Re: [Xen-devel] [PATCH v2 13/30] xen: introduce a new format specifier to print sizes in human-readable form

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

On Wed, Sep 28, 2016 at 10:24:07AM +0200, Juergen Gross wrote:
> On 27/09/16 17:57, Roger Pau Monne wrote:
> > Introduce a new %pB format specifier to print sizes (in bytes) in a
> 
> Code suggests it is pZ.

Right, first implementation used pB, but then I realized this was already 
used by Linux to print something else.
 
> > human-readable form.
> > 
> > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > ---
> > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> > Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> > Cc: Jan Beulich <jbeulich@xxxxxxxx>
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> > Cc: Tim Deegan <tim@xxxxxxx>
> > Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> > ---
> >  docs/misc/printk-formats.txt |  5 +++++
> >  xen/common/vsprintf.c        | 15 +++++++++++++++
> >  2 files changed, 20 insertions(+)
> > 
> > diff --git a/docs/misc/printk-formats.txt b/docs/misc/printk-formats.txt
> > index 525108f..0ee3504 100644
> > --- a/docs/misc/printk-formats.txt
> > +++ b/docs/misc/printk-formats.txt
> > @@ -30,3 +30,8 @@ Domain and vCPU information:
> >  
> >         %pv     Domain and vCPU ID from a 'struct vcpu *' (printed as
> >                 "d<domid>v<vcpuid>")
> > +
> > +Size in human readable form:
> > +
> > +       %pZ     Size in human-readable form (input size must be in bytes).
> > +                 e.g.  24MB
> > diff --git a/xen/common/vsprintf.c b/xen/common/vsprintf.c
> > index f92fb67..2dadaec 100644
> > --- a/xen/common/vsprintf.c
> > +++ b/xen/common/vsprintf.c
> > @@ -386,6 +386,21 @@ static char *pointer(char *str, char *end, const char 
> > **fmt_ptr,
> >              *str = 'v';
> >          return number(str + 1, end, v->vcpu_id, 10, -1, -1, 0);
> >      }
> > +    case 'Z':
> > +    {
> > +        static const char units[][3] = {"B", "KB", "MB", "GB", "TB"};
> > +        size_t size = (size_t)arg;
> > +        int i = 0;
> > +
> > +        /* Advance parents fmt string, as we have consumed 'B' */
> > +        ++*fmt_ptr;
> > +
> > +        while ( ++i < sizeof(units) && size >= 1024 )
> 
> sizeof(units) is 15. That's not what you want to check here.

Indeed, it's ARRAY_SIZE, thanks for noticing!

Roger.

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