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 -- Ivan Zhakov VisualSVN Team
