perf(runtime): reuse the cached signature tokens in JsArgConverter

When the metadata entry is resolved, JsArgConverter copied
entry->parsedSig into its own vector on every Java call, allocating one
std::string per parameter (object tokens such as Ljava/lang/String;
exceed the small-string buffer and hit the heap).

Read the tokens through a pointer instead: it points at the entry's
cached parsedSig when available, and at an owned vector only when the
converter has to parse the signature itself. The converter is a
per-call stack object while the entry is owned by the class's
MethodCallbackData for the isolate's lifetime, so the pointer cannot
outlive its target. Copying is deleted since the pointer may refer to
the converter's own member.

Author: edusperoni

test-app/runtime/src/main/cpp/JsArgConverter.cpp

@@ -28,10 +28,10 @@ JsArgConverter::JsArgConverter(const Local<Object> &caller,
                 JniSignatureParser parser(m_methodSignature);
                 entry->parsedSig = parser.Parse();
             }
-            m_tokens = entry->parsedSig;
+            m_tokens = &entry->parsedSig;
         } else {
             JniSignatureParser parser(m_methodSignature);
-            m_tokens = parser.Parse();
+            m_ownedTokens = parser.Parse();
         }
 
         m_isValid = ConvertArg(caller, 0);
@@ -63,10 +63,10 @@ JsArgConverter::JsArgConverter(const v8::FunctionCallbackInfo<Value> &args,
                 JniSignatureParser parser(m_methodSignature);
                 entry->parsedSig = parser.Parse();
             }
-            m_tokens = entry->parsedSig;
+            m_tokens = &entry->parsedSig;
         } else {
             JniSignatureParser parser(m_methodSignature);
-            m_tokens = parser.Parse();
+            m_ownedTokens = parser.Parse();
         }
 
         for (int i = 0; i < m_argsLen; i++) {
@@ -86,7 +86,7 @@ JsArgConverter::JsArgConverter(const v8::FunctionCallbackInfo<Value> &args,
     m_argsLen = args.Length();
 
     JniSignatureParser parser(m_methodSignature);
-    m_tokens = parser.Parse();
+    m_ownedTokens = parser.Parse();
 
     for (int i = 0; i < m_argsLen; i++) {
         m_isValid = ConvertArg(args[i], i);
@@ -117,7 +117,7 @@ bool JsArgConverter::ConvertArg(const Local<Value> &arg, int index) {
 
     char buff[1024];
 
-    const auto &typeSignature = m_tokens.at(index);
+    const auto &typeSignature = m_tokens->at(index);
 
     if (arg.IsEmpty()) {
         SetConvertedObject(index, nullptr);
@@ -394,7 +394,7 @@ bool JsArgConverter::ConvertJavaScriptNumber(const Local<Value> &jsValue, int in
             0
     };
 
-    const auto &typeSignature = m_tokens.at(index);
+    const auto &typeSignature = m_tokens->at(index);
     auto context = m_isolate->GetCurrentContext();
 
     const char typePrefix = typeSignature[0];
@@ -445,7 +445,7 @@ bool JsArgConverter::ConvertJavaScriptNumber(const Local<Value> &jsValue, int in
 bool JsArgConverter::ConvertJavaScriptBoolean(const Local<Value> &jsValue, int index) {
     bool success;
 
-    const auto &typeSignature = m_tokens.at(index);
+    const auto &typeSignature = m_tokens->at(index);
     auto context = m_isolate->GetCurrentContext();
 
     if (typeSignature == "Z") {
@@ -489,7 +489,7 @@ bool JsArgConverter::ConvertJavaScriptArray(const Local<Array> &jsArr, int index
 
     jsize arrLength = jsArr->Length();
 
-    const auto &arraySignature = m_tokens.at(index);
+    const auto &arraySignature = m_tokens->at(index);
     auto context = m_isolate->GetCurrentContext();
 
     string elementType = arraySignature.substr(1);
@@ -632,7 +632,7 @@ template<typename T>
 bool JsArgConverter::ConvertFromCastFunctionObject(T value, int index) {
     bool success = false;
 
-    const auto &typeSignature = m_tokens.at(index);
+    const auto &typeSignature = m_tokens->at(index);
 
     const char typeSignaturePrefix = typeSignature[0];
 

test-app/runtime/src/main/cpp/JsArgConverter.h

@@ -27,6 +27,10 @@ namespace tns {
 
         JsArgConverter(const v8::FunctionCallbackInfo<v8::Value>& args, const std::string& methodSignature);
 
+        JsArgConverter(const JsArgConverter&) = delete;
+
+        JsArgConverter& operator=(const JsArgConverter&) = delete;
+
         ~JsArgConverter();
 
         jvalue* ToArgs();
@@ -79,7 +83,10 @@ namespace tns {
 
         std::string m_methodSignature;
 
-        std::vector<std::string> m_tokens;
+        std::vector<std::string> m_ownedTokens;
+
+        // May point at m_ownedTokens, which is why the converter is not copyable.
+        const std::vector<std::string>* m_tokens = &m_ownedTokens;
 
         Error m_error;
     };