如何从 fopen FILE 结构中获取文件 HANDLE? [英] How do I get the file HANDLE from the fopen FILE structure?

问题描述

fopen 函数返回一个指向 FILE 结构的指针，应该将其视为不透明值，而不处理其内容或含义.

The fopen function returns a pointer to a FILE structure, which should be considered an opaque value, without dealing with its content or meaning.

在 Windows 上，C 运行时是 Windows API 的包装器，fopen 函数依赖于 CreateFile 函数.CreateFile 函数返回一个 HANDLE，供其他 Windows API 使用.

On Windows, the C runtime is a wrapper of the Windows API, and the fopen function relies on the CreateFile function. The CreateFile function returns a HANDLE, which is used by other Windows API.

现在，我需要在使用 fopen 和 FILE* 的库的深处使用 Windows API.那么:有没有办法从 FILE 结构中获取 HANDLE ?由于这是特定于编译器的，我的意思是在 MSVC 运行时库上.

Now, I need to use Windows API deep inside of a library that uses fopen and FILE*. So: is there a way to get the HANDLE from the FILE structure? As this is compiler specific, I mean on the MSVC runtime library.

我知道这将是一个丑陋的、不可移植的 hack，如果 Microsoft 更改 FILE 的内部格式，这可能会破坏......但我正在一个封闭的系统上开发(即在 Windows CE 嵌入式系统上)并且重构库将是困难和耗时的.

I understand that this would be an ugly, non-portable hack, and that could broke if Microsoft changes the internal format of FILE... but I'm developing on a closed system (i.e. on a Windows CE embedded system) and refactoring the library would be difficult and time consuming.

推荐答案

使用 _fileno 后跟 _get_osfhandle.完成后不要忘记_close它.

Use _fileno followed by _get_osfhandle. Don't forget to _close it when you are done.

我不清楚 _get_osfhandle 在 WinCE 上是否受支持.然而，WinCE _fileno 的文档说它返回一个文件句柄"而不是描述符".YMMV 但这表明您可以直接使用 _fileno 返回值作为 WinCE 上的句柄.

it's not clear to me that _get_osfhandle is supported on WinCE. However the docs for WinCE _fileno say it returns a "file handle" rather than "descriptor". YMMV but this suggests that you can maybe just use _fileno return value directly as a handle on WinCE.

#2 此人的经验支持该理论.

如果你看看我在 1 月 29 日发布到列表中的头文件你可以看到我是如何处理文件创建/处理问题的.我没有用句柄替换所有 FILE* 项目.请参阅以下片段文件io.cpp:

"If you take a look at the header files that I posted to the list on Jan 29 you can see how I handled the file creation/handle problem. I didn't have to replace all FILE* items with HANDLEs. See the following snippet from fileio.cpp:

#ifndef q4_WCE

  FlushFileBuffers((HANDLE) _get_osfhandle(_fileno(_file)));
  HANDLE h = ::CreateFileMapping((HANDLE)
_get_osfhandle(_fileno(_file)),
                        0, PAGE_READONLY, 0, len, 0);
#else

  FlushFileBuffers((HANDLE) _fileno(_file));
  HANDLE h = ::CreateFileMapping((HANDLE) _fileno(_file),
                    0, PAGE_READONLY, 0, len, 0);
#endif //q4_WCE

事实证明 _fileno 返回一个句柄.你只需要投射它."

It turns out that _fileno returns a handle. You just have to cast it."

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