GUID.py
Revision as of 16:08, 16 September 2015 by PeterHarding (talk | contribs)
# globally unique identifier made up of time and ip
# Copyright (C) 2002 Dr. Conan C. Albrecht
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
import random
import socket
import time
class GUID:
'''A globally-unique identifier made up of time and ip and 3 random digits: 35 characters wide
A globally unique identifier that combines ip, time, and random bits. Since the
time is listed first, you can sort records by guid. You can also extract the time
and ip if needed.
GUIDs make wonderful database keys. They require no access to the
database (to get the max index number), they are extremely unique, and they sort
automatically by time. GUIDs prevent key clashes when merging
two databases together, combining data, or generating keys in distributed
systems.
'''
rand = random.Random()
ip = ''
try:
ip = socket.gethostbyname(socket.gethostname())
except (socket.gaierror): # if we don't have an ip, default to someting in the 10.x.x.x private range
ip = '10'
for i in range(3):
ip += '.' + str(rand.randrange(1, 254))
hexip = ''.join(["%04x" % long(i) for i in ip.split('.')]) # leave space for ip v6 (65K in each sub)
lastguid = ''
def __init__(self, guid=None):
'''Constructor. Use no args if you want the guid generated (this is the normal method)
or send a string-typed guid to generate it from the string'''
if guid is None:
self.guid = self.__class__.lastguid
while self.guid == self.__class__.lastguid:
# time part
now = long(time.time() * 1000)
self.guid = ("%016x" % now) + self.__class__.hexip
# random part
self.guid += ("%03x" % (self.__class__.rand.randrange(0, 4095)))
self.__class__.lastguid = self.guid
elif type(guid) == type(self): # if a GUID object, copy its value
self.guid = str(guid)
else: # if a string, just save its value
assert self._check(guid), guid + " is not a valid GUID!"
self.guid = guid
def __eq__(self, other):
'''Return true if both GUID strings are equal'''
if isinstance(other, self.__class__):
return str(self) == str(other)
return 0
def __str__(self):
'''Returns the string value of this guid'''
return self.guid
def time(self):
'''Extracts the time portion out of the guid and returns the
number of milliseconds since the epoch'''
return long(self.guid[0:16], 16)
def ip(self):
'''Extracts the ip portion out of the guid and returns it
as a string like 10.10.10.10'''
# there's probably a more elegant way to do this
ip = []
index = 16
while index < 32:
ip.append(str(int(self.guid[index: index + 4], 16)))
index += 4
return '.'.join(ip)
def random(self):
'''Extracts the random bits from the guid (returns the bits in decimal)'''
return int(self.guid[32:], 16)
### TESTING OF GUID CLASS ###
if __name__ == "__main__":
guid = GUID()
print "GUID:", guid
print "Time:", time.strftime('%a, %d %b %Y %H:%M:%S', time.localtime(guid.time()))
print "IP: ", guid.ip()
print "Rand:", guid.random()
Here's a possibly improved version with basic GUID format checking, __eq__ implementation and a more pythonic ip implementation. Hope you like it.
thanks for sharing.
#!/usr/bin/env python
#------------------------------------------------------------------------------
# Copyright (c) 2005, Enthought, Inc.
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in enthought/LICENSE.txt and may be redistributed only
# under the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
# Thanks for using Enthought open source!
#
# Author: Enthought, Inc.
# Description: <Enthought util package component>
#------------------------------------------------------------------------------
import warnings
warnings.warn("Module is deprecated.", DeprecationWarning)
# GUID.py
# Version 2.1.
#
# Copyright (C) 2003 Dr. Conan C. Albrecht <conan_albrechtATbyu.edu>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
##################################################################################################
