From f19d6828989582bc53086ce9d8dc35e52c02dc2a Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Wed, 16 Apr 2014 22:02:01 +0300
Subject: [PATCH] Improve comments

---
 source/libr2c2/trainrouter.cpp | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/source/libr2c2/trainrouter.cpp b/source/libr2c2/trainrouter.cpp
index fec9782..ca3e93d 100644
--- a/source/libr2c2/trainrouter.cpp
+++ b/source/libr2c2/trainrouter.cpp
@@ -91,6 +91,9 @@ void TrainRouter::route_changed()
 	bool already_at_end = false;
 	if(!routes.empty())
 	{
+		/* Find the route that should be used for the next allocated block.  We
+		can't rely on the resync code in block_reserved since we may need to
+		clear the stop marker to continue allocation. */
 		TrackIter track = train.get_block_allocator().first().track_iter();
 		for(; track; track=track.next())
 		{
@@ -106,12 +109,15 @@ void TrainRouter::route_changed()
 
 	if(!already_at_end)
 	{
+		// We are not at the end of the route now, but might have been before.
 		arrival = ON_THE_WAY;
 		train.stop_at(0);
 		train.refresh_blocks_from(*fncb);
 	}
 	else if(!arrival)
 	{
+		/* If arrival wasn't set before (perhaps because we weren't on a route),
+		set it now. */
 		arrival = RESERVED_TO_END;
 		train.stop_at(&*fncb.flip());
 		train.refresh_blocks_from(*fncb);
@@ -274,13 +280,17 @@ void TrainRouter::block_reserved(Block &block, Train *t)
 		if(!t)
 			return;
 
+		// Are we waiting for the other train to pass a sequence point?
 		SequencePoint &sp = sequence_points.front();
 		if(sp.preceding_train==t && sp.block==&block)
+			/* The other train's router will advance its sequence on the same
+			signal and may not have handled it yet. */
 			sequence_check_pending = true;
 
 		return;
 	}
 
+	// Did we reach our next sequence point?
 	if(!sequence_points.empty())
 	{
 		SequencePoint &sp = sequence_points.front();
@@ -293,7 +303,7 @@ void TrainRouter::block_reserved(Block &block, Train *t)
 
 	TrackIter track = train.get_block_allocator().iter_for(block).track_iter();
 
-	// Is the block a turnout?  If so, set it to the proper path.
+	// Is the block a turnout?  If it is, set it to the correct path.
 	if(unsigned taddr = block.get_turnout_address())
 	{
 		int path = (*reserving_route)->get_turnout(taddr);
@@ -301,6 +311,8 @@ void TrainRouter::block_reserved(Block &block, Train *t)
 			track->set_active_path(path);
 	}
 
+	/* If the allocator has released blocks from the front, we may need to
+	resync reserving_route. */
 	if(reserving_route==routes.end() || !(*reserving_route)->has_track(*track))
 	{
 		reserving_route = routes.begin();
@@ -315,11 +327,13 @@ void TrainRouter::block_reserved(Block &block, Train *t)
 		}
 	}
 
-	// Do we need to move to the next route?
+	/* Keep reserving_route pointing to the route containing the block that is
+	expected to be allocated next. */
 	for(; track; track=track.next((*reserving_route)->get_path(*track)))
 	{
 		if(!advance_to_track(reserving_route, *track))
 		{
+			// We've reached the end of the route.  Stop here.
 			arrival = RESERVED_TO_END;
 			train.stop_at(&block);
 			return;
@@ -328,6 +342,7 @@ void TrainRouter::block_reserved(Block &block, Train *t)
 			break;
 	}
 
+	// Do we need to wait for another train to pass?
 	if(!sequence_points.empty())
 	{
 		SequencePoint &sp = sequence_points.front();
@@ -342,6 +357,7 @@ void TrainRouter::train_advanced(Block &block)
 
 	if(!waypoints.empty())
 	{
+		// A waypoint is considered reached when the train has advanced through it.
 		const TrackChain &wp = *waypoints.front();
 		TrackIter t_iter = b_iter.track_iter();
 		if(wp.has_track(*t_iter))
@@ -366,7 +382,7 @@ void TrainRouter::train_rear_advanced(Block &block)
 {
 	Track &track = *train.get_block_allocator().iter_for(block).endpoint().track;
 
-	// Have we left some routes completely behind?
+	// Drop any routes that are now completely behind the train.
 	for(RouteList::iterator i=routes.begin(); i!=routes.end(); ++i)
 		if((*i)->has_track(track))
 		{
-- 
2.45.2