--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/python/ppci/codegen/graph.py	Thu Dec 05 17:02:38 2013 +0100
@@ -0,0 +1,84 @@
+
+class Graph:
+    """
+       Generic graph base class.
+       Can dump to graphiz dot format for example!
+    """
+    def __init__(self):
+        self.nodes = set()
+        self.edges = set()
+
+    def addNode(self, n):
+        self.nodes.add(n)
+
+    def delNode(self, n):
+        self.nodes.remove(n)
+
+    def addEdge(self, n, m):
+        """ Add an edge from n to m """
+        self.edges.add((n, m))
+        self.edges.add((m, n))
+
+    def hasEdge(self, n, m):
+        return (n, m) in self.edges
+
+    def delEdge(self, n, m):
+        self.edges.remove((n, m))
+        self.edges.remove((m, n))
+
+    def adjecent(self, n):
+        """ Return all nodes with edges to n """
+        # TODO: this can be optimized for speed:
+        return set(m for m in self.nodes if self.hasEdge(n, m))
+
+    def to_dot(self, f):
+        """ Generate graphviz dot representation """
+        for n in self.nodes:
+            print('{} [label="{}" shape=box3d];'.format(id(n), n), file=f)
+        for n, m in self.edges:
+            print('{} -> {};'.format(id(n), id(m)), file=f)
+
+
+class Node:
+    """
+       Node in a graph.
+    """
+    def __init__(self, g):
+        self.g = g
+        self.addDegree = 0    # Hack to increase degree
+
+    @property
+    def Adjecent(self):
+        return self.g.adjecent(self)
+
+    @property
+    def Degree(self):
+        return len(self.Adjecent) + self.addDegree
+
+
+class DiGraph(Graph):
+    """
+        Directed graph.
+    """
+    def addEdge(self, n, m):
+        """ Add an edge from n to m """
+        self.edges.add((n, m))
+
+    def hasEdge(self, n, m):
+        return (n, m) in self.edges
+
+    def successors(self, n):
+        return set(m for m in self.nodes if self.hasEdge(n, m))
+
+    def predecessors(self, n):
+        return set(m for m in self.nodes if self.hasEdge(m, n))
+
+
+class DiNode(Node):
+    @property
+    def Succ(self):
+        return self.g.successors(self)
+
+    @property
+    def Pred(self):
+        return self.g.predecessors(self)