 : base64> ( base64 -- str )
     #! input length must be a multiple of 4
     [ 4 <groups> [ decode4 ] map concat ]
-    [ [ CHAR: = = not ] count-end ]
+    [ [ CHAR: = = ] count-end ]
     bi head* ;

! Copyright (C) 2008 Doug Coleman.
! See http://factorcode.org/license.txt for BSD license.
USING: kernel math sequences io.binary splitting grouping ;
IN: base64

<PRIVATE

: count-end ( seq quot -- count )
    >r [ length ] keep r> find-last drop dup [ - 1- ] [ 2drop 0 ] if ; inline

: ch>base64 ( ch -- ch )
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" nth ;

    } nth ;

: encode3 ( seq -- seq )
    be> 4 <reversed> [
        -6 * shift HEX: 3f bitand ch>base64
    ] with B{ } map-as ;

: decode4 ( str -- str )
    0 [ base64>ch swap 6 shift bitor ] reduce 3 >be ;

: >base64-rem ( str -- str )
    [ 3 0 pad-right encode3 ] [ length 1+ ] bi
    head-slice 4 CHAR: = pad-right ;

PRIVATE>

