add no-reuse-events option for background merging

Author: baltzell

reconstruction/bg/src/main/java/org/jlab/service/bg/BackgroundEngine.java

@@ -20,9 +20,12 @@ public class BackgroundEngine extends ReconstructionEngine {
     public static final String CONF_ORDERS = "orders";
     public static final String CONF_SUPPRESS_DOUBLES = "suppressDoubles";
     public static final String CONF_PRESERVE_ORDER = "preserveOrder";
+    public static final String CONF_REUSE_EVENTS = "reuseEvents";
 
     static final Logger logger = Logger.getLogger(BackgroundEngine.class.getName());
 
+    int filesUsed = 0;
+    boolean reuseEvents = true;
     EventMerger bgmerger = null;
     HipoDataSource bgreader = null;
     LinkedList<String> bgfilenames = new LinkedList<>();
@@ -40,6 +43,11 @@ public boolean init() {
 
     public boolean init(String... filenames) {
         bgfilenames.clear();
+        String detectors = getEngineConfigString(CONF_DETECTORS,"DC,FTOF");
+        String orders = getEngineConfigString(CONF_ORDERS,"NOMINAL");
+        boolean suppressDoubles = Boolean.valueOf(getEngineConfigString(CONF_SUPPRESS_DOUBLES,"true"));
+        boolean preserveOrder = Boolean.valueOf(getEngineConfigString(CONF_PRESERVE_ORDER,"true"));
+        boolean reuseEvents = Boolean.valueOf(getEngineConfigString(CONF_REUSE_EVENTS,"false"));
         for (String filename : filenames) {
             File f = new File(filename);
             if (!f.exists() || !f.isFile() || !f.canRead()) {
@@ -49,20 +57,21 @@ public boolean init(String... filenames) {
             logger.log(Level.INFO,"BackgroundEngine::  reading {0}",filename);
             bgfilenames.add(filename);
         }
-        String detectors = getEngineConfigString(CONF_DETECTORS,"DC,FTOF");
-        String orders = getEngineConfigString(CONF_ORDERS,"NOMINAL");
-        Boolean suppressDoubles = Boolean.valueOf(getEngineConfigString(CONF_SUPPRESS_DOUBLES,"true"));
-        Boolean preserveOrder = Boolean.valueOf(getEngineConfigString(CONF_PRESERVE_ORDER,"true"));
         bgmerger = new EventMerger(detectors.split(","), orders.split(","), suppressDoubles, preserveOrder);
         openNextFile();
         return true;
     }
 
     private void openNextFile() {
+        if (filesUsed>0 && filesUsed%bgfilenames.size()==0) {
+            if (reuseEvents) logger.info("BackgroundEngine::  Reopening previously used file.");
+            else throw new RuntimeException("BackgroundEngine::  Ran out of events.");
+        }
         String filename = bgfilenames.remove();
         bgfilenames.add(filename);
         bgreader = new HipoDataSource();
         bgreader.open(filename);
+        filesUsed++;
     }
 
     synchronized public DataEvent getBackgroundEvent() {