better names for SingletonThreadLocal internals

Summary: Possibly not the ideal names, but also possibly a little more helpful than the current names.

Reviewed By: luciang

Differential Revision: D53601849

fbshipit-source-id: 78be10d2f61e51e1b4bb7c5c3c66fef12de9d155

folly/SingletonThreadLocal.cpp

@@ -20,32 +20,32 @@ namespace folly {
 
 namespace detail {
 
-FOLLY_NOINLINE SingletonThreadLocalState::Wrapper::Wrapper() noexcept {}
+FOLLY_NOINLINE SingletonThreadLocalState::Tracking::Tracking() noexcept {}
 
-FOLLY_NOINLINE SingletonThreadLocalState::Wrapper::~Wrapper() {
+FOLLY_NOINLINE SingletonThreadLocalState::Tracking::~Tracking() {
   for (auto& kvp : caches) {
-    kvp.first->cache = nullptr;
+    kvp.first->object = nullptr;
   }
 }
 
 FOLLY_NOINLINE void SingletonThreadLocalState::LocalLifetime::destroy(
-    Wrapper& wrapper) noexcept {
-  auto& lifetimes = wrapper.lifetimes[this];
+    Tracking& tracking) noexcept {
+  auto& lifetimes = tracking.lifetimes[this];
   for (auto cache : lifetimes) {
-    auto const it = wrapper.caches.find(cache);
+    auto const it = tracking.caches.find(cache);
     if (!--it->second) {
-      wrapper.caches.erase(it);
-      cache->cache = nullptr;
+      tracking.caches.erase(it);
+      cache->object = nullptr;
     }
   }
-  wrapper.lifetimes.erase(this);
+  tracking.lifetimes.erase(this);
 }
 
 FOLLY_NOINLINE void SingletonThreadLocalState::LocalLifetime::track(
-    LocalCache& cache, Wrapper& wrapper, void* object) noexcept {
-  cache.cache = object;
-  auto const inserted = wrapper.lifetimes[this].insert(&cache);
-  wrapper.caches[&cache] += inserted.second;
+    LocalCache& cache, Tracking& tracking, void* object) noexcept {
+  cache.object = object;
+  auto const inserted = tracking.lifetimes[this].insert(&cache);
+  tracking.caches[&cache] += inserted.second;
 }
 
 } // namespace detail

folly/SingletonThreadLocal.h

@@ -35,7 +35,7 @@ namespace detail {
 
 struct SingletonThreadLocalState {
   struct LocalCache {
-    void* cache; // type-erased pointer to the object field of wrapper, below
+    void* object; // type-erased pointer to the object field of wrapper, below
   };
   static_assert( // pod avoids tls-init guard var and tls-fini ub use-after-dtor
       std::is_standard_layout<LocalCache>::value &&
@@ -44,7 +44,7 @@ struct SingletonThreadLocalState {
 
   struct LocalLifetime;
 
-  struct Wrapper {
+  struct Tracking {
     using LocalCacheSet = std::unordered_set<LocalCache*>;
 
     // per-cache refcounts, the number of lifetimes tracking that cache
@@ -53,13 +53,13 @@ struct SingletonThreadLocalState {
     // per-lifetime cache tracking; 1-M lifetimes may track 1-N caches
     std::unordered_map<LocalLifetime*, LocalCacheSet> lifetimes;
 
-    Wrapper() noexcept;
-    ~Wrapper();
+    Tracking() noexcept;
+    ~Tracking();
   };
 
   struct LocalLifetime {
-    void destroy(Wrapper& wrapper) noexcept;
-    void track(LocalCache& cache, Wrapper& wrapper, void* object) noexcept;
+    void destroy(Tracking& tracking) noexcept;
+    void track(LocalCache& cache, Tracking& tracking, void* object) noexcept;
   };
 };
 
@@ -117,7 +117,7 @@ class SingletonThreadLocal {
     // keep as first field in first base, to save 1 instr in the fast path
     Object object{Make{}()};
   };
-  struct Wrapper : ObjectWrapper, State::Wrapper {
+  struct Wrapper : ObjectWrapper, State::Tracking {
     /* implicit */ operator T&() { return ObjectWrapper::object; }
   };
 
@@ -152,7 +152,7 @@ class SingletonThreadLocal {
       return getWrapper();
     }
     static thread_local LocalCache cache;
-    auto* object = static_cast<Object*>(cache.cache);
+    auto* object = static_cast<Object*>(cache.object);
     return FOLLY_LIKELY(!!object) ? *object : getSlow(cache).object;
   }