don't allow change in ballot stats between loading and tabulating

src/main/java/network/brightspots/rcv/GuiConfigController.java

@@ -102,6 +102,7 @@
 import network.brightspots.rcv.Tabulator.OvervoteRule;
 import network.brightspots.rcv.Tabulator.TiebreakMode;
 import network.brightspots.rcv.Tabulator.WinnerElectionMode;
+import network.brightspots.rcv.TabulatorSession.LoadedCvrData;
 
 /**
  * View controller for config layout.
@@ -508,9 +509,9 @@ public void menuItemTabulateClicked() {
    * Tabulate whatever is currently entered into the GUI.
    * Assumes GuiTabulateController checked all prerequisites.
    */
-  public Service<Integer> parseAndCountCastVoteRecords(String configPath) {
+  public Service<LoadedCvrData> parseAndCountCastVoteRecords(String configPath) {
     setGuiIsBusy(true);
-    Service<Integer> service = new ReadCastVoteRecordsService(configPath);
+    Service<LoadedCvrData> service = new ReadCastVoteRecordsService(configPath);
     setUpAndStartService(service);
     return service;
   }
@@ -520,10 +521,13 @@ public Service<Integer> parseAndCountCastVoteRecords(String configPath) {
    * Assumes GuiTabulateController checked all prerequisites.
    */
   public Service<Boolean> startTabulation(
-        String configPath, String operatorName, boolean deleteConfigOnCompletion) {
+        String configPath,
+        String operatorName,
+        boolean deleteConfigOnCompletion,
+        LoadedCvrData expectedCvrData) {
     setGuiIsBusy(true);
     TabulatorService service = new TabulatorService(
-        configPath, operatorName, deleteConfigOnCompletion);
+        configPath, operatorName, deleteConfigOnCompletion, expectedCvrData);
     setUpAndStartService(service);
     return service;
   }
@@ -1754,10 +1758,16 @@ protected void setUpTaskCompletionTriggers(Task<Boolean> task, String failureMes
   // TabulatorService runs a tabulation in the background
   private static class TabulatorService extends ConfigReaderService {
     private final String operatorName;
+    private LoadedCvrData expectedCvrStatistics;
 
-    TabulatorService(String configPath, String operatorName, boolean deleteConfigOnCompletion) {
+    TabulatorService(
+          String configPath,
+          String operatorName,
+          boolean deleteConfigOnCompletion,
+          LoadedCvrData expectedCvrStatistics) {
       super(configPath, deleteConfigOnCompletion);
       this.operatorName = operatorName;
+      this.expectedCvrStatistics = expectedCvrStatistics;
     }
 
     @Override
@@ -1767,7 +1777,7 @@ protected Task<Boolean> createTask() {
             @Override
             protected Boolean call() {
               TabulatorSession session = new TabulatorSession(configPath);
-              List<String> errors = session.tabulate(operatorName);
+              List<String> errors = session.tabulate(operatorName, expectedCvrStatistics);
               if (errors.isEmpty()) {
                 succeeded();
               } else {
@@ -1806,27 +1816,27 @@ protected Boolean call() {
   }
 
   // ReadCastVoteRecordsService reads CVRs
-  private static class ReadCastVoteRecordsService extends Service<Integer> {
+  private static class ReadCastVoteRecordsService extends Service<LoadedCvrData> {
     private final String configPath;
 
     ReadCastVoteRecordsService(String configPath) {
       this.configPath = configPath;
     }
 
     @Override
-    protected Task<Integer> createTask() {
+    protected Task<LoadedCvrData> createTask() {
       return new Task<>() {
           @Override
-          protected Integer call() {
+          protected LoadedCvrData call() {
             TabulatorSession session = new TabulatorSession(configPath);
-            int count = session.parseAndCountCastVoteRecords();
-            if (count >= 0) {
+            LoadedCvrData cvrStatics = session.parseAndCountCastVoteRecords();
+            if (cvrStatics.successfullyReadAll) {
               succeeded();
             } else {
               Logger.warning("There were errors");
               failed();
             }
-            return count;
+            return cvrStatics;
           }
         };
     }

src/main/java/network/brightspots/rcv/GuiTabulateController.java

@@ -32,6 +32,7 @@
 import javafx.scene.text.Text;
 import javafx.stage.Stage;
 import javafx.stage.Window;
+import network.brightspots.rcv.TabulatorSession.LoadedCvrData;
 
