[wpiutil] Add DataLog and DataLogManager Stop()

ntcoreffi/src/main/native/cpp/DataLogManager.cpp

@@ -467,7 +467,16 @@ static Instance& GetInstance(std::string_view dir = "",
 
 void DataLogManager::Start(std::string_view dir, std::string_view filename,
                            double period) {
-  GetInstance(dir, filename, period);
+  auto& inst = GetInstance(dir, filename, period);
+  if (!inst.owner) {
+    inst.owner.Start(dir, MakeLogDir(filename), period);
+  }
+}
+
+void DataLogManager::Stop() {
+  auto& inst = GetInstance();
+  inst.owner.GetThread()->m_log.Stop();
+  inst.owner.Stop();
 }
 
 void DataLogManager::Log(std::string_view message) {
@@ -503,6 +512,10 @@ void DLM_Start(const char* dir, const char* filename, double period) {
   DataLogManager::Start(dir, filename, period);
 }
 
+void DLM_Stop(void) {
+  DataLogManager::Stop();
+}
+
 void DLM_Log(const char* message) {
   DataLogManager::Log(message);
 }

ntcoreffi/src/main/native/include/DataLogManager.h

@@ -52,6 +52,11 @@ class DataLogManager final {
   static void Start(std::string_view dir = "", std::string_view filename = "",
                     double period = 0.25);
 
+  /**
+   * Stop data log manager.
+   */
+  static void Stop();
+
   /**
    * Log a message to the "messages" entry. The message is also printed to
    * standard output (followed by a newline).
@@ -110,6 +115,11 @@ struct WPI_DataLog;
  */
 void DLM_Start(const char* dir, const char* filename, double period);
 
+/**
+ * Stop data log manager.
+ */
+void DLM_Stop(void);
+
 /**
  * Log a message to the "messages" entry. The message is also printed to
  * standard output (followed by a newline).

ntcoreffi/src/main/native/symbols.txt

@@ -4,6 +4,7 @@ DLM_Log
 DLM_LogNetworkTables
 DLM_SignalNewDSDataOccur
 DLM_Start
+DLM_Stop
 NT_AddListener
 NT_AddListenerMultiple
 NT_AddListenerSingle
@@ -245,6 +246,7 @@ WPI_DataLog_Resume
 WPI_DataLog_SetFilename
 WPI_DataLog_SetMetadata
 WPI_DataLog_Start
+WPI_DataLog_Stop
 WPI_DestroyEvent
 WPI_DestroySemaphore
 WPI_DestroySignalObject

wpilibc/src/main/native/cpp/DataLogManager.cpp

@@ -313,7 +313,16 @@ static Instance& GetInstance(std::string_view dir = "",
 
 void DataLogManager::Start(std::string_view dir, std::string_view filename,
                            double period) {
-  GetInstance(dir, filename, period);
+  auto& inst = GetInstance(dir, filename, period);
+  if (!inst.owner) {
+    inst.owner.Start(dir, MakeLogDir(filename), period);
+  }
+}
+
+void DataLogManager::Stop() {
+  auto& inst = GetInstance();
+  inst.owner.GetThread()->m_log.Stop();
+  inst.owner.Stop();
 }
 
 void DataLogManager::Log(std::string_view message) {

wpilibc/src/main/native/include/frc/DataLogManager.h

@@ -49,6 +49,11 @@ class DataLogManager final {
   static void Start(std::string_view dir = "", std::string_view filename = "",
                     double period = 0.25);
 
+  /**
+   * Stop data log manager.
+   */
+  static void Stop();
+
   /**
    * Log a message to the "messages" entry. The message is also printed to
    * standard output (followed by a newline).

