Esteban A. Maringolo wrote
> Hi Richard,
>
> Certainly a BitStream is beyond what I initially thought.
>
> But it could be of some use to play with it, is it available somewhere
> with a friendly open source license?
>
> I might give it a try using it for my generator (tests are already
> passing). Your example is almost complete, but if I understand it
> you're adding the size of the checksum instead of the checksum itself.
> Nonetheless I think its readability is superior, and I guess that it
> is better perfomance and memorywise.
>
> Also it could be useful for Base58Encoder I'm expermenting with.
> Encoding is "simple" but requires the use of a really large integer,
> I'm stuck at the decoding part now.
> After that there is a Base32 encoder (to implement a Bech32 encoder as
> well).
>
> So I might use it in my road of experimentation with these matters.
> Unless I diverge from this and abandon it as it normally happens. :/
BaseX encode/decode can be simple enough to fit in a small workspace:
base := 58.
base58Lookup :=
'123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'.
myNumber := 12345678901234567890.
decode := [ :string | |decodedNumber|
decodedNumber := 0.
string do: [ :char | decodedNumber := decodedNumber * base
+(base58Lookup
indexOf: char) - 1 ].
decodedNumber ].
encode := [ :number | |encodedString numDigits toEncode|
numDigits := (number numberOfDigitsInBase: base).
toEncode := number.
encodedString := String new: numDigits.
0 to: numDigits - 1 do: [ :i | |lutIndex|
encodedString at: numDigits - i put: (base58Lookup at: toEncode
\\ base +
1).
toEncode := toEncode // base. ].
encodedString ].
myString := encode value: myNumber.
(decode value: myString) = myNumber.
The appeal of Base64 is it transforms the // and \\ operations into simple
shifts / masks.
Cheers,
Henry
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