Win32 and Metro–CreateFile(2)

When a new Windows version comes out, I’m always curious about the new Windows API (Win32) functions that are added to the release.

With Windows 8, things get a little more complicated, as there are desktop apps and there are metro apps. Now, for every Windows API function the documentation states whether this API is valid for desktop apps only or for desktop apps and metro apps.

One classic function is CreateFile. This is one of the oldest functions – exists since the very first Windows NT version. In Windows 8, it’s marked for desktop apps only. This may be understandable, as the Windows Runtime has other ways to use files, such as the StorageFile class. However, Windows 8 has a new function called CreateFile2. This one, in contrast to CreateFile, can be used in desktop and metro apps. Here’s its prototype:

HANDLE WINAPI CreateFile2(

  _In_      LPCWSTR lpFileName,

  _In_      DWORD dwDesiredAccess,

  _In_      DWORD dwShareMode,

  _In_      DWORD dwCreationDisposition,

  _In_opt_  LPCREATEFILE2_EXTENDED_PARAMETERS pCreateExParams

);

Here’s the prototype of CreateFile:

HANDLE WINAPI CreateFile(

  __in      LPCTSTR lpFileName,

  __in      DWORD dwDesiredAccess,

  __in      DWORD dwShareMode,

  __in_opt  LPSECURITY_ATTRIBUTES lpSecurityAttributes,

  __in      DWORD dwCreationDisposition,

  __in      DWORD dwFlagsAndAttributes,

  __in_opt  HANDLE hTemplateFile

);

The first four arguments of CreateFile2 exist in both CreateFile and CreateFile2. The new extended parameters structure of CreateFile2 simply packages the “missing” arguments into an single optional structure:

typedef struct _CREATEFILE2_EXTENDED_PARAMETERS {

  DWORD                 dwSize;

  DWORD                 dwFileAttributes;

  DWORD                 dwFileFlags;

  DWORD                 dwSecurityQosFlags;

  LPSECURITY_ATTRIBUTES lpSecurityAttributes;

  HANDLE                hTemplateFile;

} CREATEFILE2_EXTENDED_PARAMETERS, *PCREATEFILE2_EXTENDED_PARAMETERS, *LPCREATEFILE2_EXTENDED_PARAMETERS;

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