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Copying files containing 'holes' [message #80558] Mon, 03 June 2013 23:51 Go to next message
bridger is currently offline  bridger
Messages: 19
Registered: May 2013
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Message-ID: <12376@sri-arpa.UUCP>
Date: Tue, 25-Sep-84 16:13:30 EDT
Article-I.D.: sri-arpa.12376
Posted: Tue Sep 25 16:13:30 1984
Date-Received: Sun, 30-Sep-84 00:47:14 EDT
Lines: 22

From:  Bridger Mitchell 

Under CP/M 2.2,..., files written by random access may contain 'holes'--
logical data records that have never been written.  A number of
utilities don't seem to handle this situation well.

PIP copies only at most some of the written records, missing those in higher
directory extents.

SD reports 'virtual' file size -- the number of blocks (in Kbytes)
required if the file consisted entirely of written records.  It's easy
to get multi-megabyte sizes reported.

What 'should' a well-behaved utility do  -- i.e. what's the most useful
filesize report, and which records should be copied?  On first thought,
it seems that the size should be number of *allocated* blocks (in Kbytes)
and the copy should consist of exactly those blocks, except that in the final
block only the records <= last record of file should be copied.

Have other utilities already worked this out?

--bridger
Re: Copying files containing 'holes' [message #80560 is a reply to message #80558] Mon, 03 June 2013 23:51 Go to previous message
towson is currently offline  towson
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Message-ID: <12391@sri-arpa.UUCP>
Date: Wed, 26-Sep-84 11:01:46 EDT
Article-I.D.: sri-arpa.12391
Posted: Wed Sep 26 11:01:46 1984
Date-Received: Sun, 30-Sep-84 04:13:39 EDT
Lines: 13

From:      David Towson (SECAD) 

Bridger - You have raised an interesting question.  I have never used
random CP/M files with "holes", but I have read about them.  I think I 
agree with your position on what should be copied.  I wonder, however,
how CP/M treats such a file if you ask the CCP to TYPE it.  What goes to
the screen - just the written sectors, written sectors with intervening
garbage, or what?  And if just the written sectors are displayed, in what
order do you see them?


Dave
towson@amsaa
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