Using a loop with std::strcmp to load lots of settings - c++

Question

In my game I keep track of unlocked levels with a vector std::vector<bool> lvlUnlocked_;.
The simple function to save the progress is this:
void save() {
std::stringstream ss;
std::string stringToSave = "";
std::ofstream ofile("./progress.txt");
if (ofile.good()) {
ofile.clear();
for (std::size_t i = 0; i < levelUnlocked_.size(); ++i) {
ss << "lvl" << i << "=" << (lvlUnlocked_.at(i) ? "1" : "0") << std::endl;
}
stringToSave = ss.str();
ofile << stringToSave;
ofile.close();
}
}
This works and is nice since I can just use a loop to dump the info.
Now to the part where I am stuck, the lower part of my load function (see comment in code below):
void load() {
std::ifstream ifile("./progress.txt");
if (ifile.good()) {
int begin;
int end;
std::string line;
std::string stringKey = "";
std::string stringValue = "";
unsigned int result;
while (std::getline(ifile, line)) {
stringKey = "";
stringValue = "";
for (unsigned int i = 0; i < line.length(); i++) {
if (line.at(i) == '=') {
begin = i + 1;
end = line.length();
break;
}
}
for (int i = 0; i < begin - 1; i++) {
stringKey += line.at(i);
}
for (int i = begin; i < end; i++) {
stringValue += line.at(i);
}
result = static_cast<unsigned int>(std::stoi(stringValue));
// usually I now compare the value and act accordingly, like so:
if (std::strcmp(stringKey.c_str(), "lvl0") == 0) {
lvlUnlocked_.at(0) = true;
} else if (std::strcmp(stringKey.c_str(), "lvl1") == 0) {
lvlUnlocked_.at(1) = true;
} else if (std::strcmp(stringKey.c_str(), "lvl2") == 0) {
lvlUnlocked_.at(2) = true;
}
// etc....
}
}
}
This works fine, but...
the problem is that I have 100+ levels and I want it to be dynamic based on the size of my lvlUnlocked_ vector instead of having to type it all like in the code above.
Is there a way to somehow make use of a loop like in my save function to check all levels?

Answer 1

If you parse your key to extract a suitable integer value, you can just index into the bit-vector with that:
while (std::getline(ifile, line)) {
const size_t eq = line.find('=');
if (eq == std::string::npos)
// no equals sign
continue;
auto stringKey = line.substr(0, eq);
auto stringValue = line.substr(eq+1);
if (stringKey.substr(0,3) != "lvl")
// doesn't begin with lvl
continue;
// strip off "lvl"
stringKey = stringKey.substr(3);
size_t end;
std::vector<bool>::size_type index = std::stoi(stringKey, &end);
if (end == 0 || end != stringKey.length())
// not a valid level number
continue;
if (index >= lvlUnlocked_.size())
// out of range
continue;
// Set it :-)
lvlUnlocked_[index] = stringValue=="1";
}
(I've also updated your parsing for "key=value" strings to more idiomatic C++.)