C ++ string stream issue: getline doesn't work with stringstream - c++

Question

I wrote a program that takes a file and reads it into a stringstream field in a class, and now I'm trying to interact with it. The problem is that when reading sequentially from several methods, one of the methods gives an error, or simply does not work. I guess the problem is how I read the file, how should I improve it?
There is my class:
class MatReader
{
protected:
...
stringstream text;
...
string PhysicsMaterial;
string Diffuse;
string NMap;
string Specular;
public:
/// <summary>
/// Read all lines in .mat document by string
/// </summary>
void ReadAllLines(string file_path);
/// <summary>
/// Getting PhysicsMaterial property
/// </summary>
string getPhysMaterial();
/// <summary>
/// Getting diffuse file path
/// </summary>
string getDiffuseLocation();
};
And there is my implementation file:
#include "MaterialHandler.h"
void MatReader::ReadAllLines(string mat_file)
{
ifstream infile(mat_file);
string str;
if (infile.is_open())
{
ofile = true;
while (!infile.eof())
{
getline(infile, str);
text << str+"\n";
}
}
else
throw exception("[ERROR] file does not exist or corrupted");
}
string MatReader::getPhysMaterial()
{
string line;
vector<string> seglist;
try
{
if (ofile == false)
throw exception("file not open");
while (getline(text, line, '"'))
{
if (!line.find("/>"))
break;
seglist.push_back(line);
}
for (uint16_t i{}; i < seglist.size(); i++)
{
if (seglist[i-1] == " PhysicsMaterial=")
{
PhysicsMaterial = seglist[i];
return seglist[i];
}
}
line.clear();
seglist.clear();
}
catch (const std::exception& ex)
{
cout << "[ERROR]: " << ex.what() << endl;
return "[ERROR]";
}
}
string MatReader::getDiffuseLocation()
{
string line;
vector<string> seglist;
try
{
if (ofile == false)
throw exception("file not open");
while (getline(text, line, '"'))
{
seglist.push_back(line);
}
for (uint16_t i{}; i < seglist.size(); i++)
{
if (seglist[i - 1] == " File=")
{
PhysicsMaterial = seglist[i];
return seglist[i];
}
}
}
catch (const std::exception& ex)
{
cout << "[ERROR]: " << ex.what() << endl;
return "[ERROR]";
}
}
The methods "getPhysMaterial()" and "getDiffuseLocation()" works separately without any problems, but if they are executed sequentially, they give an error or are not executed at all.
Thank you.

Answer 1

So first you need to correct the issue with your out-of-range array access.
The next issue you have is you need to reset the position of the stream in order to re-read it from the beginning.
Here is an example of how you can do that.
std::stringstream ss{ };
ss << "This is line one\n"
<< "This is line two\n"
<< "This is line three\n"
<< "This is line four\n";
// Points to the start of the stringstream.
// You can store this as a member of your class.
const std::stringstream::pos_type start{ ss.tellg( ) };
std::string line{ };
while ( std::getline( ss, line ) )
std::cout << line << '\n';
// Reset to the start of the stringstream.
ss.clear( );
ss.seekg( start );
while ( std::getline( ss, line ) )
std::cout << line << '\n';
Another issue I noticed is that you're checking for eof in the loop condition. Don't do that.. Why is iostream::eof inside a loop condition (i.e. while (!stream.eof())) considered wrong?
Do something like this instead:
std::stringstream ss{ };
if ( std::ifstream file{ "/Path/To/MyFile.txt" } )
{
std::string input{ };
while ( std::getline( file, input ) )
ss << input << '\n';
}
else
{
std::cerr << "Failed to open file\n";
return 1;
}
std::string line{ };
while ( std::getline( ss, line ) )
std::cout << line << '\n';