Data commit

Task/Base64-decode-data/Standard-ML/base64-decode-data.ml

@@ -0,0 +1,31 @@
+val debase64 = fn input =>
+let
+
+ infix 2 Worb
+ infix 2 Wandb
+ fun (p Worb q )  =  Word.orb  (p,q);
+ fun (p Wandb q ) =  Word.andb (p,q);
+
+fun decode #"/" =  0wx3F
+  | decode #"+" =  0wx3E
+  | decode c    =  if Char.isDigit c then Word.fromInt (ord c) +  0wx04
+              else if Char.isLower c then Word.fromInt (ord c) - 0wx047
+              else if Char.isUpper c then Word.fromInt (ord c) - 0wx041
+              else 0wx00 ;
+
+fun convert (a::b::c::d::_) =
+         let
+            val w = Word.<< (a,0wx12) Worb Word.<< (b,0wx0c) Worb Word.<< (c,0wx06) Worb d
+         in
+            [Word.>> (w,0wx10), Word.>> ((w Wandb 0wx00ff00),0wx08) , w Wandb 0wx0000ff ]
+         end
+  | convert _ = [] ;
+
+fun decodeLst []    = []
+  | decodeLst ilist = ( convert o  map decode )( List.take (ilist,4) ) @  decodeLst (List.drop (ilist,4))
+
+in
+
+  String.implode ( List.map (chr o Word.toInt) ( decodeLst (String.explode input ))  )
+
+end                                                                 handle Subscript  => "Invalid code\n" ;