From: Nobuyoshi Nakada <nobu@...>
Date: 2009-05-08T09:25:05+09:00
Subject: Re: base32hex (rfc 4648)

Hi,

At Thu, 7 May 2009 22:15:57 +0900,
Alex Dd wrote in [ruby-talk:336035]:
> Does anyone know if there is existing Ruby code which implements
> base32hex encoding (defined in RFC 4648)? I couldn't find one with
> google...

module Base32
  module_function
  def encode32hex(str)
    str.gsub(/\G(.{5})|(.{1,4}\z)/mn) do
      full = $1; frag = $2
      n, c = (full || frag.ljust(5, "\0")).unpack("NC")
      full = ((n << 8) | c).to_s(32).rjust(8, "0")
      if frag
        full[0, (frag.length*8+4).div(5)].ljust(8, "=")
      else
        full
      end
    end
  end

  HEX = '[0-9a-v]'
  def decode32hex(str)
    str.gsub(/\G\s*(#{HEX}{8}|#{HEX}{7}=|#{HEX}{5}={3}|#{HEX}{4}={4}|#{HEX}{2}={6}|(\S))/imno) do
      raise "invalid base32" if $2
      s = $1
      s.tr("=", "0").to_i(32).divmod(256).pack("NC")[0, (s.count("^=")*5).div(8)]
    end
  end
end

-- 
Nobu Nakada