Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!cf-cm!cf-cm!bharat
From: bharat@cf-cm.computing-maths.cardiff.ac.uk (Bharat Mediratta)
Newsgroups: comp.unix.questions
Subject: Re: bit mover
Message-ID: <1991Mar14.135610.23380@cm.cf.ac.uk>
Date: 14 Mar 91 13:56:10 GMT
References: <788@llnl.LLNL.GOV>
Sender: news@cm.cf.ac.uk (USENET News System)
Organization: University of Wales College of Cardiff
Lines: 48

In article <788@llnl.LLNL.GOV> handeli@ocfmail.ocf.llnl.gov () writes:
>I need a C function which can move arbitrary
>bits around from one memory location to another
>with a bit offset of anything. For example,
>the call might look like
>
>movebits(a1,ioff1,a2,ioff2,nbits)
>
>where a1 and a2 are char arrays
>ioff1 and ioff2 are bit offsets into the
>char arrays
>nbits is the number of bits to move.
>a1 might be source address and a2 might be
>destination address.
>
>Anybody have such a function?


DISCLAIMER: I haven't tested this, but I think it will work.

/* 
 * Off1 & Off2 are the offsets of the bit 
 * 0 = rightmost bit.
 * No error correction
 */     
movebits(src, off1, dest, off2, nbits)
int *src, *dest;
int off1, off2, nbits;
{
        off1 = 1<<off1; 
        off2 = 1<<off2; 
        while (nbits--) 
        {
		*dest &= ~off2; /* Zero out the location */
		*dest |= ((*src & off1)? 0xFFFF : 0x0000) & off2;  /* Yuk */
                off2 <<=1; 
                off1 <<=1;
        }
}

Cheers!

 -Bharat 
--
|  Bharat Mediratta  | JANET: bharat@cm.cf.ac.uk                               |
+--------------------+ UUNET: bharat%cm.cf.ac.uk%cunyvm.cuny.edu@uunet.uucp    |
|On a clear disk...  | uk.co: bharat%cm.cf.ac.uk%cunyvm.cuny.edu%uunet.uucp@ukc|
|you can seek forever| UUCP: ...!uunet!cunym.cuny.edu!cm.cf.ac.uk!bharat       |