I am trying to handle a C++ DLL which in turn connects to a C# DLL.
My problem is when I want to send or receive arrays between C++ and C# DLLs.
I have created the C# DLL and C++ DLL, so I can modified all the files. Within the C# DLL, I must necessarily have an array of string an another of double because that is where I make use of other functions unrelated to this question. (The declaration of the function that I have to use in C# DLL is Error SetMultipleChannelValues(string[] names,double[] values).
I am using CLI in Visual Studio 2015 to compile and generate all DLLs and projects.
Here it is the C# code that I have:
public static Error SetMultipleSignals(string[] signals, double[] values)
{
Error error = null;
error = workspace.SetMultipleChannelValues(signals, values);
if (error.IsError)
Console.WriteLine("[DLL] Error in SetMultipleChannelValues(). Code: " + error.Code + ". Message: " + error.Message);
return error;
}
Here it is the C++ code that I have:
bool setMultipleSignals(double* setSignal_values)
{
array<double, DEFAULT_SETSIGNAL_SIZE> values;
for (int index = 0 ; index < DEFAULT_SETSIGNAL_SIZE ;index++)
{
values[index] = *(setSignal_values + index);
}
if (!veristand_wrapper_cs::VeriStand_dll::SetMultipleSignals(setSignals_path, values)) // This is the call to C# function
return true;
else
return false;
}
Here it is the C++ header that I have:
#pragma once
#define VERISTAND_WRAPPER_CPP __declspec(dllexport)
#include <string>
#include <iostream>
#include <windows.h>
#include <array>
using namespace std;
using namespace System;
using System::Runtime::InteropServices::Marshal;
#using "veristand_wrapper_cs.dll" // This is the C# DLL
#define DEFAULT_SETSIGNAL_SIZE 100
extern "C" VERISTAND_WRAPPER_CPP bool setMultipleSignals(double* setSignal_values); // This function is called from API C++
I pass the double array with a pointer to double as a parameter from my C++ application, but I have to pass to C# DLL an array, so I have tried to build a whole array of double before pass it.
The array setSignals_path is created as a global array in this C++ DLL as array<String^, DEFAULT_SETSIGNAL_SIZE> setSignals_path;.
The problem is that the call of C# function provides me an error that says that I can not call the function with these arguments. It expects array<System::String^> ^signals, array<double> ^values and I am passing std::array<System::String^, 100Ui64>, std::array<double, 100Ui64>
The concept of my idea is simple. From the C++ API, pass a pointer to the array of doubles, so that the function of my DLL in C++ passes the array of doubles and strings to the DLL of C#, and it returns the array of modified doubles to be able to indicate to the API from C++ that the values have been modified from that memory address.
Would anyone know how to approach this problem or how to do it in some other way to make it work?
It looks like you are using c++/cli. So you can actually use .Net types in native code.
In C++/cli you need to explicitly declare if a variable is a reference, that is what the ^ is for. Your arrays is declared without this, but your method needs a reference. You will also need to allocate your array on the managed heap. So your array should probably be declared as
array<double>^ values = gcnew array< double>(DEFAULT_SETSIGNAL_SIZE);
But it was a while ago I coded c++/cli, so I may have missed something. See How to use arrays in c++/cli. It also looks like you may be able to use ref new instead of gcnew
Use following. The size of array must be 100, or add another parameter before the string array indicating length. The string in code is a byte array terminating with '\0'. c++ must use a method that will read the null terminated string. A double is 8 bytes so the 100 double can be consecutive memory locations (800 bytes).
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct StringArray
{
public IntPtr[] unmanagedArray;
}
public struct DoubleArray
{
public double[] values;
}
public static Error SetMultipleSignals(IntPtr signals, IntPtr values)
{
const int DEFAULT_SETSIGNAL_SIZE = 100;
StringArray stringStruct = new StringArray();
stringStruct.unmanagedArray = new IntPtr[DEFAULT_SETSIGNAL_SIZE];
Marshal.PtrToStructure(signals, stringStruct);
string[] strArray = new string[DEFAULT_SETSIGNAL_SIZE];
for(int i = 0; i < DEFAULT_SETSIGNAL_SIZE; i++)
{
strArray[i] = Marshal.PtrToStringAnsi(stringStruct.unmanagedArray[i]);
}
DoubleArray dArray = new DoubleArray();
dArray.values = new double[DEFAULT_SETSIGNAL_SIZE];
dArray = Marshal.PtrToStructure<DoubleArray>(values);
return null;
Here is going the other way.