 /** View controller for tabulator layout. */
 @SuppressWarnings("WeakerAccess")
@@ -86,6 +87,11 @@ public class GuiTabulateController {
    */
   private boolean lastTaskFailed = false;
 
+  /**
+   * Last-loaded CVR metadata, with the CVRs themselves discarded from memory.
+   */
+  private LoadedCvrData lastLoadedCvrData;
+
   @FXML private TextArea filepath;
   @FXML private Button saveButton;
   @FXML private Button tempSaveButton;
@@ -144,7 +150,7 @@ public void buttonloadCvrsClicked(ActionEvent actionEvent) {
     }
 
     enableButtonsUpTo(null);
-    Service<Integer> service = guiConfigController.parseAndCountCastVoteRecords(configPath);
+    Service<LoadedCvrData> service = guiConfigController.parseAndCountCastVoteRecords(configPath);
     // Dispatch a function that watches the service and updates the progress bar
     watchParseCvrServiceProgress(service);
   }
@@ -163,7 +169,7 @@ public void buttonTabulateClicked(ActionEvent actionEvent) {
     }
 
     Service<Boolean> service = guiConfigController.startTabulation(
-        configPath, userNameField.getText(), useTemporaryConfigBeforeTabulation);
+        configPath, userNameField.getText(), useTemporaryConfigBeforeTabulation, lastLoadedCvrData);
     // Dispatch a function that watches the service and updates the progress bar
     watchTabulatorServiceProgress(service);
   }
@@ -196,11 +202,14 @@ private void watchTabulatorServiceProgress(Service<Boolean> service) {
     watchGenericService(service, onSuceededEvent);
   }
 
-  private void watchParseCvrServiceProgress(Service<Integer> service) {
+  private void watchParseCvrServiceProgress(Service<LoadedCvrData> service) {
     EventHandler<WorkerStateEvent> onSuceededEvent = workerStateEvent -> {
       enableButtonsUpTo(tabulateButton);
-      numberOfBallots.setText("Number of Ballots: " + service.getValue());
+      LoadedCvrData data = service.getValue();
+      numberOfBallots.setText("Number of Ballots: " + data.numCvrs());
       numberOfBallots.setOpacity(1);
+      data.discard();
+      lastLoadedCvrData = data;
     };
 
     watchGenericService(service, onSuceededEvent);

src/main/java/network/brightspots/rcv/Main.java

@@ -83,7 +83,7 @@ public static void main(String[] args) {
         session.convertToCdf();
       } else {
         operatorName = operatorName.trim();
-        session.tabulate(operatorName);
+        session.tabulate(operatorName, TabulatorSession.LoadedCvrData.MatchesAnything);
       }
     }
 

src/main/java/network/brightspots/rcv/TabulatorSession.java

@@ -105,18 +105,19 @@ boolean convertToCdf() {
       Logger.info("Converting CVR(s) to CDF...");
       try {
         FileUtils.createOutputDirectory(config.getOutputDirectory());
-        List<CastVoteRecord> castVoteRecords = parseCastVoteRecords(config);
-        if (castVoteRecords == null) {
+        LoadedCvrData castVoteRecords = parseCastVoteRecords(config);
+        if (!castVoteRecords.successfullyReadAll) {
           Logger.severe("Aborting conversion due to cast vote record errors!");
         } else {
-          Set<String> precinctIds = new Tabulator(castVoteRecords, config).getPrecinctIds();
+          Set<String> precinctIds = new Tabulator(
+              castVoteRecords.getCvrs(), config).getPrecinctIds();
           ResultsWriter writer =
               new ResultsWriter()
                   .setNumRounds(0)
                   .setPrecinctIds(precinctIds)
                   .setContestConfig(config)
                   .setTimestampString(timestampString);
-          writer.generateCdfJson(castVoteRecords);
+          writer.generateCdfJson(castVoteRecords.getCvrs());
           conversionSuccess = true;
         }
       } catch (IOException
@@ -139,18 +140,17 @@ boolean convertToCdf() {
     return conversionSuccess;
   }
 
