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From: oz@ursa.ccs.yorku.ca (Ozan Yigit)
Newsgroups: comp.archives
Subject: [unix-questions...] Re: dbm docs?
Message-ID: <1991May25.021354.8535@ox.com>
Date: 25 May 91 02:13:54 GMT
References: <1991May18.203633.21387@dartvax.dartmouth.edu>
Sender: emv@msen.com (Edward Vielmetti, MSEN)
Reply-To: oz@ursa.ccs.yorku.ca (Ozan Yigit)
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Archive-name: database/dbm/bsd-db/1991-05-23
Archive: postgres.berkeley.edu:/pub/bsd_db.tar.Z [128.32.149.1]
Original-posting-by: oz@ursa.ccs.yorku.ca (Ozan Yigit)
Original-subject: Re: dbm docs?
Reposted-by: emv@msen.com (Edward Vielmetti, MSEN)


pete@othello.dartmouth.edu (Pete Schmitt) writes:

   I'm looking for any docs (beyond the man page) for dbm.  The information
   I'm looking for is how the data is stored in both the .dir and .pag files
   and how they are used together internally.

You can find out about the exact details of dbm/ndbm's page file format in
the sdbm implementation, as sdbm uses the very same format of dbm/ndbm.
Sdbm also comes with a few trivial utilities to work with the page files
alone, ignoring the dir file. The dir file format is simple: it is an
array of bits, and the algorithm to generate those bits is different for
sdbm and ndbm. To put it simply, it is the split history of the page file,
and any attempt to utilize it must have the same generation algorithm and
the same hash function as the database library.

Everything else you might want to know about dbm-style external hashing
algorithms is detailed in [1], ftpable from nexus.yorku.ca under pub/oz
as hash.ps.Z.

If you need a very nice and fast hashing package with full dbm/ndbm
capabilities, you should get the berkeley hash package, ftpable from
postgres.berkeley.edu as bsd_db.tar.Z. This package includes a btree
library as well.

oz
---
[1] Seltzer and Yigit, A New Hash Package for UNIX,
    Proceedings of the USENIX Technical Conference, Dallas, Texas.
    January 1991, 173-184
---
Not all good things come with three	 | internet: oz@nexus.yorku.ca
pages of dogma and an attitude. - anon   | uucp: utzoo/utai!yunexus!oz

-- comp.archives file verification
postgres.berkeley.edu
-r--r--r--  1 ftp      ftp        238109 Feb 19 00:06 /pub/bsd_db.tar.Z
found bsd-db ok
postgres.berkeley.edu:/pub/bsd_db.tar.Z