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#
# This file is part of pysnmp software.
#
# Copyright (c) 2005-2020, Ilya Etingof <etingof@gmail.com>
# License: https://www.pysnmp.com/pysnmp/license.html
#
"""
This module provides a class for generating sequential integers in a reasonably multi-thread safe manner.
Classes:
Integer: A class to generate the next integer value within a specified
range and increment.
Usage example:
integer_gen = Integer(maximum=1000, increment=256)
next_value = integer_gen()
"""
import random
random.seed()
class Integer:
"""Return a next value in a reasonably MT-safe manner."""
def __init__(self, maximum, increment=256):
"""Create a new instance of integer generator."""
self.__maximum = maximum
if increment >= maximum:
increment = maximum
self.__increment = increment
self.__threshold = increment // 2
e = random.randrange(self.__maximum - self.__increment)
self.__bank = list(range(e, e + self.__increment))
def __repr__(self):
"""Return a string representation of the object."""
return "%s(%d, %d)" % (
self.__class__.__name__,
self.__maximum,
self.__increment,
)
def __call__(self):
"""Return next integer."""
v = self.__bank.pop(0)
if v % self.__threshold:
return v
else:
# this is MT-safe unless too many (~ increment/2) threads
# bump into this code simultaneously
e = self.__bank[-1] + 1
if e > self.__maximum:
e = 0
self.__bank.extend(range(e, e + self.__threshold))
return v
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