I have 2 C++ DLLs. One of them contains the following function:
void init(const unsigned char* initData, const unsigned char* key)
The other one contains this function:
BYTE* encrypt(BYTE *inOut, UINT inputSize, BYTE *secretKey, UINT secretKeySize).
Is there a way to call these 2 functions from C#? I know you can use [DllImport] in C# to call C++ functions, but the pointers are giving me a hard time.
Any help would be appreciated!
Yes, you can call both of these from C# assuming that they are wrapped in extern "C" sections. I can't give you a detailed PInvoke signature because I don't have enough information on how the various parameters are related but the following will work.
[DllImport("yourdllName.dll")]
public static extern void init(IntPtr initData, IntPtr key);
[DllImport("yourdllName.dll")]
public static extern IntPtr encrpyt(IntPtr inout, unsigned inuputSize, IntPtr key, unsigned secretKeySize);
Pieces of information that would allow us to create a better signature
Is the return of encrypt allocated memory?
If #1 is true, how is the memory allocated
Can you give a basic description on how the parameters work?
I'm guessing that all of the pointer values represents arrays / groups of elements instead of a single element correct?
[DllImport("yourdll.dll")]
static extern void init([MarshalAs(UnmanagedType.LPArray)] byte[] initData, [MarshalAs(UnmanagedType.LPArray)] byte[] key);
[DllImport("yourdll.dll")]
static extern IntPtr encrypt([MarshalAs(UnmanagedType.LPArray)] byte[] inOut, int inputSize, [MarshalAs(UnmanagedType.LPArray)] byte[] key, int secretKeySize);
For classes, you don't need to do anything special. For value types, you need to use the ref keyword.
MSDN has an article that summarizes this:
http://msdn.microsoft.com/en-us/library/awbckfbz.aspx
For pointers, what you want to use is IntPtr.
[DllImport("whatever.dll")]
static extern void init(IntPtr initData, IntPtr key);
Related
This is my C# code:
[DllImport("Tomb.dll")]
public static extern unsafe uint InjectManualMap(ulong pId, [MarshalAs(UnmanagedType.LPCStr)]string dllPath);
and for whatever reason when I attempt to use my C++ code:
extern "C" DllExport unsigned int StdCall InjectManualMap(unsigned long pid, const char* dllPath) {
ManualMapInjector* mmp = new ManualMapInjector;
std::string dll(dllPath);
unsigned int kk = mmp->Inject(pid, dll);
delete mmp;
return kk;
}
the const char* dllPath is always a bad pointer (0x000000000).
I'm not sure what's happening here, because all other solutions point to using either a StringBuilder (tested it, did the same thing), or using MarshalAs which is something the current code I have posted does.
The issue is that C# long is 64 bits wide, but C++ long, on Windows, is 32 bits wide. The pinvoke should be:
[DllImport("Tomb.dll")]
public static extern uint InjectManualMap(uint pId, string dllPath);
Note that I also removed the unsafe directive and the MarshalAs attribute which are not needed.
-In my c code I have a struct which contains many unknown sized arrays in an unmanaged dll (c code)
-I need the data of one instance of this struct marshaled over to c#, which I will later on send back to the unmanaged c code
-I do not need to manipulate this data once it gets to csharp, only hold onto it/store it for a while (so it can remain in a byte array).
-I do not want to use the keyword 'unsafe' as it is a big project and this is just one small piece and I don't want to be compiling like that.
I tried marshaling it as a lpArray and everything looks fine but when i look at the contents after coming back to the csharp, it is always empty. This type of marshaling style worked for me for dynamic arrays of various types but not the struct.
Searching the web is drawing blanks and much more complicated scenarios than my own, but if anybody has seen such a link please post it here I would be very greatful!
Thanks.
--update here is more or less the structure of my code:
c#:
[DllImport("mydll.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
private static extern int W_Thread_Connect_NET(
[MarshalAs(UnmanagedType.LPStr, SizeConst = 100)] string IPAddress,
int DevicePort,
[MarshalAs(UnmanagedType.LPArray)] byte[] connectionHandle
);
//and call it like this, with an empty struc to be populated by c (can this be done? it is comming back without the data):
byte[] myStrucParam= new byte[100];
int result = W_Thread_Connect_NET(myStrucParam, myParam1, myParam2, ...);
c:
typedef struct myStructDef{
char* myArray1,
char* myArray2,
int myInt1,
...
