I was trying to help @joshkalderimis b/c an apparent bug running guillotine on jruby
https://github.com/technoweenie/guillotine/blob/master/lib/guillotine.rb#L46-48
The hexdigest to_i(16) was returning a bignum, and packing a bignum on unsigned integers did not looked that cool...
Then I started to dig through MRI's code
https://github.com/ruby/ruby/blob/trunk/pack.c#L240-251