Adds new build system to repo (#1)

src/main/native/cpp/support/timestamp.cpp

@@ -0,0 +1,89 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2015. 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.                                                               */
+/*----------------------------------------------------------------------------*/
+#include "support/timestamp.h"
+
+#ifdef _WIN32
+#include <cassert>
+#include <exception>
+#include <windows.h>
+#else
+#include <chrono>
+#endif
+
+// offset in microseconds
+static unsigned long long zerotime() {
+#ifdef _WIN32
+  FILETIME ft;
+  unsigned long long tmpres = 0;
+  // 100-nanosecond intervals since January 1, 1601 (UTC)
+  // which means 0.1 us
+  GetSystemTimeAsFileTime(&ft);
+  tmpres |= ft.dwHighDateTime;
+  tmpres <<= 32;
+  tmpres |= ft.dwLowDateTime;
+  // January 1st, 1970 - January 1st, 1601 UTC ~ 369 years
+  // or 116444736000000000 us
+  static const unsigned long long deltaepoch = 116444736000000000ull;
+  tmpres -= deltaepoch;
+  return tmpres;
+#else
+  // 100-ns intervals
+  using namespace std::chrono;
+  return duration_cast<nanoseconds>(
+    high_resolution_clock::now().time_since_epoch()).count() / 100u;
+#endif
+}
+
+static unsigned long long timestamp() {
+#ifdef _WIN32
+  LARGE_INTEGER li;
+  QueryPerformanceCounter(&li);
+  // there is an imprecision with the initial value,
+  // but what matters is that timestamps are monotonic and consistent
+  return static_cast<unsigned long long>(li.QuadPart);
+#else
+  // 100-ns intervals
+  using namespace std::chrono;
+  return duration_cast<nanoseconds>(
+    steady_clock::now().time_since_epoch()).count() / 100u;
+#endif
+}
+
+#ifdef _WIN32
+static unsigned long long update_frequency() {
+  LARGE_INTEGER li;
+  if (!QueryPerformanceFrequency(&li) || !li.QuadPart) {
+    // log something
+    std::terminate();
+  }
+  return static_cast<unsigned long long>(li.QuadPart);
+}
+#endif
+
+static const unsigned long long zerotime_val = zerotime();
+static const unsigned long long offset_val = timestamp();
+#ifdef _WIN32
+static const unsigned long long frequency_val = update_frequency();
+#endif
+
+unsigned long long wpi::Now() {
+#ifdef _WIN32
+  assert(offset_val > 0u);
+  assert(frequency_val > 0u);
+  unsigned long long delta = timestamp() - offset_val;
+  // because the frequency is in update per seconds, we have to multiply the
+  // delta by 10,000,000
+  unsigned long long delta_in_us = delta * 10000000ull / frequency_val;
+  return delta_in_us + zerotime_val;
+#else
+  return zerotime_val + timestamp() - offset_val;
+#endif
+}
+
+unsigned long long WPI_Now() {
+  return wpi::Now();
+}