mojo: Add a runloop utility in python

mojo/public/python/mojo/system.pyx

Index: mojo/public/python/mojo/system.pyx
diff --git a/mojo/public/python/mojo/system.pyx b/mojo/public/python/mojo/system.pyx
index bd0355032a5883f1856e7d7b08d82dffb4e4f431..84fbfefef716e78b90a8f54b3774f53c2234bee3 100644
--- a/mojo/public/python/mojo/system.pyx
+++ b/mojo/public/python/mojo/system.pyx
@@ -5,6 +5,8 @@
 # distutils language = c++
 
 cimport c_core
+cimport c_environment
+
 
 from cpython.buffer cimport PyBUF_CONTIG
 from cpython.buffer cimport PyBUF_CONTIG_RO
@@ -694,3 +696,32 @@ class DuplicateSharedBufferOptions(object):
 
   def __init__(self):
     self.flags = DuplicateSharedBufferOptions.FLAG_NONE
+
+
+cdef class RunLoop(object):
+  """RunLoop to use when using asynchronous operations on handles."""
+
+  cdef c_environment.CRunLoop c_run_loop
+
+  def Run(self):
+    """Run the runloop until Quit is called."""
+    self.c_run_loop.Run()
+
+  def RunUntilIdle(self):
+    """Run the runloop until Quit is called or no operation is waiting."""
+    self.c_run_loop.RunUntilIdle()
+
+  def Quit(self):
+    """Quit the runloop."""
+    self.c_run_loop.Quit()
+
+  def PostDelayedTask(self, runnable, delay=0):
+    """
+    Post a task on the runloop. This must be called from the thread owning the
+    runloop.
+    """
+    cdef c_environment.CClosure closure = c_environment.BuildClosure(runnable)
+    self.c_run_loop.PostDelayedTask(closure, delay)
+
+
+cdef c_environment.CEnvironment* _ENVIRONMENT = new c_environment.CEnvironment()