wpilibj/src/main/java/edu/wpi/first/wpilibj/DataLogManager.java

@@ -41,9 +41,10 @@
  */
 public final class DataLogManager {
   private static DataLog m_log;
+  private static boolean m_stopped;
   private static String m_logDir;
   private static boolean m_filenameOverride;
-  private static final Thread m_thread;
+  private static Thread m_thread;
   private static final ZoneId m_utc = ZoneId.of("UTC");
   private static final DateTimeFormatter m_timeFormatter =
       DateTimeFormatter.ofPattern("yyyyMMdd_HHmmss").withZone(m_utc);
@@ -59,11 +60,6 @@ public final class DataLogManager {
 
   private DataLogManager() {}
 
-  static {
-    m_thread = new Thread(DataLogManager::logMain, "DataLogDS");
-    m_thread.setDaemon(true);
-  }
-
   /** Start data log manager with default directory location. */
   public static synchronized void start() {
     start("", "", 0.25);
@@ -100,33 +96,54 @@ public static synchronized void start(String dir, String filename) {
    *     tradeoff
    */
   public static synchronized void start(String dir, String filename, double period) {
-    if (m_log != null) {
-      return;
-    }
-    m_logDir = makeLogDir(dir);
-    m_filenameOverride = !filename.isEmpty();
+    if (m_log == null) {
+      m_logDir = makeLogDir(dir);
+      m_filenameOverride = !filename.isEmpty();
 
-    // Delete all previously existing FRC_TBD_*.wpilog files. These only exist when the robot
-    // never connects to the DS, so they are very unlikely to have useful data and just clutter
-    // the filesystem.
-    File[] files =
-        new File(m_logDir)
-            .listFiles((d, name) -> name.startsWith("FRC_TBD_") && name.endsWith(".wpilog"));
-    if (files != null) {
-      for (File file : files) {
-        if (!file.delete()) {
-          System.err.println("DataLogManager: could not delete " + file);
+      // Delete all previously existing FRC_TBD_*.wpilog files. These only exist when the robot
+      // never connects to the DS, so they are very unlikely to have useful data and just clutter
+      // the filesystem.
+      File[] files =
+          new File(m_logDir)
+              .listFiles((d, name) -> name.startsWith("FRC_TBD_") && name.endsWith(".wpilog"));
+      if (files != null) {
+        for (File file : files) {
+          if (!file.delete()) {
+            System.err.println("DataLogManager: could not delete " + file);
+          }
         }
       }
+      m_log = new DataLog(m_logDir, makeLogFilename(filename), period);
+      m_messageLog = new StringLogEntry(m_log, "messages");
+
+      // Log all NT entries and connections
+      if (m_ntLoggerEnabled) {
+        startNtLog();
+      }
+    } else if (m_stopped) {
+      m_log.setFilename(makeLogFilename(filename));
+      m_log.resume();
+      m_stopped = false;
     }
 
-    m_log = new DataLog(m_logDir, makeLogFilename(filename), period);
-    m_messageLog = new StringLogEntry(m_log, "messages");
-    m_thread.start();
+    if (m_thread == null) {
+      m_thread = new Thread(DataLogManager::logMain, "DataLogDS");
+      m_thread.setDaemon(true);
+      m_thread.start();
+    }
+  }
 
-    // Log all NT entries and connections
-    if (m_ntLoggerEnabled) {
-      startNtLog();
+  /**
+   * Stop data log manager.
+   */
+  public static synchronized void stop() {
+    if (m_thread != null) {
+      m_thread.interrupt();
+      m_thread = null;
+    }
+    if (m_log != null) {
+      m_log.stop();
+      m_stopped = true;
     }
   }
 

wpiutil/src/main/java/edu/wpi/first/util/datalog/DataLog.java

@@ -106,11 +106,22 @@ public void pause() {
     DataLogJNI.pause(m_impl);
   }
 
-  /** Resumes appending of data records to the log. */
+  /**
+   * Resumes appending of data records to the log. If called after stop(), opens a new file (with
+   * random name if SetFilename was not called after stop()) and appends Start records and schema
+   * data values for all previously started entries and schemas.
+   */
   public void resume() {
     DataLogJNI.resume(m_impl);
   }
 
+  /**
+   * Stops appending all records to the log, and closes the log file.
+   */
+  public void stop() {
+    DataLogJNI.stop(m_impl);
+  }
+
   /**
    * Returns whether there is a data schema already registered with the given name.
    *

wpiutil/src/main/java/edu/wpi/first/util/datalog/DataLogJNI.java

@@ -18,6 +18,8 @@ public class DataLogJNI extends WPIUtilJNI {
 
   static native void resume(long impl);
 
+  static native void stop(long impl);
+
   static native void addSchema(long impl, String name, String type, byte[] schema, long timestamp);
 
   static native void addSchemaString(