r4856 - branches/sage_addition/sage/python/sage

Author: tmckay
Date: 2011-06-24 18:30:35 +0000 (Fri, 24 Jun 2011)
New Revision: 4856

Added:
   branches/sage_addition/sage/python/sage/util.py
Log:
Forgot to add util.py on initial commit


Added: branches/sage_addition/sage/python/sage/util.py
===================================================================
--- branches/sage_addition/sage/python/sage/util.py	                        (rev 0)
+++ branches/sage_addition/sage/python/sage/util.py	2011-06-24 18:30:35 UTC (rev 4856)
@@ -0,0 +1,84 @@
+from time import time, sleep
+
+class CallSync(object):
+    '''
+    General callback object for asynchronous operations.
+    The 'get_completion' method will return a function that can be
+    used as a callback when an asynchronous operation completes.
+    To change the signature of the callback function, derive from
+    this class and override 'get_completion', changing the definition
+    of the 'completion' function.
+    The 'done' method can be polled to determine if the operation has completed.
+    '''
+    def __init__(self, log=None, default=None):
+        self.data = default
+        self.got_data = False
+        self.error = False
+        self.status = None
+        self.log = log
+
+    def get_completion(self):
+        # Note that because of the way binding is done in Python,
+        # 'self' inside 'completion' is bound to 'obj' when 
+        # obj.get_completion is called and 'completion' is returned.
+        # This allows the code invoking the callback to call a simple
+        # function without an object reference (the reference is hidden
+        # inside the bound function).
+        def completion(status, data):
+            self.status = status
+            if (status == 0) or (status == "OK"):
+                self.data = data
+                self.got_data = True
+            else:
+                self.error = Exception(status)
+                msg = "CallSync: call returned with status of %s" %
str(status)
+                if self.log is not None:
+                    self.log.error(msg)
+        return completion
+
+    def done(self):
+        return self.got_data or self.error
+
+class SyncSet(object):
+    '''
+    Allows a caller to wait for completion of a set of asynchronous operations.
+    A collection of CallSync objects can be built up with calls to 'add_sync'.
+    'do_wait' will return when all CallSync objects in the set have been
completed
+    or 'timeout' seconds have elapsed.
+    '''
+    def __init__(self, log=None, timeout=5):
+        self.syncs = dict()
+        self.timeout = timeout
+        self.log = log
+
+    def add_sync(self, key, default=None):
+        sync = CallSync(self.log, default)
+        self.syncs[key] = sync
+        return sync
+
+    def do_wait(self):
+        def predicate(syncs):
+            done = 0
+            for k, sync in syncs.items():
+                if sync.done():
+                    done += 1
+            return done == len(syncs)
+
+        # Wait for all syncs in the set to complete.
+        # syncs will contain results for each call passed back
+        # through the completion callback
+        wait(predicate, timeout=self.timeout, args=self.syncs)
+        return self.syncs
+
+def wait(predicate, timeout=30, args=None):
+    start = time()
+    while True:
+        if args is not None:
+            if predicate(args):
+                return True
+        else:
+            if predicate():
+                return True
+        if time() - start > timeout:
+            return False
+        sleep(1)