Re: [PATCH v2 2/7] iov: Add helper to find skip over first n bytes of an io vector

[Stefano Brivio <sbrivio@redhat.com>]

On Wed, 28 Feb 2024 12:52:01 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> Several of the IOV functions in iov.c, and also tap_send_frames_passt()
> needs to determine which buffer element a byte offset into an IO vector
> lies in.  Split this out into a helper function iov_skip_bytes().
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  iov.c | 42 +++++++++++++++++++++++++++++++++---------
>  iov.h |  2 ++
>  tap.c | 12 +++++-------
>  3 files changed, 40 insertions(+), 16 deletions(-)
> 
> diff --git a/iov.c b/iov.c
> index 8a48acb1..e3312628 100644
> --- a/iov.c
> +++ b/iov.c
> @@ -25,6 +25,36 @@
>  #include "util.h"
>  #include "iov.h"
>  
> +
> +/* iov_skip_bytes() - Skip the first n bytes into an IO vector
> + * @iov:	IO vector
> + * @n:		Number of entries in @iov

...which is a different 'n' compared to two lines above.

> + * @vec_offset: Total byte offset into the IO vector

This doesn't clearly correlate with the description of the function
("first n bytes").

Same here, I have no other comments about the series, so I'll
apply this and try to improve this a bit as a follow-up.

> + * @buf_offset:	Offset into a single buffer of the IO vector
> + *
> + * Return: index I of individual struct iovec which contains the byte at
> + *         @vec_offset bytes into the vector (as though all its buffers were
> + *         contiguous).  If @buf_offset is non-NULL, update it to the offset of
> + *         that byte within @iov[I] (guaranteed to be less than @iov[I].iov_len)
> + *	   If the whole vector has <= @vec_offset bytes, return @n.
> + */
> +size_t iov_skip_bytes(const struct iovec *iov, size_t n,
> +		      size_t vec_offset, size_t *buf_offset)

-- 
Stefano