Alert the user if a connection is made which causes

feedback, and preserve the route graph in the state
that it was in before the feedback was introduced. The
intent being to simplify the code, reduce the number of
areas of code which must consider feedback, and fix a
few bugs.


git-svn-id: svn://localhost/ardour2/branches/3.0@10510 d708f5d6-7413-0410-9779-e7cbd77b26cf

1 files changed, 241 insertions, 0 deletions

diff --git a/libs/ardour/route_graph.cc b/libs/ardour/route_graph.cc
new file mode 100644
index 0000000000..fbf406fd92
--- /dev/null
+++ b/libs/ardour/route_graph.cc
@@ -0,0 +1,241 @@
+/*
+    Copyright (C) 2011 Paul Davis
+    Author: Carl Hetherington <cth@carlh.net>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
+#include "ardour/route.h"
+#include "ardour/route_graph.h"
+
+#include "i18n.h"
+
+using namespace std;
+using namespace ARDOUR;
+
+void
+GraphEdges::add (GraphVertex from, GraphVertex to, bool via_sends_only)
+{
+	insert (_from_to, from, to);
+	insert (_to_from, to, from);
+
+	EdgeMapWithSends::iterator i = find_in_from_to_with_sends (from, to);
+	if (i != _from_to_with_sends.end ()) {
+		i->second.second = via_sends_only;
+	} else {
+		_from_to_with_sends.insert (
+			make_pair (from, make_pair (to, via_sends_only))
+			);
+	}
+}
+
+/** Find a from/to pair in the _from_to_with_sends map.
+ *  @return iterator to the edge, or _from_to_with_sends.end().
+ */
+GraphEdges::EdgeMapWithSends::iterator
+GraphEdges::find_in_from_to_with_sends (GraphVertex from, GraphVertex to)
+{
+	typedef EdgeMapWithSends::iterator Iter;
+	pair<Iter, Iter> r = _from_to_with_sends.equal_range (from);
+	for (Iter i = r.first; i != r.second; ++i) {
+		if (i->second.first == to) {
+			return i;
+		}
+	}
+
+	return _from_to_with_sends.end ();
+}
+
+/** @param via_sends_only if non-0, filled in with true if the edge is a
+ *  path via a send only.
+ *  @return true if the given edge is present.
+ */
+bool
+GraphEdges::has (GraphVertex from, GraphVertex to, bool* via_sends_only)
+{
+	EdgeMapWithSends::iterator i = find_in_from_to_with_sends (from, to);
+	if (i == _from_to_with_sends.end ()) {
+		return false;
+	}
+	
+	if (via_sends_only) {
+		*via_sends_only = i->second.second;
+	}
+
+	return true;
+}
+
+/** @return the vertices that are fed from `r' */
+set<GraphVertex>
+GraphEdges::from (GraphVertex r) const
+{
+	EdgeMap::const_iterator i = _from_to.find (r);
+	if (i == _from_to.end ()) {
+		return set<GraphVertex> ();
+	}
+	
+	return i->second;
+}
+
+void
+GraphEdges::remove (GraphVertex from, GraphVertex to)
+{
+	EdgeMap::iterator i = _from_to.find (from);
+	assert (i != _from_to.end ());
+	i->second.erase (to);
+	if (i->second.empty ()) {
+		_from_to.erase (i);
+	}
+	
+	EdgeMap::iterator j = _to_from.find (to);
+	assert (j != _to_from.end ());
+	j->second.erase (from);
+	if (j->second.empty ()) {
+		_to_from.erase (j);
+	}
+
+	EdgeMapWithSends::iterator k = find_in_from_to_with_sends (from, to);
+	assert (k != _from_to_with_sends.end ());
+	_from_to_with_sends.erase (k);
+}
+
+/** @param to `To' route.
+ *  @return true if there are no edges going to `to'.
+ */
+
+bool
+GraphEdges::has_none_to (GraphVertex to) const
+{
+	return _to_from.find (to) == _to_from.end ();
