Find number of items in .txt file - c++

Question

I'm looking for a way to find the number of items in a .txt file.
The file structure is as follows:
students.txt pricem 1441912123
house.pdf jatkins 1442000124
users.txt kevin_tomlinson 1442001032
accounts.mdb kevin_tomlinson 1442210121
vacation.jpg smitty83 1442300125
calendar.cpp burtons 1442588012
The result should be 18 in this example since there are 18 separate "words" in this file.
I need that value so I can iterate through the items and assign them to an array of structures (maybe there's a way to accomplish both of these steps together?):
// my structure
struct AccessRecord
{
string filename;
string username;
long timestamp;
};
// new instance of AccessRecord
// max possible records: 500
AccessRecord logRecords[500];
// while file has content
while (!fin.eof())
{
// loop through file until end
// max possible records: 500
for (int i = 0; i < 500; i++) // need to figure out how to iterate
{
fin >> logRecords[i].filename
>> logRecords[i].username
>> logRecords[i].timestamp;
}
}
Which will then be written to the screen.
So the question is, how do I find the count? Or is there a better way?

Answer 1

You know that each line contains a string, a string and a long, so you can iterate with:
std::vector<AccessRecord> logs;
std::string fname, uname;
long tstamp;
while(fin >> fname >> uname >> tstamp) {
logs.push_back(AccessRecord(fname, uname, tstamp));
//To avoid copies, use: (thanks #Rakete1111!)
//logs.emplace_back(std::move(fname), std::move(uname), tstamp);
}
This is assuming you've created a constructor for your struct like:
AccessRecord(std::string f, std::string u, long t)
: filename(f), username(u), timestamp(t) { }
Notice that I'm using an std::vector here instead of an array so that we don't even have to worry about the number of items, since the vector will resize itself dynamically!

Answer 2

You should overload operator>> for your structure:
struct AccessRecord
{
string filename;
string username;
long timestamp;
friend std::istream& operator>>(std::istream& input, AccessRecord& ar);
};
std::istream& operator>>(std::istream& input, AccessRecord& ar)
{
input >> ar.filename;
input >> ar.username;
input >> ar.timestamp;
return input;
}
This allows you to simplify your input function:
AccessRecord ar;
std::vector<AccessRecord> logs;
//...
while (fin >> ar)
{
database.push_back(ar);
}
Usually, if you are accessing an objects data members directly outside of the class or structure, something is wrong. Search the internet for "data hiding", "c++ encapsulation" and "c++ loose coupling".