是否有一个Windows等同于fdopen的手柄？ [英] Is there a Windows equivalent to fdopen for HANDLEs?

问题描述

在Unix上，如果有一个文件描述符（从插座，管道例如，或者从你的父进程继承），你可以打开一个缓冲I / O FILE * 流它与 fdopen（3） 。

In Unix, if you have a file descriptor (e.g. from a socket, pipe, or inherited from your parent process), you can open a buffered I/O FILE* stream on it with fdopen(3).

是否有 HANDLE S于Windows中的相同呢？如果你有一个 HANDLE 这是从你的父进程（从标准输入，标准输出，或标准错误不同），或从 CreatePipe ，是有可能得到一个缓冲 FILE * 流？ MSDN文档是否 _fdopen ，但适用于>按 _open HANDLE 秒。

Is there an equivalent on Windows for HANDLEs? If you have a HANDLE that was inherited from your parent process (different from stdin, stdout, or stderr) or a pipe from CreatePipe, is it possible to get a buffered FILE* stream from it? MSDN does document _fdopen, but that works with integer file descriptors returned by _open, not generic HANDLEs.

推荐答案

不幸的是， HANDLE 是由 FILE *完全不同的野兽 S和文件描述符。 CRT的最终处理在 HANDLE 取值方面的文件和相关联的 HANDLE s到文件描述符。在将这些文件描述符 FILE *备份结构的指针。

Unfortunately, HANDLEs are completely different beasts from FILE*s and file descriptors. The CRT ultimately handles files in terms of HANDLEs and associates those HANDLEs to a file descriptor. Those file descriptors in turn backs the structure pointer by FILE*.

幸运的是，在描述函数提供了这个MSDN页面方法来改变的文件结构，文件描述符，和一个Win32文件句柄的文件重新presentation：

Fortunately, there is a section on this MSDN page that describes functions that "provide a way to change the representation of the file between a FILE structure, a file descriptor, and a Win32 file handle":

  
• _fdopen ， _wfdopen ：与关联起来，这是一个文件流
    previously打开低级别的I / O，并返回一个指向打开
    流。

  
• _fileno ：获取与流相关的文件描述符

  
• _get_osfhandle ：返回操作系统文件句柄相关联
    与现有的C运行时文件描述符

  
• _open_osfhandle ：Associates的C运行时文件与描述符
    现有的操作系​​统文件句柄。

  

• _fdopen, _wfdopen: Associates a stream with a file that was previously opened for low-level I/O and returns a pointer to the open stream.
• _fileno: Gets the file descriptor associated with a stream.
• _get_osfhandle: Return operating-system file handle associated with existing C run-time file descriptor
• _open_osfhandle: Associates C run-time file descriptor with an existing operating-system file handle.

看起来像你需要的是 _open_osfhandle 后跟 _fdopen 来>获得 FILE * 从 HANDLE 。

Looks like what you need is _open_osfhandle followed by _fdopen to obtain a FILE* from a HANDLE.

下面是涉及 HANDLE一个例子■从获得的CreateFile（）。当我测试了它，它显示的文件的test.txt的前255个字符并追加---世界您好---！在文件的结尾：

Here's an example involving HANDLEs obtained from CreateFile(). When I tested it, it shows the first 255 characters of the file "test.txt" and appends " --- Hello World! --- " at the end of the file:

#include <windows.h>
#include <io.h>
#include <fcntl.h>
#include <cstdio>

int main()
{
    HANDLE h = CreateFile("test.txt", GENERIC_READ | GENERIC_WRITE, 0, 0,
        OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0);
    if(h != INVALID_HANDLE_VALUE)
    {
        int fd = _open_osfhandle((intptr_t)h, _O_APPEND | _O_RDONLY);
        if(fd != -1)
        {
            FILE* f = _fdopen(fd, "a+");
            if(f != 0)
            {
                char rbuffer[256];
                memset(rbuffer, 0, 256);
                fread(rbuffer, 1, 255, f);
                printf("read: %s\n", rbuffer);
                fseek(f, 0, SEEK_CUR); // Switch from read to write
                const char* wbuffer = " --- Hello World! --- \n";
                fwrite(wbuffer, 1, strlen(wbuffer), f);
                fclose(f); // Also calls _close()
            }
            else
            {
                _close(fd); // Also calls CloseHandle()
            }
        }
        else
        {
            CloseHandle(h);
        }
    }
}

这应该管正常工作。

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