C++ File Handling: Text Streams, Binary Serialization & File Pointer Seeking

File handling in C++ is managed through the <fstream> library, which provides three stream classes: std::ifstream (reading), std::ofstream (writing), and std::fstream (bidirectional read and write).

Figure 16: The C++ Stream I/O Class Hierarchy Architecture

1. Writing and Reading Text Files

#include <iostream>
#include <fstream>
#include <string>

int main() {
    // 1. Write text to a file
    {
        std::ofstream outFile("veewom_notes.txt");
        if (outFile.is_open()) {
            outFile << "Mastering C++ File Streams\n";
            outFile << "Built with RAII principles.\n";
        }
    } // Automatically flushed and closed on scope exit!

    // 2. Read text line-by-line
    {
        std::ifstream inFile("veewom_notes.txt");
        std::string line;
        while (std::getline(inFile, line)) {
            std::cout << "[READ]: " << line << "\n";
        }
    }

    return 0;
}

2. Binary File I/O: Serializing Structs Directly to Disk

#include <iostream>
#include <fstream>

struct PlayerData {
    int id;
    int score;
    double health;
};

int main() {
    PlayerData p1{101, 4500, 98.5};

    // Write binary bytes directly to file
    std::ofstream out("save.dat", std::ios::binary);
    out.write(reinterpret_cast<const char*>(&p1), sizeof(PlayerData));
    out.close();

    // Read binary bytes back from file
    PlayerData loadedPlayer{};
    std::ifstream in("save.dat", std::ios::binary);
    in.read(reinterpret_cast<char*>(&loadedPlayer), sizeof(PlayerData));
    in.close();

    std::cout << "Loaded Player ID: " << loadedPlayer.id << " | Score: " << loadedPlayer.score << "\n";
    return 0;
}