SendableChooser generic value (#433)

* Java SendableChooser now decorates with type (non-breaking change)

* C++ SendableChooser now is templated on the type instead of using void* and stores values (breaking change)

* C++ SendableChooser now uses llvm::StringMap instead of std::map

wpilibc/shared/include/SmartDashboard/SendableChooser.inc

@@ -0,0 +1,83 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2011-2017. All Rights Reserved.                        */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <algorithm>
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace frc {
+
+/**
+ * Adds the given object to the list of options.
+ *
+ * On the {@link SmartDashboard} on the desktop, the object will appear as the
+ * given name.
+ *
+ * @param name   the name of the option
+ * @param object the option
+ */
+template <class T>
+void SendableChooser<T>::AddObject(llvm::StringRef name, const T& object) {
+  m_choices[name] = object;
+}
+
+/**
+ * Add the given object to the list of options and marks it as the default.
+ *
+ * Functionally, this is very close to {@link SendableChooser#AddObject(const
+ * char *name, void *object) AddObject(...)} except that it will use this as
+ * the default option if none other is explicitly selected.
+ *
+ * @param name   the name of the option
+ * @param object the option
+ */
+template <class T>
+void SendableChooser<T>::AddDefault(llvm::StringRef name, const T& object) {
+  m_defaultChoice = name;
+  AddObject(name, object);
+}
+
+/**
+ * Returns the selected option.
+ *
+ * If there is none selected, it will return the default.  If there is none
+ * selected and no default, then it will return {@code nullptr}.
+ *
+ * @return the option selected
+ */
+template <class T>
+T SendableChooser<T>::GetSelected() {
+  std::string selected = m_table->GetString(kSelected, m_defaultChoice);
+  if (selected == "") {
+    return nullptr;
+  } else {
+    return m_choices[selected];
+  }
+}
+
+template <class T>
+void SendableChooser<T>::InitTable(std::shared_ptr<ITable> subtable) {
+  std::vector<std::string> keys;
+  m_table = subtable;
+  if (m_table != nullptr) {
+    for (const auto& choice : m_choices) {
+      keys.push_back(choice.first());
+    }
+
+    // Unlike std::map, llvm::StringMap elements are not sorted
+    std::sort(keys.begin(), keys.end());
+
+    m_table->PutValue(kOptions, nt::Value::MakeStringArray(std::move(keys)));
+    m_table->PutString(kDefault, m_defaultChoice);
+  }
+}
+
+}  // namespace frc