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rebolek/base32.red

Created Aug 16, 2017
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Base 32 encoder and decoder
Red [
file: %base32.red
date: 17-Sep-2015
author: "Graham Chiu"
red-version: "Boleslav Březovský"
version: 0.0.3
notes: {
encodes string to base32 or base32hex
padding to 5 characters is not required in this method
>> to-base32/decode/hex to-base32/hex "yessir"
== "yessir"
}
]
to-base32: function [
st [string!]
/hex {output base32hex}
/decode {returns decoded base32/hex string}
][
accepted: either hex
["0123456789abcdefghijklmnopqrstuv"]; base32hex
["abcdefghijklmnopqrstuvwxyz234567"]; base32
base2: [16 8 4 2 1]
rejoin either not decode [
; turn st, to be encoded, into a "binary" string
b2: enbase/base st 2
; convert each block of 5 into a char from the accepted list
collect [
while [not empty? b2][
five: take/part b2 5
; convert this "binary" into decimal, and look at blocks of 5 eg. "01111"
offset: 0
repeat i 5 [
if #"1" = take five [
offset: offset + base2/:i
]
]
keep pick accepted offset + 1
]
]
][
; find each character in the string, and form a 5 bit binary representation
str: copy st ; so as not to affect the original
result: rejoin collect [
while [not empty? st][
keep rejoin collect [
index: -1 + index? find accepted form take st
repeat i 5 [
keep either positive? index AND base2/:i ["1"]["0"]
]
]
]
]
; we now have a very long string of "binary". We need to take it in blocks of 8 and convert back to characters
collect [
while [not empty? result][
attempt [
keep to-char debase/base take/part result 8 2
]
]
]
]
]
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