On May 13, 2010, at 11:52 AM, Louis Gerbarg wrote: > On May 13, 2010, at 11:05 AM, Michael Ash <michael....@gmail.com> wrote: > >> On Thu, May 13, 2010 at 10:56 AM, Thomas Davie <tom.da...@gmail.com> wrote: >>> >>> On 13 May 2010, at 15:33, Eric Gorr wrote: >>> >>>> So long as it is ok for the string to be unique for the network the user >>>> is on only. From the docs: >>>> >>>> The ID includes the host name, process ID, and a time stamp, which ensures >>>> that the ID is unique for the network. >>>> >>>> A UUID (Universally Unique Identifier) is entirely unique. >>> >>> No it's not, as can easily be proven by observing that there are only a >>> finite number of 40 character strings. A UUID is probabilistically unique. >> >> CFUUID includes the MAC address, so unless your MAC address is cloned >> or you manage to generate two UUIDs on the same device in the same >> 100ns time interval or the calendar rolls over (which will take about >> 3700 years), they are entirely unique within the universe of CFUUID >> strings. > > No, it doesn't use the MAC address. MAC addresses are uses as part of type 1 > uuids, CFUUID has generated type 4 (random) uuids by default since Tiger, and > has always generated type 4 on iPhone. If you look at the source to CF there > is a way to force it to generate type 1 uuids, but I doubt that is supported.
From the documentation: http://bit.ly/9m1Ggb UUIDs (Universally Unique Identifiers), also known as GUIDs (Globally Unique Identifiers) or IIDs (Interface Identifiers), are 128-bit values guaranteed to be unique. A UUID is made unique over both space and time by combining a value unique to the computer on which it was generated—usually the Ethernet hardware address—and a value representing the number of 100-nanosecond intervals since October 15, 1582 at 00:00:00. So, regardless, a UUID (via the CFUUID API) is going to be better then [[NSProcessInfo processInfo] globallyUniqueString] _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
