[ntcore] Provide mechanism to reset internals of NT instance (#4653)

ntcore/src/main/native/cpp/InstanceImpl.cpp

@@ -174,3 +174,15 @@ std::shared_ptr<INetworkClient> InstanceImpl::GetClient() {
   std::scoped_lock lock{m_mutex};
   return m_networkClient;
 }
+
+void InstanceImpl::Reset() {
+  std::scoped_lock lock{m_mutex};
+  m_networkServer.reset();
+  m_networkClient.reset();
+  m_servers.clear();
+  networkMode = NT_NET_MODE_NONE;
+
+  listenerStorage.Reset();
+  // connectionList should have been cleared by destroying networkClient/server
+  localStorage.Reset();
+}

ntcore/src/main/native/cpp/InstanceImpl.h

@@ -56,6 +56,8 @@ class InstanceImpl {
   std::shared_ptr<NetworkServer> GetServer();
   std::shared_ptr<INetworkClient> GetClient();
 
+  void Reset();
+
   ListenerStorage listenerStorage;
   LoggerImpl logger_impl;
   wpi::Logger logger;

ntcore/src/main/native/cpp/ListenerStorage.cpp

@@ -320,6 +320,19 @@ bool ListenerStorage::WaitForListenerQueue(double timeout) {
   return wpi::WaitForObject(h, timeout, &timedOut);
 }
 
+void ListenerStorage::Reset() {
+  std::scoped_lock lock{m_mutex};
+  m_pollers.clear();
+  m_listeners.clear();
+  m_connListeners.clear();
+  m_topicListeners.clear();
+  m_valueListeners.clear();
+  m_logListeners.clear();
+  if (m_thread) {
+    m_thread.Stop();
+  }
+}
+
 std::vector<std::pair<NT_Listener, unsigned int>>
 ListenerStorage::DoRemoveListeners(std::span<const NT_Listener> handles) {
   std::vector<std::pair<NT_Listener, unsigned int>> rv;

ntcore/src/main/native/cpp/ListenerStorage.h

@@ -59,6 +59,8 @@ class ListenerStorage final : public IListenerStorage {
 
   bool WaitForListenerQueue(double timeout);
 
+  void Reset();
+
  private:
   // these assume the mutex is already held
   NT_Listener DoAddListener(NT_ListenerPoller pollerHandle);

ntcore/src/main/native/cpp/LocalStorage.cpp

@@ -2187,3 +2187,9 @@ void LocalStorage::StopDataLog(NT_DataLogger logger) {
     }
   }
 }
+
+void LocalStorage::Reset() {
+  std::scoped_lock lock{m_mutex};
+  m_impl = std::make_unique<Impl>(m_impl->m_inst, m_impl->m_listenerStorage,
+                                  m_impl->m_logger);
+}

ntcore/src/main/native/cpp/LocalStorage.h

@@ -209,6 +209,8 @@ class LocalStorage final : public net::ILocalStorage {
                              std::string_view logPrefix);
   void StopDataLog(NT_DataLogger logger);
 
+  void Reset();
+
  private:
   class Impl;
   std::unique_ptr<Impl> m_impl;

ntcore/src/main/native/cpp/ntcore_cpp.cpp

@@ -45,6 +45,12 @@ NT_Inst CreateInstance() {
   return Handle{InstanceImpl::Alloc(), 0, Handle::kInstance};
 }
 
+void ResetInstance(NT_Inst inst) {
+  if (auto ii = InstanceImpl::GetTyped(inst, Handle::kInstance)) {
+    ii->Reset();
+  }
+}
+
 void DestroyInstance(NT_Inst inst) {
   int i = Handle{inst}.GetTypedInst(Handle::kInstance);
   if (i < 0) {