[wpiutil] Split C++ header files

wpiutil/src/main/native/include/wpi/util/timestamp.hpp

@@ -0,0 +1,41 @@
+// 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 <stdint.h>
+
+namespace wpi::util {
+
+/**
+ * The default implementation used for Now().
+ * In general this is the time returned by the operating system.
+ * @return Time in microseconds.
+ */
+uint64_t NowDefault();
+
+/**
+ * Set the implementation used by Now().
+ * The implementation must return monotonic time in microseconds to maintain
+ * the contract of Now().
+ * @param func Function called by Now() to return the time.
+ */
+void SetNowImpl(uint64_t (*func)());
+
+/**
+ * Return a value representing the current time in microseconds.
+ * This is a monotonic clock with an undefined epoch.
+ * @return Time in microseconds.
+ */
+uint64_t Now();
+
+/**
+ * Return the current system time in microseconds since the Unix epoch
+ * (January 1st, 1970 00:00 UTC).
+ *
+ * @return Time in microseconds.
+ */
+uint64_t GetSystemTime();
+
+}  // namespace wpi::util