} mystrucObj, *pMystrucObj;
//method that i am wanting to marshal the struct as a paramter here..
MYDLL_DLLIMPORT int APIENTRY W_Thread_Connect_NET(pMystrucObj strucReturn_handle, char * IPAddress, int DevicePort, ...)
{
//(omitted)
}
You say that the C# code does not need to manipulate the struct. That makes it a pretty simple problem to solve. You can treat the struct pointer as an opaque pointer, that is an IntPtr.
First of all you add a new function to your native code:
pMystrucObj CreateStruct(void)
{
pMystrucObj res = malloc(sizeof(*res));
return res;
}
Then in your C# code you call it like this:
[DllImport("mydll.dll", CallingConvention=CallingConvention.Cdecl)]
private static extern IntPtr CreateStruct();
Now declare W_Thread_Connect_NET like this:
[DllImport("mydll.dll", CallingConvention=CallingConvention.Cdecl)]
private static extern int W_Thread_Connect_NET(
IntPtr theStructPtr,
string IPAddress,
int DevicePort,
....
);
And call it all like this:
IntPtr theStructPtr = CreateStruct();
int res = W_Thread_Connect_NET(theStructPtr, IPAddress, DevicePort, ...);
And of course you'll want to add another function named DestroyStruct to deallocate the struct's memory once you are done with it.
I hav a function in c++ DLL that has following prototype
int function(RefPar ¶ms);
how can i call this function from a c# program using "DLLImport".
when i tried like below, AccessViolationException happened while running in visual studio 2008..
[DllImport("VistaGMMDLL.dll", EntryPoint = "function"]
unsafe static extern int function(ref RefPar params);
and called as..
int ret=function(ref params);
Note:RefPar structure has many
unsigned integer values and 1 enum
value as its members.
pls anyone help me to call the function correctly..
A couple of things jump out at me. First of all I don't see why you need to use unsafe. Secondly, you probably have a calling convention mismatch, cdecl in the C++ and stdcall in the C#.
I'd do it like this:
C++
struct RESOURCE_PARAMETERS{
unsigned int uSurfaceHeight;
unsigned int uSurfaceDepth;
unsigned int uSurfaceWidth;
unsigned int uMSAAHeight;
unsigned int uMSAAWidth;
unsigned int uArraySize;
unsigned int uNumSamples;
unsigned int uMaxLod;
unsigned int uBpp;
unsigned int uprefFlag;
unsigned int uusageFlag;
RESOURCE_TYPE_REC ResourceType;
int ResourceFormat;
int iBuildNumber;
};
int function(RefPar ¶meters)
{
}
C#
[StructLayout(LayoutKind.Sequential)]
public struct RESOURCE_PARAMETERS
{
uint uSurfaceHeight;
uint uSurfaceDepth;
uint uSurfaceWidth;
uint uMSAAHeight;
uint uMSAAWidth;
uint uArraySize;
uint uNumSamples;
uint uMaxLod;
uint uBpp;
uint uprefFlag;
uint uusageFlag;
[MarshalAs(UnmanagedType.U4)]
ResourceType ResourceType;
int ResourceFormat;
int iBuildNumber;
}
[DllImport("VistaGMMDLL.dll", CallingConvention = CallingConvention.Cdecl)]
static extern int function(ref RESOURCE_PARAMETERS parameters);
RESOURCE_PARAMETERS parameters = new RESOURCE_PARAMETERS();
int result = function(ref parameters);
I'm not sure how big the enum is on the C++ size. That's why I've put an explicit MarshalAs in the C# code. If it's just a single byte, then use UnmanagedType.U1 instead. I trust you get the idea.
