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

[Michael S. Tsirkin]

On Mon, Sep 24, 2012 at 07:34:00PM -0500, Anthony Liguori wrote:
> "Michael S. Tsirkin" <address@hidden> writes:
> 
> > Add API to copy part of iovec safely.
> >
> > Signed-off-by: Michael S. Tsirkin <address@hidden>
> > ---
> >  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.

I was thinking about memcpy but maybe that's not a good model to follow.
Will fix.

> Otherwise:
> 
> Reviewed-by: Anthony Liguori <address@hidden>
> 
> 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