[libvirt] [PATCH 1/3] util: Add a helper to check if all bits of a bitmap are clear

[John Ferlan]

On 04/02/2013 01:42 AM, Osier Yang wrote:
> ---
>  src/libvirt_private.syms |  1 +
>  src/util/virbitmap.c     | 30 ++++++++++++++++++++++++++++++
>  src/util/virbitmap.h     |  3 +++
>  3 files changed, 34 insertions(+)
> 

Since there already is a "virBitmapIsAllSet()" - why isn't it used?  I
see callers which do "if (virBitmapIsAllSet(...)" and "if
(!virBitmapIsAllSet(...)".

If you're going to have a AllClear(), then why not change those !
callers to use AllClear()...

I only wonder about the last comparison - it's the "-1" logic that
throws me off especially since the IsAllSet() code is doing a comparison.

It also stands to reason that tests/virbitmaptest.c could add new tests
to ensure you did get the logic right.

John

> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index 96eea0a..35ac957 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -1048,6 +1048,7 @@ virBitmapEqual;
>  virBitmapFormat;
>  virBitmapFree;
>  virBitmapGetBit;
> +virBitmapIsAllClear;
>  virBitmapIsAllSet;
>  virBitmapNew;
>  virBitmapNewCopy;
> diff --git a/src/util/virbitmap.c b/src/util/virbitmap.c
> index 21509ac..99a8572 100644
> --- a/src/util/virbitmap.c
> +++ b/src/util/virbitmap.c
> @@ -591,6 +591,36 @@ bool virBitmapIsAllSet(virBitmapPtr bitmap)
>  }
>  
>  /**
> + * virBitmapIsAllClear:
> + * @bitmap: the bitmap to check
> + *
> + * check if all bits in @bitmap are clear
> + */
> +bool virBitmapIsAllClear(virBitmapPtr bitmap)
> +{
> +    int i;
> +    int unusedBits;
> +    size_t sz;
> +
> +    unusedBits = bitmap->map_len * VIR_BITMAP_BITS_PER_UNIT - bitmap->max_bit;
> +
> +    sz = bitmap->map_len;
> +    if (unusedBits > 0)
> +        sz--;
> +
> +    for (i = 0; i < sz; i++)
> +        if (bitmap->map[i] != 0)
> +            return false;
> +
> +    if (unusedBits > 0) {
> +        if ((bitmap->map[sz] & ((1UL << (VIR_BITMAP_BITS_PER_UNIT - unusedBits)) - 1)))
> +            return false;
> +    }
> +
> +    return true;
> +}
> +
> +/**
>   * virBitmapNextSetBit:
>   * @bitmap: the bitmap
>   * @pos: the position after which to search for a set bit
> diff --git a/src/util/virbitmap.h b/src/util/virbitmap.h
> index 044c7a6..b682523 100644
> --- a/src/util/virbitmap.h
> +++ b/src/util/virbitmap.h
> @@ -100,6 +100,9 @@ void virBitmapClearAll(virBitmapPtr bitmap)
>  bool virBitmapIsAllSet(virBitmapPtr bitmap)
>      ATTRIBUTE_NONNULL(1);
>  
> +bool virBitmapIsAllClear(virBitmapPtr bitmap)
> +    ATTRIBUTE_NONNULL(1);
> +
>  ssize_t virBitmapNextSetBit(virBitmapPtr bitmap, ssize_t pos)
>      ATTRIBUTE_NONNULL(1);
>  
>