module Random::Formatter

Random::Formatter#alphanumeric generates a random alphanumeric string.

The argument n specifies the length, in characters, of the alphanumeric string to be generated.

If n is not specified or is nil, 16 is assumed. It may be larger in the future.

The result may contain A-Z, a-z and 0-9.

require 'random/formatter'

prng.alphanumeric     #=> "2BuBuLf3WfSKyQbR"
prng.alphanumeric(10) #=> "i6K93NdqiH"

# File random/formatter.rb, line 212
def alphanumeric(n=nil)
  n = 16 if n.nil?
  choose(ALPHANUMERIC, n)
end

Random::Formatter#base64 generates a random base64 string.

The argument n specifies the length, in bytes, of the random number to be generated. The length of the result string is about 4/3 of n.

If n is not specified or is nil, 16 is assumed. It may be larger in the future.

The result may contain A-Z, a-z, 0-9, “+”, “/” and “=”.

require 'random/formatter'

prng.base64 #=> "/2BuBuLf3+WfSKyQbRcc/A=="
prng.base64 #=> "6BbW0pxO0YENxn38HMUbcQ=="

See RFC 3548 for the definition of base64.

# File random/formatter.rb, line 92
def base64(n=nil)
  [random_bytes(n)].pack("m0")
end

Random::Formatter#hex generates a random hexadecimal string.

The argument n specifies the length, in bytes, of the random number to be generated. The length of the resulting hexadecimal string is twice of n.

If n is not specified or is nil, 16 is assumed. It may be larger in the future.

The result may contain 0-9 and a-f.

require 'random/formatter'

prng.hex #=> "eb693ec8252cd630102fd0d0fb7c3485"
prng.hex #=> "91dc3bfb4de5b11d029d376634589b61"

# File random/formatter.rb, line 72
def hex(n=nil)
  random_bytes(n).unpack1("H*")
end

Random::Formatter#random_bytes generates a random binary string.

The argument n specifies the length of the result string.

If n is not specified or is nil, 16 is assumed. It may be larger in future.

The result may contain any byte: “x00” - “xff”.

require 'random/formatter'

prng.random_bytes #=> "\xD8\\\xE0\xF4\r\xB2\xFC*WM\xFF\x83\x18\xF45\xB6"
prng.random_bytes #=> "m\xDC\xFC/\a\x00Uf\xB2\xB2P\xBD\xFF6S\x97"

# File random/formatter.rb, line 53
def random_bytes(n=nil)
  n = n ? n.to_int : 16
  gen_random(n)
end

Random::Formatter#urlsafe_base64 generates a random URL-safe base64 string.

The argument n specifies the length, in bytes, of the random number to be generated. The length of the result string is about 4/3 of n.

If n is not specified or is nil, 16 is assumed. It may be larger in the future.

The boolean argument padding specifies the padding. If it is false or nil, padding is not generated. Otherwise padding is generated. By default, padding is not generated because “=” may be used as a URL delimiter.

The result may contain A-Z, a-z, 0-9, “-” and “_”. “=” is also used if padding is true.

require 'random/formatter'

prng.urlsafe_base64 #=> "b4GOKm4pOYU_-BOXcrUGDg"
prng.urlsafe_base64 #=> "UZLdOkzop70Ddx-IJR0ABg"

prng.urlsafe_base64(nil, true) #=> "i0XQ-7gglIsHGV2_BNPrdQ=="
prng.urlsafe_base64(nil, true) #=> "-M8rLhr7JEpJlqFGUMmOxg=="

See RFC 3548 for the definition of URL-safe base64.

# File random/formatter.rb, line 121
def urlsafe_base64(n=nil, padding=false)
  s = [random_bytes(n)].pack("m0")
  s.tr!("+/", "-_")
  s.delete!("=") unless padding
  s
end

Random::Formatter#uuid generates a random v4 UUID (Universally Unique IDentifier).

require 'random/formatter'

prng.uuid #=> "2d931510-d99f-494a-8c67-87feb05e1594"
prng.uuid #=> "bad85eb9-0713-4da7-8d36-07a8e4b00eab"
prng.uuid #=> "62936e70-1815-439b-bf89-8492855a7e6b"

The version 4 UUID is purely random (except the version). It doesn’t contain meaningful information such as MAC addresses, timestamps, etc.

The result contains 122 random bits (15.25 random bytes).

See RFC 4122 for details of UUID.

# File random/formatter.rb, line 143
def uuid
  ary = random_bytes(16).unpack("NnnnnN")
  ary[2] = (ary[2] & 0x0fff) | 0x4000
  ary[3] = (ary[3] & 0x3fff) | 0x8000
  "%08x-%04x-%04x-%04x-%04x%08x" % ary
end

Random::Formatter#choose generates a string that randomly draws from a source array of characters.

The argument source specifies the array of characters from which to generate the string. The argument n specifies the length, in characters, of the string to be generated.

The result may contain whatever characters are in the source array.

require 'random/formatter'

prng.choose([*'l'..'r'], 16) #=> "lmrqpoonmmlqlron"
prng.choose([*'0'..'9'], 5)  #=> "27309"

# File random/formatter.rb, line 168
        def choose(source, n)
  size = source.size
  m = 1
  limit = size
  while limit * size <= 0x100000000
    limit *= size
    m += 1
  end
  result = ''.dup
  while m <= n
    rs = random_number(limit)
    is = rs.digits(size)
    (m-is.length).times { is << 0 }
    result << source.values_at(*is).join('')
    n -= m
  end
  if 0 < n
    rs = random_number(limit)
    is = rs.digits(size)
    if is.length < n
      (n-is.length).times { is << 0 }
    else
      is.pop while n < is.length
    end
    result.concat source.values_at(*is).join('')
  end
  result
end