Re: [sqlite] vfs implementation question
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Jeffrey Becker wrote: > Cool. I'm actually working on extending Robert Simson's ADO.Net > provider to allow vfs implementations to be written in managed code. I'm doing the same in my Python wrapper for SQLite (APSW). One feature I have implemented is that the VFS can inherit from an existing one. That makes it easier for the developer to do things like a VFS that is like an existing one, but with only specified changes. For example you could easily make one that obfuscates the file by xoring the data with a constant by writing about 10 lines of code. To make testing easier you can make an xWrite that will do I/O errors on demand to verify your own code can handle SQLite telling you there was an I/O error. Roger -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFIq2zZmOOfHg372QQRApzOAJ9W2sGJe7iwk3B9XlzuWEJol/FQXgCg48qu ExBykKM3fDTqrUtwgBSU7zc= =zx60 -END PGP SIGNATURE- ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] vfs implementation question
Cool. I'm actually working on extending Robert Simson's ADO.Net provider to allow vfs implementations to be written in managed code. I hope to get at least two custom vfs implementations into his codebase, a custom memory backed vfs and a true client-server vfs. On Tue, Aug 19, 2008 at 5:45 PM, Richard Klein <[EMAIL PROTECTED]> wrote: > D. Richard Hipp wrote: >> On Aug 19, 2008, at 9:02 AM, Jeffrey Becker wrote: >> >> >>> Should the xLock member of sqlite3_io_methods object block until the >>> lock can be acquired? >> >> xLock does not block on any of the built-in VFSes. But if you want to >> make your own custom VFS that blocks on locks, I don't know of any >> reason why that wouldn't work. > I wrote a custom VFS that blocks on locks, and it works just fine. > > I also implemented a subset of the five locking levels of SQLite: > just UNLOCKED and EXCLUSIVE. This means that as soon as a transaction > asks for a SHARED lock, it actually gets an EXCLUSIVE lock, which > locks out all other transactions until the first one commits. > > This works fine in an embedded application where there are only a > few threads, whose transactions execute quickly. > > - Richard Klein > > ___ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] vfs implementation question
D. Richard Hipp wrote: > On Aug 19, 2008, at 9:02 AM, Jeffrey Becker wrote: > > >> Should the xLock member of sqlite3_io_methods object block until the >> lock can be acquired? > > xLock does not block on any of the built-in VFSes. But if you want to > make your own custom VFS that blocks on locks, I don't know of any > reason why that wouldn't work. I wrote a custom VFS that blocks on locks, and it works just fine. I also implemented a subset of the five locking levels of SQLite: just UNLOCKED and EXCLUSIVE. This means that as soon as a transaction asks for a SHARED lock, it actually gets an EXCLUSIVE lock, which locks out all other transactions until the first one commits. This works fine in an embedded application where there are only a few threads, whose transactions execute quickly. - Richard Klein ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] vfs implementation question
On Aug 19, 2008, at 9:37 AM, Jeffrey Becker wrote: > So in the cases where the lock cant be acquired, the built in vfs > implementations return SQLITE_BUSY? > Yes D. Richard Hipp [EMAIL PROTECTED] ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] vfs implementation question
So in the cases where the lock cant be acquired, the built in vfs implementations return SQLITE_BUSY? On Tue, Aug 19, 2008 at 9:16 AM, D. Richard Hipp <[EMAIL PROTECTED]> wrote: > > On Aug 19, 2008, at 9:02 AM, Jeffrey Becker wrote: > >> Should the xLock member of sqlite3_io_methods object block until the >> lock can be acquired? > > xLock does not block on any of the built-in VFSes. But if you want to > make your own custom VFS that blocks on locks, I don't know of any > reason why that wouldn't work. > > D. Richard Hipp > [EMAIL PROTECTED] > > > > ___ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] vfs implementation question
On Aug 19, 2008, at 9:02 AM, Jeffrey Becker wrote: > Should the xLock member of sqlite3_io_methods object block until the > lock can be acquired? xLock does not block on any of the built-in VFSes. But if you want to make your own custom VFS that blocks on locks, I don't know of any reason why that wouldn't work. D. Richard Hipp [EMAIL PROTECTED] ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
[sqlite] vfs implementation question
Should the xLock member of sqlite3_io_methods object block until the lock can be acquired? ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
