--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/main/gov/nasa/jpf/listener/CGMonitor.java	Fri Jan 23 10:14:01 2015 -0800
@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) 2014, United States Government, as represented by the
+ * Administrator of the National Aeronautics and Space Administration.
+ * All rights reserved.
+ *
+ * The Java Pathfinder core (jpf-core) platform is licensed under the
+ * Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ * 
+ *        http://www.apache.org/licenses/LICENSE-2.0. 
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and 
+ * limitations under the License.
+ */
+package gov.nasa.jpf.listener;
+
+import gov.nasa.jpf.Config;
+import gov.nasa.jpf.ListenerAdapter;
+import gov.nasa.jpf.search.Search;
+import gov.nasa.jpf.vm.ChoiceGenerator;
+import gov.nasa.jpf.vm.VM;
+import java.io.PrintStream;
+
+/**
+ * listener to report out what CGs and choices are processed during the search.
+ * This is a simple tool to find out about the SUT state space
+ */
+public class CGMonitor extends ListenerAdapter {
+  
+  protected PrintStream out;
+  
+  protected int depth;
+  
+  // display options
+  protected boolean showInsn = false;   // show the insn that caused the CG
+  protected boolean showChoice = false; // show the choice value (-> show each CG.advance())
+  protected boolean showDepth = true;   // show search depth at point of CG set/advance
+  
+  public CGMonitor (Config conf) {
+    showInsn = conf.getBoolean("cgm.show_insn", showInsn);
+    showChoice = conf.getBoolean("cgm.show_choice", showChoice);
+    showDepth = conf.getBoolean("cgm.show_depth", showDepth);
+    
+    out = System.out;
+  }
+  
+  @Override
+  public void stateAdvanced (Search search) {
+    depth++;
+  }
+  
+  @Override
+  public void stateBacktracked (Search search) {
+    depth--;
+  }
+  
+  @Override
+  public void stateRestored (Search search) {
+    depth = search.getDepth();    
+  }
+  
+  void printPrefix(char c) {
+    for (int i=0; i<depth; i++) {
+      System.out.print(c);
+    }
+  }
+  
+  void printCG (ChoiceGenerator<?> cg, boolean printChoice){
+    if (showDepth){
+      printPrefix('.');
+    }
+    
+    out.print(cg);
+
+    if (printChoice){
+      out.print(", ");
+      out.print(cg.getNextChoice());
+    }
+
+    if (showInsn){
+      out.print(", \"");
+      out.print(cg.getInsn());
+      out.print('\"');
+    }
+
+    out.println();    
+  }
+  
+  @Override
+  public void choiceGeneratorSet (VM vm, ChoiceGenerator<?> currentCG) {
+    if (!showChoice){
+      printCG( vm.getChoiceGenerator(), false);
+    }
+  }
+  
+  @Override
+  public void choiceGeneratorAdvanced (VM vm, ChoiceGenerator<?> currentCG) {
+    if (showChoice){
+      printCG( vm.getChoiceGenerator(), true);      
+    }
+  }
+
+}