Re: remove bitmap_shift_*() bitmap length limits

[Paul Jackson <pj@sgi.com>]

Bill,

Here's roughly what I mean by slow and stupid (code untested, just a way
of presenting an alternative idea).  Perhaps my head is in a weird
place, but I find the following easier to understand.

lib/bitmap.c:
=============

    static void _setbitval(unsigned long *dst,
			    unsigned int n, int val, unsigned int nbits)
    {
	    if (n >= nbits)
		    return;
	    if (val)
		    set_bit(n, dst);
	    else
		    clear_bit(n, dst);
    }

    static int _getbitval(unsigned long *src, unsigned int n, unsigned int nbits)
    {
	    if (n >= nbits)
		    return 0;
	    return test_bit(n, src) ? 1 : 0;
    }

    void bitmap_shift_right(unsigned long *dst,
			    const unsigned long *src, int shift, int bits)
    {
	    int k;
	    for (k = 0; k < bits; k++)
		    _setbitval(dst, k, _getbitval(src, k+shift, bits), bits);
    }
    EXPORT_SYMBOL(bitmap_shift_right);

    void bitmap_shift_left(unsigned long *dst,
			    const unsigned long *src, int shift, int bits)
    {
	    int k;
	    for (k = 0; k < bits; k++)
		    _setbitval(dst, k, _getbitval(src, k-shift, bits), bits);
    }
    EXPORT_SYMBOL(bitmap_shift_left);

-- 
                          I won't rest till it's the best ...
                          Programmer, Linux Scalability
                          Paul Jackson <pj@sgi.com> 1.650.933.1373