Hi, On Wed, 22 Mar 2017, James Richters wrote:
> No, it is not only freepascal, but not every program either. I'm no Windows expert, but Windows API seems to have a way do to this directly. CreateFile() API seems to have a flag, which has a value FILE_FLAG_WRITE_THROUGH, which will cause the file not go through the write cache, but gets written directly to the underlying disk, without delays. However, this obviously has performance implications on write (will be a lot slower), and as the documentation notes, it's not supported on every hardware or file system. Also, I'm not sure if you can do this somehow together with Free Pascal's file handling API, or you have to restrict yourself to using direct Windows API calls entirely for writing this file. Relevant MSDN page: https://msdn.microsoft.com/en-us/library/windows/desktop/aa363858(v=vs.85).aspx#caching_behavior However, please note that transactional file handling on power loss is a quite delicate scenario, so you might not be able to solve all the related problems with this - what happens exactly when you get a power loss during a write, might be matter of pure luck. The usual way to work this problem around on Linux systems at least, is to write a new file, then do an overwriting rename to the old file name. There rename is an "atomic" operation, which will be either committed to the disk or not, but if it was unsuccessful, you won't end up with half-written files. But IIRC Windows didn't support atomic renames. Maybe someone with more Windows knowledge will fix me. You definitely don't want to implement a copy though, and that's anything but atomic. Charlie _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
