Class: SubnetCalc

Inherits:
Object
  • Object
show all
Defined in:
lib/subnet_calc.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(inputs = {hosts: 254}) ⇒ SubnetCalc 



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# File 'lib/subnet_calc.rb', line 27

def initialize(inputs={hosts: 254})

  @inputs = inputs
  default_inputs = {hosts: 254, ip: '192.168.0.0'}.merge(inputs)
  
  # Using the input(s) supplied:

  hosts = default_inputs[:hosts]
  

  @prefixes = 1.upto(32).each_slice(8).to_a
  
=begin
  #=> [
       [1, 2, 3, 4, 5, 6, 7, 8], [9, 10, 11, 12, 13, 14, 15, 16], 
       [17, 18, 19, 20, 21, 22, 23, 24], [25, 26, 27, 28, 29, 30, 31, 32]
      ]
=end

  

  octets = @prefixes.map.with_index do |octet, j|

    a = octet.map.with_index do |prefix, i|
      
      decimal = 2 ** (octet.length - 1 - i )

      h = {
            prefix: prefix,
            decimal: decimal,
            hosts_per_subnet: (2 ** 8) ** (@prefixes.length - 1 - j) * decimal
          }

      OpenStruct.new h
      
    end

    OpenStruct.new mask: nil, bits: a

  end
  
  hosts_per_subnet = octets.map.with_index do |x,i| 
    x.bits.map.with_index {|y,j| [i, j, y.hosts_per_subnet] }
  end.flatten(1)
  

  # determine what class of network we are using

  class_type = hosts <= 254 ? 'c' : 'b'

  # Identify the network bits and the host bits

  classes = ('a'..'d')

  # identify the initial network bits for a class *a,b or c*

  class_n = (classes.to_a.index(class_type) + 1)
  network_bits = class_n.times.map {|x| Array.new(8, 1)}
  host_bits = (classes.to_a.length - class_n).times.map {|x| Array.new(8, 0)}
  address_bits = network_bits + host_bits

  # add the mask to each octet

  octets.each.with_index do |octet, i|
    octet.mask = address_bits[i].join.to_i(2)
  end

  # ------------------------------------



  # find the smallest decimal value to match the 
  # required number of hosts on a network    
  
  octet_n, col = hosts_per_subnet.reverse.detect {|x| x.last >  hosts + 1}    

  bit = octets[octet_n].bits[col]

  magic_number, prefix = bit.hosts_per_subnet, bit.prefix    
  
  no_of_subnets = (2 ** 8.0) / bit.hosts_per_subnet

  segments = (no_of_subnets >= 1 ? no_of_subnets : 256 / (256 * no_of_subnets)).to_i
  n =  col

  # add the new mask to the octet

  octets[octet_n].mask = octets[octet_n].bits.map(&:decimal)[0..n].inject(:+)
  subnet_mask = octets.map(&:mask).join('.')

  subnets = case class_type
  when 'c'
    class_subnets(segments, magic_number)
  when 'b'
    class_b_subnets(256 / segments, bit.decimal)
  end

  ip = (default_inputs[:ip] + ' ') .split('.')[0..octet_n-1]
  
  first_ip = (ip + [subnets.first.first]).join('.')
  last_ip = (ip + [subnets.first.last]).join('.')

  result = {
    class_type: class_type.upcase,
    magic_number: magic_number,
    hosts: magic_number - 2,
    subnet_mask: subnet_mask,
    subnet_bitmask: subnet_mask.split('.').map {|x| x.to_i.to_s(2)},
    prefix: prefix,
    subnets: subnets,
    range: "%s-%s" % [first_ip, last_ip],
    subnet_bits: n+1,
    max_subnets: segments
  }

  @octet_n = octet_n
  @h = result
end

Instance Attribute Details

#to_h ⇒ Object (readonly)

Returns the value of attribute to_h.



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# File 'lib/subnet_calc.rb', line 25

def to_h
  @to_h
end

Instance Method Details

#to_s ⇒ Object 



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# File 'lib/subnet_calc.rb', line 146

def to_s()


  tfo = TableFormatter.new

  tfo.source = @h[:subnets].map.with_index{|x,i| ([i] + x.to_h.values).map(&:to_s) }
  tfo.labels = %w(index Network 1st last broadcast)
  full_subnets_table = tfo.display(markdown: true).to_s
  
  subnets_table = if full_subnets_table.lines.length > 14 then
    (full_subnets_table.lines[0..13] + ["\n    ...  "]).join
  else
    full_subnets_table
  end

  # octet broken down

  tfo2 = TableFormatter.new

  prefixes = @prefixes[@octet_n].map {|x| '/' + x.to_s}
  tfo2.source = [@h[:subnet_bitmask][@octet_n].chars, prefixes]
  tfo2.labels = 8.times.map {|n| (2 ** n).to_s }.reverse
  octet_table = tfo2.display(markdown: true).to_s

"\n\nSubnet calculator\n=================\n\nInputs: \n\n\#{Kvx.new(@inputs).to_s.lines.map {|x| ' ' * 2 + x}.join}\n\nSummary\n-------\n\n* Network class: \#{@h[:class_type]}\n* magic number: \#{@h[:magic_number]}\n* hosts per subnet (magic number - 2 ): \#{@h[:hosts]}\n* subnet mask: \#{@h[:subnet_mask]}\n* subnet bitmask: \#{@h[:subnet_bitmask].join('.')}\n* prefix bit-length: \#{@h[:prefix]}\n* range: \#{@h[:range]}\n\n* subnet_bits: \#{@h[:subnet_bits]}\n* maximum subnets: \#{@h[:max_subnets]}\n\n\n\nBreakdown\n---------\n\n\#{(@octet_n + 1).ordinal} octet:\n\n\#{indent octet_table}\n\n### Subnets\n\n\n\#{indent subnets_table}\n\n-----------------------------------------------\n\n"

end