ruby_ipv4_notations.rb

# How to convert IPv4 addresses between integer <=> dot-decimal notation

INTEGER = 1698212032
DOT_DECIMAL = '192.168.56.101'

# [ 192, 168, 56, 101 ]
DOT_DECIMAL_PARTS = DOT_DECIMAL.split('.').map(&:to_i)

####################################
# integer to dot-decimal
####################################
# 1698212032 => '192.168.56.101'
puts "=== from INTEGER to DOT-DECIMAL ==="

# MANUALLY
number = INTEGER
p1 = (number) & 255     # 192
p2 = (number>>8) & 255  # 168
p3 = (number>>16) & 255 # 56
p4 = (number>>24) & 255 # 101
puts "MANU: #{p1}.#{p2}.#{p3}.#{p4}"

# AUTOMATICALLY
number = INTEGER
result = []
4.times do
  # bitwise AND 255 bits
  result.push number & 255
  
  # bitwise SHIFT RIGHT 8 bits
  number = number >> 8
end
puts "AUTO: #{result.join('.')}"

# You can Update Integer class it self 

class Integer
  def to_decimal
    number = self
    result = []
    4.times do
	result.push number & 255
	number = number >> 8
    end

    result.join('.')
  end
end

# Then 
INTEGER.to_decimal  # => 192.168.56.101


####################################
# dot-decimal to Integer
####################################
# '192.168.56.101' => 1698212032
puts "=== from DOT-DECIMAL to INTEGER ==="

# MANUALLY
parts = DOT_DECIMAL_PARTS
manually_int = parts[0] +
              (parts[1] << 8) +
              (parts[2] << 16) +
              (parts[3] << 24)
puts "MANU: #{manually_int}"

# AUTOMATICALLY
number = DOT_DECIMAL
parts = DOT_DECIMAL_PARTS.dup
# sum up the integer beginning at 0
result = 4.times.inject(0) do |integer, index|
  # take next part
  part = parts.shift
  
  # bitwise SHIFT LEFT
  add = part << (8 * index)
  
  # add to sum by returning it
  integer += add
end
puts "AUTO: #{result}"