From 83c2811157e9861a72e1ece34160cb014ef35fb5 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Thu, 27 Jun 2013 00:23:27 +0300
Subject: [PATCH] Make train advancement logic more robust

---
 source/libr2c2/blockallocator.cpp | 17 ++++++++++++-----
 source/libr2c2/blockallocator.h   |  1 +
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/source/libr2c2/blockallocator.cpp b/source/libr2c2/blockallocator.cpp
index 003ffb0..ff5776d 100644
--- a/source/libr2c2/blockallocator.cpp
+++ b/source/libr2c2/blockallocator.cpp
@@ -30,7 +30,8 @@ BlockAllocator::BlockAllocator(Train &t):
 	cur_blocks_end(blocks.end()),
 	pending_block(0),
 	stop_at_block(0),
-	reserving(false)
+	reserving(false),
+	advancing(false)
 {
 	Layout &layout = train.get_layout();
 	layout.signal_block_reserved.connect(sigc::mem_fun(this, &BlockAllocator::block_reserved));
@@ -81,8 +82,8 @@ void BlockAllocator::rewind_to(const Block &block)
 
 void BlockAllocator::clear()
 {
-	active = false;
 	release_blocks_begin(blocks.end());
+	active = false;
 	pending_block = 0;
 	stop_at_block = 0;
 }
@@ -294,6 +295,8 @@ void BlockAllocator::release_blocks_end(const BlockList::iterator &begin)
 
 void BlockAllocator::release_block(const BlockList::iterator &i)
 {
+	if(advancing)
+		throw logic_error("cannot release while advancing");
 	if(i==cur_blocks_end)
 		++cur_blocks_end;
 	if(&**i==pending_block)
@@ -372,10 +375,14 @@ void BlockAllocator::sensor_state_changed(Sensor &sensor, Sensor::State state)
 
 		if(result==1)
 		{
-			// Move blocks up to the next sensor to our current blocks
-			for(BlockList::iterator j=cur_blocks_end; j!=end; ++j)
-				train.signal_advanced.emit(**j);
+			/* Advance the train to the new blocks.  Update cur_blocks_end first
+			to keep things in sync. */
+			SetFlag setf(advancing);
+			BlockList::iterator i = cur_blocks_end;
 			cur_blocks_end = end;
+			for(; i!=end; ++i)
+				train.signal_advanced.emit(**i);
+			advancing = false;
 
 			if(active)
 				reserve_more();
diff --git a/source/libr2c2/blockallocator.h b/source/libr2c2/blockallocator.h
index 6ad3891..c0c265a 100644
--- a/source/libr2c2/blockallocator.h
+++ b/source/libr2c2/blockallocator.h
@@ -39,6 +39,7 @@ private:
 	Block *pending_block;
 	const Block *stop_at_block;
 	bool reserving;
+	bool advancing;
 
 public:
 	BlockAllocator(Train &);
-- 
2.45.2