KSUID generator

ksuid.py

"Functions for generating key-sortable unique IDs (KSUIDs)."

import os
import time
import typing

EPOCH = 1400000000 # segment.io epoch (March 5th, 2014)
DIGITS = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'

def timestamp_bytes() -> bytes:
    "Generate four bytes for seconds since ``EPOCH``."
    seconds = int(time.time() - EPOCH)
    return int(seconds).to_bytes(4, byteorder='big')

def random_bytes(length: int = 16) -> bytes:
    "Generate ``length`` random bytes."
    return os.urandom(length)

def base62_digits(bignum: int) -> typing.Generator[str, None, None]:
    "Yield digits."
    assert isinstance(bignum, int) and bignum > 0, "Can only encode positive integers."
    while True:
        yield DIGITS[bignum % 62]
        bignum = bignum // 62
        if bignum <= 0:
            break
    else:
        yield '0'

def base62(buf: bytes) -> str:
    "Encode ``buf` as base62."
    bignum = int.from_bytes(buf, 'big', signed=False)
    digits = list(base62_digits(bignum))
    digits.reverse()
    return ''.join(digits)

def ksuid():
    "Return a segment.io KSUID."
    return base62(timestamp_bytes() + random_bytes())

if __name__ == '__main__':
    print(ksuid())