[libvirt] [PATCH 2/2] Introduce safewrite_str

[Daniel P. Berrange]

On Tue, Feb 23, 2016 at 01:19:38PM +0000, Daniel P. Berrange wrote:
> On Thu, Feb 18, 2016 at 07:40:12AM -0500, John Ferlan wrote:
> > 
> > 
> > On 02/12/2016 08:59 AM, Ján Tomko wrote:
> > > Just like safewrite, but calls strlen first to figure out
> > > the length of the string.
> > > ---
> > >  src/conf/virchrdev.c       |  2 +-
> > >  src/libvirt_private.syms   |  1 +
> > >  src/lxc/lxc_process.c      |  4 ++--
> > >  src/network/leaseshelper.c |  2 +-
> > >  src/openvz/openvz_conf.c   | 15 ++++++---------
> > >  src/qemu/qemu_domain.c     |  2 +-
> > >  src/util/vircommand.c      |  4 ++--
> > >  src/util/virfile.c         |  9 ++++++++-
> > >  src/util/virfile.h         |  1 +
> > >  src/util/virlog.c          |  6 +++---
> > >  src/util/virpidfile.c      |  4 ++--
> > >  src/util/virxml.c          | 17 ++++++-----------
> > >  tools/vsh.c                |  4 +---
> > >  13 files changed, 35 insertions(+), 36 deletions(-)
> > > 
> > 
> > Conflicted about this one - the difference between the two appears to be
> > 'safewrite' will write a some length of a string (e.g. a counted length)
> > while safewrite_str writes the entire string.  To make things more
> > interesting some safewrite calls use sizeof instead of strlen, but in
> > reality are just writing everything in the buffer.
> > 
> > So, perhaps 'safewrite_all' or 'safewrite_full' better describes the new
> > functionality?
> 
> I don't think we need any new function actually.
> 
> Just add this to existing safewrite() method:
> 
>    if (len == -1)
>       len = strlen(data)
> 
> and then update the callers which pass a NULL terminated string
> to just pass -1.  This matches our behaviour with virBuffer APIs
> which acccept a length of -1.

In fact for the case where the caller passes a literal string we could
add

  #define safewritelit(fd_, literal_string_) \
      safewrite(fd_, "" literal_string_ "", sizeof(literal_string_) - 1)

which moves the performance hit of strlen() to be compile time instead
of runtime.

Regards,
Daniel
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