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#!/usr/bin/env python
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# encoding: utf-8
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# GUID.py
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# Version 2.6
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#
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# Copyright (c) 2006 Conan C. Albrecht
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is furnished
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# to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in all
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# copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
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# INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
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# PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
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# FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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# DEALINGS IN THE SOFTWARE.
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##################################################################################################
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### A globally-unique identifier made up of time and ip and 8 digits for a counter:
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### each GUID is 40 characters wide
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###
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### A globally unique identifier that combines ip, time, and a counter. Since the
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### time is listed first, you can sort records by guid. You can also extract the time
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### and ip if needed.
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###
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### Since the counter has eight hex characters, you can create up to
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### 0xffffffff (4294967295) GUIDs every millisecond. If your processor
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### is somehow fast enough to create more than that in a millisecond (looking
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### toward the future, of course), the function will wait until the next
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### millisecond to return.
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###
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### GUIDs make wonderful database keys. They require no access to the
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### database (to get the max index number), they are extremely unique, and they sort
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### automatically by time. GUIDs prevent key clashes when merging
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### two databases together, combining data, or generating keys in distributed
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### systems.
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###
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### There is an Internet Draft for UUIDs, but this module does not implement it.
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### If the draft catches on, perhaps I'll conform the module to it.
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###
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# Changelog
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# Sometime, 1997 Created the Java version of GUID
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# Went through many versions in Java
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# Sometime, 2002 Created the Python version of GUID, mirroring the Java version
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# November 24, 2003 Changed Python version to be more pythonic, took out object and made just a module
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# December 2, 2003 Fixed duplicating GUIDs. Sometimes they duplicate if multiples are created
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# in the same millisecond (it checks the last 100 GUIDs now and has a larger random part)
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# December 9, 2003 Fixed MAX_RANDOM, which was going over sys.maxint
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# June 12, 2004 Allowed a custom IP address to be sent in rather than always using the
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# local IP address.
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# November 4, 2005 Changed the random part to a counter variable. Now GUIDs are totally
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# unique and more efficient, as long as they are created by only
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# on runtime on a given machine. The counter part is after the time
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# part so it sorts correctly.
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# November 8, 2005 The counter variable now starts at a random long now and cycles
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# around. This is in case two guids are created on the same
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# machine at the same millisecond (by different processes). Even though
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# it is possible the GUID can be created, this makes it highly unlikely
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# since the counter will likely be different.
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# November 11, 2005 Fixed a bug in the new IP getting algorithm. Also, use IPv6 range
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# for IP when we make it up (when it's no accessible)
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# November 21, 2005 Added better IP-finding code. It finds IP address better now.
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# January 5, 2006 Fixed a small bug caused in old versions of python (random module use)
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import math
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import socket
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import random
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import sys
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import time
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import threading
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#############################
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### global module variables
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#Makes a hex IP from a decimal dot-separated ip (eg: 127.0.0.1)
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make_hexip = lambda ip: ''.join(["%04x" % long(i) for i in ip.split('.')]) # leave space for ip v6 (65K in each sub)
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MAX_COUNTER = 0xfffffffe
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counter = 0L
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firstcounter = MAX_COUNTER
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lasttime = 0
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ip = ''
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lock = threading.RLock()
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try: # only need to get the IP addresss once
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ip = socket.getaddrinfo(socket.gethostname(),0)[-1][-1][0]
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hexip = make_hexip(ip)
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except: # if we don't have an ip, default to someting in the 10.x.x.x private range
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ip = '10'
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rand = random.Random()
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for i in range(3):
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ip += '.' + str(rand.randrange(1, 0xffff)) # might as well use IPv6 range if we're making it up
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hexip = make_hexip(ip)
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#################################
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### Public module functions
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def generate(ip=None):
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'''Generates a new guid. A guid is unique in space and time because it combines
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the machine IP with the current time in milliseconds. Be careful about sending in
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a specified IP address because the ip makes it unique in space. You could send in
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the same IP address that is created on another machine.
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'''
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global counter, firstcounter, lasttime
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lock.acquire() # can't generate two guids at the same time
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try:
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parts = []
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# do we need to wait for the next millisecond (are we out of counters?)
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now = long(time.time() * 1000)
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while lasttime == now and counter == firstcounter:
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time.sleep(.01)
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now = long(time.time() * 1000)
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# time part
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parts.append("%016x" % now)
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# counter part
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if lasttime != now: # time to start counter over since we have a different millisecond
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firstcounter = long(random.uniform(1, MAX_COUNTER)) # start at random position
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counter = firstcounter
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counter += 1
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if counter > MAX_COUNTER:
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counter = 0
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lasttime = now
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parts.append("%08x" % (counter))
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# ip part
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parts.append(hexip)
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# put them all together
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return ''.join(parts)
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finally:
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lock.release()
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def extract_time(guid):
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'''Extracts the time portion out of the guid and returns the
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number of seconds since the epoch as a float'''
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return float(long(guid[0:16], 16)) / 1000.0
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def extract_counter(guid):
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'''Extracts the counter from the guid (returns the bits in decimal)'''
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return int(guid[16:24], 16)
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def extract_ip(guid):
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'''Extracts the ip portion out of the guid and returns it
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as a string like 10.10.10.10'''
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# there's probably a more elegant way to do this
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thisip = []
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for index in range(24, 40, 4):
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thisip.append(str(int(guid[index: index + 4], 16)))
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return '.'.join(thisip)
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