: _ilen ( length of str in IBUF )
    IBUF BEGIN C@+ EOL? UNTIL IBUF - 1- ;
: _I
    IBUF _type EDPOS @ 64 MOD ( cno )
    63 -^ _ilen ( rbuffsize ilen )
    2DUP > IF
        SWAP OVER - ( ilen chars-to-move )
        SWAP EDPOS @ _cpos 2DUP + ( ctm ilen a a+ilen )
        3 PICK MOVE- ( ctm ilen )
        SWAP DROP ( ilen )
    ELSE DROP ( ilen becomes rbuffsize )
    THEN
    DUP IBUF EDPOS @ _cpos ROT MOVE ( ilen )
    EDPOS +! EDPOS @ 64 / _pln
;