Using fstream and fstream.eof. Working with files

Question

I'm trying to make a programm, which will read the file, change specified word to symbols '@' and write back to same file. But I have problems with that.

1st question. It seems like I need to store file in buffer before writing it to the file. How should I do it?

2nd question: I cant understand why loop in this code never ends? It's about 200 words in that file, but I always get memory exception and i gets 10075.

int main(int argc, char* argv[]){
    char** temp = new char*[10000];
    int i = 0;
    fstream fTemp("D:\doc.txt", ios_base::in);
    while (!fTemp.eof()){
        temp[i] = new char[50];
        fTemp >> temp[i];
        temp[i][1] = '@';
        cout << temp[i] << endl;
        i++;
    }
    fTemp.open("D:\doc.txt", ios_base::trunc);
    for (int i = 0; i < sizeof(*temp); i++){
        fTemp << temp[i];
    }
    _getch();
}

Answer 1

First, you should use getline as your usage of eof is incorrect (eof bit is set only after failed read). Next, store the strings in a std::vector<string> . This will allow you to not care about memory management (current one is leaking) and provide a more flexible solution.

std::string buffer;
std::vector<string> data;
while(std::getline(fTemp,buffer)) {
      data.push_back(buffer);
}

The problem you probably have, is the incorrect eof() call, buy you should check you cout output to determine the problem with this code.

Answer 2

to store the data of file in a buffer, you can get the size of file and use the function read to get all file data. see this code:

// Load file in a buffer
ifstream fl(FileName);
fl.seekg(0, ios::end);
size_t len = fl.tellg();
char* fdata = new char[len];
fl.seekg(0, ios::beg);
fl.read(fdata, len);
fl.close();

in your case the same fstream that you used to open are being used to write without close the file before reopen.

Your loop never ends because it is a pointer, and it size isn't managed, the better way is get the size of file while it is open, in this case the size of file is the "size_t len".

to rewrite your code you can create another stream, see this code:

// Write File
ofstream flOut(FileName, ios_base::trunc);
flOut.write(fdata, len);
flOut.close();

between these two codes above, you can change the data of fdata, but what exactly you wanna make? is replace some word to symbol '@'? which word?