On 26.02.2011 07:32, Ivan Zhakov wrote: > 2011/2/26 Branko Čibej <br...@e-reka.si>: >> On 25.02.2011 16:53, Julian Foad wrote: >>> On Thu, 2011-02-24, Branko Čibej wrote: >>>> On 24.02.2011 18:03, Julian Foad wrote: >>>>> On Wed, 2011-02-23, Daniel Shahaf wrote: >>>>>> julianf...@apache.org wrote on Tue, Feb 22, 2011 at 15:38:35 -0000: > [...] > >>>> It is not the business of the wc_db+pristine-store to track >>>> every process that happens to have an open handle to the pristine file. >>>> A deletion of the pristine file should succeed even if there are open >>>> handles referring to it. >>> So you're suggesting we should promise that a reader can continue >>> reading the file (at least once through to the end, not sure about >>> rewinding) even if something else deletes the file from the store part >>> way through. I think you're suggesting those semantics are more >>> reasonable than "you have to hold some sort of lock while you read it", >>> which is what my design boiled down to. >> Yes, indeed, they're far more reasonable because the OS already gives >> them to you. On Unix, when you delete a file, it vanishes from the >> directory; but open handles remain valid, and the backing store of the >> data still exists. The file only really goes away when the last handle >> is closed. >> >> On Windows, the situation is pretty much the same (assuming >> FILE_SHARE_DELETE which we've already determined APR always does -- >> guess why :), *except* that the file only vanishes from the directory >> after it's been deleted once the last handle to it is closed, that's why >> I mentioned the tricky part of re-instating the file. >> > [..] >>> I guess I'll have to figure out how to implement this "trifle more >>> involved" part on Windows, now. >> Lucky you, the name of the file is the digest of its contents, so in >> order to reinstate the file on Windows you only have get the system to >> twiddle it's "deleted" bit. "Only." I seem to recall that's not even >> hard to do, but my last battle with Windows filesystem internals was >> more than 10 years ago. If you can't find relevant docs, you could try >> asking APR for that functionality. I'm sure Will Rowe will give you a >> dozen reasons why doing that is not a good idea, and also explain how to >> do it. :) >> > Problem of re-installing file over marked for deletion file can be > solved using the following trick: > 1. Rename file to temporary name. > 2. Delete it
(If the proper share bits are set.) Yes, that'd work, but if there's a way to unmark the deletion bit, that's even better, since then you'd not even have to create another file (with identical contents). -- Brane
