Path: utzoo!attcan!uunet!portal!cup.portal.com!thad
From: thad@cup.portal.com
Newsgroups: comp.lang.c
Subject: Re: Packed structures (was: Absolute size of 'short')
Message-ID: <8535@cup.portal.com>
Date: 29 Aug 88 06:28:07 GMT
References: <214@ISIDAPS5.UUCP> <9641@dartvax.Dartmouth.EDU> <62505@sun.uuc
Organization: The Portal System (TM)
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XPortal-User-Id: 1.1001.2826

But, the machine for which I *NEEDED* that capability (DECSYSTEM-20) does
have pointers to bits (bits of any size from 1 to 36 bits).  I also needed
needed the equivalent of "packed structures" (and implemented that, too).

The original "program" comprised some 1,000,000 lines of assembly code of
which I did approx. 50% (parsers, code gen, runtime, etc.).  3 years ago
began the re-implementation in C (to ease porting to other architectures),
but approx. 25% of the DEC-20 implementation remains in assembly with which
the new C code must co-exist (esp. data structures).

For the VAX and 68020 implementations, nearly all bit fields (AND unions)
have been removed.

The discussion re: packed structures earlier in this newsgroup brings home
a requirement that sometimes storage efficiency "weighs more" than does
processing efficiency.

Some of my clients have databases (processed using my product) exceeding
100,000,000 "records"; for them, storage efficiency is critical (also
reduces I/O bandwidth).

Having the sources to the compiler was a lifesaver; was able to timely
and cost-effectively solve a real problem (fully realizing the non-portability
of my solution).