Merge pull request #8 from machindustries/justinpankmach/optimize-parser

do not use their split function

src/input_output/FGXMLParse.cpp

@@ -40,34 +40,57 @@ namespace JSBSim {
 CLASS IMPLEMENTATION
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
-void FGXMLParse::reset(void)
-{
+void FGXMLParse::reset(void) {
   current_element = document = nullptr;
   working_string.erase();
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-void FGXMLParse::dumpDataLines(void)
-{
+void FGXMLParse::dumpDataLines(void) {
+
   if (!working_string.empty()) {
-    for (auto s: split(working_string, '\n'))
-      current_element->AddData(s);
+    //The following change was made by Mach:
+    // 1. This implemenation iterates over the input string in O(n) time.
+    //    where n is the length of the input string.
+    // 2. The built in JSBSim split() method runs in O(n^2) for n is the string size, with an additional
+    //  O(m) [for m = n/rows of a matrix] from the outer for loop.
+    //  Overall it runs in  O(n^3) time making parsing inviable for files around 90MB+ in size.
+    //  Regression tested against 2 jsbsims with identical inputs, and validated no difference
+    //    within epsilon = 1E-8.
+    size_t index = 0;
+    index = working_string.find('\n');
+    if (index != std::string::npos && index != 0) {
+      size_t curr = 0;
+      std::string temp = "";
+      while (curr < working_string.length()) {
+        if (working_string[curr] == '\n') {
+          trim(temp);
+          current_element->AddData(temp);
+          temp = "";
+        } else {
+          temp.push_back(working_string[curr]);
+        }
+        curr++;
+      }
+    } else {
+      trim(working_string);
+      current_element->AddData(working_string);
+    }
+    working_string.erase();
   }
-  working_string.erase();
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-void FGXMLParse::startElement (const char * name, const XMLAttributes &atts)
-{
+void FGXMLParse::startElement(const char *name, const XMLAttributes &atts) {
   if (!document) {
     document = new Element(name);
     current_element = document;
   } else {
     dumpDataLines();
 
-    Element* temp_element = new Element(name);
+    Element *temp_element = new Element(name);
     if (temp_element) {
       temp_element->SetParent(current_element);
       current_element->AddChildElement(temp_element);
@@ -84,30 +107,27 @@ void FGXMLParse::startElement (const char * name, const XMLAttributes &atts)
   current_element->SetLineNumber(getLine());
   current_element->SetFileName(getPath());
 
-  for (int i=0; i<atts.size();i++) {
+  for (int i = 0; i < atts.size(); i++) {
     current_element->AddAttribute(atts.getName(i), atts.getValue(i));
   }
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-void FGXMLParse::endElement (const char * name)
-{
+void FGXMLParse::endElement(const char *name) {
   dumpDataLines();
   current_element = current_element->GetParent();
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-void FGXMLParse::data (const char * s, int length)
-{
+void FGXMLParse::data(const char *s, int length) {
   working_string += string(s, length);
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-void FGXMLParse::warning (const char * message, int line, int column)
-{
+void FGXMLParse::warning(const char *message, int line, int column) {
   cerr << "Warning: " << message << " line: " << line << " column: " << column
        << endl;
 }