LOFFSET
memcpy(cp->page, lp, LOFFSET(lp));
sp->bt_int_pgfree += HOFFSET(h) - LOFFSET(h);
sp->bt_leaf_pgfree += HOFFSET(h) - LOFFSET(h);
sp->bt_leaf_pgfree += HOFFSET(h) - LOFFSET(h);
memcpy(h, tp, LOFFSET(tp));
#define P_FREESPACE(pg) (HOFFSET(pg) - LOFFSET(pg))