Class: SerialNumber

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

Overview

Handles serial values, adjusting correctly for wraparound.

From the DNS and Bind book, p. 139:

“The DNS serial number is a 32-bit unsigned integer whose value ranges from 0 to 4,294,967,295. The serial number uses sequence space arithmetic, which means that for any serial number, half the numbers in the number space (2,147,483,647 numbers) are less than the serial number, and half the numbers are larger.”“

Constant Summary collapse

MIN_VALUE = 
0
MAX_VALUE =

(4_294_967_295)

0xFFFF_FFFF
MAX_DIFFERENCE =

(2_147_483_648)

0x8000_0000

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(value) ⇒ SerialNumber

Returns a new instance of SerialNumber.



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# File 'lib/mock_dns_server/serial_number.rb', line 20

def initialize(value)
  self.class.validate(value)
  @value = value
end

Instance Attribute Details

#value ⇒ Object

Returns the value of attribute value.



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# File 'lib/mock_dns_server/serial_number.rb', line 18

def value
  @value
end

Class Method Details

.compare(sss1, sss2) ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 62

def self.compare(sss1, sss2)
  compare_values(sss1.value, sss2.value)
end

.compare_values(value_1, value_2) ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 47

def self.compare_values(value_1, value_2)
  distance = (value_1 - value_2).abs

  if distance == 0
    0
  elsif distance < MAX_DIFFERENCE
    value_1 - value_2
  elsif distance > MAX_DIFFERENCE
    value_2 - value_1
  else # distance == MAX_DIFFERENCE
    raise "Cannot compare 2 numbers whose difference is exactly #{MAX_DIFFERENCE.to_s(16)} (#{value_1}, #{value_2})."
  end
end

.next_serial_value(value) ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 67

def self.next_serial_value(value)
  validate(value)
  value == MAX_VALUE ? 0 : value + 1
end

.object(thing) ⇒ Object

Call this when you have an object that may be either a SerialNumber or a Fixnum/Bignum, and you want to ensure that you have a SerialNumber.



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# File 'lib/mock_dns_server/serial_number.rb', line 29

def self.object(thing)
  if thing.is_a?(SerialNumber)
    thing
  elsif thing.nil?
    nil
  else
    SerialNumber.new(thing)
  end
end

.validate(value) ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 40

def self.validate(value)
  if value < MIN_VALUE || value > MAX_VALUE
    raise "Invalid value (#{value}), must be between #{MIN_VALUE} and #{MAX_VALUE}."
  end
end

Instance Method Details

#<(other) ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 88

def <(other)
  self.<=>(other) < 0
end

#<=(other) ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 98

def <=(other)
  self.<=>(other) <= 0
end

#<=>(other) ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 78

def <=>(other)
  self.class.compare(self, other)
end

#==(other) ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 103

def ==(other)
  self.class == other.class &&
  self.value == other.value
end

#>(other) ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 83

def >(other)
  self.<=>(other) > 0
end

#>=(other) ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 93

def >=(other)
  self.<=>(other) >= 0
end

#eql?(other) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/mock_dns_server/serial_number.rb', line 113

def eql?(other)
  self.==(other)
end

#hash ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 109

def hash
  value.hash
end

#next_serial ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 73

def next_serial
  self.class.new(self.class.next_serial_value(value))
end

#to_i ⇒ Object

Can be used to normalize an object that may be a Fixnum or a SerialNumber to an int:



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# File 'lib/mock_dns_server/serial_number.rb', line 118

def to_i
  value
end

#to_s ⇒ Object 



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# File 'lib/mock_dns_server/serial_number.rb', line 123

def to_s
  "#{self.class}: value = #{value}"
end