MethodStatistics: Use const references in API

Use transparent comparator for efficiency

Test: simpleperf using Oboetester
Bug: 238654698
Merged-In: Ie1d0f66094ac5b54ff35649b7f1971fb4eb87465
Change-Id: Ie1d0f66094ac5b54ff35649b7f1971fb4eb87465
diff --git a/media/utils/MethodStatistics.cpp b/media/utils/MethodStatistics.cpp
index b179b20..086757b 100644
--- a/media/utils/MethodStatistics.cpp
+++ b/media/utils/MethodStatistics.cpp
@@ -22,7 +22,8 @@
 
 std::shared_ptr<std::vector<std::string>>
 getStatisticsClassesForModule(std::string_view moduleName) {
-    static const std::map<std::string, std::shared_ptr<std::vector<std::string>>> m {
+    static const std::map<std::string, std::shared_ptr<std::vector<std::string>>,
+            std::less<> /* transparent comparator */> m {
         {
             METHOD_STATISTICS_MODULE_NAME_AUDIO_HIDL,
             std::shared_ptr<std::vector<std::string>>(
@@ -34,13 +35,14 @@
               })
         },
     };
-    auto it = m.find({moduleName.begin(), moduleName.end()});
+    auto it = m.find(moduleName);
     if (it == m.end()) return {};
     return it->second;
 }
 
 static void addClassesToMap(const std::shared_ptr<std::vector<std::string>> &classNames,
-        std::map<std::string, std::shared_ptr<MethodStatistics<std::string>>> &map) {
+        std::map<std::string, std::shared_ptr<MethodStatistics<std::string>>,
+                std::less<> /* transparent comparator */> &map) {
     if (classNames) {
         for (const auto& className : *classNames) {
             map.emplace(className, std::make_shared<MethodStatistics<std::string>>());
@@ -51,17 +53,18 @@
 // singleton statistics for DeviceHalHidl StreamOutHalHidl StreamInHalHidl
 std::shared_ptr<MethodStatistics<std::string>>
 getStatisticsForClass(std::string_view className) {
-    static const std::map<std::string, std::shared_ptr<MethodStatistics<std::string>>> m =
+    static const std::map<std::string, std::shared_ptr<MethodStatistics<std::string>>,
+            std::less<> /* transparent comparator */> m =
         // copy elided initialization of map m.
         [](){
-            std::map<std::string, std::shared_ptr<MethodStatistics<std::string>>> m;
+            std::map<std::string, std::shared_ptr<MethodStatistics<std::string>>, std::less<>> m;
             addClassesToMap(
                     getStatisticsClassesForModule(METHOD_STATISTICS_MODULE_NAME_AUDIO_HIDL),
                     m);
             return m;
         }();
 
-    auto it = m.find({className.begin(), className.end()});
+    auto it = m.find(className);
     if (it == m.end()) return {};
     return it->second;
 }
diff --git a/media/utils/include/mediautils/MethodStatistics.h b/media/utils/include/mediautils/MethodStatistics.h
index 700fbaa..6d7e990 100644
--- a/media/utils/include/mediautils/MethodStatistics.h
+++ b/media/utils/include/mediautils/MethodStatistics.h
@@ -55,15 +55,23 @@
     /**
      * Adds a method event, typically execution time in ms.
      */
-    void event(Code code, FloatType executeMs) {
+    template <typename C>
+    void event(C&& code, FloatType executeMs) {
         std::lock_guard lg(mLock);
-        mStatisticsMap[code].add(executeMs);
+        auto it = mStatisticsMap.lower_bound(code);
+        if (it != mStatisticsMap.end() && it->first == code) {
+            it->second.add(executeMs);
+        } else {
+            // StatsType ctor takes an optional array of data for initialization.
+            FloatType dataArray[1] = { executeMs };
+            mStatisticsMap.emplace_hint(it, std::forward<C>(code), dataArray);
+        }
     }
 
     /**
      * Returns the name for the method code.
      */
-    std::string getMethodForCode(Code code) const {
+    std::string getMethodForCode(const Code& code) const {
         auto it = mMethodMap.find(code);
         return it == mMethodMap.end() ? std::to_string((int)code) : it->second;
     }
@@ -71,7 +79,7 @@
     /**
      * Returns the number of times the method was invoked by event().
      */
-    size_t getMethodCount(Code code) const {
+    size_t getMethodCount(const Code& code) const {
         std::lock_guard lg(mLock);
         auto it = mStatisticsMap.find(code);
         return it == mStatisticsMap.end() ? 0 : it->second.getN();
@@ -80,7 +88,7 @@
     /**
      * Returns the statistics object for the method.
      */
-    StatsType getStatistics(Code code) const {
+    StatsType getStatistics(const Code& code) const {
         std::lock_guard lg(mLock);
         auto it = mStatisticsMap.find(code);
         return it == mStatisticsMap.end() ? StatsType{} : it->second;
@@ -107,9 +115,10 @@
     }
 
 private:
-    const std::map<Code, std::string> mMethodMap;
+    // Note: we use a transparent comparator std::less<> for heterogeneous key lookup.
+    const std::map<Code, std::string, std::less<>> mMethodMap;
     mutable std::mutex mLock;
-    std::map<Code, StatsType> mStatisticsMap GUARDED_BY(mLock);
+    std::map<Code, StatsType, std::less<>> mStatisticsMap GUARDED_BY(mLock);
 };
 
 // Managed Statistics support.