Add Timestamp to/from milliseconds conversion (#30)

Summary: Pull Request resolved: #30

Differential Revision: D30270922

Pulled By: mbasmanova

fbshipit-source-id: cd04038078cf664e76c77e7349b5c4de18abf729

velox/serializers/PrestoSerializer.cpp

@@ -165,7 +165,7 @@ void readValues<bool>(
 
 Timestamp readTimestamp(ByteStream* source) {
   int64_t millis = source->read<int64_t>();
-  return Timestamp(millis / 1000, (millis % 1000) * 1'000'000);
+  return Timestamp::fromMillis(millis);
 }
 
 template <>
@@ -721,19 +721,13 @@ inline void VectorStream::append(folly::Range<const StringView*> values) {
   }
 }
 
-int64_t timestampToPrestoMillis(Timestamp timestamp) {
-  return timestamp.getSeconds() * 1000 + timestamp.getNanos() / 1000000;
-}
-
 template <>
 void VectorStream::append(folly::Range<const Timestamp*> values) {
   for (auto& value : values) {
-    appendOne(timestampToPrestoMillis(value));
+    appendOne(value.toMillis());
   }
 }
 
-int64_t timestampToPrestoMillis(Timestamp timestamp);
-
 template <>
 void VectorStream::append(folly::Range<const bool*> values) {
   // A bool constant is serialized via this. Accessing consecutive

velox/type/Timestamp.h

@@ -41,6 +41,14 @@ struct Timestamp {
     return nanos_;
   }
 
+  int64_t toMillis() const {
+    return seconds_ * 1'000 + nanos_ / 1'000'000;
+  }
+
+  static Timestamp fromMillis(int64_t millis) {
+    return Timestamp(millis / 1'000, (millis % 1'000) * 1'000'000);
+  }
+
   // Converts the unix epoch represented by this object (assumes it's GMT)
   // to the given timezone.
   void toTimezone(const date::time_zone& zone);