From: ian <ian>
Date: Sat, 19 Apr 2008 00:13:50 +0000 (+0000)
Subject: wip new safety
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ijackson/git?a=commitdiff_plain;h=5e2c972fc896f163f345d9f05569b4084e88dae7;p=trains.git

wip new safety
---

diff --git a/hostside/safety.c b/hostside/safety.c
index 2ae6eda..d676e8a 100644
--- a/hostside/safety.c
+++ b/hostside/safety.c
@@ -89,49 +89,56 @@ Segment *segments;
  * the new ownership.
  *
  * If not then we issue an signal stop command (we'd better not be
- * doing that already!) or countermand the speed increase or whatever */
-
- * Having advanced the head, we 
-
- owner		train which owns this for signalling purposes
-		no other train may interfere
-
- physical	in an unowned segment, this has no particular
- feature		relationship to anything
-  &
- movposcomb	in an owned segment, if moving, means that
-  &			we have a promise that the feature
- moving			will be OK by the time we get there
-			at our current speed
-
- move_reservation
-		0 for unowned segments (although during prediction
-			may be non-0 for a bit, in which case
-			we garbage collect it in a bit)
-
-		for an owned segment is our reservation which
-			allows us to know that we are going to
-			be able to change this segment between
-			the tail leaving it and the head arriving
-
- det_ignore	we expect interference detection here due to a crossing
-			(unowned segment)
-		or this is part of the body of a train which we've
-			already detected here (owned segment)
-
- det_expected	this is the next place we expect owner train to arrive
-		(it is not valid to have both det_ignore and _expected)
-
-VALID DURING PREDICTION ETC. ONLY
-
- pred_present	in our prediction, the train physically occupies this
-		until_here tells us when will be
-
- pred_vacated   in our prediction, the train does not occupy this
-			although it did in previous predictions
-		until_here tells us when it will have been vacated
-		if set together with pred_present, means was vacated
-			and then reentered; do not record vacation again
+ * doing that already!) or countermand the speed increase or whatever
+ */
+/*
+ * Here is how we use the stuff in the Segment:
+ *
+ *  owner		train which owns this for signalling purposes
+ * 				no other train may interfere
+ * 
+ *  physical		in an unowned segment, this has no particular
+ *  feature			relationship to anything
+ *   &
+ *  movposcomb		in an owned segment, if moving, means that
+ *   &				we have a promise that the feature
+ *  moving			will be OK by the time we get there
+ * 				at our current speed
+ * 
+ *  move_reservation 	0 for unowned segments (although during prediction
+ * 				may be non-0 for a bit, in which case
+ * 				we garbage collect it in a bit)
+ * 
+ * 			for an owned segment is our reservation which
+ * 				allows us to know that we are going to
+ * 				be able to change this segment between
+ * 				the tail leaving it and the head arriving
+ * 
+ *  det_ignore		we expect interference detection here due to a
+ *				crossing (unowned segment), or
+ * 			this is part of the body of a train which we've
+ * 				already detected here (owned segment)
+ * 
+ *  det_expected	this is the next place we expect owner train
+ *				to arrive
+ * 			(it is not valid to have both det_ignore
+ *			 and _expected)
+ * 
+ * VALID DURING PREDICTION ETC. ONLY
+ * 
+ *  pred_present	in our prediction, the train physically occupies this
+ * 				until_here tells us when will be
+ * 
+ *  pred_vacated 	in our prediction, the train does not occupy this
+ * 				although it did in previous predictions
+ * 			until_here tells us when it will have been vacated
+ * 			if set together with pred_present, means was vacated
+ * 				and then reentered; do not record vacation
+ *				again
+ *
+ *			iff either of these is set, this train is going
+ *				to own the segment when we're finished
+ */
 
 /* ============ OLD CODE ========== */
 
diff --git a/hostside/safety.h b/hostside/safety.h
index f99f12b..66de2ac 100644
--- a/hostside/safety.h
+++ b/hostside/safety.h
@@ -69,10 +69,7 @@ struct Segment {
     ho_backwards:1, /* home train has its front and rear backwards wrt track */
     cm_autostop:1, /* train should stop on detection */
     seg_inverted:1, /* polarity is inverted */
-    det_ignore:1,
-    det_expected:1,
-    pred_enter:1, /* for use by safety.c:lay_train etc.; otherwise 0 */
-    pred_vacate:1, /* for use by safety.c:lay_train etc.; otherwise 0 */
+    det_ignore:1, det_expected:1, pred_enter:1, pred_vacate:1, /* safety.c */
     res_detect:1; /* detection noticed here during resolution */
   TimeInterval until_here; /* ) nonnegative; */  /* ) always valid but      */
                            /* ) 0 if already */  /* )  meaningful iff owner */