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From: stevesu@copper.UUCP
Newsgroups: comp.lang.c
Subject: Re: Copying a constant number of bytes
Message-ID: <1120@copper.TEK.COM>
Date: Sat, 13-Jun-87 17:00:39 EDT
Article-I.D.: copper.1120
Posted: Sat Jun 13 17:00:39 1987
Date-Received: Sun, 14-Jun-87 18:36:48 EDT
References: <900@bloom-beacon.MIT.EDU>
Organization: Tektronix Inc., Beaverton, Or.
Lines: 23

In article <900@bloom-beacon.MIT.EDU>, newman@athena.mit.edu (Ron Newman) writes:
> I want to copy a constant number of bytes...  Which is the more
> efficient method for most compilers and machines currently in use?
> 
> Method 1)
> 
>       bcopy ((char *)a, (char *)b, NBYTES);
> 
> Method (1) has the disadvantage that it always involves a subroutine
> call and return.

How sure are you that this is a disadvantage?  I always use
bcopy, and I've never found it to be an efficiency bottleneck.
Until you've profiled your code and proved that bcopy itself or
the associated function call overhead is significant, don't fuss
with other methods.  (BTW, the structure-assignment trick does
work, under "reasonable" compilers, and produces nice, tight
code, but it certainly "looks" fishy enough that I'd be loathe to
use it in bulletproof, portable code even if somebody can come up
with an argument that it's legal.)

                                           Steve Summit
                                           stevesu@copper.tek.com