[wpimath] Move debouncer to filters (#3838)

wpimath/src/main/native/cpp/filter/Debouncer.cpp

@@ -0,0 +1,45 @@
+// 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.
+
+#include "frc/filter/Debouncer.h"
+
+using namespace frc;
+
+Debouncer::Debouncer(units::second_t debounceTime, DebounceType type)
+    : m_debounceTime(debounceTime), m_debounceType(type) {
+  switch (type) {
+    case DebounceType::kBoth:  // fall-through
+    case DebounceType::kRising:
+      m_baseline = false;
+      break;
+    case DebounceType::kFalling:
+      m_baseline = true;
+      break;
+  }
+  ResetTimer();
+}
+
+void Debouncer::ResetTimer() {
+  m_prevTime = units::microsecond_t(wpi::Now());
+}
+
+bool Debouncer::HasElapsed() const {
+  return units::microsecond_t(wpi::Now()) - m_prevTime >= m_debounceTime;
+}
+
+bool Debouncer::Calculate(bool input) {
+  if (input == m_baseline) {
+    ResetTimer();
+  }
+
+  if (HasElapsed()) {
+    if (m_debounceType == DebounceType::kBoth) {
+      m_baseline = input;
+      ResetTimer();
+    }
+    return input;
+  } else {
+    return m_baseline;
+  }
+}

wpimath/src/main/native/include/frc/filter/Debouncer.h

@@ -0,0 +1,51 @@
+// 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 <wpi/timestamp.h>
+
+#include "units/time.h"
+
+namespace frc {
+/**
+ * A simple debounce filter for boolean streams.  Requires that the boolean
+ * change value from baseline for a specified period of time before the filtered
+ * value changes.
+ */
+class WPILIB_DLLEXPORT Debouncer {
+ public:
+  enum DebounceType { kRising, kFalling, kBoth };
+
+  /**
+   * Creates a new Debouncer.
+   *
+   * @param debounceTime The number of seconds the value must change from
+   *                     baseline for the filtered value to change.
+   * @param type         Which type of state change the debouncing will be
+   *                     performed on.
+   */
+  explicit Debouncer(units::second_t debounceTime,
+                     DebounceType type = DebounceType::kRising);
+
+  /**
+   * Applies the debouncer to the input stream.
+   *
+   * @param input The current value of the input stream.
+   * @return The debounced value of the input stream.
+   */
+  bool Calculate(bool input);
+
+ private:
+  units::second_t m_debounceTime;
+  bool m_baseline;
+  DebounceType m_debounceType;
+
+  units::second_t m_prevTime;
+
+  void ResetTimer();
+
+  bool HasElapsed() const;
+};
+}  // namespace frc