将字符串与ifstream :: getline生成的字符串进行比较

Question

I am working on a project where I need to read postscript and parse data from the file to use in my program. I am working on a function to test whether the postscript is valid by making sure it has opening and closing delimiters.

Below is the segment of code I have written to accomplish this. I am confident that there are no additional spaces or anything of the sort in the postscript file to cause any discrepancy between delimitStr and lineStr. I also attempted to set delimitStr to "%%%BEGIN\\0" and "%%%BEGIN", but the comparison never works.

string lineStr;
bool beginFlag = false; //Switches to true when begin statement in postscript is found
string delimitStr = "%%%BEGIN"; //Starts as opening  delimiter. Switches to closing when opening is found.
while(psfile) {
    getline(psfile, lineStr);
    if(!beginFlag && lineStr == delimitStr) {
        beginFlag = true;
        delimitStr = "%%%END";
        cerr << "Begin found." << endl;
    }
    else if(beginFlag && lineStr == delimitStr)
        return true; //Only return true if file has beginning and ending delimiters.

Any help would be greatly appreciated.

Answer 1

Change delimitStr to delimitStr = "%%%BEGIN"; because getline discards the '\\n' and compare strings like this lineStr == delimitStr . DO NOT compare strings with c_str() as that returns a const char* .

Example showing the differences:

std::string s1("%%%BEGIN");
std::string s2("%%%BEGIN\n");
std::string s3("%%%BEGIN\0"); // Same as s1 because std::string stops at '\0'

std::cout << std::boolalpha << (s1 == s2) << '\n';      // Outputs: false
std::cout << (s1 == s3) << '\n';      // Outputs: true 
std::cout << (s2 == s3) << std::endl; // Outputs: false