-  int parseAndCountCastVoteRecords() {
+  LoadedCvrData parseAndCountCastVoteRecords() {
     ContestConfig config = ContestConfig.loadContestConfig(configPath);
-    List<CastVoteRecord> cvrs = parseCastVoteRecords(config);
-    return cvrs == null ? -1 : cvrs.size();
+    return parseCastVoteRecords(config);
   }
 
   // Returns a List of exception class names that were thrown while tabulating.
   // Operator name is required for the audit logs.
   // Note: An exception MUST be returned any time tabulation does not run.
   // In general, that means any Logger.severe in this function should be accompanied
   // by an exceptionsEncountered.add(...) call.
-  List<String> tabulate(String operatorName) {
+  List<String> tabulate(String operatorName, LoadedCvrData expectedCvrData) {
     Logger.info("Starting tabulation session...");
     List<String> exceptionsEncountered = new LinkedList<>();
     ContestConfig config = ContestConfig.loadContestConfig(configPath);
@@ -192,16 +192,22 @@ List<String> tabulate(String operatorName) {
           Logger.info(
               "Beginning tabulation for seat #%d...", config.getSequentialWinners().size() + 1);
           // Read cast vote records and precinct IDs from CVR files
-          List<CastVoteRecord> castVoteRecords = parseCastVoteRecords(config);
-          if (castVoteRecords == null) {
+          LoadedCvrData castVoteRecords = parseCastVoteRecords(config);
+          if (config.getSequentialWinners().isEmpty()
+                && !castVoteRecords.metadataMatches(expectedCvrData)) {
+            Logger.severe("CVR Data has changed between loading the CVRs and reading them!");
+            exceptionsEncountered.add(TabulationAbortedException.class.toString());
+            break;
+          }
+          if (!castVoteRecords.successfullyReadAll) {
             String errorMessage = "Aborting tabulation due to cast vote record errors!";
             exceptionsEncountered.add(errorMessage);
             Logger.severe(errorMessage);
             break;
           }
           Set<String> newWinnerSet;
           try {
-            newWinnerSet = runTabulationForConfig(config, castVoteRecords);
+            newWinnerSet = runTabulationForConfig(config, castVoteRecords.getCvrs());
           } catch (TabulationAbortedException exception) {
             exceptionsEncountered.add(exception.getClass().toString());
             Logger.severe(exception.getMessage());
@@ -230,14 +236,17 @@ List<String> tabulate(String operatorName) {
       } else {
         // normal operation (not multi-pass IRV, a.k.a. sequential multi-seat)
         // Read cast vote records and precinct IDs from CVR files
-        List<CastVoteRecord> castVoteRecords = parseCastVoteRecords(config);
-        if (castVoteRecords == null) {
+        LoadedCvrData castVoteRecords = parseCastVoteRecords(config);
+        if (!castVoteRecords.metadataMatches(expectedCvrData)) {
+          Logger.severe("CVR Data has changed between loading the CVRs and reading them!");
+          exceptionsEncountered.add(TabulationAbortedException.class.toString());
+        } else if (!castVoteRecords.successfullyReadAll) {
           String errorMessage = "Aborting tabulation due to cast vote record errors!";
           exceptionsEncountered.add(errorMessage);
           Logger.severe(errorMessage);
         } else {
           try {
-            runTabulationForConfig(config, castVoteRecords);
+            runTabulationForConfig(config, castVoteRecords.getCvrs());
             tabulationSuccess = true;
           } catch (TabulationAbortedException exception) {
             exceptionsEncountered.add(exception.getClass().toString());
@@ -290,7 +299,7 @@ private Set<String> runTabulationForConfig(
   // parse CVR files referenced in the ContestConfig object into a list of CastVoteRecords
   // param: config object containing CVR file paths to parse
   // returns: list of parsed CVRs or null if an error was encountered
-  private List<CastVoteRecord> parseCastVoteRecords(ContestConfig config) {
+  private LoadedCvrData parseCastVoteRecords(ContestConfig config) {
     Logger.info("Parsing cast vote records...");
     List<CastVoteRecord> castVoteRecords = new ArrayList<>();
     boolean encounteredSourceProblem = false;
@@ -381,7 +390,7 @@ private List<CastVoteRecord> parseCastVoteRecords(ContestConfig config) {
     } else {
       Logger.info("Parsed %d cast vote records successfully.", castVoteRecords.size());
     }
-    return castVoteRecords;
+    return new LoadedCvrData(castVoteRecords);
   }
 
