Re: [Qemu-devel] [RFC 04/29] bitmap: introduce bitmap_invert()

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Peter Xu (peterx@redhat.com) wrote:
> It is used to invert the whole bitmap.

Would it be easier to change bitmap_complement to use ^
in it's macro and slow_bitmap_complement, and then you could call it
with src==dst  to do the same thing with just that small change?

Dave

> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  include/qemu/bitmap.h | 10 ++++++++++
>  util/bitmap.c         | 13 +++++++++++++
>  2 files changed, 23 insertions(+)
> 
> diff --git a/include/qemu/bitmap.h b/include/qemu/bitmap.h
> index c318da1..460d899 100644
> --- a/include/qemu/bitmap.h
> +++ b/include/qemu/bitmap.h
> @@ -82,6 +82,7 @@ int slow_bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
>                         const unsigned long *bitmap2, long bits);
>  int slow_bitmap_intersects(const unsigned long *bitmap1,
>                             const unsigned long *bitmap2, long bits);
> +void slow_bitmap_invert(unsigned long *bitmap, long nbits);
>  
>  static inline unsigned long *bitmap_try_new(long nbits)
>  {
> @@ -216,6 +217,15 @@ static inline int bitmap_intersects(const unsigned long *src1,
>      }
>  }
>  
> +static inline void bitmap_invert(unsigned long *bitmap, long nbits)
> +{
> +    if (small_nbits(nbits)) {
> +        *bitmap ^= BITMAP_LAST_WORD_MASK(nbits);
> +    } else {
> +        slow_bitmap_invert(bitmap, nbits);
> +    }
> +}
> +
>  void bitmap_set(unsigned long *map, long i, long len);
>  void bitmap_set_atomic(unsigned long *map, long i, long len);
>  void bitmap_clear(unsigned long *map, long start, long nr);
> diff --git a/util/bitmap.c b/util/bitmap.c
> index efced9a..9b7408c 100644
> --- a/util/bitmap.c
> +++ b/util/bitmap.c
> @@ -355,3 +355,16 @@ int slow_bitmap_intersects(const unsigned long *bitmap1,
>      }
>      return 0;
>  }
> +
> +void slow_bitmap_invert(unsigned long *bitmap, long nbits)
> +{
> +    long k, lim = nbits/BITS_PER_LONG;
> +
> +    for (k = 0; k < lim; k++) {
> +        bitmap[k] ^= ULONG_MAX;
> +    }
> +
> +    if (nbits % BITS_PER_LONG) {
> +        bitmap[k] ^= BITMAP_LAST_WORD_MASK(nbits);
> +    }
> +}
> -- 
> 2.7.4
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK