[DUG] Setting Data File Size

[John Bird]

Is there a simple way to alter the size of an existing file - particularly to decrease the size?

If increasing I can append some blank data on the end no problem using TFilestream, no problem.

The thing I am not sure about is if I can DECREASE the size of a file by a known number of bytes

(Background - this is a single data file in use by more than one place in the file from time to time, so I prefer to access it using TFileStream, as that can do a better job of simultaneous access than assignfile/text file/file (which does tend to lock  a file for exclusive access at times).  I use fs := Tfilestream.create(FileName, fmOpenRead or fmShareDenyNone);

>From time to time the file needs to have records added or deleted.  Up to now I did this by recreating the file with a temporary name then renaming it over the original.

Despite taking all the care to make sure no process is reading the file when I do this, Windows does frequently complain about it being in use by another process - I think it is an issue to do with Windows cached reads and writes still not completed, or Windows being a little out of date with its record of what is using the file.

I think I will have switch to rewriting the data in place by rewriting the part of the file that has changed, which I know how to do, except I don't know how to shorten the file if needed.)

John
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