[hal, wpilib] Switch PCM to be a single object that is allowed to be duplicated (#3475)

Having PCM as a singleton is a problem, as multiple things need to use it, and that gets really ugly. This changes PCM's to be a reference counted object, that can be passed around and constructed from multiple places.

In Java, this is using a map to hold a data store with a ref count, and allocating new objects any time a duplicate is requested.

In C++, this uses a trick constructor to store a PCM instance in the data store itself. This instance can then be passed to base objects using std::shared_ptr's aliasing constructor, which means constructing a solenoid from a PCM is not allocating after the 1st one.

This did require removing sendable from PCM. A compressor class was added back in to act as sendable for the PCM.

After this change is finished, the only change RobotBuilder and Team Code would require is passing a module type to solenoid constructors.

Co-authored-by: sciencewhiz <sciencewhiz@users.noreply.github.com>

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

@@ -0,0 +1,116 @@
+// 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 <hal/Types.h>
+#include <wpi/sendable/Sendable.h>
+#include <wpi/sendable/SendableHelper.h>
+
+#include "frc/PneumaticsBase.h"
+#include "frc/PneumaticsModuleType.h"
+#include "frc/SensorUtil.h"
+
+namespace frc {
+
+/**
+ * Class for operating a compressor connected to a pneumatics module.
+ *
+ * The module will automatically run in closed loop mode by default whenever a
+ * Solenoid object is created. For most cases, a Compressor object does not need
+ * to be instantiated or used in a robot program. This class is only required in
+ * cases where the robot program needs a more detailed status of the compressor
+ * or to enable/disable closed loop control.
+ *
+ * Note: you cannot operate the compressor directly from this class as doing so
+ * would circumvent the safety provided by using the pressure switch and closed
+ * loop control. You can only turn off closed loop control, thereby stopping
+ * the compressor from operating.
+ */
+class Compressor : public wpi::Sendable,
+                   public wpi::SendableHelper<Compressor> {
+ public:
+  /**
+   * Constructs a compressor for a specified module and type.
+   *
+   * @param module The module ID to use.
+   * @param moduleType The module type to use.
+   */
+  Compressor(int module, PneumaticsModuleType moduleType);
+
+  /**
+   * Constructs a compressor for a default module and specified type.
+   *
+   * @param moduleType The module type to use.
+   */
+  explicit Compressor(PneumaticsModuleType moduleType);
+
+  ~Compressor() override;
+
+  Compressor(const Compressor&) = delete;
+  Compressor& operator=(const Compressor&) = delete;
+
+  Compressor(Compressor&&) = default;
+  Compressor& operator=(Compressor&&) = default;
+
+  /**
+   * Starts closed-loop control. Note that closed loop control is enabled by
+   * default.
+   */
+  void Start();
+
+  /**
+   * Stops closed-loop control. Note that closed loop control is enabled by
+   * default.
+   */
+  void Stop();
+
+  /**
+   * Check if compressor output is active.
+   *
+   * @return true if the compressor is on
+   */
+  bool Enabled() const;
+
+  /**
+   * Check if the pressure switch is triggered.
+   *
+   * @return true if pressure is low
+   */
+  bool GetPressureSwitchValue() const;
+
+  /**
+   * Query how much current the compressor is drawing.
+   *
+   * @return The current through the compressor, in amps
+   */
+  double GetCompressorCurrent() const;
+
+  /**
+   * Enables or disables automatically turning the compressor on when the
+   * pressure is low.
+   *
+   * @param on Set to true to enable closed loop control of the compressor.
+   *           False to disable.
+   */
+  void SetClosedLoopControl(bool on);
+
+  /**
+   * Returns true if the compressor will automatically turn on when the
+   * pressure is low.
+   *
+   * @return True if closed loop control of the compressor is enabled. False if
+   *         disabled.
+   */
+  bool GetClosedLoopControl() const;
+
+  void InitSendable(wpi::SendableBuilder& builder) override;
+
+ private:
+  std::shared_ptr<PneumaticsBase> m_module;
+};
+
+}  // namespace frc