improve MessageTypeSupport performance. (#562)

* improve MessageTypeSupport performance.

Signed-off-by: Tomoya Fujita <Tomoya.Fujita@sony.com>

* address review comments.

Signed-off-by: Tomoya Fujita <Tomoya.Fujita@sony.com>

---------

Signed-off-by: Tomoya Fujita <Tomoya.Fujita@sony.com>

Author: Tomoya Fujita

rmw_cyclonedds_cpp/src/MessageTypeSupport_impl.hpp

@@ -17,8 +17,6 @@
 
 #include <cassert>
 #include <memory>
-#include <regex>
-#include <sstream>
 #include <string>
 
 #include "MessageTypeSupport.hpp"
@@ -33,16 +31,31 @@ MessageTypeSupport<MembersType>::MessageTypeSupport(const MembersType * members)
   assert(members);
   this->members_ = members;
 
-  std::ostringstream ss;
-  std::string message_namespace(this->members_->message_namespace_);
   std::string message_name(this->members_->message_name_);
-  if (!message_namespace.empty()) {
+
+  std::string name;
+  if (this->members_->message_namespace_ != nullptr &&
+    this->members_->message_namespace_[0] != '\0')
+  {
+    std::string message_namespace(this->members_->message_namespace_);
     // Find and replace C namespace separator with C++, in case this is using C typesupport
-    message_namespace = std::regex_replace(message_namespace, std::regex("__"), "::");
-    ss << message_namespace << "::";
+    std::string::size_type pos = 0;
+    while ((pos = message_namespace.find("__", pos)) != std::string::npos) {
+      message_namespace.replace(pos, 2, "::");
+      pos += 2;
+    }
+    name.reserve(
+      message_namespace.size() + 2 + 5 + message_name.size() + 1);  // "::" + "dds_::" + "_"
+    name += message_namespace;
+    name += "::";
+  } else {
+    name.reserve(5 + message_name.size() + 1);  // "dds_::" + "_"
   }
-  ss << "dds_::" << message_name << "_";
-  this->setName(ss.str().c_str());
+  name += "dds_::";
+  name += message_name;
+  name += '_';
+
+  this->setName(name);
 }
 
 }  // namespace rmw_cyclonedds_cpp