typedef struct block_s {
	struct block_s *next; /* next block in the hash chain */
	unsigned short refs;  /* reference count    */
	unsigned short size;  /* length of the string plus sizeof of struct + 1 */
} block_t;

#define NEXT(x) (x)->next
#define REFS(x) (x)->refs
#define SIZE(x) (x)->size
#define BLOCK(x) (((block_t *)(x)) - 1) /* pointer arithmetic */
#define STRING(x) ((char *)(x + 1))

#define SVALUE_STRLEN(x) (((x)->subtype == STRING_SHARED) ? \
   (SIZE(BLOCK((x)->u.string)) - sizeof(block_t) - 1) : strlen((x)->u.string))