On Friday, August 30, 2002, at 02:53 PM, Joseph J. Strout wrote:
At 2:45 PM -0400 8/30/02, Charles Yeomans wrote:
It would be safer to write the new file to a temporary file, then
swap the contents of the two files. There are MacOS File Manager
functions that you can use to do this. I assume that the Windows
API supports this sort of operation as well.
Though not quite as good as swapping the file contents, there's
another method that's almost and good but more portable. Write out
your new file to the same folder but with a temporary file name
(just make up one that doesn't already exist). Then, when that's
done successfully, rename the old file to a different temporary
name, name your new file to its proper name, and delete the old
file.
In any case, the idea is to put off deleting the old file as long
as possible, so that if you crash (lose power, etc.) in the middle
of saving, the user's data isn't lost.
Sure, but it's much more macho to use a toolbox call.
Charles Yeomans
The toolbox call also has the advantage that you don't lose meta-data
(original creation date, finder comments, custom icons, label, other
things).
If you use the 2nd method above (swapping names) don't forget to copy
the metadata too. (Used to be GetFInfo() call I think, but you can
do some of it in RB.)
It involves twice as much data be written, but you could copy the old
file into a temp file (.BAK), close it, zero the length of the
original file & write your data into it, close it, then delete the
temp copy. Whew! Guess that's why there's a system call!
Dave
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