Sync from upstream.

Descriptions:
======================================================================
Implement new version of ResultState and ResultStateManager to 1)
enforce a page byte size limit and 2) improve handling of pagination
when we encounter deleted documents.
======================================================================
Fix bugs in IcingDynamicTrie::Delete.
======================================================================
Implement IcingDynamicTrie::IsBranchingTerm.
======================================================================
Change Icing default logging level to INFO
======================================================================
Refactor KeyMapper class to be an interface.
======================================================================
Improve NamespaceChecker logic to improve Suggest latency.
======================================================================
Change icing native log tag to "AppSearchIcing"
======================================================================
Implement Index Compaction rather than rebuilding index during
Compaction.
======================================================================
Implement reverse iterator for IcingDynamicTrie
======================================================================
Avoid adding unnecessary branch points during index compaction
======================================================================
Invalidate expired result states when adding to/retrieving from
ResultStateManager.
======================================================================
Add new methods (MutableView, MutableArrayView, Append, Allocate) to
FileBackedVector
======================================================================
Create and implement PersistentHashMap class.
======================================================================
Implement RFC822 Tokenizer
======================================================================
Remove uses of StringPrintf in ICING_LOG statements
======================================================================
Properly set query latency when an error is encountered or results are
empty.
======================================================================

Bug: 146903474
Bug: 152934343
Bug: 193919210
Bug: 193453081
Bug: 231368517
Bug: 235395538
Bug: 236412165
Change-Id: I8aa278cebb12b25b39deb0ef584c0f198952659d

1 files changed, 27 insertions, 0 deletions

diff --git a/icing/util/clock.h b/icing/util/clock.h
index 2bb7818..9e57854 100644
--- a/icing/util/clock.h
+++ b/icing/util/clock.h
@@ -16,6 +16,7 @@
 #define ICING_UTIL_CLOCK_H_
 
 #include <cstdint>
+#include <functional>
 #include <memory>
 
 namespace icing {
@@ -69,6 +70,32 @@ class Clock {
   virtual std::unique_ptr<Timer> GetNewTimer() const;
 };
 
+// A convenient RAII timer class that receives a callback. Upon destruction, the
+// callback will be called with the elapsed milliseconds or nanoseconds passed
+// as a parameter, depending on which Unit was passed in the constructor.
+class ScopedTimer {
+ public:
+  enum class Unit { kMillisecond, kNanosecond };
+
+  ScopedTimer(std::unique_ptr<Timer> timer,
+              std::function<void(int64_t)> callback,
+              Unit unit = Unit::kMillisecond)
+      : timer_(std::move(timer)), callback_(std::move(callback)), unit_(unit) {}
+
+  ~ScopedTimer() {
+    if (unit_ == Unit::kMillisecond) {
+      callback_(timer_->GetElapsedMilliseconds());
+    } else {
+      callback_(timer_->GetElapsedNanoseconds());
+    }
+  }
+
+ private:
+  std::unique_ptr<Timer> timer_;
+  std::function<void(int64_t)> callback_;
+  Unit unit_;
+};
+
 }  // namespace lib
 }  // namespace icing