Organization IPs

orgs.rb

input = [
  [1, 0, 0, 0, 256,   "AU-8a888ca7567d"],
  [1, 0, 1, 0, 256,   "CN-8173da22ea8b"],
  [1, 0, 2, 0, 512,   "CN-8173da22ea8b"],
  [1, 0, 4, 0, 1024,  "AU-4d44a4952b26"],
  [1, 0, 8, 0, 2048,  "CN-cc1064bf6999"],
  [1, 0, 16, 0, 4096, "JP-9413fa3d189a"],
  [1, 0, 32, 0, 8192, "CN-cc1064bf6999"]
]

class IPItem
  attr_accessor :ip
  attr_accessor :len
  attr_accessor :org

  def initialize(ip, len, org)
    @ip = ip
    @len = len
    @org = org
  end

  # Returns -1, 0, or 1, if other_ip is, respectively, less than, equal to, or
  # larger than the item's IP range
  def compare_ip(other_ip)
    if other_ip < ip
      return -1
    elsif other_ip - ip < len
      return 0
    end
    return 1
  end
end

# returns 32bit number corresponding to the IP given as (a, b, c, d)
def get_ipnum(a, b, c, d)
  a << 24 | b << 16 | c << 8 | d
end

# returns an org name corresponding to the ip given as (a, b, c, d), or nil if
# such org does not exist
def get_org(db, a, b, c, d)
  req_ip = get_ipnum(a, b, c, d)

  # lower and upper indices, both are inclusive
  l = 0
  h = db.length - 1

  # loop until we find a needed ip item, or figure that the item does not exist
  while l <= h do
    idx = l + (h - l) / 2
    case db[idx].compare_ip req_ip
    when -1
      h = idx - 1
    when 1
      l = idx + 1
    else
      # found an item
      return db[idx].org
    end
  end

  # requested item does not exist
  nil
end

def get_org_p(db, a, b, c, d)
  p "#{a}.#{b}.#{c}.#{d}: #{get_org(db, a, b, c, d)}"
end

db = input.map do |a, b, c, d, e, f|
  IPItem.new(get_ipnum(a, b, c, d), e, f)
end

# try to find a few orgs

get_org_p(db, 0, 255, 255, 255)
get_org_p(db, 1, 0, 0, 0)
get_org_p(db, 1, 0, 0, 255)
get_org_p(db, 1, 0, 1, 0)
get_org_p(db, 1, 0, 32, 128)
get_org_p(db, 1, 5, 32, 128)