File IO between C/C++ libs and .NET Framework

[Eat_My_Shortz]

I'm trying to interoperate between file IO operations, on an open file,
between unmanaged C++ code and Managed C++, using the .NET framework.

Basically, at present, I have a C-style FILE* object, with an open
file. I would like to do some operations on this file, then while it's
still open, convert it into a .NET FileStream and do some processing
there.

I've noted that .NET's FileStream has a constructor:
public FileStream(IntPtr handle, System.IO.FileAccess access)
I assume the IntPtr argument is designed to interop with unmanaged
code. I've tried passing the FILE* in there, but get the error "The
handle is invalid" (Note this is a perfectly valid open file, opened
with fopen and can be read/written to using fread/fwrite/fgetc/fprintf,
etc).

So, next I go looking for the C++ library's file operations. I try some
sample code with the std:fstream object:
std:fstream outData;

outData.open("test.txt", ios::app);

outData << "Hello World!" << endl;

// Now add .NET Framework FileStream
IntPtr odNet = IntPtr(&outData);

FileStream* fs = new FileStream(odNet, FileAccess::Write);

Still the same: The Handle is invalid.

I've googled everywhere, and the most information anyone can provide on
this overload is that indeed, it does take an IntPtr, which is a Handle
to a file. Thanks a lot.

So, can anyone answer:
1. How do you get a Handle to a file, if this isnt the right way?
2. Can FileStream actually interop with C's FILE*?
3. Can FileStream actually interop with C++'s std:fstream?
4. How do I "plug" it in?

Note: I'd really rather interop with C's FILE* if that's at all
possible, since I have a LOT of code using it.

If not, I assume I just have to store the file position, close the
file, then reopen it in .NET, and seek to that position again, right?
Annoying...
Thanks to anyone who replies.

 

[Ioannis Vranos]

I'm trying to interoperate between file IO operations, on an open file,
between unmanaged C++ code and Managed C++, using the .NET framework.

Basically, at present, I have a C-style FILE* object, with an open
file. I would like to do some operations on this file, then while it's
still open, convert it into a .NET FileStream and do some processing
there.

I've noted that .NET's FileStream has a constructor:
public FileStream(IntPtr handle, System.IO.FileAccess access)
I assume the IntPtr argument is designed to interop with unmanaged
code. I've tried passing the FILE* in there, but get the error "The
handle is invalid" (Note this is a perfectly valid open file, opened
with fopen and can be read/written to using fread/fwrite/fgetc/fprintf,
etc).

So, next I go looking for the C++ library's file operations. I try some
sample code with the std:fstream object:
std:fstream outData;

outData.open("test.txt", ios::app);

outData << "Hello World!" << endl;

// Now add .NET Framework FileStream
IntPtr odNet = IntPtr(&outData);

FileStream* fs = new FileStream(odNet, FileAccess::Write);

Still the same: The Handle is invalid.

I've googled everywhere, and the most information anyone can provide on
this overload is that indeed, it does take an IntPtr, which is a Handle
to a file. Thanks a lot.

So, can anyone answer:
1. How do you get a Handle to a file, if this isnt the right way?
2. Can FileStream actually interop with C's FILE*?
3. Can FileStream actually interop with C++'s std:fstream?
4. How do I "plug" it in?

Note: I'd really rather interop with C's FILE* if that's at all
possible, since I have a LOT of code using it.

If not, I assume I just have to store the file position, close the
file, then reopen it in .NET, and seek to that position again, right?
Annoying...
Thanks to anyone who replies.

This is off topic in clc++, you should ask in
microsoft.public.dotnet.languages.vc.


If it doesn't appear in your news server use the public MS news server:

msnews.microsoft.com


I think however that the cleanest way is the one you mentioned in the end.


Or use one method only.

 

[Eat_My_Shortz]

Sorry about that. This usenet thing is hard to navigate!
Thanks, I think I'll just close and reopen the file... hrm. Thx for ur
help.