Better function signature?

[dense grove]

I have a function that loads a file. From this file it has to a get a number and return it. The way I currently do it is to return a bool for the status of the operation (because file opening, reading, etc.. can fail) and get the number as a parameter by reference. It works, but I think it's ugly and doesn't do the name of the function justice. Would there be a better way where I return the int and still convey if the opening/reading of the file failed somehow?

bool get_number_of(const char* file_name, const unsigned size_of, unsigned& number)
{
    std::ifstream file(file_name, std::ios::binary|std::ios::in);

    // try to open file
    if(!file.is_open())
        return false;

    if(file.tellg() > 0)
    {
        file.seekg(0, std::ios::end);

        number = file.tellg() / sizeof(size_of);
    }
    else
        number = 0;

    file.close();

    return file.good();
}

[oak wind]

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[dense grove]

Also before anyone says anything - this a part of a homework and I'm quite limited in what I can use. I'm not allowed to use the C++17 filesystem, nor any "modern" stl structures.

[vast hound]

exceptions

you also really don't need to explicitly close a file

the destructor of the fstream takes care of that

i'm not exactly sure what you mean by "get a number from it"

it seems you're trying to get the file size?

[dense grove]

uhh no, the file contains serialized structs and this way I calculate the number of them inside the file.

So the only real way is exceptions? I would've like to avoid them for the purpose of the homework, but if it's the only way

size_of is the size of the struct

[vast hound]

well, you can return a struct with a bool and the result, or an optional, or smth

there are many ways to handle errors ^^

[vast hound]

k^^

just be advised that this way of getting the size of a file is technically not a good idea

it's just what most people will tell you to do

but it's technically non-portable

[dense grove]

yeah I know. but like I said above i'm not allowed to use std::filesystem::exists()

[timid sparrow]

are you allowed to use std::optional? if not you could do it the way the person above me suggested, with a struct that has two variables, one that is a boolean that tells you if the function has executed correctly and one that contains the actual result

but imo std::optional is the best since it's so commonly used

[tardy sluice]

std::expected