If your C++ function treats its parameter as an in/out parameter then using ref on the C# side is correct. If its actually an out parameter then change the code to be like this:
[DllImport("VistaGMMDLL.dll", CallingConvention = CallingConvention.Cdecl)]
static extern int function(out RESOURCE_PARAMETERS parameters);
RESOURCE_PARAMETERS parameters;
int result = function(out parameters);
Try in this way:
[StructLayout(LayoutKind.Sequential)]
public struct RefPar
{
UInt32 uint1;
UInt32 unti2;
....
}
[DllImport("VistaGMMDLL.dll", EntryPoint = "function"]
unsafe static extern int function(IntPtr params);
//calling
//fill the refParStructure
//create the IntPtr
refParStruct rs = new RefPar();
IntPtr refparPtr = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(refPar)));
Marshal.StructureToPtr(refParStruct, refparPtr,false);
ret=function(refParPtr);
Let Me know if you need more details
Another very simple way to call this function is:
Create a c++ dll warapper that link your original dll and contains this function
//c++ code
function2(uint param1, uint param2.....)
{
RefPar refpar;
refpar.param1=param1
refpar.param2=param2
function(&refpar)
}
in this way you have just to import (in C#) the dll wrapper function in this way
[DllImport("wrapperdll.dll", EntryPoint = "function2"]
static extern int function2(Uint32 param1,Uint32 param2....);
that is very simple to call.
Regards
I want to invoke one/many functions of a native library but I am unsure on the type mappings. The function in particular I am currently trying is as follows, here is the small console app which I am spiking in:
extern char *tgetstr (const char *name, char **area);
And here is my attempt at mapping this to use in a .NET console. I get an error saying, trying to read or write protected memory.
class Program
{
[DllImport("termcap.dll")]
public static extern IntPtr tgetstr(IntPtr name, IntPtr area);
static void Main(string[] args)
{
IntPtr ptr1 = new IntPtr();
IntPtr a = tgetstr(Marshal.StringToCoTaskMemAnsi("cl"), ptr1);
Console.WriteLine(Marshal.PtrToStringBSTR(a));
}
}
TIA
Andrew
You need to pass your IntPtr by ref, so the function can overwrite it. Then you also need to free the string after you've copied it, hopefully the DLL provides a matching deallocation function. StringToCoTaskMemAnsi isn't helping you any either, it's just leaking memory.
The correct p/invoke declaration is probably
[DllImport("termcap.dll", CharSet = CharSet.Ansi)]
public static extern IntPtr tgetstr(string name, ref IntPtr area);
I haven't worked with unmanaged code since 3 years but I think you can do it by marking the method parameters with MarshalAs attribute. Check this article,
MSDN
You have to pin your ptr1.
GCHandle handle = GCHandle.Alloc(ptr1, GCHandleType.Pinned);
I am making a wrapper to read TDM and TDMS files but i have a problem
[DllImport(lib, CharSet = CharSet.Auto)]
static extern int DDC_OpenFileEx(
[MarshalAs(UnmanagedType.LPStr)]
string filePath,
[MarshalAs(UnmanagedType.LPStr)]
string fileType,
int read_only,
ref long file);
works fine but
[DllImport(lib, CharSet = CharSet.Auto, SetLastError = true)]
static extern int DDC_GetNumChannelGroups(long file,
[MarshalAs(UnmanagedType.U4)]
ref int numChannelGroups);
int numGru = 0;
errCode = ReadTDM.DDC_GetNumChannelGroups(file,ref numGru);
System.Console.WriteLine("Error Code {0} GetNumChannelGroups", errCode);
gives an error -6202, // An invalid argument was passed to the library.
i have tried ref uint, uint * (unsafe), UIntPtr. The def from .h file
int __stdcall DDC_GetNumChannelGroups (DDCFileHandle file,unsigned int *numChannelGroups);
the second parametr is the problem.
it seems that unsigned int* != uint.
Does anyone have an idea how to call this function form the dll?
http://forums.ni.com/ni/board/message?board.id=60&thread.id=11821
It is the 1st argument that's declared wrong. That throws off the stack frame and prevents the unmanaged code from properly reading the pointer for the 2nd argument. "long" is 64-bits, DDCFileHandle is almost certainly a pointer, 32-bits on a 32-bit operating system.
Change the argument declaration to IntPtr. You'll also need to change the declaration of the function that returns that handle.