问题描述

有什么方法可以利用 Win32 API 中的文件创建标志，例如 FILE_FLAG_DELETE_ON_CLOSE 或 FILE_FLAG_WRITE_THROUGH，如此处所述http://msdn.microsoft.com/en-us/library/aa363858(VS.85).aspx ，然后将该句柄强制转换为 std::ofstream ?

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?

ofstream 的接口显然是平台无关的；我想在幕后"中强制执行一些平台相关的设置.

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

推荐答案

可以将 C++ std::ofstream 附加到 Windows 文件句柄.以下代码适用于 VS2008:

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
";

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

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

这适用于 FILE_FLAG_DELETE_ON_CLOSE，但 FILE_FLAG_WRITE_THROUGH 可能没有预期的效果，因为数据将被 std::ofstream 对象缓冲，而不是直接写入磁盘.但是，当调用 stream.close() 时，缓冲区中的任何数据都将刷新到操作系统.

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.

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