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(*
* Copyright (C) 2006-2009 Citrix Systems Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published
* by the Free Software Foundation; version 2.1 only. with the special
* exception on linking described in file LICENSE.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*)
open Stringext
let code = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
let padding = '='
let of_char x = if x = padding then 0 else String.index code x
let to_char x = code.[x]
let strip_whitespace s =
String.implode (List.filter (fun x->not (List.mem x [' ';'\t';'\n';'\r'])) (String.explode s))
let decode x =
let x = strip_whitespace x in
let words = String.length x / 4 in
let padding =
if String.length x = 0 then 0 else (
if x.[String.length x - 2] = padding
then 2 else (if x.[String.length x - 1] = padding then 1 else 0)) in
let output = String.make (words * 3 - padding) '\000' in
for i = 0 to words - 1 do
let a = of_char x.[4 * i + 0]
and b = of_char x.[4 * i + 1]
and c = of_char x.[4 * i + 2]
and d = of_char x.[4 * i + 3] in
let n = (a lsl 18) lor (b lsl 12) lor (c lsl 6) lor d in
let x = (n lsr 16) land 255
and y = (n lsr 8) land 255
and z = n land 255 in
output.[3 * i + 0] <- char_of_int x;
if i <> words - 1 || padding < 2 then output.[3 * i + 1] <- char_of_int y;
if i <> words - 1 || padding < 1 then output.[3 * i + 2] <- char_of_int z;
done;
output
let encode x =
let length = String.length x in
let words = (length + 2) / 3 in (* rounded up *)
let padding = if length mod 3 = 0 then 0 else 3 - (length mod 3) in
let output = String.make (words * 4) '\000' in
let get i = if i >= length then 0 else int_of_char x.[i] in
for i = 0 to words - 1 do
let x = get (3 * i + 0)
and y = get (3 * i + 1)
and z = get (3 * i + 2) in
let n = (x lsl 16) lor (y lsl 8) lor z in
let a = (n lsr 18) land 63
and b = (n lsr 12) land 63
and c = (n lsr 6) land 63
and d = n land 63 in
output.[4 * i + 0] <- to_char a;
output.[4 * i + 1] <- to_char b;
output.[4 * i + 2] <- to_char c;
output.[4 * i + 3] <- to_char d;
done;
for i = 1 to padding do
output.[String.length output - i] <- '=';
done;
output
let test x =
let x' = encode x in
let x'' = decode x' in
if x <> x''
then failwith (Printf.sprintf "Original: '%s'; encoded = '%s'; decoded = '%s'" x x' x'')
let tests = [ "hello";
"this is a basic test"; "1"; "22"; "333"; "4444"; "5555";
"\000"; "\000\000"; "\000\000\000"; "\000\000\000\000" ]
(*
let _ = List.iter test tests
*)
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