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From: bzs@bu-cs.BU.EDU (Barry Shein)
Newsgroups: comp.lang.c
Subject: Re: Portable C vs Efficient C or "Cost of Portability"
Message-ID: <6980@bu-cs.BU.EDU>
Date: Mon, 27-Apr-87 00:42:40 EDT
Article-I.D.: bu-cs.6980
Posted: Mon Apr 27 00:42:40 1987
Date-Received: Tue, 28-Apr-87 02:03:15 EDT
References: <213@pyuxe.UUCP> <636@edge.UUCP> <1316@frog.UUCP> <658@edge.UUCP> <1017@ubc-cs.UUCP> <682@edge.UUCP> <1103@epimass.UUCP>
Organization: Boston U. Comp. Sci.
Lines: 34
In-reply-to: jbuck@epimass.UUCP's message of 26 Apr 87 20:14:26 GMT

Posting-Front-End: GNU Emacs 18.41.4 of Mon Mar 23 1987 on bu-cs (berkeley-unix)



Everyone, in retort to Doug Pardee's note about character handling in
C vs Asm mentions library routines (and possibly inline asm.)

How about the now well established structure assignment:

struct string {
	char thechars[STRSIZE];
};

If I declare s1 and s2 to be struct strings and do a:

	s1 = s2;

my Vax generates a movc3, my Encore (NS32K) generates a MOVSD
instruction, my Sun (68K) generates a tight dbra loop and my IBM3090
generates a MVCL, all of that is quite optimal if you want to save
yourself a trip to the prin-ops.

I think the problem is (if there is one) that most (all?) machine
architectures don't have a lot to deal with null term'd strings. Oh,
you can use a LOCC on a Vax or even a TRT on an IBM (370, not PC),
minor, but most assembler programmers will go for fixed length string
formats that will match the hardware (not a slur, it's the right thing
if you're after raw speed and can stand some loss in flexibility.)

I can't argue with the success of C's null terminated string formats,
but I've coded in a BCPL string style in C programs to speed up certain
operations and I still have all 10 of my fingers.

It just doesn't often matter much (tho you want to profile strcpy()
when your text processing slows down, you might change your mind.)

	-Barry Shein, Boston University