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From: wirzeniu@cs.Helsinki.FI (Lars Wirzenius)
Newsgroups: comp.lang.c
Subject: Re: Finding NULL byte in a long
Message-ID: <9918@hydra.Helsinki.FI>
Date: 11 Dec 90 11:40:26 GMT
References: <1990Dec5.033206.10463@nimbus3.uucp> <198@nazgul.UUCP>
Sender: news@cs.Helsinki.FI
Organization: University of Helsinki, Department of Computer Science
Lines: 19

In article <198@nazgul.UUCP> bright@nazgul.UUCP (Walter Bright) writes:
>In article <1990Dec5.033206.10463@nimbus3.uucp> djs@nimbus3.UUCP (Doug) writes:
>/I know this has been on the net before, since I thought I saved it,
>/but can't find it now.  Anyway, could someone tell me what the
>/C expression is that tells you if a long has a NULL byte in it.
>/This is without masking each byte and testing it for 0.  It is very
>/clever and non-obvious.  Thanks.
>
>Hmmm, how about:
>	p = memchr(&x,0,sizeof(x));

How about (assuming sizeof(x) == 4, easily modified for other sizes):

	((char *) &x)[0] == 0 ||
	((char *) &x)[1] == 0 ||
	((char *) &x)[2] == 0 ||
	((char *) &x)[3] == 0

Lars Wirzenius    wirzeniu@cs.helsinki.fi    wirzenius@cc.helsinki.fi