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- Newsgroups: comp.sys.next.sysadmin
- Path: sparky!uunet!europa.asd.contel.com!darwin.sura.net!haven.umd.edu!ni.umd.edu!sayshell.umd.edu!louie
- From: louie@sayshell.umd.edu (Louis A. Mamakos)
- Subject: Re: WangDAT: How to fseek() ?
- Message-ID: <1992Jul28.215226.9960@ni.umd.edu>
- Keywords: cron
- Sender: usenet@ni.umd.edu (USENET News System)
- Nntp-Posting-Host: sayshell.umd.edu
- Organization: University of Maryland College Park
- References: <1992Jul26.115817.27702@mic.ucla.edu> <nq9sp2o@zuni.esd.sgi.com>
- Date: Tue, 28 Jul 1992 21:52:26 GMT
- Lines: 29
-
- In article <nq9sp2o@zuni.esd.sgi.com> olson@anchor.esd.sgi.com (Dave Olson) writes:
- >In <1992Jul26.115817.27702@mic.ucla.edu> iwelch@agsm.ucla.edu (Ivo Welch) writes:
- >| I would like to write a few programs to lay out our large databases onto a DAT
- >| tape. Unfortunately, I lack all expertise with tape drives, and my Wang
- >| manual is less than explicit.
- >|
- >| I understand how to use devices (/dev/rxt0, /dev/nrxt0) to read and write data
- >| byte by byte and file by file. What I really would like, though, is the
- >| additional ability to keep an index on disk, and do a fast fseek() that
- >| employs the WangDATs fast seek facilities. How would I do this in a C program?
- >|
- >| I.e. could some kind sole please send me replacements for fseek() and ftell()
- >| with such DAT tape drives, please?
- >
- >The drive has the ability to do fast seeks, but fseek and ftell are
- >unlikely to work. It may also be that the NeXT tape drive doesn't
- >provide this functionality.
-
- There is no "built-in" support for random seeking to blocks on DAT
- tape media, but it is not too difficult to issue "raw" SCSI commands
- to the tape driver with the appropriate commands to perform the
- seeking.
-
- Seeking is the easy part; maintaining the database of where to seek
- *to* is the tough part. This is one of the features of the Safetynet
- program mentioned in the original article.
-
- louie
-
-