From 247b23114d4782d9e6b2d3f4410f76fb85b31fb4 Mon Sep 17 00:00:00 2001
From: Craig Tiller <ctiller@google.com>
Date: Mon, 9 Oct 2017 09:16:19 -0700
Subject: C++ize PidController

---
 src/core/lib/transport/pid_controller.h | 112 ++++++++++++++++++++++----------
 1 file changed, 78 insertions(+), 34 deletions(-)

(limited to 'src/core/lib/transport/pid_controller.h')

diff --git a/src/core/lib/transport/pid_controller.h b/src/core/lib/transport/pid_controller.h
index 17feabfd39..87e59a1a90 100644
--- a/src/core/lib/transport/pid_controller.h
+++ b/src/core/lib/transport/pid_controller.h
@@ -19,9 +19,7 @@
 #ifndef GRPC_CORE_LIB_TRANSPORT_PID_CONTROLLER_H
 #define GRPC_CORE_LIB_TRANSPORT_PID_CONTROLLER_H
 
-#ifdef __cplusplus
-extern "C" {
-#endif
+#include <limits>
 
 /* \file Simple PID controller.
    Implements a proportional-integral-derivative controller.
@@ -30,41 +28,87 @@ extern "C" {
    Gains can be set to adjust sensitivity to current error (p), the integral
    of error (i), and the derivative of error (d). */
 
-typedef struct {
-  double gain_p;
-  double gain_i;
-  double gain_d;
-  double initial_control_value;
-  double min_control_value;
-  double max_control_value;
-  double integral_range;
-} grpc_pid_controller_args;
+namespace grpc_core {
 
-typedef struct {
-  double last_error;
-  double error_integral;
-  double last_control_value;
-  double last_dc_dt;
-  grpc_pid_controller_args args;
-} grpc_pid_controller;
+class PidController {
+ public:
+  class Args {
+   public:
+    double gain_p() const { return gain_p_; }
+    double gain_i() const { return gain_i_; }
+    double gain_d() const { return gain_d_; }
+    double initial_control_value() const { return initial_control_value_; }
+    double min_control_value() const { return min_control_value_; }
+    double max_control_value() const { return max_control_value_; }
+    double integral_range() const { return integral_range_; }
 
-/** Initialize the controller */
-void grpc_pid_controller_init(grpc_pid_controller *pid_controller,
-                              grpc_pid_controller_args args);
+    Args& set_gain_p(double gain_p) {
+      gain_p_ = gain_p;
+      return *this;
+    }
+    Args& set_gain_i(double gain_i) {
+      gain_i_ = gain_i;
+      return *this;
+    }
+    Args& set_gain_d(double gain_d) {
+      gain_d_ = gain_d;
+      return *this;
+    }
+    Args& set_initial_control_value(double initial_control_value) {
+      initial_control_value_ = initial_control_value;
+      return *this;
+    }
+    Args& set_min_control_value(double min_control_value) {
+      min_control_value_ = min_control_value;
+      return *this;
+    }
+    Args& set_max_control_value(double max_control_value) {
+      max_control_value_ = max_control_value;
+      return *this;
+    }
+    Args& set_integral_range(double integral_range) {
+      integral_range_ = integral_range;
+      return *this;
+    }
 
-/** Reset the controller: useful when things have changed significantly */
-void grpc_pid_controller_reset(grpc_pid_controller *pid_controller);
+   private:
+    double gain_p_ = 0.0;
+    double gain_i_ = 0.0;
+    double gain_d_ = 0.0;
+    double initial_control_value_ = 0.0;
+    double min_control_value_ = std::numeric_limits<double>::min();
+    double max_control_value_ = std::numeric_limits<double>::max();
+    double integral_range_ = std::numeric_limits<double>::max();
+  };
 
-/** Update the controller: given a current error estimate, and the time since
-    the last update, returns a new control value */
-double grpc_pid_controller_update(grpc_pid_controller *pid_controller,
-                                  double error, double dt);
+  explicit PidController(const Args& args);
 
-/** Returns the last control value calculated */
-double grpc_pid_controller_last(grpc_pid_controller *pid_controller);
+  /// Reset the controller internal state: useful when the environment has
+  /// changed significantly
+  void Reset() {
+    last_error_ = 0.0;
+    last_dc_dt_ = 0.0;
+    error_integral_ = 0.0;
+  }
 
-#ifdef __cplusplus
-}
-#endif
+  /// Update the controller: given a current error estimate, and the time since
+  /// the last update, returns a new control value
+  double Update(double error, double dt);
 
-#endif /* GRPC_CORE_LIB_TRANSPORT_PID_CONTROLLER_H */
\ No newline at end of file
+  /// Returns the last control value calculated
+  double last_control_value() const { return last_control_value_; }
+
+  /// Returns the current error integral (mostly for testing)
+  double error_integral() const { return error_integral_; }
+
+ private:
+  double last_error_ = 0.0;
+  double error_integral_ = 0.0;
+  double last_control_value_;
+  double last_dc_dt_ = 0.0;
+  const Args args_;
+};
+
+}  // namespace grpc_core
+
+#endif /* GRPC_CORE_LIB_TRANSPORT_PID_CONTROLLER_H */
-- 
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