Can I use CreateFile, but force the handle into a std::ofstream?

Question

Is there any way to take advantage of the file creation flags in the Win32 API such as FILE_FLAG_DELETE_ON_CLOSE or FILE_FLAG_WRITE_THROUGH as described here http://msdn.microsoft.com/en-us/library/aa363858(VS.85).aspx , but then force that handle into a std::ofstream?

The interface to ofstream is obviously platform independent; I'd like to force some platform dependent settings in 'under the hood' as it were.

Answer 1

It is possible to attach a C++ std::ofstream to a Windows file handle. The following code works in VS2008:

HANDLE file_handle = CreateFile(
    file_name, GENERIC_WRITE,
    0, NULL, CREATE_ALWAYS,
    FILE_ATTRIBUTE_NORMAL, NULL);

if (file_handle != INVALID_HANDLE_VALUE) {
    int file_descriptor = _open_osfhandle((intptr_t)file_handle, 0);

    if (file_descriptor != -1) {
        FILE* file = _fdopen(file_descriptor, "w");

        if (file != NULL) {
            std::ofstream stream(file);

            stream << "Hello World\n";

            // Closes stream, file, file_descriptor, and file_handle.
            stream.close();

            file = NULL;
            file_descriptor = -1;
            file_handle = INVALID_HANDLE_VALUE;
        }
}

This works with FILE_FLAG_DELETE_ON_CLOSE, but FILE_FLAG_WRITE_THROUGH may not have the desired effect, as data will be buffered by the std::ofstream object, and not be written directly to disk. Any data in the buffer will be flushed to the OS when stream.close() is called, however.