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'''Functions for generating random numbers.'''
import os
from rsa import common, transform
def read_random_int(nbits):
"""Reads a random integer of approximately nbits bits.
The number of bits is rounded down to whole bytes to ensure that the
resulting number can be stored in ``nbits`` bits.
"""
randomdata = os.urandom(nbits / 8)
return transform.bytes2int(randomdata)
def randint(maxvalue):
"""Returns a random integer x with 1 <= x <= maxvalue"""
# Safety - get a lot of random data even if the range is fairly
# small
readbits = max(common.bit_size(maxvalue), 32)
return (read_random_int(readbits) % maxvalue) + 1
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