digraph: add update and clear methods

Also, optimize the add method to avoid creating a lot of
duplicate priorities when called by the update method.

Acked-by: Brian Dolbec <dolsen@gentoo.org>

2 files changed, 27 insertions, 3 deletions

diff --git a/pym/portage/tests/util/test_digraph.py b/pym/portage/tests/util/test_digraph.py
index f519536d3..01e075c99 100644
--- a/pym/portage/tests/util/test_digraph.py
+++ b/pym/portage/tests/util/test_digraph.py
@@ -88,7 +88,9 @@ class DigraphTest(TestCase):
 		g.add("D", "A", 2)
 
 		f = g.clone()
-		for x in g, f:
+		h = digraph()
+		h.update(f)
+		for x in g, f, h:
 			self.assertEqual(bool(x), True)
 			self.assertEqual(x.contains("A"), True)
 			self.assertEqual(x.firstzero(), None)
diff --git a/pym/portage/util/digraph.py b/pym/portage/util/digraph.py
index 99b24fa1d..ba0e81c07 100644
--- a/pym/portage/util/digraph.py
+++ b/pym/portage/util/digraph.py
@@ -44,8 +44,10 @@ class digraph(object):
 			priorities = []
 			self.nodes[node][1][parent] = priorities
 			self.nodes[parent][0][node] = priorities
-		priorities.append(priority)
-		priorities.sort()
+
+		if not priorities or priorities[-1] is not priority:
+			priorities.append(priority)
+			priorities.sort()
 
 	def discard(self, node):
 		"""
@@ -73,6 +75,26 @@ class digraph(object):
 		del self.nodes[node]
 		self.order.remove(node)
 
+	def update(self, other):
+		"""
+		Add all nodes and edges from another digraph instance.
+		"""
+		for node in other.order:
+			children, parents, node = other.nodes[node]
+			if parents:
+				for parent, priorities in parents.items():
+					for priority in priorities:
+						self.add(node, parent, priority=priority)
+			else:
+				self.add(node, None)
+
+	def clear(self):
+		"""
+		Remove all nodes and edges.
+		"""
+		self.nodes.clear()
+		del self.order[:]
+
 	def difference_update(self, t):
 		"""
 		Remove all given nodes from node_set. This is more efficient