[ntcore] NetworkTables 4 (#3217)

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

@@ -0,0 +1,54 @@
+// 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 <memory>
+#include <utility>
+
+#include <wpi/UidVector.h>
+
+#include "Handle.h"
+
+namespace nt {
+
+// Utility wrapper class for our UidVectors
+template <typename T, size_t Size>
+class HandleMap : public wpi::UidVector<std::unique_ptr<T>, Size> {
+ public:
+  template <typename... Args>
+  T* Add(int inst, Args&&... args) {
+    auto i = this->emplace_back();
+    auto& it = (*this)[i];
+    it = std::make_unique<T>(Handle(inst, i, T::kType),
+                             std::forward<Args>(args)...);
+    return it.get();
+  }
+
+  std::unique_ptr<T> Remove(NT_Handle handle) {
+    Handle h{handle};
+    if (!h.IsType(T::kType)) {
+      return {};
+    }
+    unsigned int i = h.GetIndex();
+    if (i >= this->size()) {
+      return {};
+    }
+    return this->erase(i);
+  }
+
+  T* Get(NT_Handle handle) {
+    Handle h{handle};
+    if (!h.IsType(T::kType)) {
+      return {};
+    }
+    unsigned int i = h.GetIndex();
+    if (i >= this->size()) {
+      return {};
+    }
+    return (*this)[i].get();
+  }
+};
+
+}  // namespace nt