bit mover

[Bharat Mediratta]

In article <788 at llnl.LLNL.GOV> handeli at 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 
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