   static class UnrecognizedCandidatesException extends Exception {
@@ -393,4 +402,68 @@ static class UnrecognizedCandidatesException extends Exception {
       this.candidateCounts = candidateCounts;
     }
   }
+
+  /**
+   * A summary of the cast vote records that have been read.
+   * Manages CVR in memory, so you can retain metadata about the loaded CVRs without
+   * keeping them all in memory. Use .discard() to free up memory. After memory is freed,
+   * all other operations except for getCvrs() are still valid.
+   */
+  public static class LoadedCvrData {
+    public static LoadedCvrData MatchesAnything = new LoadedCvrData(true);
+    public final boolean successfullyReadAll;
+
+    private List<CastVoteRecord> cvrs;
+    private int numCvrs;
+    private boolean isDiscarded;
+    private boolean doesMatchAllMetadata;
+
+    public LoadedCvrData(List<CastVoteRecord> cvrs) {
+      this.cvrs = cvrs;
+      this.successfullyReadAll = cvrs != null;
+      this.numCvrs = cvrs != null ? cvrs.size() : 0;
+      this.isDiscarded = false;
+      this.doesMatchAllMetadata = false;
+    }
+
+    /**
+     * This constructor will cause metadataMatches to always return true.
+     */
+    private LoadedCvrData(boolean doesMatchAllMetadata) {
+      this.cvrs = null;
+      this.successfullyReadAll = false;
+      this.numCvrs = 0;
+      this.isDiscarded = false;
+      this.doesMatchAllMetadata = true;
+    }
+
+    /**
+     * Currently only checks if the number of CVRs matches, but can be extended to ensure
+     * exact matches or meet other needs.
+     *
+     * @param other The loaded CVRs to compare against
+     * @return whether the metadata matches
+     */
+    public boolean metadataMatches(LoadedCvrData other) {
+      return other.doesMatchAllMetadata
+          || this.doesMatchAllMetadata
+          || other.numCvrs() == this.numCvrs();
+    }
+
+    public int numCvrs() {
+      return numCvrs;
+    }
+
+    public void discard() {
+      cvrs = null;
+      isDiscarded = true;
+    }
+
+    public List<CastVoteRecord> getCvrs() {
+      if (isDiscarded) {
+        throw new IllegalStateException("CVRs have been discarded from memory.");
+      }
+      return cvrs;
+    }
+  }
 }

src/main/resources/network/brightspots/rcv/GuiTabulationPopup.fxml

@@ -101,7 +101,7 @@
       <ProgressBar fx:id="progressBar" layoutX="19.0" layoutY="429.0" prefHeight="20.0" prefWidth="563.0" progress="0.0" />
       <HBox layoutX="21.0" layoutY="367.0" prefHeight="42.0" prefWidth="556.0" spacing="20.0">
          <children>
-            <Button fx:id="loadCvrButton" defaultButton="true" disable="true" mnemonicParsing="false" onAction="#buttonloadCvrsClicked" prefHeight="42.0" prefWidth="200.0" text="Load CVRs" />
+            <Button fx:id="loadCvrButton" defaultButton="true" disable="true" mnemonicParsing="false" onAction="#buttonloadCvrsClicked" prefHeight="42.0" prefWidth="200.0" text="Check Ballot Counts" />
             <Text layoutY="21.0" strokeType="OUTSIDE" strokeWidth="0.0" text="&gt;" textAlignment="CENTER" translateY="11.0" />
             <Button fx:id="tabulateButton" defaultButton="true" disable="true" layoutX="10.0" layoutY="10.0" mnemonicParsing="false" onAction="#buttonTabulateClicked" prefHeight="42.0" prefWidth="200.0" text="Tabulate" />
             <Text strokeType="OUTSIDE" strokeWidth="0.0" text="&gt;" textAlignment="CENTER" translateY="11.0" />