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Base64 decode data: Difference between revisions
→{{header|Tcl}}: +standard ML
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</pre>
=={{header|Standard ML}}==
<lang Standard ML>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" ;</lang>
call
<pre>
val input = "VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLSBQYXVsIFIuIEVocmxpY2g=";
print (debase64 input) ;
To err is human, but to really foul things up you need a computer.
-- Paul R. Ehrlich </pre>
=={{header|Tcl}}==
<lang tcl>package require tcl 8.6
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