Re: [PATCH v2 2/3] python: Extract registered watch search logic from xspy_read_watch()

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

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On Thu, Sep 21, 2017 at 05:47:07PM +0100, Euan Harris wrote:
> When a watch fires, xspy_read_watch() checks whether the client has
> registered interest in the path which changed and, if so, returns the
> path and a client-supplied token.   The binding for xs_check_watch()
> needs to do the same, so this patch extracts the search code into a
> separate function.
> 
> 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>

> ---
> Changed since v1:
>  * Remove stray newline
>  * Fix indentation
> 
>  tools/python/xen/lowlevel/xs/xs.c | 60 ++++++++++++++++++++++++---------------
>  1 file changed, 37 insertions(+), 23 deletions(-)
> 
> diff --git a/tools/python/xen/lowlevel/xs/xs.c b/tools/python/xen/lowlevel/xs/xs.c
> index 9f1b916..2af5e07 100644
> --- a/tools/python/xen/lowlevel/xs/xs.c
> +++ b/tools/python/xen/lowlevel/xs/xs.c
> @@ -77,6 +77,8 @@ static inline struct xs_handle *xshandle(XsHandle *self)
>  
>  static void remove_watch(XsHandle *xsh, PyObject *token);
>  
> +static PyObject *match_watch_by_token(XsHandle *self, char **xsval);
> +
>  static PyObject *none(bool result);
>  
>  static int parse_transaction_path(XsHandle *self, PyObject *args,
> @@ -484,8 +486,6 @@ static PyObject *xspy_read_watch(XsHandle *self, PyObject *args)
>      struct xs_handle *xh = xshandle(self);
>      PyObject *val = NULL;
>      char **xsval;
> -    PyObject *token;
> -    int i;
>      unsigned int num;
>  
>      if (!xh)
> @@ -497,29 +497,16 @@ again:
>      Py_END_ALLOW_THREADS
>      if (!xsval) {
>          PyErr_SetFromErrno(xs_error);
> -        goto exit;
> -    }
> -    if (sscanf(xsval[XS_WATCH_TOKEN], "%li", (unsigned long *)&token) != 1) {
> -	xs_set_error(EINVAL);
> -        goto exit;
> -    }
> -    for (i = 0; i < PyList_Size(self->watches); i++) {
> -        if (token == PyList_GetItem(self->watches, i))
> -            break;
> -    }
> -    if (i == PyList_Size(self->watches)) {
> -      /* We do not have a registered watch for the one that has just fired.
> -         Ignore this -- a watch that has been recently deregistered can still
> -         have watches in transit.  This is a blocking method, so go back to
> -         read again.
> -      */
> -      free(xsval);
> -      goto again;
> +        return val;
>      }
> -    /* Create tuple (path, token). */
> -    val = Py_BuildValue("(sO)", xsval[XS_WATCH_PATH], token);
> - exit:
> +
> +    val = match_watch_by_token(self, xsval);
>      free(xsval);
> +
> +    if (!val && errno == EAGAIN) {
> +        goto again;
> +    }
> +
>      return val;
>  }
>  
> @@ -868,6 +855,33 @@ static int parse_transaction_path(XsHandle *self, PyObject *args,
>  }
>  
>  
> +static PyObject *match_watch_by_token(XsHandle *self, char **xsval)
> +{
> +    PyObject *token;
> +    int i;
> +
> +    if (sscanf(xsval[XS_WATCH_TOKEN], "%li", (unsigned long *)&token) != 1) {
> +        xs_set_error(EINVAL);
> +        return NULL;
> +    }
> +    for (i = 0; i < PyList_Size(self->watches); i++) {
> +        if (token == PyList_GetItem(self->watches, i))
> +            break;
> +    }
> +    if (i == PyList_Size(self->watches)) {
> +        /* We do not have a registered watch for the one that has just fired.
> +           Ignore this -- a watch that has been recently deregistered can still
> +           have watches in transit.
> +        */
> +        xs_set_error(EAGAIN);
> +        return NULL;
> +    }
> +
> +    /* Create tuple (path, token). */
> +    return Py_BuildValue("(sO)", xsval[XS_WATCH_PATH], token);
> +}
> +
> +
>  static PyObject *none(bool result)
>  {
>      if (result) {

-- 
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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