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From "William A. Rowe, Jr." <wr...@rowe-clan.net>
Subject apr-util/dbm/sdbm page sizes
Date Fri, 19 Sep 2003 19:56:03 GMT
As a few here already know, we used the 'Standard' page size for our
apr-util SDBM implementation.  This assures that you can modify our
sdbm files from perl and other tools.

However, it's pretty clear that 1024 just doesn't cut it when it comes
to huge objects from ssl caching and other sorts of large blobs.  The
modssl project (1.3) had tweaked sdbm to take larger page sizes, but
this leads to an inflexible implementation (another fixed page size, but
incompatible with other implementations.)

I'd like to see apr-util support alternate sized dbm pages, but without
making fixed assumptions about those sizes (other than this - the 
structure uses short's for offsets, so the page size does have a cap.)

The attached patch allows the SDBM to be of any arbitrary data and
directory page sizes.  However, I've not hacked in any method of
declaring what those sizes should be (they are the 'standard' defaults
at the moment.)

What do folks believe is the most rational approach to expanding support 
to create an sdbm with alternate page sizes?  And how best can we embed 
that info into the sdbm so that later accesses to the file use the correct
page size?  My current thought is to embed a NULL-key record at the head
of the file, with a specific known value element containing some identifier
string such as "APR-SDBM" followed by two ints, the page and data len.
If that record is missing (or created with default sizes), the file is treated 
as a standard sdbm with 1024/4096 sized pages.

Other thoughts, suggestions or observations?

Bill
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