Module: Obfuskey::Utils

Defined in:
lib/obfuskey/utils.rb

Class Method Summary collapse

Class Method Details

.decode(value, alphabet) ⇒ Object 



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# File 'lib/obfuskey/utils.rb', line 7

def decode(value, alphabet)
  chars = value.chars
  unless chars.all? { |c| alphabet.include?(c) }
    raise UnknownKeyError,
      "The value contains characters not found in the current alphabet."
  end

  return alphabet.index(value) if chars.length == 1

  base = alphabet.length
  result = 0
  chars.each do |c|
    result = result * base + alphabet.index(c)
  end
  result
end

.encode(value, alphabet) ⇒ Object

Raises:



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# File 'lib/obfuskey/utils.rb', line 24

def encode(value, alphabet)
  raise NegativeValueError, "The value must be greater than or equal to zero." if value < 0

  return alphabet[value] if value < alphabet.length

  base = alphabet.length
  key = +""
  while value > 0
    value, i = value.divmod(base)
    key << alphabet[i]
  end
  key.reverse
end

.generate_prime(alphabet, key_length, prime_multiplier = PRIME_MULTIPLIER) ⇒ Object 



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# File 'lib/obfuskey/utils.rb', line 38

def generate_prime(alphabet, key_length, prime_multiplier = PRIME_MULTIPLIER)
  # Mirror Python's Decimal(float) conversion: Rational(float) preserves
  # the exact binary representation of a Float, matching Python's behavior.
  factor = prime_multiplier.is_a?(Float) ? Rational(prime_multiplier) : prime_multiplier
  target = ((alphabet.length**key_length - 1) * factor).to_i
  Math.next_prime(target)
end