Implement the Timestamp class to ease the usage of time_point. (#134

)

- Allows creating `time_point`s from int values.
- Keeps track of timestamps' time unit.

layer/support/csv_logging.cc

@@ -46,8 +46,8 @@ std::string ValueToCSVString(Duration value) {
   return std::to_string(value.ToNanoseconds());
 }
 
-std::string ValueToCSVString(TimestampClock::time_point value) {
-  return std::to_string(ToUnixNanos(value));
+std::string ValueToCSVString(Timestamp value) {
+  return std::to_string(value.ToNanoseconds());
 }
 
 // Takes an `Event` instance as an input and generates a csv string containing

layer/support/csv_logging.h

@@ -29,11 +29,11 @@ std::string ValueToCSVString(const int64_t value);
 
 std::string ValueToCSVString(const std::vector<int64_t> &values);
 
-// Converts a `DurationClock::duration` to its nanoseconds representation.
+// Converts a `Duration` to its nanoseconds representation.
 std::string ValueToCSVString(Duration value);
 
-// Converts a `TimestampClock::time_point` to its nanoseconds representation.
-std::string ValueToCSVString(TimestampClock::time_point value);
+// Converts a `Timestamp` to its nanoseconds representation.
+std::string ValueToCSVString(Timestamp value);
 
 // Takes an `Event` instance as an input and generates a csv string containing
 // `event`'s name and attribute values. The duration values will be logged in

layer/support/event_logging.h

@@ -123,13 +123,13 @@ class TimestampAttr : public Attribute {
  public:
   static constexpr ValueType id_ = ValueType::kTimestamp;
 
-  TimestampAttr(const char *name, const TimestampClock::time_point &value)
+  TimestampAttr(const char *name, const Timestamp &value)
       : Attribute(name, ValueType::kTimestamp), value_(value) {}
 
-  TimestampClock::time_point GetValue() const { return value_; };
+  Timestamp GetValue() const { return value_; };
 
  private:
-  TimestampClock::time_point value_;
+  Timestamp value_;
 };
 
 using BoolAttr = AttributeImpl<bool, ValueType::kBool>;
@@ -219,14 +219,12 @@ class Event {
         log_level_(log_level),
         creation_time_({"timestamp", GetTimestamp()}) {}
 
-  Event(const char *name, int64_t timestamp,
+  Event(const char *name, int64_t timestamp_ns,
         LogLevel log_level = LogLevel::kLow)
       : name_(name),
         log_level_(log_level),
         creation_time_(
-            {"timestamp",
-             TimestampClock::time_point(TimestampClock::duration(timestamp))}) {
-  }
+            {"timestamp", Timestamp::FromNanoseconds(timestamp_ns)}) {}
 
   virtual ~Event() = default;
 

layer/support/layer_utils.cc

@@ -21,15 +21,6 @@ TimestampClock::time_point GetTimestamp() { return TimestampClock::now(); }
 
 DurationClock::time_point Now() { return DurationClock::now(); }
 
-int64_t ToUnixNanos(TimestampClock::time_point time) {
-  return std::chrono::nanoseconds(time.time_since_epoch()).count();
-}
-
-double ToUnixMillis(TimestampClock::time_point time) {
-  return std::chrono::duration<double, std::milli>(time.time_since_epoch())
-      .count();
-}
-
 FunctionInterceptor::FunctionInterceptor(
     InterceptedVulkanFunc intercepted_function) {
   FunctionNameToPtr& registered_functions = GetInterceptedFunctions();

layer/support/layer_utils.h

@@ -74,12 +74,6 @@ TimestampClock::time_point GetTimestamp();
 // Returns a monotonic time_point to be used for measuring duration.
 DurationClock::time_point Now();
 
