commit 53b0c49ed15243c761b9ccd2e7ca12501ecafc09
author Ady Abraham <adyabr@google.com> Mon Oct 23 11:47:14 2023 -0700
committer Ady Abraham <adyabr@google.com> Fri Oct 27 19:51:19 2023 +0000
tree 2c37ac417ca1fddfb14dbf9b977ddc018438d22b
parent 0e5421dcdc7c8a46d0d9f9d18ce19a7e53e60a85

SF: make FlagManager singleton

Test: presubmit
Change-Id: Id16425757e818c4867b76548d21fb33cbb3f72d4

services/surfaceflinger/FlagManager.h

diff --git a/services/surfaceflinger/FlagManager.h b/services/surfaceflinger/FlagManager.h
index e834142..8af0b4f 100644
--- a/services/surfaceflinger/FlagManager.h
+++ b/services/surfaceflinger/FlagManager.h
@@ -17,15 +17,23 @@
 #pragma once
 
 #include <cstdint>
+#include <mutex>
 #include <optional>
 #include <string>
 
 namespace android {
 // Manages flags for SurfaceFlinger, including default values, system properties, and Mendel
-// experiment configuration values.
+// experiment configuration values. Can be called from any thread.
 class FlagManager {
+private:
+    // Effectively making the constructor private, while allowing std::make_unique to work
+    struct ConstructorTag {};
+
 public:
-    FlagManager() = default;
+    static FlagManager& getInstance();
+
+    FlagManager(ConstructorTag);
+
     virtual ~FlagManager();
     void dump(std::string& result) const;
 
@@ -38,11 +46,16 @@
 private:
     friend class FlagManagerTest;
 
+    FlagManager(const FlagManager&) = delete;
+
     // Wrapper for mocking in test.
     virtual std::string getServerConfigurableFlag(const std::string& experimentFlagName) const;
 
     template <typename T>
     T getValue(const std::string& experimentFlagName, std::optional<T> systemPropertyOpt,
                T defaultValue) const;
+
+    static std::unique_ptr<FlagManager> mInstance;
+    static std::once_flag mOnce;
 };
 } // namespace android