Unmanaged pointer

  • Thread starter Thread starter eusebiu
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eusebiu

Hello... I am making a Sytem.IntPtr with Marshal.AllocHGlobal(int)
(Allocates memory from the unmanaged memory of the process using
GlobalAlloc - MSDN Definition for Marshal.AllocHGlobal) and after
copying the data from a byte[] buffer to the IntPtr(with
Marshal.Copy), I send the IntPtr to an unmanaged library. In the
unmanaged library the function's signature has a unsigned char *
parameter(my IntPtr from C#) and in function's code-block I want to
get the pointer's value.

I use this code to put the pointer's value into a txt file

//C++ code
char* b = new char[10];
sprintf(b,"%2d", (int)pMyPointer);
ofstream out((char *)"aaa.txt");
out.write((const char*)b, 10);
delete[] b;

In C#, when debugging, I have a value for my System.IntPtr but when I
open the txt file, I see other value.

Why is that? Isn't Marshal.AllocHGlobal return pointer a pointer on
the unmanaged heap to an unmanaged memory?
Thanks
 
It seems like you are just trying to pass a string to your function.
Why not just use a String parameter and declare the function with the
MarshalAs attribute with a value of UnmanagedType.LPStr?
 
eusebiu said:
Hello... I am making a Sytem.IntPtr with Marshal.AllocHGlobal(int)
(Allocates memory from the unmanaged memory of the process using
GlobalAlloc - MSDN Definition for Marshal.AllocHGlobal) and after
copying the data from a byte[] buffer to the IntPtr(with
Marshal.Copy), I send the IntPtr to an unmanaged library. In the
unmanaged library the function's signature has a unsigned char *
parameter(my IntPtr from C#) and in function's code-block I want to
get the pointer's value.

I use this code to put the pointer's value into a txt file

//C++ code
char* b = new char[10];
sprintf(b,"%2d", (int)pMyPointer);
ofstream out((char *)"aaa.txt");
out.write((const char*)b, 10);
delete[] b;
Click to expand...

I think that ought to work, but really, that's some atrocious code. Try
instead:

ofstream out("aaa.txt");
out << hex << pMyPointer << flush;
In C#, when debugging, I have a value for my System.IntPtr but when I
open the txt file, I see other value.
Click to expand...

Maybe two different runs of the program? The pointer isn't guaranteed to be
the same every time.

Anyway, is there are reason you aren't using a pinned byte*?
 
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