diff options
Diffstat (limited to 'lib/random/formatter.rb')
| -rw-r--r-- | lib/random/formatter.rb | 144 |
1 files changed, 136 insertions, 8 deletions
diff --git a/lib/random/formatter.rb b/lib/random/formatter.rb index 4dea61c16c..037f9d8748 100644 --- a/lib/random/formatter.rb +++ b/lib/random/formatter.rb @@ -165,15 +165,134 @@ module Random::Formatter # # The result contains 122 random bits (15.25 random bytes). # - # See RFC4122[https://datatracker.ietf.org/doc/html/rfc4122] for details of UUID. + # See RFC4122[https://www.rfc-editor.org/rfc/rfc4122] for details of UUID. # 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 + 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 draft-ietf-uuidrev-rfc4122bis[https://datatracker.ietf.org/doc/draft-ietf-uuidrev-rfc4122bis/] + # 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.ietf.org/archive/id/draft-ietf-uuidrev-rfc4122bis-07.html#monotonicity_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 @@ -221,16 +340,20 @@ module Random::Formatter result end + # The default character list for #alphanumeric. ALPHANUMERIC = [*'A'..'Z', *'a'..'z', *'0'..'9'] + # 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. + # The result may contain A-Z, a-z and 0-9, unless _chars_ is specified. # # require 'random/formatter' # @@ -238,8 +361,13 @@ module Random::Formatter # # or # prng = Random.new # prng.alphanumeric(10) #=> "i6K93NdqiH" - def alphanumeric(n=nil) + # + # 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(ALPHANUMERIC, n) + choose(chars, n) end end |