std::fstream::tellg() outputs file cursor pointer incorrectly? - c++

Question

I have a std::fstream, which I imported using
std::fstream myFile { "C:/path/to/file.txt" };
When I want to read the first byte, I use
char c;
cout << myFile.tellg() << endl; // Correctly outputs 0 (begining of file)
myFile.read(&c, 1);
cout << myFile.tellg() << endl; // Should output 1, but it outputs
// FFFFFFFFFFFFFFFA
myFile.read(&c, 1);
cout << myFile.tellg() << endl; // Should output 2, but it outputs
// FFFFFFFFFFFFFFFB
What's happening here?
I tried putting
midi_file.seekg(0, ios_base::beg);
or
midi_file.seekg(0, myFile.beg);
But the cursor moves to FFFFFFFFFFFFFFFA whenever I try to read a byte.
EDIT:
I don't know if it has something to do, but I did an endianness test and these are the results:
bool endianness = *reinterpret_cast<short*>("10") & 1; // Outputs 1
EDIT 2:
The file is broken, as the output is not the same with another file, but why is it?
Here is the byte data from the file, taken from HxD, which is a .midi file:
4D 54 68 64 00 00 00 06 00 01 00 03 00 04 4D 54
72 6B 00 00 00 A1 00 C0 69 00 90 3C 5A 01 41 5A
01 45 5A 01 48 5A 01 49 5A 01 48 5A 01 45 5A 01
41 5A 01 3C 5A 01 37 5A 01 33 5A 01 30 5A 01 30
5A 01 30 5A 01 33 5A 01 37 5A 01 3C 5A 01 41 5A
01 45 5A 01 48 5A 01 49 5A 01 48 5A 01 45 5A 01
41 5A 01 3C 5A 01 37 5A 01 33 5A 01 30 5A 01 30
5A 01 30 5A 01 33 5A 01 37 5A 01 3C 5A 01 41 5A
01 45 5A 01 48 5A 01 49 5A 01 48 5A 01 45 5A 01
41 5A 01 3C 5A 01 37 5A 01 33 5A 01 30 5A 01 30
5A 01 30 5A 01 33 5A 01 37 5A 01 3C 5A 01 41 5A
01 45 00 00 FF 2F 00 4D 54 72 6B 00 00 00 41 00
C1 72 05 91 3C 5A 00 40 5A 00 43 5A 00 48 5A 0A
35 5A 00 41 5A 00 44 5A 00 49 5A 0A 37 5A 00 40
5A 00 43 5A 00 48 5A 0A 41 5A 00 47 5A 0A 30 5A
00 40 5A 00 43 5A 00 48 5A 05 32 00 00 FF 2F 00
4D 54 72 6B 00 00 00 26 00 C2 47 0A 92 50 64 01
52 64 09 50 78 00 52 78 0A 50 00 01 52 00 09 50
78 01 50 00 0A 52 00 00 50 00 00 FF 2F 00
EDIT 3:
Here is the full code of this test:
#include <fstream>
#include <iostream>
int main() {
cout << std::hex << std::setfill('0') << std::uppercase;
fstream midi_file{ "D:/Descargas/OutFile.midi" };
cout << midi_file.good() << endl; // Outputs 1
char c;
cout << midi_file.tellg() << endl; // Correctly outputs 0 (begining of file)
midi_file.read(&c, 1);
cout << midi_file.tellg() << endl; // Erroneously outputs FFFFFFFFFFFFFFFA
midi_file.read(&c, 1);
cout << midi_file.tellg() << endl; // Erroneously outputs FFFFFFFFFFFFFFFB
// Endianness test:
cout << (*reinterpret_cast<short*>("10") & 1) << endl; // Outputs 1
return 0;
}

Answer 1

The return value of tellg is NOT a number. It is a pos_type, which has some rules it needs to follow but being understandable when printed isn't one of them. See http://en.cppreference.com/w/cpp/io/fpos
It's primary purpose is to allow a seek operation to return to a saved position.
Also, your "endianness test" is very, very messed up. Reinterpreting a character string as a short? C doesn't work that way. Maybe if you had used "\x01\x00"

Answer 2

File open mode must be in ios::binary mode not to catch special characters.