Re: [Xen-devel] [Patch v3 2/2] tools/libxc: Implement writev_exact() in the same style as write_exact()

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2014-07-18 at 10:20 +0100, Andrew Cooper wrote:
> On 18/07/14 02:14, Wen Congyang wrote:
> > At 07/16/2014 10:32 PM, Andrew Cooper Wrote:
> >> This implementation of writev_exact() will cope with an iovcnt greater than
> >> IOV_MAX because glibc will actually let this work anyway, and it is very
> >> useful not to have to work about this in the caller of writev_exact().  The
> >> caller is still required to ensure that the sum of iov_len's doesn't 
> >> overflow
> >> a ssize_t.
> >>
> >> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> >> CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
> >> CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> >>
> >> ---
> >> v3:
> >>  * Re-add adjustment for partial writes.
> >>  * Split min/max adjustment into separate patch.
> >>
> >> v2:
> >>  * Remove adjustment for partial writes of a specific iov[] entry.
> >> ---
> >>  tools/libxc/xc_private.c |   60 
> >> ++++++++++++++++++++++++++++++++++++++++++++++
> >>  tools/libxc/xc_private.h |    2 ++
> >>  2 files changed, 62 insertions(+)
> >>
> >> diff --git a/tools/libxc/xc_private.c b/tools/libxc/xc_private.c
> >> index 1c214dd..0941b06 100644
> >> --- a/tools/libxc/xc_private.c
> >> +++ b/tools/libxc/xc_private.c
> >> @@ -858,6 +858,66 @@ int write_exact(int fd, const void *data, size_t size)
> >>      return 0;
> >>  }
> >>  
> >> +int writev_exact(int fd, const struct iovec *iov, int iovcnt)
> >> +{
> >> +    struct iovec *local_iov = NULL;
> >> +    int rc = 0, iov_idx = 0, saved_errno = 0;
> >> +    ssize_t len;
> >> +
> >> +    while ( iov_idx < iovcnt )
> >> +    {
> >> +        /* Skip over iov[] entries with 0 length. */
> >> +        while ( iov[iov_idx].iov_len == 0 )
> >> +            if ( ++iov_idx == iovcnt )
> >> +                goto out;
> > set saved_errn to 0 before goto out?
> 
> Good catch.

Isn't this a success path? errno is generally undefined on success.

Ian.


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel