I have three C++ structures that I need to send as parameters when calling a DLL method from C#.
I simplified them as the following:
typedef struct
{
int data1;
int data2;
} A;
typedef struct
{
int numStructA;
A *pStructA;
int moreData;
} B;
typedef struct
{
TCHAR *pStr;
B structB;
} C;
The following is the C++ function I need to call from C#:
int func(C *pStructC, int numStructC);
In my C# code, I define the structs as the following:
[StructLayout(LayoutKind.Sequential, Pack = 1)]
private struct A
{
public int data1;
public int data2;
}
[StructLayout(LayoutKind.Sequential, Pack = 1)]
private struct B
{
public int numStuctA;
public IntPtr structA;
public int moreData;
}
[StructLayout(LayoutKind.Sequential, Pack = 1)]
private struct C
{
[MarshalAs(UnmanagedType.LPTStr)]
public string Str;
[MarshalAs(UnmanagedType.Struct)]
public B structB;
}
[DllImport("somedll.dll")]
private static extern int func(IntPtr pStructC, int size);
I tried to marshal the nested structures. However, the C++ function does not receive the data correctly. So far only the data that comes before the nested structure is sent correctly to the C++ function.
How can I marshal the nested structures so the C++ method receives the correct data? Thanks in advance.
Related
How would you marshall this nested array of structure in C#?
C struct:
typedef struct
{
unsigned int appVersionNumber;
unsigned int networkId;
struct
{
int code;
int endDate;
} profiles[4];
} CardEnvHolder;
My C# attempt:
[StructLayout(LayoutKind.Sequential)]
unsafe struct CardEnvHolder
{
public uint appVersionNumber;
public uint networkId;
public Profiles[] profiles;
}
[StructLayout(LayoutKind.Sequential)]
struct Profiles
{
public int code;
public int endDate;
}
C# Main:
unsafe
{
CardEnvHolder envhold = new CardEnvHolder();
void* ptr = (void*)&envhold; //Error here
EnvHolderTest(ptr);
Console.WriteLine(envhold.profil[1].code);
}
Unfortunately I get the error CS0208 "Cannot take the address of, get the size of, or declare a pointer to a managed type ('T')"
As requested,
EnvHolder C function:
void EnvHoldInit(CardEnvHolder* envhold)
{
envhold->appVersionNumber = 4;
envhold->networkId = 8;
envhold->profiles[1].code = 84;
printf("%d\n", envhold->profiles[1].code);
envhold->profiles[1].code++;
}
EXPORT void EnvHolderTest(void* envhold)
{
EnvHoldInit(envhold);
}
EnvHolder C# prototype:
[DllImport("Sandbox.dll", CallingConvention = CallingConvention.Cdecl)]
extern static unsafe void EnvHolderTest([In, Out] void* envhold);
The Sctruct
I am not much of a C# or C programmer and have not found much guidance on specifying pointers and structs within a struct. I am attempting to import the following from a C dll into a C# program:
#define MAXFILENAME 259
struct IDentry {
char* IDname;
int length;
};
typedef struct IDentry idEntry;
struct SMOutputAPI {
char name[MAXFILENAME + 1];
FILE* file;
struct IDentry *elementNames;
long Nperiods;
int FlowUnits;
int Nsubcatch;
int Nnodes;
int Nlinks;
int Npolluts;
int SubcatchVars;
int NodeVars;
int LinkVars;
int SysVars;
double StartDate;
int ReportStep;
__int64 IDPos;
__int64 ObjPropPos;
__int64 ResultsPos;
__int64 BytesPerPeriod;
};
I am not sure how to handle the *elementsNames, file or name properties. What I have so far in C# is:
int MAXFILENAME = 259
[StructLayout(LayoutKind.Sequential)]
public struct SMOutputAPI
{
[MarshalAs(UnmanagedType.ByValArray, SizeConst = MAXFILENAME+1)]
public string name;
IntPtr file;
IntPtr elementNames;
public long Nperiods;
public int FlowUnits;
public int Nsubcatch;
public int Nnodes;
public int Nlinks;
public int Npolluts;
public int SubcatchVars;
public int NodeVars;
public int LinkVars;
public int SysVars;
public double StartDate;
public int ReportStep;
public int IDPos;
public int ObjPropPos;
public int ResultsPos;
public int BytesPerPeriod;
};
The C# application builds fine, but when I call the C initialization function that should return a new SMOutputAPI struct I get an error:
System.Runtime.InteropServices.MarshalDirectiveException
Method's type signature is not PInvoke compatible.
Any thoughts on how to properly specify this struct in C# would be much appreciated. Thanks!
Initializing the Struct
The struct is initialized in the c-code with:
SMOutputAPI* DLLEXPORT SMO_init(void)
//
// Purpose: Returns an initialized pointer for the opaque SMOutputAPI
// structure.
//
{
SMOutputAPI *smoapi = malloc(sizeof(struct SMOutputAPI));
smoapi->elementNames = NULL;
return smoapi;
}
The corresponding c# code is:
[DllImport("swmm-output.dll")]
static extern SMOutputAPI SMO_init();
static void Main(string[] args)
{
Console.Write("Hello World!");
SMOutputAPI SMO = SMO_init();
}
I am trying to send an array of simple struct from c# to a c++ DLL and to get the size elements of the array.
My c++ code is:
struct TestStruct
{
int m_Int;
};
unsigned int _declspec(dllexport) __stdcall GetSysData(LPSAFEARRAY FAR* ppsaFiles)
{
return (*ppsaFiles)->rgsabound[1].cElements;
}
My c# code is:
[StructLayout(LayoutKind.Sequential, Pack = 1)]
public struct InnerStruct
{
public int m_Int;
}
[DllImport("DimMonitorDll.dll", EntryPoint = "GetSysData", CallingConvention = CallingConvention.StdCall)]
public static extern int GetSysData([MarshalAs(UnmanagedType.LPArray)] ref InnerStruct[] x);
public void run()
{
InnerStruct[] test_struct;
test_struct = new InnerStruct[5];
var count = GetSysData(ref test_struct);
}
The problem is that I get count = 0 .
I have tried many things I found on the web, but I didn't success to figure it out.
I will appreciate any help,
Thanks!
as i am new to the unmanaged world, and after a success test of interacting with c++ DLL on a simple task,
i am now trying to consume in c#, data manipulated by c++ via an array of struct
i have also tried to wrap the struct[] within another struct to simplify the marshal but i did not succeed in any way.
what is the correct (and most efficient performance wise) way to handle the data returned from c++ given the code below.
C#
[StructLayout(LayoutKind.Sequential)]
public struct chars
{
public int V;
//[MarshalAsAttribute(UnmanagedType.ByValTStr, SizeConst = 10)]
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 32)]
public char[] testStr;
}
[DllImport("ExportStructArr.dll", CallingConvention = CallingConvention.Cdecl), SuppressUnmanagedCodeSecurity]
public static extern void dodata(int requestedMasterArrLength, int requestedStringSize,[MarshalAs(UnmanagedType.LPArray), Out()] chars[] Cars);
//tried also this signature
public static extern void dodata(
int requestedMasterArrLength,
int requestedStringSize,
out IntPtr chars);
c++
#ifdef EXPORTSTRUCTARR_EXPORTS
#define EXPORTSTRUCTARR_API extern "C" __declspec(dllexport)
typedef struct {
int Id;
char *StrVal;
}Unit;
EXPORTSTRUCTARR_API void dodata(int requestedMasterArrLength,int requestedStringSize, Unit **UntArr)
{
int ccountr,count;
count=0;
*UntArr = (Unit*)LocalAlloc(0, requestedMasterArrLength * sizeof(Unit));
Unit *CurU = *UntArr;
while(count!= requestedMasterArrLength)
{
char dummyStringDataObject[]= "abcdefgHi";
CurU[count].StrVal = NULL;
dummyStringDataObject[0] = count+'0';
CurU[count].Id = count;
CurU[count].StrVal= (char*) LocalAlloc(0,(sizeof(char)* requestedStringSize));
ccountr=0;
while(ccountr!= requestedStringSize){
CurU[count].StrVal[ccountr] = dummyStringDataObject[ccountr];
++ccountr;
}
++count;
}
}
I am trying to figure out how to embed a simple structure inside another structure that is passed to a C dll from c#. How do you marshall the embedded structure? Stripped down to essentials.
//The C code
typedef struct {
int a;
int b;
} A;
typedef struct {
int c;
A myStruct;
} B;
//The c# code:
using System.Runtime.InteropServices;
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class A{
int a;
int b;
}
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class B{
int c;
public IntPtr A;
}
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class B{
int c;
public A a;
}
You need IntPtr only if B is defined as:
typedef struct {
int c;
A* myStruct;
} B;