add nf7::Stopwatch

CMakeLists.txt

@@ -121,6 +121,7 @@ target_sources(nf7
     common/ring_buffer.hh
     common/sequencer.hh
     common/squashed_history.hh
+    common/stopwatch.hh
     common/task.hh
     common/thread.hh
     common/timed_queue.hh

common/stopwatch.hh

@@ -0,0 +1,61 @@
+#pragma once
+
+#include <chrono>
+#include <iostream>
+
+#include "nf7.hh"
+
+
+namespace nf7 {
+
+class Stopwatch final {
+ public:
+  struct Benchmark;
+
+  Stopwatch() = default;
+  Stopwatch(const Stopwatch&) = default;
+  Stopwatch(Stopwatch&&) = default;
+  Stopwatch& operator=(const Stopwatch&) = default;
+  Stopwatch& operator=(Stopwatch&&) = default;
+
+  void Begin() noexcept {
+    begin_ = nf7::Env::Clock::now();
+  }
+  void End() noexcept {
+    end_ = nf7::Env::Clock::now();
+  }
+
+  auto dur() const noexcept {
+    return std::chrono::duration_cast<std::chrono::microseconds>(end_ - begin_);
+  }
+  nf7::Env::Time beginTime() const noexcept { return begin_; }
+  nf7::Env::Time endTime() const noexcept { return end_; }
+
+ private:
+  nf7::Env::Time begin_;
+  nf7::Env::Time end_;
+};
+inline std::ostream& operator << (std::ostream& out, const Stopwatch& sw) {
+  return out << sw.dur().count() << " usecs";
+}
+
+struct Stopwatch::Benchmark final {
+ public:
+  Benchmark(const char* name) noexcept : name_(name) {
+    sw_.Begin();
+  }
+  ~Benchmark() noexcept {
+    sw_.End();
+    std::cout << name_ << ": " << sw_ << std::endl;
+  }
+  Benchmark(const Benchmark&) = delete;
+  Benchmark(Benchmark&&) = delete;
+  Benchmark& operator=(const Benchmark&) = delete;
+  Benchmark& operator=(Benchmark&&) = delete;
+
+ private:
+  const char* name_;
+  Stopwatch   sw_;
+};
+
+}  // namespace nf7