-// Converts a chrono time_point to a Unix int64 nanoseconds representation.
-int64_t ToUnixNanos(TimestampClock::time_point time);
-
-// Converts a chrono time_point to a Unix int64 milliseconds representation.
-double ToUnixMillis(TimestampClock::time_point time);
-
 // A wrapper around `DurationClock::duration` to keep track of the time unit.
 // When the `Duration` is used, we know it's either created from a
 // `DurationClock::duration` that has nanosecond-level precision or an int that
@@ -104,6 +98,36 @@ class Duration {
   DurationClock::duration duration_;
 };
 
+// A wrapper around `TimestampClock::time_point` to keep track of the time unit.
+// When the `Timestamp` is used, we know it's either created from a
+// `GetTimestamp()` that has nanosecond-level precision or an int that
+// represents duration in nanoseconds.
+class Timestamp {
+ public:
+  // A `time_point` is a point in time offset to a "zero" epoch. The given input
+  // has no epoch information. To create a time_point from it, it should be
+  // converted into a duration representing the offset from the zero epoch.
+  static Timestamp FromNanoseconds(int64_t nanos) {
+    return Timestamp(
+        TimestampClock::time_point(TimestampClock::duration(nanos)));
+  }
+
+  Timestamp(TimestampClock::time_point timestamp) : timestamp_{timestamp} {}
+
+  int64_t ToNanoseconds() const {
+    return std::chrono::nanoseconds(timestamp_.time_since_epoch()).count();
+  }
+
+  double ToMilliseconds() const {
+    return std::chrono::duration<double, std::milli>(
+               timestamp_.time_since_epoch())
+        .count();
+  }
+
+ private:
+  TimestampClock::time_point timestamp_;
+};
+
 // Represents a type-erased layer function pointer intercepting a known
 // Vulkan function. Should be constructed with the type safe |Create|
 // function.

layer/unittest/common_log_tests.cc

@@ -30,7 +30,7 @@ TEST(CommonLogger, MethodCheck) {
   CommonLogger logger(&out);
   VectorInt64Attr hashes("hashes", {2, 3});
   CreateGraphicsPipelinesEvent pipeline_event(
-      "create_graphics_pipeline", hashes, DurationClock::duration(4),
+      "create_graphics_pipeline", hashes, Duration::FromNanoseconds(4),
       LogLevel::kHigh);
   logger.StartLog();
   logger.AddEvent(&pipeline_event);
@@ -41,7 +41,7 @@ TEST(CommonLogger, MethodCheck) {
 
   std::stringstream event_str;
   int64_t timestamp_in_ns =
-      ToUnixNanos(pipeline_event.GetCreationTime().GetValue());
+      pipeline_event.GetCreationTime().GetValue().ToNanoseconds();
   event_str << "create_graphics_pipeline,timestamp:" << timestamp_in_ns
             << ",hashes:\"[0x2,0x3]\",duration:4";
   EXPECT_THAT(out.GetLog(), ElementsAre(event_str.str()));

layer/unittest/trace_event_log_tests.cc

@@ -56,8 +56,8 @@ std::string ValueToJsonString(Duration value) {
 
 // Converts the timestamp to milliseconds, the defualt time unit in the `Trace
 // Event` format.
-std::string ValueToJsonString(TimestampClock::time_point value) {
-  return std::to_string(ToUnixMillis(value));
+std::string ValueToJsonString(Timestamp value) {
+  return std::to_string(value.ToMilliseconds());
 }
 
 // Appends all given attributes, including the type-specific attribute, to the
@@ -117,7 +117,7 @@ void AppendCompleteEvent(TimestampAttr timestamp,
   assert(duration_attr && "Duration not found.");
 
   double duration_ms = duration_attr->GetValue().ToMilliseconds();
-  double end_timestamp_ms = ToUnixMillis(timestamp.GetValue());
+  double end_timestamp_ms = timestamp.GetValue().ToMilliseconds();
   double start_timestamp_ms = end_timestamp_ms - duration_ms;
   json_stream << ", " << std::quoted("ts") << " : " << std::fixed
               << start_timestamp_ms << ", " << std::quoted("dur") << " : "