Add global_event_loop() and GlibEventLoop.

This causes all PollScheduler instances within a given process to share
a singleton EventLoop instance, and also makes it possible to swap in
glib's main loop for all portage event loops in the main process.

3 files changed, 58 insertions, 0 deletions

diff --git a/pym/portage/util/_eventloop/EventLoop.py b/pym/portage/util/_eventloop/EventLoop.py
index 3f4d35445..aa78ccd15 100644
--- a/pym/portage/util/_eventloop/EventLoop.py
+++ b/pym/portage/util/_eventloop/EventLoop.py
@@ -13,6 +13,8 @@ from _emerge.PollSelectAdapter import PollSelectAdapter
 
 class EventLoop(object):
 
+	supports_multiprocessing = True
+
 	class _idle_callback_class(SlotObject):
 		__slots__ = ("args", "callback", "source_id")
 
diff --git a/pym/portage/util/_eventloop/GlibEventLoop.py b/pym/portage/util/_eventloop/GlibEventLoop.py
new file mode 100644
index 000000000..b35772e7f
--- /dev/null
+++ b/pym/portage/util/_eventloop/GlibEventLoop.py
@@ -0,0 +1,20 @@
+# Copyright 2012 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+
+import portage
+portage.proxy.lazyimport.lazyimport(globals(),
+	'glib',
+)
+
+class GlibEventLoop(object):
+
+	# TODO: Support multiprocessing by using a separate glib.MainContext
+	# instance for each process.
+	supports_multiprocessing = False
+
+	def __init__(self):
+		self.iteration = glib.main_context_default().iteration
+		self.idle_add = glib.idle_add
+		self.io_add_watch = glib.io_add_watch
+		self.timeout_add = glib.timeout_add
+		self.source_remove = glib.source_remove
diff --git a/pym/portage/util/_eventloop/global_event_loop.py b/pym/portage/util/_eventloop/global_event_loop.py
new file mode 100644
index 000000000..0f0c53f2b
--- /dev/null
+++ b/pym/portage/util/_eventloop/global_event_loop.py
@@ -0,0 +1,36 @@
+# Copyright 2012 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+
+import os
+
+from portage.util._eventloop.EventLoop import EventLoop
+
+_default_constructor = EventLoop
+#from portage.util._eventloop.GlibEventLoop \
+#	import GlibEventLoop as _default_constructor
+
+# If _default_constructor doesn't support multiprocessing,
+# then _multiprocessing_constructor is used in subprocesses.
+_multiprocessing_constructor = EventLoop
+
+_MAIN_PID = os.getpid()
+_instances = {}
+
+def global_event_loop():
+	"""
+	Get a global EventLoop (or compatible object) instance which
+	belongs exclusively to the current process.
+	"""
+
+	pid = os.getpid()
+	instance = _instances.get(pid)
+	if instance is not None:
+		return instance
+
+	constructor = _default_constructor
+	if not constructor.supports_multiprocessing and pid != _MAIN_PID:
+		constructor = _multiprocessing_constructor
+
+	instance = constructor()
+	_instances[pid] = instance
+	return instance