magic cookies given back by ftell, and used in fseek

[Dave Jones]

in article <129 at lakart.UUCP>, dg at lakart.UUCP (David Goodenough) says:
> 
> There has been much discussion in this group on the fact that on certain
> systems (VMS I believe), ftell & fseek use magic cookies to tell about
> file position. I have my asbestos suit ready if this suggestion is out of
> line, but have the ANSI comittee considered providing some means to convert
> from cookie format to and from character position in file.

The problem is that some operating systems have file-format built into
them :-(, whereas UNIX has unformated byte-streams :-).

One example is to store "lines" in variable length records, prefixed by a 
line-length number. So now if the devil chooses a byte-count offset x, and 
says fseek(x), you've got to do some pretty fancy stepping to find the
correct record and offset into it.  For such a file, ftell would
presumably return a magic cookie which codes for record number and
offset.

Sigh.


		-- Dave J.