timer: add simple linux watchclock timer

1 files changed, 52 insertions, 0 deletions

diff --git a/timer.h b/timer.h
new file mode 100644
index 0000000..933c02c
--- /dev/null
+++ b/timer.h
@@ -0,0 +1,52 @@
+#include <cstdint>
+#include <ctime>
+
+namespace timer {
+struct timer {
+  constexpr timer() = default;
+
+  void start() {
+    clock_gettime(kClock, &m_start);
+  }
+
+  void stop() {
+    timespec end;
+    clock_gettime(kClock, &end);
+
+    m_nanos += ((end.tv_sec - m_start.tv_sec) * 1000000000ull) +
+               (end.tv_nsec - m_start.tv_nsec);
+  }
+
+  constexpr double as_sec() const {
+    return as_msec() / 1000.0;
+  }
+
+  constexpr double as_msec() const {
+    return as_usec() / 1000.0;
+  }
+
+  constexpr double as_usec() const {
+    return static_cast<double>(m_nanos) / 1000.0;
+  }
+
+ private:
+  static constexpr clockid_t kClock = CLOCK_MONOTONIC_RAW;
+
+  timespec m_start{};
+  std::uint64_t m_nanos{0};
+};
+
+struct scoped_timer {
+  explicit scoped_timer(timer& t) : m_timer(t) {
+    m_timer.start();
+  }
+
+  ~scoped_timer() {
+    m_timer.stop();
+  }
+
+ private:
+  timer& m_timer;
+};
+
+}  // namespace timer