CopyFile fails with error code 3 (ERROR_PATH_NOT_FOUND) - c++

Question

So, before starting, I have been researching (not only on Stack Overflow) and I can't find a solution to my problem.
I am trying to copy a file to a certain place (and if possible, change its name at the same time I copy it) using Windows' CopyFile function.
I've created a sample program to show the error.
#include <iostream>
#include <Windows.h>
using namespace std;
int main()
{
cout << "Copy in progress" << endl;
bool X = CopyFile(L"test.txt", L"C:\\", 1); //NOT C: nor C:\\
if (!X){ cout << "FALLO AL COPIAR\n"; cout << "Error: "<<GetLastError();}
else{ cout << "COPIADO CORRECTO"; }
cin.get(); cin.get();
return 0;
}
GetLastError() returns 3 - which means ERROR_PATH_NOT_FOUND - but, believe me, I've checked every file (test.txt is in the same place as the built .exe, I'm running as admin...) and it still gives 3.
I can't manage to make it work. Notice the L"test" this is done because I use Visual Studio with certain character set settings, I've tried to change that config and use "test.txt" -> Still error 3.

Answer 1

You need to provide a filename:
bool X = CopyFile(L"test.txt", L"C:\\test.txt", 1);

Answer 2

You may check the function signature from the MSDN:
BOOL WINAPI CopyFile(
_In_ LPCTSTR lpExistingFileName,
_In_ LPCTSTR lpNewFileName,
_In_ BOOL bFailIfExists
);
I suppose, it requires not target directory (as e.g. cp command would), but the entire file name. Hint: make sure that all directories before the final file name are created when you call CopyFile.
Yet another hint: on POSIX systems, you have no similar routine (well, you have something similar on OS X, but it's OS-specific). However, here's what you can do (and this is how CopyFile actually works behind the scene):
Open two file handles via open for POSIX or CreateFile for Windows. One handle is opened for reading (source file) and the other one is opened for writing (destination file).
Read from the handle that you opened for reading into the temporary buffer (BUFSIZ buffer size is usually enough).
Write the data from the buffer into the handle opened for writing.
Repeat until there are bytes available into the readable handle.
This is how it generally works, though OS-specific routines may be tuned with some black magic (e.g. they can perform memory mapping, send file from one descriptor into the other without exiting from kernel mode, etc.).

Answer 3

try:
CopyFile(L"test.txt", L"C:\\test.txt", 1);