[Qemu-block] [PATCH 08/11] iotests: add QMP event waiting queue

[John Snow]

A filter is added to allow callers to request very specific
events to be pulled from the event queue, while leaving undesired
events still in the stream.

This allows to poll for completion data for multiple asynchronous
events in any arbitrary order.

Signed-off-by: John Snow <address@hidden>
---
 tests/qemu-iotests/iotests.py | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 0522501..98d399f 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -78,6 +78,23 @@ def create_image(name, size):
         i = i + 512
     file.close()
 
+# Test if 'match' is a recursive subset of 'event'
+def event_match(event, match = None):
+    if match is None:
+        return True
+
+    for key in match:
+        if key in event:
+            if isinstance(event[key], dict):
+                if not event_match(event[key], match[key]):
+                    return False
+            elif event[key] != match[key]:
+                return False
+        else:
+            return False
+
+    return True
+
 class VM(object):
     '''A QEMU VM'''
 
@@ -92,6 +109,7 @@ class VM(object):
                      '-machine', 'accel=qtest',
                      '-display', 'none', '-vga', 'none']
         self._num_drives = 0
+        self._events = []
 
     # This can be used to add an unused monitor instance.
     def add_monitor_telnet(self, ip, port):
@@ -202,14 +220,34 @@ class VM(object):
 
     def get_qmp_event(self, wait=False):
         '''Poll for one queued QMP events and return it'''
+        if len(self._events) > 0:
+            return self._events.pop(0)
         return self._qmp.pull_event(wait=wait)
 
     def get_qmp_events(self, wait=False):
         '''Poll for queued QMP events and return a list of dicts'''
         events = self._qmp.get_events(wait=wait)
+        events.extend(self._events)
+        del self._events[:]
         self._qmp.clear_events()
         return events
 
+    def event_wait(self, name='BLOCK_JOB_COMPLETED', maxtries=3, match=None):
+        # Search cached events
+        for event in self._events:
+            if (event['event'] == name) and event_match(event, match):
+                self._events.remove(event)
+                return event
+
+        # Poll for new events
+        for _ in range(maxtries):
+            event = self._qmp.pull_event(wait=True)
+            if (event['event'] == name) and event_match(event, match):
+                return event
+            self._events.append(event)
+
+        return None
+
 index_re = re.compile(r'([^\[]+)\[([^\]]+)\]')
 
 class QMPTestCase(unittest.TestCase):
-- 
1.9.3