Re: [Qemu-devel] [PATCH 03/14] iov: add iov_cpy

[Anthony Liguori <anthony@codemonkey.ws>]

"Michael S. Tsirkin" <mst@redhat.com> writes:

> Add API to copy part of iovec safely.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  iov.c | 23 +++++++++++++++++++++++
>  iov.h |  9 +++++++++
>  2 files changed, 32 insertions(+)
>
> diff --git a/iov.c b/iov.c
> index c6a66f0..0dfcb28 100644
> --- a/iov.c
> +++ b/iov.c
> @@ -228,3 +228,26 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
>          fprintf(fp, "\n");
>      }
>  }
> +
> +unsigned iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
> +                 const struct iovec *iov, unsigned int iov_cnt,
> +                 size_t offset, size_t bytes)

I think the readability f the cde wuld be imprved if yu added the
missing 'o' to iov_cpy.

Otherwise:

Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>

Regards,

Anthony Liguori

> +{
> +    size_t len;
> +    unsigned int i, j;
> +    for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
> +        if (offset >= iov[i].iov_len) {
> +            offset -= iov[i].iov_len;
> +            continue;
> +        }
> +        len = MIN(bytes, iov[i].iov_len - offset);
> +
> +        dst_iov[j].iov_base = iov[i].iov_base + offset;
> +        dst_iov[j].iov_len = len;
> +        j++;
> +        bytes -= len;
> +        offset = 0;
> +    }
> +    assert(offset == 0);
> +    return j;
> +}
> diff --git a/iov.h b/iov.h
> index a73569f..f0daefa 100644
> --- a/iov.h
> +++ b/iov.h
> @@ -86,3 +86,12 @@ ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt,
>   */
>  void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
>                   FILE *fp, const char *prefix, size_t limit);
> +
> +/*
> + * Partial copy of vector from iov to dst_iov (data is not copied).
> + * dst_iov overlaps iov at a specified offset.
> + * size of dst_iov is at most bytes. Actual size is returned.
> + */
> +size_t iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
> +               const struct iovec *iov, unsigned int iov_cnt,
> +               size_t offset, size_t bytes);
> -- 
> MST