Calculate leading zero bits for string

pow.rb

#!/usr/bin/env ruby

def hex_to_bytes(s)
  s.scan(/.{1,2}/).map{|b| b.to_i(16)}
end

def zero_bits(b)
    n = 0

    if b == 0
      return 8
    end

    while true do
        b >>= 1

        if b != 0
          n += 1
        else
          break
        end
    end

    return 7 - n;
end

def count_leading_zero_bits(hash)
  total = 0

  for i in 0...32 do
    bits = zero_bits(hash[i]);
    total += bits;

    break if (bits != 8)
  end

  return total
end

# x = hex_to_bytes('000000000e9d97a1ab09fc381030b346cdd7a142ad57e6df0b46dc9bef6c7e2d')
# puts count_leading_zero_bits(x) # => 36