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Browse - programming tips - win32 get stdio handle from windows file handle

Date: 2010may6
OS: Windows
Language: C/C++

Q.  How do I convert a Window file HANDLE into a stdio FILE * handle?


A.  Use _open_osfhandle() and _fdopen() like this:

	#include <stdio.h>
	#include <io.h>
	#include <fcntl.h>

	#if (_MSC_VER >= 1400)		// Visual C++ 8.0 (Visual Sutdio 2005)
	#define OSF_HANDLE_TYPE		intptr_t
	#else
	#define OSF_HANDLE_TYPE		long
	#endif

	FILE *OsHandleToStd(HANDLE h, LPCSTR szMode)
	{
		int		flags = 0;
	  	int		n;
	
		if (strchr(szMode, 'a')) flags |= O_APPEND;
		if (strchr(szMode, 'r')) flags |= O_RDONLY;
		if (strchr(szMode, 't')) flags |= O_TEXT;
	
		if ((n = _open_osfhandle((OSF_HANDLE_TYPE)h, flags)) < 0) return NULL;
		return _fdopen(n, (LPSTR)szMode);
	}

	void ExampleUse()	// Error checking remove for clarity
	{
		HANDLE		h;
		FILE		*f;

		h = OpenForRead("myfile.txt");	// This function is defined elsewhere on davekb.com
		f = OsHandleToStd(h, "rt");	// Use the above function
	}

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