P/Invoke and FILE*

[SamoK]

Hy!

I have to invoke a function that has a FILE pointer for its parameter.
e.g.
int myfunct(FILE *f);

Does anyone know how can P/Invoke such function? And would it be possible to
pass StreamReader as a parameter to an invoked function (I know it is not
possible to do so directly)?
Thanks in advance
- Samo

[Mattias Sjögren]

Does anyone know how can P/Invoke such function?
Well first you have to aquire a FILE* from some function that uses the
same C runtime library as the DLL containing myfunc.

And would it be possible to
pass StreamReader as a parameter to an invoked function (I know it is not
possible to do so directly)?

Not directly, no.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Niki Estner]

> I have to invoke a function that has a FILE pointer for its parameter.

e.g.
int myfunct(FILE *f);
The FILE structure is (AFAIK) an internal of the standard C library, so you
won't be able to recreate it in C#. I think it can even differ between
debug/release or single-threaded/multi-threaded build. Best way to go is
probably building a wrapper in managed C++.
Does anyone know how can P/Invoke such function? And would it be possible to pass StreamReader as a parameter to an invoked function (I know it is not
possible to do so directly)?

I think there are microsoft-specific C functions that enable you to create a
FILE from a win32 HANDLE. Maybe you can create an unnamed pipe, connect one
end to the FILE, and another to your StreamReader.
Of course, this only works if your C-function treats the file as a stream,
too (i.e. doesn't reposition the file pointer)

Niki

[SamoK]

Oh my... whole bunch of stuff... :)
I think it would be beteer to dig in and rewrite this one in pure C# since
this wouldn be such on overkill.
;)

But thanks for your help.

"Niki Estner" <ni*********@cube.net> wrote in message
news:%2****************@TK2MSFTNGP11.phx.gbl...

I have to invoke a function that has a FILE pointer for its parameter.
e.g.
int myfunct(FILE *f);
The FILE structure is (AFAIK) an internal of the standard C library, so

you won't be able to recreate it in C#. I think it can even differ between
debug/release or single-threaded/multi-threaded build. Best way to go is
probably building a wrapper in managed C++.

Does anyone know how can P/Invoke such function? And would it be possible

to

pass StreamReader as a parameter to an invoked function (I know it is

not possible to do so directly)?

I think there are microsoft-specific C functions that enable you to create

a FILE from a win32 HANDLE. Maybe you can create an unnamed pipe, connect one end to the FILE, and another to your StreamReader.
Of course, this only works if your C-function treats the file as a stream,
too (i.e. doesn't reposition the file pointer)

Niki

[Dr. Len]

On Sun, 20 Jun 2004 14:55:21 +0200, "SamoK" <sn***@wetsoftware.com>
wrote:

Hy!

I have to invoke a function that has a FILE pointer for its parameter.
e.g.
int myfunct(FILE *f);

Does anyone know how can P/Invoke such function? And would it be possible to
pass StreamReader as a parameter to an invoked function (I know it is not
possible to do so directly)?
Thanks in advance
- Samo

Well, treat the FILE pointer in C# as an IntPtr. You can then import
such function using C# P/Invoke like so:

[ DllImport("YourLibrary.dll") ]
public static extern int myfunct(IntPtr filehandle);

Of course, you also need some other function the returns an usable
FILE* handle for you (I quickly made this up, dunno if it actually
works):

[ DllImport("msvcrt.dll", CharSet=CharSet.Auto) ]
public static extern IntPtr fopen(string file, string mode);