Add high level way of getting systemserver nt instance

hal/BUILD.bazel

@@ -69,6 +69,8 @@ cc_library(
         ":generated_cc_headers",
         ":mrc_cc_headers",
         ":generated_mrc_cc_headers",
+        "//ntcore:ntcore.static",
+        "//wpinet:wpinet.static",
         "//wpiutil:wpiutil.static",
     ] + HAL_DEPS,
 )
@@ -78,6 +80,8 @@ java_library(
     srcs = [":generated_java"] + glob(["src/main/java/**/*.java"]),
     visibility = ["//visibility:public"],
     deps = [
+        "//ntcore:networktables-java",
+        "//wpinet:wpinet-java",
         "//wpiutil:wpiutil-java",
     ],
 )

hal/CMakeLists.txt

@@ -22,7 +22,7 @@ target_include_directories(
         $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/src/generated/main/native/include>
         $<INSTALL_INTERFACE:${include_dest}/hal>
 )
-target_link_libraries(hal PUBLIC wpiutil)
+target_link_libraries(hal PUBLIC ntcore wpiutil)
 
 set_property(TARGET hal PROPERTY FOLDER "libraries")
 

hal/src/main/java/edu/wpi/first/hal/SystemServerJNI.java

@@ -0,0 +1,23 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+package edu.wpi.first.hal;
+
+/**
+ * SystemServer JNI Functions.
+ *
+ * @see "SystemServer.h"
+ */
+public class SystemServerJNI extends JNIWrapper {
+  /**
+   * Gets the system server NT handle.
+   *
+   * @return The system server NT handle
+   * @see "HAL_GetSystemServerHandle"
+   */
+  public static native int getSystemServerHandle();
+
+  /** Utility class. */
+  private SystemServerJNI() {}
+}

hal/src/main/native/cpp/jni/SystemServerJNI.cpp

@@ -0,0 +1,24 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <jni.h>
+
+#include "edu_wpi_first_hal_SystemServerJNI.h"
+#include "hal/SystemServer.h"
+
+extern "C" {
+
+/*
+ * Class:     edu_wpi_first_hal_SystemServerJNI
+ * Method:    getSystemServerHandle
+ * Signature: ()I
+ */
+JNIEXPORT jint JNICALL
+Java_edu_wpi_first_hal_SystemServerJNI_getSystemServerHandle
+  (JNIEnv*, jclass)
+{
+  return HAL_GetSystemServerHandle();
+}
+
+}  // extern "C"

hal/src/main/native/include/hal/SystemServer.h

@@ -0,0 +1,17 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#include <ntcore_c.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+NT_Inst HAL_GetSystemServerHandle(void);
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif

hal/src/main/native/sim/SystemServer.cpp

@@ -0,0 +1,12 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "hal/SystemServer.h"
+
+extern "C" {
+
+NT_Inst HAL_GetSystemServerHandle(void) {
+  return 0;
+}
+}  // extern "C"

hal/src/main/native/systemcore/FRCDriverStation.cpp

@@ -27,7 +27,7 @@
 #include <wpi/timestamp.h>
 
 #include "HALInitializer.h"
-#include "SystemServer.h"
+#include "SystemServerInternal.h"
 #include "hal/DriverStation.h"
 #include "hal/Errors.h"
 #include "hal/proto/ControlData.h"

hal/src/main/native/systemcore/HAL.cpp

@@ -27,7 +27,7 @@
 #include "CANInternal.h"
 #include "HALInitializer.h"
 #include "HALInternal.h"
-#include "SystemServer.h"
+#include "SystemServerInternal.h"
 #include "hal/DriverStation.h"
 #include "hal/Errors.h"
 #include "hal/Notifier.h"

hal/src/main/native/systemcore/SmartIo.cpp

@@ -7,7 +7,7 @@
 #include <atomic>
 
 #include "HALInitializer.h"
-#include "SystemServer.h"
+#include "SystemServerInternal.h"
 
 namespace hal {
 

hal/src/main/native/systemcore/SystemServer.cpp

@@ -2,8 +2,9 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-#include "SystemServer.h"
+#include "hal/SystemServer.h"
 
+#include "SystemServerInternal.h"
 #include "mrc/NtNetComm.h"
 
 namespace hal {
@@ -33,3 +34,10 @@ nt::NetworkTableInstance GetSystemServer() {
 }
 
 }  // namespace hal
+
+extern "C" {
+
+NT_Inst HAL_GetSystemServerHandle(void) {
+  return hal::ServerInstance.GetHandle();
+}
+}  // extern "C"

ntcore/src/generate/main/java/NetworkTableInstance.java.jinja

@@ -134,6 +134,16 @@ public final class NetworkTableInstance implements AutoCloseable {
     return inst;
   }
 
+  /**
+   * Create an instance from a native handle. This instance is not owned, closing will do nothing.
+   *
+   * @param handle Native instance handle
+   * @return Instance
+   */
+  public static NetworkTableInstance fromNativeHandle(int handle) {
+    return new NetworkTableInstance(handle);
+  }
+
   /**
    * Gets the native handle for the instance.
    *

wpilibc/src/main/native/cpp/SystemServer.cpp

@@ -0,0 +1,15 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "frc/SystemServer.h"
+
+#include <hal/SystemServer.h>
+
+namespace frc {
+
+nt::NetworkTableInstance SystemServer::GetSystemServer() {
+  return nt::NetworkTableInstance{HAL_GetSystemServerHandle()};
+}
+
+}  // namespace frc

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

@@ -0,0 +1,18 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#include <networktables/NetworkTableInstance.h>
+
+namespace frc {
+
+class SystemServer {
+ public:
+  SystemServer() = delete;
+
+  static nt::NetworkTableInstance GetSystemServer();
+};
+
+}  // namespace frc

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

@@ -0,0 +1,23 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+package edu.wpi.first.wpilibj;
+
+import edu.wpi.first.hal.SystemServerJNI;
+import edu.wpi.first.networktables.NetworkTableInstance;
+
+/** Class to get system server NT instance. */
+public final class SystemServer {
+  /**
+   * Gets the system server NT Instance.
+   *
+   * @return NT Instance
+   */
+  public static NetworkTableInstance getSystemServer() {
+    return NetworkTableInstance.fromNativeHandle(SystemServerJNI.getSystemServerHandle());
+  }
+
+  /** Utility Class. */
+  private SystemServer() {}
+}