# module Random::Formatter

## Random number formatter.¶ ↑

Formats generated random numbers in many manners. When `'random/formatter'` is required, several methods are added to empty core module `Random::Formatter`, making them available as Random’s instance and module methods.

Standard library `SecureRandom` is also extended with the module, and the methods described below are available as a module methods in it.

### Examples¶ ↑

Generate random hexadecimal strings:

    require 'random/formatter'

    prng = Random.new
    prng.hex(10) #=> "52750b30ffbc7de3b362"
    prng.hex(10) #=> "92b15d6c8dc4beb5f559"
    prng.hex(13) #=> "39b290146bea6ce975c37cfc23"
    # or just
    Random.hex #=> "1aed0c631e41be7f77365415541052ee"

Generate random base64 strings:

    prng.base64(10) #=> "EcmTPZwWRAozdA=="
    prng.base64(10) #=> "KO1nIU+p9DKxGg=="
    prng.base64(12) #=> "7kJSM/MzBJI+75j8"
    Random.base64(4) #=> "bsQ3fQ=="

Generate random binary strings:

    prng.random_bytes(10) #=> "\016\t{\370g\310pbr\301"
    prng.random_bytes(10) #=> "\323U\030TO\234\357\020\a\337"
    Random.random_bytes(6) #=> "\xA1\xE6Lr\xC43"

Generate alphanumeric strings:

    prng.alphanumeric(10) #=> "S8baxMJnPl"
    prng.alphanumeric(10) #=> "aOxAg8BAJe"
    Random.alphanumeric #=> "TmP9OsJHJLtaZYhP"

Generate UUIDs:

    prng.uuid #=> "2d931510-d99f-494a-8c67-87feb05e1594"
    prng.uuid #=> "bad85eb9-0713-4da7-8d36-07a8e4b00eab"
    Random.uuid #=> "f14e0271-de96-45cc-8911-8910292a42cd"

All methods are available in the standard library `SecureRandom`, too:

    SecureRandom.hex #=> "05b45376a30c67238eb93b16499e50cf"

Generate a random number in the given range as `Random` does

    prng.random_number       #=> 0.5816771641321361
    prng.random_number(1000) #=> 485
    prng.random_number(1..6) #=> 3
    prng.rand                #=> 0.5816771641321361
    prng.rand(1000)          #=> 485
    prng.rand(1..6)          #=> 3

### Constants

ALPHANUMERIC

### Public Instance Methods

alphanumeric(n=nil) click to toggle source

Generate 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'

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

    # File lib/random/formatter.rb, line 240
    def alphanumeric(n=nil)
      n = 16 if n.nil?
      choose(ALPHANUMERIC, n)
    end

base64(n=nil) click to toggle source

Generate 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'

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

See RFC 3548 for the definition of base64.

    # File lib/random/formatter.rb, line 114
    def base64(n=nil)
      [random_bytes(n)].pack("m0")
    end

hex(n=nil) click to toggle source

Generate 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'

    Random.hex #=> "eb693ec8252cd630102fd0d0fb7c3485"
    # or
    prng = Random.new
    prng.hex #=> "91dc3bfb4de5b11d029d376634589b61"

    # File lib/random/formatter.rb, line 92
    def hex(n=nil)
      random_bytes(n).unpack1("H*")
    end

rand → float
rand(max) → number
rand(range) → number

Generates formatted random number from raw random bytes. See `Random#rand`.

Alias for: random_number
random_bytes(n=nil) click to toggle source

Generate 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'

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

    # File lib/random/formatter.rb, line 71
    def random_bytes(n=nil)
      n = n ? n.to_int : 16
      gen_random(n)
    end

random_number → float click to toggle source
random_number(max) → number
random_number(range) → number

Generates formatted random number from raw random bytes. See `Random#rand`.

    static VALUE
    rand_random_number(int argc, VALUE *argv, VALUE obj)
    {
        rb_random_t *rnd = try_get_rnd(obj);
        VALUE v = rand_random(argc, argv, obj, rnd);
        if (NIL_P(v)) v = rand_random(0, 0, obj, rnd);
        else if (!v) invalid_argument(argv[0]);
        return v;
    }

Also aliased as: rand
urlsafe_base64(n=nil, padding=false) click to toggle source

Generate 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'

    Random.urlsafe_base64 #=> "b4GOKm4pOYU_-BOXcrUGDg"
    # or
    prng = Random.new
    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 lib/random/formatter.rb, line 145
    def urlsafe_base64(n=nil, padding=false)
      s = [random_bytes(n)].pack("m0")
      s.tr!("+/", "-_")
      s.delete!("=") unless padding
      s
    end

uuid() click to toggle source

Generate a random v4 UUID (Universally Unique IDentifier).

    require 'random/formatter'

    Random.uuid #=> "2d931510-d99f-494a-8c67-87feb05e1594"
    Random.uuid #=> "bad85eb9-0713-4da7-8d36-07a8e4b00eab"
    # or
    prng = Random.new
    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 RFC4122 for details of UUID.

    # File lib/random/formatter.rb, line 169
    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

### Private Instance Methods

choose(source, n) click to toggle source

Generate 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 lib/random/formatter.rb, line 194
            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

gen_random(n) click to toggle source

    # File lib/random/formatter.rb, line 176
            def gen_random(n)
      self.bytes(n)
    end