiler understands packed and aligned pragmas, use those */
#if defined(pg_attribute_packed) && defined(pg_attribute_aligned)
pg_attribute_packed()
pg_attribute_aligned(2)
#endif
ItemPointerData;

typedef ItemPointerData *ItemPointer;



/*
 * BlockIdGetBlockNumber
 *		Retrieve the block number from a block identifier.
 */
#define BlockIdGetBlockNumber(blockId) \
( \
	(BlockNumber) (((blockId)->bi_hi << 16) | ((uint16) (blockId)->bi_lo)) \
)


/*
 * ItemPointerGetBlockNumber
 *		Returns the block number of a disk item pointer.
 */
#define ItemPointerGetBlockNumber(pointer) \
( \
	BlockIdGetBlockNumber(&(pointer)->ip_blkid) \
)

int main() {
	ItemPointerData ip;

	return ItemPointerGetBlockNumber(&ip);
}