Source code for nats.nuid

# Copyright 2016-2018 The NATS Authors
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

from __future__ import annotations

from random import Random
from secrets import randbelow, token_bytes
from sys import maxsize as MaxInt

DIGITS = b'0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
BASE = 62
PREFIX_LENGTH = 12
SEQ_LENGTH = 10
MAX_SEQ = 839299365868340224  # BASE**10
MIN_INC = 33
MAX_INC = 333
INC = MAX_INC - MIN_INC
TOTAL_LENGTH = PREFIX_LENGTH + SEQ_LENGTH


[docs] class NUID: """ NUID is an implementation of the approach for fast generation of unique identifiers used for inboxes in NATS. """ def __init__(self) -> None: self._prand = Random(randbelow(MaxInt)) self._seq = self._prand.randint(0, MAX_SEQ) self._inc = MIN_INC + self._prand.randint(BASE + 1, INC) self._prefix = bytearray() self.randomize_prefix()
[docs] def next(self) -> bytearray: """ next returns the next unique identifier. """ self._seq += self._inc if self._seq >= MAX_SEQ: self.randomize_prefix() self.reset_sequential() l = self._seq prefix = self._prefix[:] suffix = bytearray(SEQ_LENGTH) for i in reversed(range(SEQ_LENGTH)): suffix[i] = DIGITS[int(l) % BASE] l //= BASE prefix.extend(suffix) return prefix
def randomize_prefix(self) -> None: random_bytes = token_bytes(PREFIX_LENGTH) self._prefix = bytearray(DIGITS[c % BASE] for c in random_bytes) def reset_sequential(self) -> None: self._seq = self._prand.randint(0, MAX_SEQ) self._inc = MIN_INC + self._prand.randint(0, INC)