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Date: Wed, 25 May 2011 18:15:22 -0300
From: Luiz Capitulino <lcapitulino@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/2] QMP: add get_events(wait=True) option
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To: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Cc: qemu-devel@nongnu.org

On Wed, 25 May 2011 19:48:00 +0100
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> wrote:

> The get_events() function polls for new QMP events and then returns.  It
> can be useful to wait for the next QMP event so add the boolean 'wait'
> keyword argument.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> ---
>  QMP/qmp.py |   11 ++++++++---
>  1 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/QMP/qmp.py b/QMP/qmp.py
> index 14ce8b0..2565508 100644
> --- a/QMP/qmp.py
> +++ b/QMP/qmp.py
> @@ -43,7 +43,7 @@ class QEMUMonitorProtocol:
>              family = socket.AF_UNIX
>          return socket.socket(family, socket.SOCK_STREAM)
>  
> -    def __json_read(self):
> +    def __json_read(self, only_event=False):
>          while True:
>              data = self.__sockfile.readline()
>              if not data:
> @@ -51,7 +51,8 @@ class QEMUMonitorProtocol:
>              resp = json.loads(data)
>              if 'event' in resp:
>                  self.__events.append(resp)
> -                continue
> +                if not only_event:
> +                    continue
>              return resp
>  
>      error = socket.error
> @@ -106,9 +107,11 @@ class QEMUMonitorProtocol:
>              qmp_cmd['id'] = id
>          return self.cmd_obj(qmp_cmd)
>  
> -    def get_events(self):
> +    def get_events(self, wait=False):
>          """
>          Get a list of available QMP events.
> +
> +        @param wait: block until an event is available (bool)
>          """
>          self.__sock.setblocking(0)
>          try:
> @@ -118,6 +121,8 @@ class QEMUMonitorProtocol:
>                  # No data available
>                  pass
>          self.__sock.setblocking(1)
> +        if not self.__events and wait:
> +            self.__json_read(only_event=True)
>          return self.__events

Maybe this is better (untested):

    def get_events(self, wait=False):
        """
        Get a list of available QMP events.

        @param wait: block until an event is available (bool)
        """
        if not wait:
            self.__sock.setblocking(0)
        try:
            self.__json_read(only_event=wait)
        except socket.error, err:
            if err[0] == errno.EAGAIN:
                # No data available
                pass
        if not wait:
            self.__sock.setblocking(1)
        return self.__events

>  
>      def clear_events(self):