# 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"

def random_bytes(n=nil)

n = n ? n.to_int : 16

gen_random(n)

end

# 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"

def hex(n=nil)

random_bytes(n).unpack1("H*")

end

# 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.

def base64(n=nil)

[random_bytes(n)].pack("m0")

end

# 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.

def urlsafe_base64(n=nil, padding=false)

s = [random_bytes(n)].pack("m0")

s.tr!("+/", "-_")

s.delete!("=") unless padding

s

end

# 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 RFC9562[https://www.rfc-editor.org/rfc/rfc9562] for details of UUIDv4.

#

def uuid

ary = random_bytes(16)

ary.setbyte(6, (ary.getbyte(6) & 0x0f) | 0x40)

ary.setbyte(8, (ary.getbyte(8) & 0x3f) | 0x80)

ary.unpack("H8H4H4H4H12").join(?-)

end

alias uuid_v4 uuid

# Generate a random v7 UUID (Universally Unique IDentifier).

#

# require 'random/formatter'

#

# Random.uuid_v7 # => "0188d4c3-1311-7f96-85c7-242a7aa58f1e"

# Random.uuid_v7 # => "0188d4c3-16fe-744f-86af-38fa04c62bb5"

# Random.uuid_v7 # => "0188d4c3-1af8-764f-b049-c204ce0afa23"

# Random.uuid_v7 # => "0188d4c3-1e74-7085-b14f-ef6415dc6f31"

# # |<--sorted-->| |<----- random ---->|

#

# # or

# prng = Random.new

# prng.uuid_v7 # => "0188ca51-5e72-7950-a11d-def7ff977c98"

#

# The version 7 UUID starts with the least significant 48 bits of a 64 bit

# Unix timestamp (milliseconds since the epoch) and fills the remaining bits

# with random data, excluding the version and variant bits.

#

# This allows version 7 UUIDs to be sorted by creation time. Time ordered

# UUIDs can be used for better database index locality of newly inserted

# records, which may have a significant performance benefit compared to random

# data inserts.

#

# The result contains 74 random bits (9.25 random bytes).

#

# Note that this method cannot be made reproducible because its output

# includes not only random bits but also timestamp.

#

# See RFC9562[https://www.rfc-editor.org/rfc/rfc9562] for details of UUIDv7.

#

# ==== Monotonicity

#

# UUIDv7 has millisecond precision by default, so multiple UUIDs created

# within the same millisecond are not issued in monotonically increasing

# order. To create UUIDs that are time-ordered with sub-millisecond

# precision, up to 12 bits of additional timestamp may added with

# +extra_timestamp_bits+. The extra timestamp precision comes at the expense

# of random bits. Setting <tt>extra_timestamp_bits: 12</tt> provides ~244ns

# of precision, but only 62 random bits (7.75 random bytes).

#

# prng = Random.new

# Array.new(4) { prng.uuid_v7(extra_timestamp_bits: 12) }

# # =>

# ["0188d4c7-13da-74f9-8b53-22a786ffdd5a",

# "0188d4c7-13da-753b-83a5-7fb9b2afaeea",

# "0188d4c7-13da-754a-88ea-ac0baeedd8db",

# "0188d4c7-13da-7557-83e1-7cad9cda0d8d"]

# # |<--- sorted --->| |<-- random --->|

#

# Array.new(4) { prng.uuid_v7(extra_timestamp_bits: 8) }

# # =>

# ["0188d4c7-3333-7a95-850a-de6edb858f7e",

# "0188d4c7-3333-7ae8-842e-bc3a8b7d0cf9", # <- out of order

# "0188d4c7-3333-7ae2-995a-9f135dc44ead", # <- out of order

# "0188d4c7-3333-7af9-87c3-8f612edac82e"]

# # |<--- sorted -->||<---- random --->|

#

# Any rollbacks of the system clock will break monotonicity. UUIDv7 is based

# on UTC, which excludes leap seconds and can rollback the clock. To avoid

# this, the system clock can synchronize with an NTP server configured to use

# a "leap smear" approach. NTP or PTP will also be needed to synchronize

# across distributed nodes.

#

# Counters and other mechanisms for stronger guarantees of monotonicity are

# not implemented. Applications with stricter requirements should follow

# {Section 6.2}[https://www.rfc-editor.org/rfc/rfc9562.html#name-monotonicity-and-counters]

# of the specification.

#

def uuid_v7(extra_timestamp_bits: 0)

case (extra_timestamp_bits = Integer(extra_timestamp_bits))

when 0 # min timestamp precision

ms = Process.clock_gettime(Process::CLOCK_REALTIME, :millisecond)

rand = random_bytes(10)

rand.setbyte(0, rand.getbyte(0) & 0x0f | 0x70) # version

rand.setbyte(2, rand.getbyte(2) & 0x3f | 0x80) # variant

"%08x-%04x-%s" % [

(ms & 0x0000_ffff_ffff_0000) >> 16,

(ms & 0x0000_0000_0000_ffff),

rand.unpack("H4H4H12").join("-")

]

when 12 # max timestamp precision

ms, ns = Process.clock_gettime(Process::CLOCK_REALTIME, :nanosecond)

.divmod(1_000_000)

extra_bits = ns * 4096 / 1_000_000

rand = random_bytes(8)

rand.setbyte(0, rand.getbyte(0) & 0x3f | 0x80) # variant

"%08x-%04x-7%03x-%s" % [

(ms & 0x0000_ffff_ffff_0000) >> 16,

(ms & 0x0000_0000_0000_ffff),

extra_bits,

rand.unpack("H4H12").join("-")

]

when (0..12) # the generic version is slower than the special cases above

rand_a, rand_b1, rand_b2, rand_b3 = random_bytes(10).unpack("nnnN")

rand_mask_bits = 12 - extra_timestamp_bits

ms, ns = Process.clock_gettime(Process::CLOCK_REALTIME, :nanosecond)

.divmod(1_000_000)

"%08x-%04x-%04x-%04x-%04x%08x" % [

(ms & 0x0000_ffff_ffff_0000) >> 16,

(ms & 0x0000_0000_0000_ffff),

0x7000 |

((ns * (1 << extra_timestamp_bits) / 1_000_000) << rand_mask_bits) |

rand_a & ((1 << rand_mask_bits) - 1),

0x8000 | (rand_b1 & 0x3fff),

rand_b2,

rand_b3

]

else

raise ArgumentError, "extra_timestamp_bits must be in 0..12"

end

end

# Internal interface to Random; Generate random data _n_ bytes.

private def gen_random(n)

self.bytes(n)

end

# 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"

private 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

# The default character list for #alphanumeric.

ALPHANUMERIC = [*'A'..'Z', *'a'..'z', *'0'..'9'].map(&:freeze).freeze

# Generate a random alphanumeric string.

#

# The argument _n_ specifies the length, in characters, of the alphanumeric

# string to be generated.

# The argument _chars_ specifies the character list which the result is

# consist of.

#

# 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, unless _chars_ is specified.

#

# require 'random/formatter'

#

# Random.alphanumeric #=> "2BuBuLf3WfSKyQbR"

# # or

# prng = Random.new

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

#

# Random.alphanumeric(4, chars: [*"0".."9"]) #=> "2952"

# # or

# prng = Random.new

# prng.alphanumeric(10, chars: [*"!".."/"]) #=> ",.,++%/''."

def alphanumeric(n = nil, chars: ALPHANUMERIC)

n = 16 if n.nil?

choose(chars, n)

end