Class: Integer

Inherits:
Object show all
Defined in:
lib/crypto_toolchain/extensions/integer_extensions.rb

Constant Summary collapse

ROUNDING =

rosettacode.org/wiki/Nth_root#Ruby (with modifications)

%i(up down none)

Instance Method Summary collapse

Instance Method Details

#invmod(n) ⇒ Object Also known as: mod_inverse, modinv

From Wikipedia: en.wikipedia.org/wiki/Extended_Euclidean_algorithm#Pseudocode

Raises:

  • (ArgumentError) 


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# File 'lib/crypto_toolchain/extensions/integer_extensions.rb', line 31

def invmod(n)
  a = self
  t = 0
  new_t = 1
  r = n
  new_r = a
  while new_r != 0
      quotient = r / new_r
      t, new_t = new_t, (t - quotient * new_t)
      r, new_r = new_r, (r - quotient * new_r)
  end
  raise ArgumentError.new("#{self} is not invertible") if r > 1
  t += n if t < 0
  t
end

#lrot(num) ⇒ Object 



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# File 'lib/crypto_toolchain/extensions/integer_extensions.rb', line 19

def lrot(num)
  ((self << num) & 0xffffffff) |
    ((self & 0xffffffff) >> (32 - num))
end

#modexp(exponent, mod) ⇒ Object Also known as: modpow

Raises:

  • (ArgumentError) 


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# File 'lib/crypto_toolchain/extensions/integer_extensions.rb', line 76

def modexp(exponent, mod)
  raise ArgumentError.new("Exponent must be non-negative") if exponent < 0
  product = 1
  base = self % mod
  while exponent > 0
    if exponent & 0x01 == 1
      product = (product * base) % mod
    end
    exponent = exponent >> 1
    base = (base**2) % mod
  end
  product
end

#root(n, round: :down) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/crypto_toolchain/extensions/integer_extensions.rb', line 52

def root(n, round: :down)
  raise ArgumentError.new("round must be in [#{ROUNDING.join(', ')}]") unless ROUNDING.include?(round)
  raise ArgumentError.new("Can't be called on 0") if self == 0
  x = self
  loop do
    prev = x
    x = ((n - 1) * prev) + (self / (prev ** (n - 1)))
    x /= n
    break if (prev - x) <= 0
  end
  if x**n == self
    x
  else
    case round
    when :up
      x+1
    when :down
      x
    when :none
      raise ArgumentError.new("#{self} has no #{n}th root")
    end
  end
end

#rrot(num) ⇒ Object 



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# File 'lib/crypto_toolchain/extensions/integer_extensions.rb', line 24

def rrot(num)
  ((self & 0xffffffff) >> num) |
    ((self << (32 - num)) & 0xffffffff)
end

#to_bin_string ⇒ Object 



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# File 'lib/crypto_toolchain/extensions/integer_extensions.rb', line 11

def to_bin_string
  to_hex_string.from_hex
end

#to_bits(pack_arg = "L>") ⇒ Object 



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# File 'lib/crypto_toolchain/extensions/integer_extensions.rb', line 15

def to_bits(pack_arg = "L>")
  [self].pack(pack_arg).to_bits
end

#to_hex_string ⇒ Object 



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# File 'lib/crypto_toolchain/extensions/integer_extensions.rb', line 3

def to_hex_string
  ret = to_s(16)
  if ret.length.odd?
    ret = "0#{ret}"
  end
  ret
end

#updiv(other) ⇒ Object 



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# File 'lib/crypto_toolchain/extensions/integer_extensions.rb', line 91

def updiv(other)
  quot, remainder = self.divmod(other)
  if remainder == 0
    quot
  else
    quot + 1
  end
end