From: Sung Pae <sungpae@...>
Date: 2012-08-01T10:44:34+09:00
Subject: Re: working with large binary strings?

bob hope <lists@ruby-forum.com> writes:

> I need to work with multiple large binary strings, and to do XOR
> operations on their 'rows'. This is all fine, but I am having a slow
> time to get binary representation in this fashion:
> 
> a = SecureRandom.random_bytes(250_000).unpack("B*")[0].to_i.to_s(2)

You are asking ruby to convert a string into a _number_ 250,000 places
wide, then asking to convert this very large base-10 number into a
string using radix 2.

> I know there must be a quick way to do it, because a =
> SecureRandom.random_bytes(250_000) is very fast, so I don't know why
> it would be slow to convert that into a bit string of 1's and 0's

SecureRandom.random_bytes(250_000).unpack("B*") returns a random string
of 1's and 0's

> that will allow me to manipulate it on a bit by bit basis. Is there a
> faster way to do this? Generating that string takes about one second,
> but then getting its binary form as 1's and 0's takes a few minutes.

If you need fast bitwise operations, why are you using strings?

guns