Re: [Qemu-devel] [PATCH v4 1/6] cutils: extract buffer_is_zero() from qemu-img.c

[Kevin Wolf <kwolf@redhat.com>]

Am 18.01.2012 15:59, schrieb Stefan Hajnoczi:
> The qemu-img.c:is_not_zero() function checks if a buffer contains all
> zeroes.  This function will come in handy for zero-detection in the
> block layer, so clean it up and move it to cutils.c.
> 
> Note that the function now returns true if the buffer is all zeroes.
> This avoids the double-negatives (i.e. !is_not_zero()) that the old
> function can cause in callers.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> ---
>  cutils.c      |   34 ++++++++++++++++++++++++++++++++++
>  qemu-common.h |    2 ++
>  qemu-img.c    |   46 +++++++---------------------------------------
>  3 files changed, 43 insertions(+), 39 deletions(-)
> 
> diff --git a/cutils.c b/cutils.c
> index a6ffd46..2ea9c3c 100644
> --- a/cutils.c
> +++ b/cutils.c
> @@ -303,6 +303,40 @@ void qemu_iovec_memset_skip(QEMUIOVector *qiov, int c, size_t count,
>      }
>  }
>  
> +/*
> + * Checks if a buffer is all zeroes
> + *
> + * Attention! The len must be a multiple of 4 * sizeof(long) due to
> + * restriction of optimizations in this function.
> + */

Sounds like something to assert(), while you're touching the code.

Kevin