[sim] Add WPILib-class-taking constructors (#2538)

When not direct mapped, make index constructors private and add factory
functions for channel and index.

Co-authored-by: GabrielDeml <gabrielddeml@gmail.com>

wpilibc/src/main/native/include/frc/simulation/AnalogOutputSim.h

@@ -0,0 +1,79 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018-2020 FIRST. 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 <memory>
+#include <utility>
+
+#include <hal/simulation/AnalogOutData.h>
+
+#include "CallbackStore.h"
+#include "frc/AnalogOutput.h"
+
+namespace frc {
+namespace sim {
+
+/**
+ * Class to control a simulated analog output.
+ */
+class AnalogOutputSim {
+ public:
+  /**
+   * Constructs from an AnalogOutput object.
+   *
+   * @param analogOutput AnalogOutput to simulate
+   */
+  explicit AnalogOutputSim(const AnalogOutput& analogOutput)
+      : m_index{analogOutput.GetChannel()} {}
+
+  /**
+   * Constructs from an analog output channel number.
+   *
+   * @param channel Channel number
+   */
+  explicit AnalogOutputSim(int channel) : m_index{channel} {}
+
+  std::unique_ptr<CallbackStore> RegisterVoltageCallback(
+      NotifyCallback callback, bool initialNotify) {
+    auto store = std::make_unique<CallbackStore>(
+        m_index, -1, callback, &HALSIM_CancelAnalogOutVoltageCallback);
+    store->SetUid(HALSIM_RegisterAnalogOutVoltageCallback(
+        m_index, &CallbackStoreThunk, store.get(), initialNotify));
+    return store;
+  }
+
+  double GetVoltage() const { return HALSIM_GetAnalogOutVoltage(m_index); }
+
+  void SetVoltage(double voltage) {
+    HALSIM_SetAnalogOutVoltage(m_index, voltage);
+  }
+
+  std::unique_ptr<CallbackStore> RegisterInitializedCallback(
+      NotifyCallback callback, bool initialNotify) {
+    auto store = std::make_unique<CallbackStore>(
+        m_index, -1, callback, &HALSIM_CancelAnalogOutInitializedCallback);
+    store->SetUid(HALSIM_RegisterAnalogOutInitializedCallback(
+        m_index, &CallbackStoreThunk, store.get(), initialNotify));
+    return store;
+  }
+
+  bool GetInitialized() const {
+    return HALSIM_GetAnalogOutInitialized(m_index);
+  }
+
+  void SetInitialized(bool initialized) {
+    HALSIM_SetAnalogOutInitialized(m_index, initialized);
+  }
+
+  void ResetData() { HALSIM_ResetAnalogOutData(m_index); }
+
+ private:
+  int m_index;
+};
+}  // namespace sim
+}  // namespace frc