From: matz@... (Yukihiro Matsumoto)
Date: 2002-06-12T01:49:54+09:00
Subject: Re: pack()ing Bignums

Hi,

In message "pack()ing Bignums"
    on 02/06/12, Dan Debertin <airboss@nodewarrior.org> writes:

|I have a 128-bit Bignum that I need to pack into a binary string in
|order to pass it to MD5.digest(). But there doesn't appear to be a
|format for Array#pack that would accommodate such a large number; the
|biggest appears to be "L", which is only a quarter the size I need.
|
|What's the best way to do this?

Perhaps not as efficient as you expect:

a)

  b = 128-bit bignum value
  data = []
  4.times{|i|
    data.unshift (b>>i*32)&0xffffffff
  }
  data.pack("NNNN")

b)

  [sprintf("%0128b", b)].pack("B*")

							matz.