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct StringArray
{
public IntPtr[] unmanagedArray;
}
static void Main(string[] args)
{
string[] strArray = { "Message 1", "Message 2", "Message 3"};
StringArray stringStruct = new StringArray();
stringStruct.unmanagedArray = new IntPtr[strArray.Length];
for (int i = 0; i < strArray.Length; i++)
{
stringStruct.unmanagedArray[i] = Marshal.StringToBSTR(strArray[i]);
}
IntPtr unmanagedArray = Marshal.AllocHGlobal(Marshal.SizeOf(stringStruct));
Marshal.StructureToPtr(stringStruct, unmanagedArray, false);
}
Related
Alright, here is the deal. I am trying to interface a C++ dll with an indicator written for the NinjaTrader platform (which is written in ninjascript...essentially C# with some platform specific code additions). TO make my dll work the way it is intended, I need to be able to pass a struct array from the indicator to the dll. In the indicator code, I am passing the struct array via ref. In the dll, I am trying to accept the struct array as a pointer. This allows me to edit the contents in the dll, without trying to figure out a way to pass a horde of information back to NinjaTrader. Basically, the dll receives the struct array pointer, which gives it access to the contents directly. Then, when the dll function returns a bool true flag to Ninja, it accesses the struct array and renders the information to the chart. Sounds simple right? I thought so too.
Here is the problem. NinjaTrader does not allow unsafe code. So, when I try to pass the struct array to the dll, and receive it as a pointer, it immediately crashes the platform. If I receive the struct array as a pointer to a ref (*&), then it works, but....once control is passed back to Ninja, all the edits done in the struct array are non-existent.
So, to speed up this process, I have created a very brief indicator, and dll code set which demonstrates what I am trying to do.
Here is the ninja indicator code:
[StructLayout(LayoutKind.Sequential)]
public struct TestStruct
{
public int x, y;
}
TestStruct[] test = new TestStruct[2];
protected override void OnBarUpdate()
{
if(CurrentBar < Count - 2) {return;}
test[0].x = 10;
test[0].y = 2;
test[1].x = 0;
test[1].y = 0;
Print(GetDLL.TestFunk(ref test));
Print("X0: " + test[0].x.ToString() + " Y0: " + test[0].y.ToString());
Print("X1: " + test[1].x.ToString() + " Y1: " + test[1].y.ToString());
}
class GetDLL
{
GetDLL() {}
~GetDLL() {}
[DllImport("testdll.dll", CallingConvention = CallingConvention.StdCall, EntryPoint = "TestFunk")]
public static extern int TestFunk(
[In,MarshalAs(UnmanagedType.LPArray)] ref TestStruct[] test );
}
And now the C++ dll code:
#define WIN32_LEAN_AND_MEAN
#include "stdafx.h"
#include <windows.h>
#include <stdlib.h>
#include <stdio.h>
struct TestStruct
{
int x, y;
};
extern "C" __declspec(dllexport) int __stdcall TestFunk( TestStruct *testy )
{
testy[1].x = 20;
testy[1].y = 9;
int one = testy[1].x;
int two = testy[1].y;
return (one + two);
}
Now, please keep in mind, this code I have pasted in above WILL cause NinjaTrader to crash the moment you place the indicator on a chart and it becomes active. The only way I have been able to make it NOT crash is to change the arg in the C++ TestFunk function to either TestStruct *&testy or TestStruct **testy, noting that the . operators will have to be changed to -> also.
Now that I have said all that, does anyone know how to get around this limitation and get access to the actual pointer, so the dll can edit the actual values stored in the struct array, which will be reflected inside NinjaTrader....but not crash?
Huzzah! I finally figured it. First, let me post the relevant code, then I will explain.
First the C#/Ninjascript
public class TestIndicator : Indicator
{
[StructLayout(LayoutKind.Sequential)]
public struct TestStruct { public int x, y; }
static TestStruct[] testy = new TestStruct[2];
protected override void OnBarUpdate()
{
if(CurrentBar < Count - 2) {return;}
GetDLL.TestFunk( ref testy[0] );
Print("X0: " + testy[0].x.ToString() + " Y0: " + testy[0].y.ToString());
Print("X1: " + testy[1].x.ToString() + " Y1: " + testy[1].y.ToString());
}
class GetDLL
{
GetDLL() {}
~GetDLL() {}
[DllImport("testdll.dll", CallingConvention = CallingConvention.StdCall, EntryPoint = "TestFunk")]
public static extern void TestFunk( ref TestStruct testy );
}
}
And the C++ code:
struct TestStruct { int x, y; };
extern "C" __declspec(dllexport) void __stdcall TestFunk( void *t)
{
TestStruct* ptE = (TestStruct*)t;
ptE->x = 10; ptE->y = 2;
ptE++;
ptE->x = 20; ptE->y = 9;
}
First, I had to declare the struct array as static, using new, giving it a fixed memory location on the heap. Then I pass it as a ref to my C++ dll.
Inside the dll, the arg is captured as a void* data type. Next, I typecast the arg into a `TestStruct* and store it in another pointer variable (to keep my zero element reference intact).
From that point, I have a pointer that references element zero, which I can use to edit the values at element zero in the struct array. To gain access to the following elements, all I needed to do was increment the pointer. Once I did that, I had access to element one in the array.
Nothing was passed back to NinjaTrader because the dll was editing the actual values in their original memory locations. No need to pass anything back, thus attaining the reduced cpu cycles/memory operations necessary...which was my original intent.
Hopefully this helps someone stuck in a similar situation.
I asked a similar question yesterday, but this is slightly different. I am having problems passing arrays of struct from c# to c++, and getting this back again.
Here is the c++ code. Firstly, the struct:
struct Tri
{
public:
int v1, v2, v3;
}
and now the c++ dll part:
extern "C" __declspec(dllexport) void Dll_TriArray(Tri *tri)
{
int num = 10;
tri = new Tri[num];
for (int i = 0; i < num; i++)
{
tri[i].v1 = i + 5;
tri[i].v2 = i + 10;
tri[i].v3 = i + 25;
}
}
and here's the c# code, again starting with the struct:
[StructLayout(LayoutKind.Sequential)]
public struct Tri
{
public int v1, v2, v3;
}
public class Testing
{
[DllImport("testing.dll")]
static extern void Dll_TriArray(out Tri[] tryArray);
public GetTriArray()
{
Tri[] triArray;
Dll_TriArray(out triArray);
}
}
So the triArray i get when calling the GetTriArray method will come back as null. I have thought about passing an IntPtr in as the argument, but then how does one marshal an intptr into/from an array of struct?
BTW - at this stage, i'm not interested in memory leaks.
I'm not an expert (by any means) in C# but the C++ part gets passed a pointer to Tri-struct, which in C++ can be used like an dynamic array you allocate and fill that correctly but you don't have a way to get it back, because from C-perspective you'd need to modify the caller's (C#) pointer but you only get a copy and not a reference to the original.
In C++ the closest thing to what you are tying to do, would be to change the prototype to void Dll_TriArray(Tri *&tri) (call by ref, not call by copy) but I'm not sure how to interface that with C# (probably Dll_TriArray(ref triArray); ).
I need to send a struct from C# managed code to a C library. The C library will populate the values in the struct. I have been trying to pass the struct as a reference so that the C# code will get the updated data values.
This is an example C function in libshlib.so:
void sharedStruct(struct data* d)
{
d->number = calcSomething();
d->message = doSomething();
}
I can send individual parameters (int and StringBuilder) and the library code runs and returns new values to the C# code that called it.
But how can I create a struct in C# that contains both int and string and send it to the unmanaged code (C library) which will populate the values to be used back in the C# code?
The C struct might be like this:
struct data
{
int number;
char* message;
};
Right now I'm trying to establish the best way to manipulate data in the C library for use in C#. I am writing both pieces of code so I am flexible but right now I haven't been able to get it working.
If you want the struct to be populated by the C code, then you are probably looking for an out variable. Note that the mono runtime by default will use free() to deallocate any strings you pass in and you might have to take extra care with padding in structures (see the StructLayout stuff in msdn). For strings, further problems can be had with character sets.
Sample code:
Managed.cs:
using System;
using System.Runtime.InteropServices;
struct Data
{
public int number;
public string message;
}
class Managed
{
[DllImport("unmanaged")]
extern static void Foo(out Data data);
static void Main()
{
Data data;
Foo(out data);
Console.WriteLine("number = {0}, message = {1}", data.number, data.message);
}
}
unmanaged.c:
#include <string.h>
struct data
{
int number;
char* message;
};
void Foo(struct data* data)
{
data->number = 42;
data->message = strdup("Hello from unmanaged code!");
}
Test run:
$ mcs Managed.cs
$ gcc -shared -fPIC -o libunmanaged.so unmanaged.c
$ LD_LIBRARY_PATH=$PWD mono Managed.exe
number = 42, message = Hello from unmanaged code!
this is what i have so far... basically I use the c++ dll to populate the tree components set them and then return them to the managed csharp code. I am running into problems and have tried the entire day with no success. All I want to accomplish is to send a struct with a string array from c# to c++ dll where it sets all the components of the tree and then sends it back to the c#. here is what i got.. the only this that has to stay is in the c++ code is the data is set from a TCHAR array.
c++ unmanged code:
struct GetTreeStruct
{
char** components;
};
extern "C" __declspec(dllexport) void __stdcall GetTree(GetTreeStruct* myStruct);
void __stdcall GetTree(GetTreeStruct* myStruct)
{
myStruct->components = new char *[sNumberReturned]; //sNumberReturned = some #
for(i = 0;i<sNumberReturned;i++)
{
myStruct->components[i] = (char*)(arrayItem[i]); //arrayItem is TCHAR array
}
}
c# managed code:
public struct GetTreeStruct
{
[MarshalAs(UnmanagedType.LPArray)]
public string[] treeComponents;
}
[DllImport(#"C:\Users\James\Desktop\ShaggyDLL\Release\ShaggyDLL.dll")]
public static extern void GetTree(ref GetTreeStruct theStruct);
in my main..
