gistfile1.py

"""
Derived from the uuid module in standard lib.
"""

from uuid import UUID, getnode
import time, random

def uuid1(timestamp=None):
    """
    Generate a type 1 UUID from a timestamp, (or the current time).
    """

    if timestamp is None: nanoseconds = int(time.time() * 1e9)
    else: nanoseconds = int(timestamp * 1e9)

    # 0x01b21dd213814000 is the number of 100-ns intervals between the
    # UUID epoch 1582-10-15 00:00:00 and the Unix epoch 1970-01-01 00:00:00.
    timestamp = int(nanoseconds//100) + 0x01b21dd213814000L

    clock_seq = random.randrange(1<<14L) # instead of stable storage
    time_low = timestamp & 0xffffffffL
    time_mid = (timestamp >> 32L) & 0xffffL
    time_hi_version = (timestamp >> 48L) & 0x0fffL
    clock_seq_low = clock_seq & 0xffL
    clock_seq_hi_variant = (clock_seq >> 8L) & 0x3fL
    node = getnode()

    return UUID(fields=(time_low, time_mid, time_hi_version,
                        clock_seq_hi_variant, clock_seq_low, node), version=1)

def datetime_for_uuid1(uuid):
    """
    Return a Python datetime for a type 1 UUID.
    """
    from datetime import datetime

    # 0x01b21dd213814000 is the number of 100-ns intervals between the
    # UUID epoch 1582-10-15 00:00:00 and the Unix epoch 1970-01-01 00:00:00.
    nanos = ((uuid.get_time() - 0x01b21dd213814000L) * 1e2)

    return datetime.fromtimestamp(nanos / 1e9)