Squashed 'third_party/allwpilib_2019/' content from commit bd05dfa1c
Change-Id: I2b1c2250cdb9b055133780c33593292098c375b7
git-subtree-dir: third_party/allwpilib_2019
git-subtree-split: bd05dfa1c7cca74c4fac451e7b9d6a37e7b53447
diff --git a/wpiutil/src/main/native/cpp/timestamp.cpp b/wpiutil/src/main/native/cpp/timestamp.cpp
new file mode 100644
index 0000000..7f3b0cf
--- /dev/null
+++ b/wpiutil/src/main/native/cpp/timestamp.cpp
@@ -0,0 +1,108 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2015-2018 FIRST. 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 "wpi/timestamp.h"
+
+#include <atomic>
+
+#ifdef _WIN32
+#include <windows.h>
+
+#include <cassert>
+#include <exception>
+#else
+#include <chrono>
+#endif
+
+// offset in microseconds
+static uint64_t zerotime() {
+#ifdef _WIN32
+ FILETIME ft;
+ uint64_t 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;
+ tmpres /= 10u; // convert to us
+ // January 1st, 1970 - January 1st, 1601 UTC ~ 369 years
+ // or 11644473600000000 us
+ static const uint64_t deltaepoch = 11644473600000000ull;
+ tmpres -= deltaepoch;
+ return tmpres;
+#else
+ // 1-us intervals
+ return std::chrono::duration_cast<std::chrono::microseconds>(
+ std::chrono::high_resolution_clock::now().time_since_epoch())
+ .count();
+#endif
+}
+
+static uint64_t 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<uint64_t>(li.QuadPart);
+#else
+ // 1-us intervals
+ return std::chrono::duration_cast<std::chrono::microseconds>(
+ std::chrono::steady_clock::now().time_since_epoch())
+ .count();
+#endif
+}
+
+#ifdef _WIN32
+static uint64_t update_frequency() {
+ LARGE_INTEGER li;
+ if (!QueryPerformanceFrequency(&li) || !li.QuadPart) {
+ // log something
+ std::terminate();
+ }
+ return static_cast<uint64_t>(li.QuadPart);
+}
+#endif
+
+static const uint64_t zerotime_val = zerotime();
+static const uint64_t offset_val = timestamp();
+#ifdef _WIN32
+static const uint64_t frequency_val = update_frequency();
+#endif
+
+uint64_t wpi::NowDefault() {
+#ifdef _WIN32
+ assert(offset_val > 0u);
+ assert(frequency_val > 0u);
+ uint64_t delta = timestamp() - offset_val;
+ // because the frequency is in update per seconds, we have to multiply the
+ // delta by 1,000,000
+ uint64_t delta_in_us = delta * 1000000ull / frequency_val;
+ return delta_in_us + zerotime_val;
+#else
+ return zerotime_val + timestamp() - offset_val;
+#endif
+}
+
+static std::atomic<uint64_t (*)()> now_impl{wpi::NowDefault};
+
+void wpi::SetNowImpl(uint64_t (*func)(void)) {
+ now_impl = func ? func : NowDefault;
+}
+
+uint64_t wpi::Now() { return (now_impl.load())(); }
+
+extern "C" {
+
+uint64_t WPI_NowDefault(void) { return wpi::NowDefault(); }
+
+void WPI_SetNowImpl(uint64_t (*func)(void)) { wpi::SetNowImpl(func); }
+
+uint64_t WPI_Now(void) { return wpi::Now(); }
+
+} // extern "C"