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unsigned char ** equivalent in c# and have to write the return value in a file
I have to call a win32 dll function
int func1(int arg1, unsigned char *arg2, int *arg3);
and i wrote wrapped c# as
public extern int fuc1(int arg1, out IntPtr arg2, out IntPtr arg3);
The arg2 has to allocate 2048 bytes and send it to the win32 dll. I'll get arg2 and arg3 as output.
how can i declare in c# test application as well as c# wrapper. am i doing it right ?
byte in C# is unsigned 8-bit int. byte[] is an array of them. To get a pointer to this array, use:
var myArray = new byte[2048];
fixed(byte* arg2 = myArray)
{
// use arg2
}
or:
var myArray = new byte[2048];
GCHandle pinnedRawData = GCHandle.Alloc(myArray, GCHandleType.Pinned);
try
{
// Get the address of the data array
IntPtr pinnedRawDataPtr = pinnedRawData.AddrOfPinnedObject();
}
finally
{
// must explicitly release
pinnedRawData.Free();
}
Alternatively, if the called function will not cache a pointer to the array, you can simply do this:
public static extern int fuc1(int arg1, [In,Out] byte[] arg2, ref int arg3);
var arg1 = 0;
var arg2 = new byte[2048];
int arg3 = 42; // If this value won't be used, you can skip initializing arg3 and mark arg3 as out instead of ref (of course, this is pedantic and extraneous, and C# shouldn't even have 'out' as a keyword)
func1(arg1, arg2, ref arg3);
P/Invoke will pin it automatically.