Re: [PATCH v2 3/3] python: Add binding for non-blocking xs_check_watch()

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Thu, Sep 21, 2017 at 05:47:08PM +0100, Euan Harris wrote:
> xs_check_watch() checks for watch notifications without blocking.
> Together with the binding for xs_fileno(), this makes it possible
> to write event-driven clients in Python.
> 
> Signed-off-by: Euan Harris <euan.harris@citrix.com>
> Reviewed-by: Wei Liu <wei.liu2@citrix.com>

Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

> ---
>  tools/python/xen/lowlevel/xs/xs.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/tools/python/xen/lowlevel/xs/xs.c b/tools/python/xen/lowlevel/xs/xs.c
> index 2af5e07..4710002 100644
> --- a/tools/python/xen/lowlevel/xs/xs.c
> +++ b/tools/python/xen/lowlevel/xs/xs.c
> @@ -474,6 +474,33 @@ static PyObject *xspy_fileno(XsHandle *self)
>  }
>  
>  
> +#define xspy_check_watch_doc "\n"				\
> +	"Check for watch notifications without blocking.\n"	\
> +	"\n"							\
> +	"Returns: [tuple] (path, token).\n"			\
> +	"         None if no watches have fired.\n"             \
> +	"Raises xen.lowlevel.xs.Error on error.\n"	        \
> +	"\n"
> +
> +static PyObject *xspy_check_watch(XsHandle *self, PyObject *args)
> +{
> +    struct xs_handle *xh = xshandle(self);
> +    PyObject *val = NULL;
> +    char **xsval;
> +
> +    if (!xh)
> +        return NULL;
> +
> +    xsval = xs_check_watch(xh);
> +    if (!xsval) {
> +        return none(errno == EAGAIN);
> +    }
> +
> +    val = match_watch_by_token(self, xsval);
> +    free(xsval);
> +    return val;
> +}
> +
>  #define xspy_read_watch_doc "\n"				\
>  	"Read a watch notification.\n"				\
>  	"\n"							\
> @@ -911,6 +938,7 @@ static PyMethodDef xshandle_methods[] = {
>      XSPY_METH(set_permissions,   METH_VARARGS),
>      XSPY_METH(watch,             METH_VARARGS),
>      XSPY_METH(read_watch,        METH_NOARGS),
> +    XSPY_METH(check_watch,       METH_NOARGS),
>      XSPY_METH(unwatch,           METH_VARARGS),
>      XSPY_METH(transaction_start, METH_NOARGS),
>      XSPY_METH(transaction_end,   METH_VARARGS | METH_KEYWORDS),

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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