How to determine the size of a file??

[jhonny6721]

Thanks to read this message. I want load the data from a file to a dynamic array.

I dont know how to determine the size of the file. I can post the code if you want.

[nvrmnd]

inline std::ios::pos_type filesize( const char* location )
{
    std::ifstream fin( location, std::ios::binary );
    fin.seekg( 0, std::ios::end );
    return fin.tellg();
}

or (from stack overflow)

ifstream file( "example.txt", ios::binary | ios::ate);
return file.tellg();

[OUIJ]

Why not use a vector and use the push_back() function to add elements to the vector until all data is stored and then use .size() function to determine the size of the vector

[Smac89]

That will take longer because of:

Memory allocation
Function calls

The method mentioned above is the way I will do it because you don't need to declare any extra variables, there is only one or two function calls you do and it is fast.

[ne555]

It seems idiotic to open the file, check the size, close it, reopen it, and read it.


if you only care about the size http://www.cplusplus.com/forum/general/71333/#msg380507

[modoran]

On windows I think stat is implemented using GetFileAttributesEx, but even so I am not sure if it opens the file behind the scenes.
http://msdn.microsoft.com/en-us/library/windows/desktop/aa364946.aspx

[Smac89]

@ne555, you don't need to close the file in order to read it after you find the size. Consider this code:

string contents;
cin.seekg(0, ios::end);
contents.resize(cin.tellg());
cin.seekg(0, ios::beg);
cin.read(&contents[0], contents.size());
istringstream iss(contents);

The above code will read an entire file content into a string. The file needs to be redirected to the program

[ne555]

but you can't avoid to close it if you use your shadow fiend `filesize()' function

> cin.read(&contents[0], contents.size());
don't forget the '\0' terminator
edit: nvm, looks fine.