Subj : HW 100.2
To   : Amcleod
From : Prime
Date : Sat Dec 08 2001 06:20 am

RE: HW 100.2
BY: Amcleod to Prime on Thu Dec 06 2001 16:04:00

 > RE: HW 100.2
 > BY: Prime to Amcleod on Tue Sep 19 2000 07:31 am
 > 
 >  >  > Don't try doing arithmetic with file handles!  :)  The arithmetic will
 >  >  > fine, but the files themselves are likely to go to hell very shortly
 >  >  > thereafter!
 >  > 
 >  > What, exactly, _WOULD_ happen if you _did_ do arithmetic with file handle
 >  > 
 > 
 > Well, handles are just integers, and they can be just about anything.  for
 > instance they may represent integer indexes into a table of file-control-blo
 > so if you added your third and fifth handles you would get the handle of som
 > file furthur up the table -- possibkly one never opened --  and the results 
 > accessing that file would be (most likely) a dismal failure with interesting
 > side-effects.  Possibly the the handle is the actuall _address_ of the FCB a
 > so monkeying with them could give a pointer into some random part of memory
 > which would again, give interesting and unpredictable side effects if you tr
 > to use it.
 > 
 > You can probably experiment safely with _writing_ the file handle to the
 > console.  Open three or four files and print the file handles as integers.  
 > may get a series of integers like 3, 4, 5, 6 for the four filehandles.  SO y
 > add two to the first file handle and it suddenly becomes the third
 > filehandle...
 > \/s

Just a thought, but shouldn't there be some mechinism to prevent the accidental
adding of file handles?


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