Reading file into buffer

Question

I have a little problem that i can't figure out.
I am trying to read a file into a buffer, My problem is that sometimes it adds a random character at the end of the text. (sometimes ? and abs etc.). So i wonder why that is happening. I haven't found any solution yet. The problem happens randomly, not every time i read the file.

    static char text[1024 * 16];
    std::ifstream File(FilePath, std::ios::in | std::ios::out | std::ios::binary | std::ios::ate);
    std::streamsize Size = File.tellg();
    File.seekg(0, std::ios::beg);
    char *string = new char[Size + 1];
    if (File.is_open()) 
    {
         File.read(string, Size);
         memset(text, 0, sizeof(text));
         snprintf(text, sizeof(text), "%s", string);

    }
    File.close();
    delete[] string;

Answer 1

Note that read() does not append a null terminator, it's just a raw binary read. In other words, the data is not a string, it's an array of bytes. You are probably trying to print it out or something, and it just keeps going until it sees a null terminator, potentially into uninitialized memory. You should manually allocate size + 1 and add the null terminator at the end.

A couple style notes: its not recommended to use variable names such as "File" or "Size". Its legal but bad practice, you can check out some popular style guides for more information ( Google , LLVM )

Secondly, I would try to get this working with std::string rather than allocating memory manually, even on the stack. Check out reserve() and data()

Here's a cleaner example using std::string. More readable, easier to write, and just as efficient.

const char *somefile = "main.cpp";
std::ifstream fh(somefile, std::ios::in | std::ios::out | std::ios::binary |
                               std::ios::ate);
const size_t sz = fh.tellg();
if (sz <= 0) {
    // error handling here
}
fh.seekg(0, std::ios::beg);
// Initalizes a std::string with length sz, filled with null
std::string str = std::string(sz, '\0');
if (fh.is_open())
    fh.read(&str[0], sz);
fh.close();
std::cout << str << "[EOF]\n";