C++ Finding an incomplete string from a text file - c++

Question

I have a program which reads text files and parses information from them, and I am trying to accomplish a task like this:
A text file which has about 500 characters of data in it, in this data lies user name like so:
this_just_some_random_data_in_the_file_hdfhehhr2342t543t3y3y
_please_don't_mind_about_me(username: "sara123452")reldgfhfh
2134242gt3gfd2342353ggf43t436tygrghrhtyj7i6789679jhkjhkuklll
The thing is that we only need to find and write sara123452 to a string from that text file. The user name is unknown of course, and does not have fixed length.
Here is what I have managed to do so far:
std::string Profile = "http://something.com/all_users/data.txt";
std::string FileName = "profileInfo.txt";
std::string Buffer, ProfileName;
std::ifstream FileReader;
DeleteUrlCacheEntryA(Profile .c_str());
URLDownloadToFileA(0, Profile .c_str(), FileName.c_str(), 0, 0);
FileReader.open(FileName);
if (FileReader.is_open())
{
std::ostringstream FileBuffer;
FileBuffer << FileReader.rdbuf();
Buffer= FileBuffer.str();
if (Buffer.find("(username: ") != std::string::npos) {
cout << "dont know how to continue" << endl;
}
FileReader.close();
DeleteFileA(FileName.c_str());
}
else {
}
cin.get();
So how can I get the user name string and assign/copy it to ProfileName string?

Answer 1

I believe what you're looking for is something like the code below -- possibly with minor tweaks to account for the username being quoted. The key here is to remember that your Buffer variable is a std::string and you can use substring once you have a definite start and end.
std::size_t userNameStartIndex, userNameEndIndex
...
userNameStartIndex = Buffer.find("(username: ")) + 11;
if (userNameStartIndex != std::string::npos) {
userNameEndIndex = Buffer.find(")", userNameStartIndex);
if (userNameEndIndex != std::string::npos)
{
ProfileName = Buffer.substr(userNameStartIndex, userNameEndIndex - userNameStartIndex)
}
}

Answer 2

There are many other ways to do it, but this one would be less painful I guess.
#include <regex>
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
struct Profile
{ // ...
string name;
};
int main(int argc, const char * argv[])
{
std::cout.sync_with_stdio(false); // optional
// read from file
string filename {"data1.txt"};
ifstream in {filename};
vector<Profile> profiles;
// tweaks this pattern in case you're not happy with it
regex pat {R"(\(username:\s*\"(.*?)\"\))"};
for (string line; getline(in,line); ) {
Profile p;
sregex_iterator first(cbegin(line), cend(line), pat);
const sregex_iterator last;
while (first != last) {
// By dereferencing a first, you get a smatch object.
// [1] gives you the matched sub-string:
p.name = (*first)[1]; // (*first)[1] = sara123452
profiles.push_back(p);
++first;
}
}
// Test
for (const auto& p : profiles)
cout << p.name << '\n';
}