Re: On NSIncrementalStore UUID Uniqueness
Re: On NSIncrementalStore UUID Uniqueness
- Subject: Re: On NSIncrementalStore UUID Uniqueness
- From: Jean-Daniel <email@hidden>
- Date: Fri, 20 Jan 2017 01:00:15 +0100
> Le 19 janv. 2017 à 22:18, Daryle Walker <email@hidden> a écrit :
>
>
>> On Jan 16, 2017, at 12:08 PM, Charles Srstka <email@hidden> wrote:
>>
>>> On Jan 14, 2017, at 4:41 AM, Daryle Walker <email@hidden <mailto:email@hidden>> wrote:
>>>
>>> Could I base the UUID off a hash of the URL? Maybe, but it wouldn’t survive file moves. There are file references in macOS, which would be more stable, but I read that there’s a bug in the URL class where it would degrade file-reference URLs to standard-file URLs, so that’ll be problematic. Another solution would to create bookmark data from a file URL and take a hash of that. But are multiple bookmark data blocks of the same file URL consistent enough for this idea to work?
>>
>> The thing with file reference URLs degrading to file path URLs is in the Swift is actually not a bug, it’s deliberate (https://bugs.swift.org/browse/SR-2728 <https://bugs.swift.org/browse/SR-2728>). The Swift team decided that file reference URLs are not appropriate for the Swift URL value type. However, if you’re using Objective-C, file reference URLs will still work fine, and you can always make an Objective-C wrapper that stores a file reference URL and use that from Swift.
>
> I looked at some code that gives a workaround for the file-reference URL problem. It grabs the reference ID as a 128-bit value, dumps it into 2 64-bit values, then sprinkles those onto a URL string template. Since UUIDs are 128-bit values, I could just copy a reference ID directly into a UUID.
The file reference URL content is an implementation details and relying on the fact that a reference ID is 128 bit is very fragile IMHO, especially as Apple is planning to introduce a new FS soon. On APFS they may decide to use something completely different for file reference.
_______________________________________________
Cocoa-dev mailing list (email@hidden)
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:
This email sent to email@hidden