+}
+
+bool
+GraphEdges::empty () const
+{
+	assert (_from_to.empty () == _to_from.empty ());
+	return _from_to.empty ();
+}
+
+void
+GraphEdges::dump () const
+{
+	for (EdgeMap::const_iterator i = _from_to.begin(); i != _from_to.end(); ++i) {
+		cout << "FROM: " << i->first->name() << " ";
+		for (set<GraphVertex>::const_iterator j = i->second.begin(); j != i->second.end(); ++j) {
+			cout << (*j)->name() << " ";
+		}
+		cout << "\n";
+	}
+	
+	for (EdgeMap::const_iterator i = _to_from.begin(); i != _to_from.end(); ++i) {
+		cout << "TO: " << i->first->name() << " ";
+		for (set<GraphVertex>::const_iterator j = i->second.begin(); j != i->second.end(); ++j) {
+			cout << (*j)->name() << " ";
+		}
+		cout << "\n";
+	}
+}
+
+/** Insert an edge into one of the EdgeMaps */
+void
+GraphEdges::insert (EdgeMap& e, GraphVertex a, GraphVertex b)
+{
+	EdgeMap::iterator i = e.find (a);
+	if (i != e.end ()) {
+		i->second.insert (b);
+	} else {
+		set<GraphVertex> v;
+		v.insert (b);
+		e.insert (make_pair (a, v));
+	}
+}
+
+struct RouteRecEnabledComparator
+{
+	bool operator () (GraphVertex r1, GraphVertex r2) const
+	{
+		if (r1->record_enabled()) {
+			if (r2->record_enabled()) {
+				/* both rec-enabled, just use signal order */
+				return r1->order_key(N_("signal")) < r2->order_key(N_("signal"));
+			} else {
+				/* r1 rec-enabled, r2 not rec-enabled, run r2 early */
+				return false;
+			}
+		} else {
+			if (r2->record_enabled()) {
+				/* r2 rec-enabled, r1 not rec-enabled, run r1 early */
+				return true;
+			} else {
+				/* neither rec-enabled, use signal order */
+				return r1->order_key(N_("signal")) < r2->order_key(N_("signal"));
+			}
+		}
+	}
+};
+
+/** Perform a topological sort of a list of routes using a directed graph representing connections.
+ *  @return Sorted list of routes, or 0 if the graph contains cycles (feedback loops).
+ */
+boost::shared_ptr<RouteList>
+ARDOUR::topological_sort (
+	boost::shared_ptr<RouteList> routes,
+	GraphEdges edges
+	)
+{
+	boost::shared_ptr<RouteList> sorted_routes (new RouteList);
+	
+	/* queue of routes to process */
+	RouteList queue;
+
+	/* initial queue has routes that are not fed by anything */
+	for (RouteList::iterator i = routes->begin(); i != routes->end(); ++i) {
+		if (edges.has_none_to (*i)) {
+			queue.push_back (*i);
+		}
+	}
+
+	/* Sort the initial queue so that non-rec-enabled routes are run first.
+	   This is so that routes can record things coming from other routes
+	   via external connections.
+	*/
+	queue.sort (RouteRecEnabledComparator ());
+
+	/* Do the sort: algorithm is Kahn's from Wikipedia.
+	   `Topological sorting of large networks', Communications of the ACM 5(11):558-562.
+	*/
+	
+	while (!queue.empty ()) {
+		GraphVertex r = queue.front ();
+		queue.pop_front ();
+		sorted_routes->push_back (r);
+		set<GraphVertex> e = edges.from (r);
+		for (set<GraphVertex>::iterator i = e.begin(); i != e.end(); ++i) {
+			edges.remove (r, *i);
+			if (edges.has_none_to (*i)) {
+				queue.push_back (*i);
+			}
+		}
+	}
+
+	if (!edges.empty ()) {
+		edges.dump ();
+		/* There are cycles in the graph, so we can't do a topological sort */
+		return boost::shared_ptr<RouteList> ();
+	}
+
+	return sorted_routes;
+}