Re: [Qemu-devel] [PATCH v4 1/4] bitmap: bitmap_count_one_with_offset

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

* Wei Wang (wei.w.wang@intel.com) wrote:
> Count the number of 1s in a bitmap starting from an offset.
> 
> Signed-off-by: Wei Wang <wei.w.wang@intel.com>
> CC: Dr. David Alan Gilbert <dgilbert@redhat.com>
> CC: Juan Quintela <quintela@redhat.com>
> CC: Michael S. Tsirkin <mst@redhat.com>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  include/qemu/bitmap.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/include/qemu/bitmap.h b/include/qemu/bitmap.h
> index 509eedd..e3f31f1 100644
> --- a/include/qemu/bitmap.h
> +++ b/include/qemu/bitmap.h
> @@ -228,6 +228,19 @@ static inline long bitmap_count_one(const unsigned long *bitmap, long nbits)
>      }
>  }
>  
> +static inline long bitmap_count_one_with_offset(const unsigned long *bitmap,
> +                                                long offset, long nbits)
> +{
> +    long aligned_offset = QEMU_ALIGN_DOWN(offset, BITS_PER_LONG);
> +    long redundant_bits = offset - aligned_offset;
> +    long bits_to_count = nbits + redundant_bits;
> +    const unsigned long *bitmap_start = bitmap +
> +                                        aligned_offset / BITS_PER_LONG;
> +
> +    return bitmap_count_one(bitmap_start, bits_to_count) -
> +           bitmap_count_one(bitmap_start, redundant_bits);
> +}
> +
>  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);
> -- 
> 1.8.3.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK