From ada37f44b9c44d726ecc3467ecdfdeb1c4137e44 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 26 May 2013 01:54:24 +0300
Subject: [PATCH] Refactor TrackIter::block_iter

The new implementation is slightly more efficient in certain cases and
won't choke at the end of a line.
---
 source/libr2c2/trackiter.cpp | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/source/libr2c2/trackiter.cpp b/source/libr2c2/trackiter.cpp
index c3bb7d4..31ebf08 100644
--- a/source/libr2c2/trackiter.cpp
+++ b/source/libr2c2/trackiter.cpp
@@ -30,27 +30,29 @@ BlockIter TrackIter::block_iter() const
 	Block &block = _track->get_block();
 	const vector<Block::Endpoint> &beps = block.get_endpoints();
 
-	if(_track->get_type().is_turnout())
-	{
-		/* A turnouts is the only track in its block.  Go ahead and find the
-		matching endpoint in the block. */
-		for(unsigned i=0; i<beps.size(); ++i)
-			if(beps[i].track==_track && beps[i].track_ep==_entry)
-				return BlockIter(&block, i);
-	}
-	else
+	// See if this track matches an endpoint in the block
+	for(unsigned i=0; i<beps.size(); ++i)
+		if(beps[i].track==_track && beps[i].track_ep==_entry)
+			return BlockIter(&block, i);
+
+	if(!_track->get_type().is_turnout())
 	{
 		TrackIter rev = reverse();
+		TrackIter last;
 		while(rev && &rev.track()->get_block()==&block)
 		{
-			TrackIter fwd = rev.reverse();
-
-			for(unsigned i=0; i<beps.size(); ++i)
-				if(beps[i].track==fwd.track() && beps[i].track_ep==fwd.entry())
-					return BlockIter(&block, i);
-
+			last = rev;
 			rev = rev.next();
+
+			// If we ran out of tracks, return an empty iterator
+			if(!rev)
+				return BlockIter();
 		}
+
+		TrackIter fwd = last.reverse();
+		for(unsigned i=0; i<beps.size(); ++i)
+			if(beps[i].track==fwd.track() && beps[i].track_ep==fwd.entry())
+				return BlockIter(&block, i);
 	}
 
 	throw logic_error("internal error (didn't find block entry endpoint)");
-- 
2.43.0