Continue a while loop until EOF (Qt) - c++

Question

I'm working on a program to create a list from a large QStringList. So basically after a string match, a while loop will start to add the next strings into a list. This part is working fine. The only problem I have is that the program quits unexpectedly because I don't know how I should add the EOF mechanism.
Update with a more detailed code
Sorry for not providing with enough details about my code. This is how my code looks now. So after the first time the string "PACKAGE TYPE" is detected, I use the function storeLines() function to store the next strings into one of three lists dependent. And this will continue until the next "PACKAGE TYPE" match or EOF. The only thing that is not working correctly now is when the iterator is on the last string of the QStringList. It somehow doesn't detect that the next is inputline.end()
void storeLines(QString department, QStringList::iterator current_line, QStringList::iterator endline){
while(QString::compare(*(current_line + 1),"PACKAGE TYPE") && (++current_line != endline)){ //this is not working
if(!QString::compare(department, "MDA")) mda_list.push_back(*current_line);
else if(!QString::compare(department, "SDA")) sda_list.push_back(*current_line);
else mix_list.push_back(*current_line);
}
}
void void MainWindow::on_pushButton_clicked(){
QString input = ui->listinput->toPlainText().toLatin1();
QStringList inputline = input.split("\n", QString::SkipEmptyParts );
for(QStringList::iterator pkg_header(inputline.begin()); pkg_header != inputline.end(); ++pkg_header){
if(!QString::compare(*pkg_header,"PACKAGE TYPE")){
++pkg_header;
if(!QString::compare(*pkg_header,"Department-mda:")) storeLines("MDA", pkg_header, inputline.end());
else if(!QString::compare(*pkg_header,"Department-sda:")) storeLines("SDA", pkg_header, inputline.end());
else storeLines("MIX", pkg_header, inputline.end());
}
}
}
Thanks in advance!

Answer 1

You're writing a parser - it's often simplest to write it like you'd usually write one, by making the states explicit and iterating in sequence over every element of the input stream. You won't make any off-by-one iterator errors that way.
This code matches the intent in your question, and makes it obvious that you've missed a case: when you expect a department, you don't react to the PACKAGE TYPE being present. You could signal an error, or stay in the DEPARTMENT state, but I presume you should handle it and not just ignore it.
QStringList mda_list, sda_list, mix_list;
void parse(const QString & input) {
enum {
TYPE,
DEPARTMENT,
ITEMS
} state = TYPE;
auto list = &mix_list;
auto const kPackageType = QStringLiteral("PACKAGE TYPE");
for (auto const element : input.split("\n", QString::SkipEmptyParts)) {
switch (state) {
case TYPE:
if (element == kPackageType)
state = DEPARTMENT;
break;
case DEPARTMENT:
if (element == QStringLiteral("Department-mda:"))
list = &mda_list;
else if (element == QStringLiteral("Department-sda:"))
list = &sda_list;
state = ITEMS;
break;
case ITEMS:
if (element == kPackageType)
state = DEPARTMENT;
else
*list << element;
break;
}
}
}
The use of QStringLiteral gives you compile-time-built string instances to compare against. The code would work about just as well if you removed the QStringLiteral(...) wrappers, at a cost due to inevitable premature pessimization though.

Answer 2

Your apparent intent is to find the string "PACKAGE TYPE" in the existing list, and then copy the remaining elements in the list to a new list.
If that's the case, then why not do exactly that?
for(QStringList::iterator current_line(inputline.begin()); current_line != inputline.end(); ++current_line){
if(!QString::compare(*current_line,"PACKAGE TYPE"){
list.insert(list.end(), ++current_line, inputline.end());
break;
}
}