Class: Base31encoder

Inherits:
Object
  • Object
show all
Defined in:
lib/base31_encoder.rb

Overview

This module is used to convert a base10 integer into an equivalent base31 guid string (and vice-versa). The base31 number is represented as a alpha-numeric characters (excluding the vowel charatcers A, E, I, O, U); this is done to avoid confusion between numbers and letters (eg. 1 and I, 0 and O) and also to avoid nasty words from being generated from their equivalent decimal values.

Constant Summary collapse

Dec_vals =

base31/base10 equivalent string definitions

{
  "0" => "0","1" => "1","2" => "2","3" => "3","4" => "4","5" => "5",
  "6" => "6","7" => "7","8" => "8","9" => "9","10" => "B","11" => "C",
  "12" => "D","13" => "F","14" => "G","15" => "H","16" => "J",
  "17" => "K","18" => "L","19" => "M","20" => "N","21" => "P",
  "22" => "Q","23" => "R","24" => "S","25" => "T","26" => "V",
  "27" => "W","28" => "X","29" => "Y","30" => "Z","B" => "10",
  "C" => "11","D" => "12","F" => "13","G" => "14","H" => "15",
  "J" => "16","K" => "17","L" => "18","M" => "19","N" => "20",
  "P" => "21","Q" => "22","R" => "23","S" => "24","T" => "25",
  "V" => "26","W" => "27","X" => "28","Y" => "29","Z" => "30"
}

Instance Method Summary collapse

Constructor Details

#initialize(base_length = 6) ⇒ Base31encoder

Returns a new instance of Base31encoder.



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# File 'lib/base31_encoder.rb', line 21

def initialize(base_length=6)
  @base_length = base_length
end

Instance Method Details

#base31str_to_int(str) ⇒ Object 



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# File 'lib/base31_encoder.rb', line 25

def base31str_to_int(str)
  if not str.is_a?(String)
    raise StandardError, "Received value is not a valid string"
  end
  
  len = pos = str.length
  total = 0
  
  while pos > 0 do
    val = str[(len - pos), 1]
    intval = Dec_vals[val].to_i
    
    tmp = pos
    while (tmp - 1) > 0 do
      intval = intval * 31
      tmp -= 1
    end
    
    total += intval
    pos -= 1
  end
  
  return total
end

#int_to_base31(num) ⇒ Object 



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# File 'lib/base31_encoder.rb', line 50

def int_to_base31(num)
  if not num.is_a?(Integer)
    raise StandardError, "Received value is not a valid integer"
  end
  
  base31 = ""
  
  while num > 0 do
    rem = num % 31
    num = num / 31
    val = Dec_vals[rem.to_s]
    
    base31 = val + base31
  end
  
  while base31.length < @base_length do
    base31 = "0" + base31
  end
  
  return base31
end