### A globally-unique identifier made up of time and ip and 8 random digits: 40 characters wide
###
### A globally unique identifier that combines ip, time, and random bits. Since the
### time is listed first, you can sort records by guid. You can also extract the time
### and ip if needed.
###
### GUIDs make wonderful database keys. They require no access to the
### database (to get the max index number), they are extremely unique, and they sort
### automatically by time. GUIDs prevent key clashes when merging
### two databases together, combining data, or generating keys in distributed
### systems.
###
### There is an Internet Draft for UUIDs, but this module does not implement it.
### If the draft catches on, perhaps I'll conform the module to it.
###
# Changelog
# Sometime, 1997 Created the Java version of GUID
# Went through many versions in Java
# Sometime, 2002 Created the Python version of GUID, mirroring the Java version
# November 24, 2003 Changed Python version to be more pythonic, took out object and made just a module
# December 2, 2003 Fixed duplicating GUIDs. Sometimes they duplicate if multiples are created
# in the same millisecond (it checks the last 100 GUIDs now and has a larger random part)
# December 9, 2003 Fixed MAX_RANDOM, which was going over sys.maxint
#
import random
import socket
import sys
import time
import threading
# The size of the circular queue. Larger sizes give more assurance for uniqueness.
# Smaller sizes take less memory and are a tiny bit faster
QUEUE_SIZE = 100
#############################
### global module variables
MAX_RANDOM = sys.maxint # converted to hex goes to 8 chars (at least, in Python 2.3)
rand = random.Random()
ip = ''
lock = threading.RLock()
lastguid = ''
try:
ip = socket.gethostbyname(socket.gethostname())
except (socket.gaierror): # if we don't have an ip, default to someting in the 10.x.x.x private range
ip = '10'
for i in range(3):
ip += '.' + str(rand.randrange(1, 254))
hexip = ''.join(["%04x" % long(i) for i in ip.split('.')]) # leave space for ip v6 (65K in each sub)
#######################################
### A simple circular set
### to ensure we don't duplicate
### GUIDs in the same millisecond
class CircularSet:
'''A circular set. A set that maxes at a given size, replacing the oldest element after maximum size.
This implementation is NOT thread safe. (generate() below is thread safe, though)
'''
def __init__(self):
self.queue = []
self.queue_map = {} # for efficiency, we keep a map of everything
self.queueindex = 0
def add(self, val):
'''Adds a value to the queue'''
# check to see if we have this value. If so, throw an exception
assert not self.queue_map.has_key(val), 'This value is already in the set!'
# add the new one to the list
if len(self.queue) > self.queueindex:
# first remove the previous key at this location
del self.queue_map[self.queue[self.queueindex]]
self.queue[self.queueindex] = val
else:
self.queue.append(val)
# now add to the map for efficiency
self.queue_map[val] = val
# increment the queue index
self.queueindex += 1
if self.queueindex >= QUEUE_SIZE:
self.queueindex = 0
queue = CircularSet()
#################################
### Public module functions
def generate():
'''Generates a new guid'''
global lock, queue # since we modify the module variable
try:
lock.acquire() # can't generate two guids at the same time
while 1:
parts = []
# time part
parts.append("%016x" % (long(time.time() * 1000)))
# ip part
parts.append(hexip)
# random part
parts.append(("%08x" % (rand.random() * MAX_RANDOM))[:8]) # limit to 8 chars, just in case maxint goes up in future Pythons
# put them all together
guid = ''.join(parts)
try:
queue.add(guid) # throws the AssertionError if this GUID is a duplicate of the queue
return guid
except AssertionError: # signals we already have this GUID in the queue
pass
finally:
lock.release()
def extract_time(guid):
'''Extracts the time portion out of the guid and returns the
number of seconds since the epoch as a float'''
return float(long(guid[0:16], 16)) / 1000
def extract_ip(guid):
'''Extracts the ip portion out of the guid and returns it
as a string like 10.10.10.10'''
# there's probably a more elegant way to do this
ip = ''
index = 16
while index < 32:
if ip != '':
ip += "."
ip += str(int(guid[index: index + 4], 16))
index += 4
return ip
def extract_random(guid):
'''Extracts the random bits from the guid (returns the bits in decimal)'''
return int(guid[32:], 16)
### TESTING OF GUID CLASS ###
if __name__ == "__main__":
guid = generate()
print "GUID:", guid
print "Time:", time.strftime('%a, %d %b %Y %H:%M:%S', time.localtime(extract_time(guid)))
print "IP: ", extract_ip(guid)
print "Rand:", extract_random(guid)