ss: 2D query fixes

Return an empty iterable instead of throwing an exception when
the collection of quarks is empty.
Fix a null pointer exception in the iterables.

Change-Id: Id8c3d71396943bd796211c9c68aba7640050c132
Signed-off-by: Loïc Prieur-Drevon <loic.prieurdrevon@gmail.com>
Reviewed-on: https://git.eclipse.org/r/101647
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>

2 files changed, 12 insertions, 1 deletions

diff --git a/statesystem/org.eclipse.tracecompass.statesystem.core/src/org/eclipse/tracecompass/internal/statesystem/core/StateSystem.java b/statesystem/org.eclipse.tracecompass.statesystem.core/src/org/eclipse/tracecompass/internal/statesystem/core/StateSystem.java
index 4351314005..464fb30aec 100644
--- a/statesystem/org.eclipse.tracecompass.statesystem.core/src/org/eclipse/tracecompass/internal/statesystem/core/StateSystem.java
+++ b/statesystem/org.eclipse.tracecompass.statesystem.core/src/org/eclipse/tracecompass/internal/statesystem/core/StateSystem.java
@@ -18,6 +18,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.concurrent.CountDownLatch;
@@ -626,6 +627,9 @@ public class StateSystem implements ITmfStateSystemBuilder {
         if (isDisposed) {
             throw new StateSystemDisposedException();
         }
+        if (times.isEmpty()) {
+            return Collections.emptyList();
+        }
 
         TimeRangeCondition timeCondition = TimeRangeCondition.forDiscreteRange(times);
         return query2D(quarks, timeCondition);
@@ -648,6 +652,10 @@ public class StateSystem implements ITmfStateSystemBuilder {
             throw new TimeRangeException();
         }
 
+        if (quarks.isEmpty()) {
+            return Collections.emptyList();
+        }
+
         IntegerRangeCondition quarkCondition = IntegerRangeCondition.forDiscreteRange(quarks);
         if (quarkCondition.min() < 0 || quarkCondition.max() >= getNbAttributes()) {
             throw new IndexOutOfBoundsException();
diff --git a/statesystem/org.eclipse.tracecompass.statesystem.core/src/org/eclipse/tracecompass/internal/statesystem/core/backend/historytree/HistoryTreeBackend.java b/statesystem/org.eclipse.tracecompass.statesystem.core/src/org/eclipse/tracecompass/internal/statesystem/core/backend/historytree/HistoryTreeBackend.java
index d4ed26d2f4..02d96d9f8f 100644
--- a/statesystem/org.eclipse.tracecompass.statesystem.core/src/org/eclipse/tracecompass/internal/statesystem/core/backend/historytree/HistoryTreeBackend.java
+++ b/statesystem/org.eclipse.tracecompass.statesystem.core/src/org/eclipse/tracecompass/internal/statesystem/core/backend/historytree/HistoryTreeBackend.java
@@ -384,7 +384,10 @@ public class HistoryTreeBackend implements IStateHistoryBackend {
                 /* Recursive call to flatten children */
                 return flatten(getSHT().readNode(seqNum), quarks, subTimes);
             } catch (ClosedChannelException e) {
-                return null;
+                /**
+                 * return node since we were able to read it.
+                 */
+                return Collections.singleton(node);
             }
         });
         /* BFS */