From: "Martin Boßlet" <martin.bosslet@...>
Date: 2012-03-17T02:26:34+09:00
Subject: Re: Converting Bignum into bytes

> I'm trying to convert a variable size BigNum into a variable length byte
> representation and I don't know if there exists a direct way. I'm thinking
> of Array#pack and String#unpack.
>
> Something similar to, for ex:
> big = 111111111111111111111111111111111111111
> bytes = [big].pack("l*")
> and then
> big = bytes.unpack("l*")
>

#pack and #unpack won't work for Bignums, but you can operate on their
hex representations for example. The following should do it:

big = 111111111111111111111111111111111111111

bytes = big.to_s(16).unpack('H*')[0]
big2 = [bytes].pack('H*').to_i(16)
puts big == big2 # => true

Regards,
Martin