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From: gwyn@brl-smoke.UUCP
Newsgroups: comp.lang.c
Subject: Re: Copying a constant number of bytes
Message-ID: <5976@brl-smoke.ARPA>
Date: Sat, 13-Jun-87 22:36:46 EDT
Article-I.D.: brl-smok.5976
Posted: Sat Jun 13 22:36:46 1987
Date-Received: Sun, 14-Jun-87 05:42:36 EDT
References: <900@bloom-beacon.MIT.EDU>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Distribution: world
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 17

In article <900@bloom-beacon.MIT.EDU> newman@athena.mit.edu (Ron Newman) writes:
>I want to copy a constant number of bytes NBYTES from address "a"
>to address "b", where "a" and "b" are pointers of unspecified type.
>      bcopy ((char *)a, (char *)b, NBYTES);

Always works (use memcpy rather than bcopy on ANSI-compatible systems).
Does not necessarily involve a subroutine call (depends on implementation),
and the calling overhead is not normally significant anyway.

>      struct nbytes {char s[NBYTES];};
>      *(struct nbytes *)b = *(struct nbytes *)a;

Not guaranteed to work.

The reason for the existence of the str*() and mem*() routines in the
first place is to provide implementation-independent access to
implementation-specific "best" methods of doing these things.  Use them.