//getTree
getTreeStruct.treeComponents = null;
Console.WriteLine("Get Tree:");
NativeMethods.GetTree(ref getTreeStruct);
list<string> list = getTreeStruct.treeComponents.ToList();
//print list
//... you know the code
any help at all would be very much appreciated. Thanks, James.
Wouldn't you need to pass 16-bit characters for C# to get it? (pun intended)
i am having trouble importing c++ unmanaged dll into C# [winform]. Can someone help?
Basically i am just trying to create a safearray of strings in c++ and trying to send it to C#.
Here is my c++ code.
extern "C" __declspec(dllexport) BOOL GetStringArr(SAFEARRAY* arr)
{
SAFEARRAY* myArray;
SAFEARRAYBOUND rgsabound[1];
rgsabound[0].lLbound = 0;
rgsabound[0].cElements = 5;
myArray = SafeArrayCreate(VT_BSTR, 1, rgsabound);
VARIANT* pvData = (VARIANT*)(myArray->pvData);
pvData[0].vt = VT_BSTR;
pvData[0].bstrVal = SysAllocString(L"FirstString");
pvData[1].vt = VT_BSTR;
pvData[1].bstrVal = SysAllocString(L"SecondString");
pvData[2].vt = VT_BSTR;
pvData[2].bstrVal = SysAllocString(L"ThirdString");
pvData[3].vt = VT_BSTR;
pvData[3].bstrVal = SysAllocString(L"FourthString");
pvData[4].vt = VT_BSTR;
pvData[4].bstrVal = SysAllocString(L"FifthString");
arr = myArray;
return true;
}
Here is my c# code.
[DllImport("MyData.dll", EntryPoint = "GetStringArr")]
public static extern bool GetStringArr([MarshalAs(UnmanagedType.SafeArray)] out Array strServerList);
i am getting exception when i call GetStringArr from C#. i am sure there is something silly i am doing. Can someone please help?
Thanks in advance.
Several problems in your C++ code. You are returning an array, that requires the argument to be SAFEARRAY**. You also are stuffing the array with the wrong data, you created an array of strings but you are writing VARIANTs. Not sure what the intention was, I'll keep variants in the code fix:
extern "C" __declspec(dllexport) BOOL GetStringArr(SAFEARRAY** arr)
{
SAFEARRAY* myArray;
SAFEARRAYBOUND rgsabound[1];
rgsabound[0].lLbound = 0;
rgsabound[0].cElements = 5;
myArray = SafeArrayCreate(VT_VARIANT, 1, rgsabound);
VARIANT* pvData = 0;
SafeArrayAccessData(myArray, (void**)&pvData);
pvData[0].vt = VT_BSTR;
pvData[0].bstrVal = SysAllocString(L"FirstString");
// etc..
SafeArrayUnaccessData(myArray);
*arr = myArray;
return true;
}
C# code:
object[] array;
bool ok = GetStringArr(out array);
[DllImport(#"blah.dll", EntryPoint = "GetStringArr")]
[return: MarshalAs(UnmanagedType.U1)]
public static extern bool GetStringArr([MarshalAs(UnmanagedType.SafeArray)] out object[] strServerList);
Some problems on both the C and .NET side of things
On the C side
Incorrect argument indirection. Since you are allocating the SAFEARRAY descriptor in the function you need a SAFEARRAY**.
The SAFEARRAY is not being filled correctly. You created the SAFEARRAY descriptor with a base type of VT_BSTR, this means that the data elements should be BSTRs.
C Code
extern "C" __declspec(dllexport)
BOOL GetStringArr(SAFEARRAY** arr)
{
SAFEARRAY* myArray;
SAFEARRAYBOUND rgsabound[1];
rgsabound[0].lLbound = 0;
rgsabound[0].cElements = 5;
myArray = SafeArrayCreate(VT_BSTR, 1, rgsabound);
BSTR* pvData = (BSTR*)(myArray->pvData);
pvData[0] = SysAllocString(L"FirstString");
pvData[1] = SysAllocString(L"SecondString");
pvData[2] = SysAllocString(L"ThirdString");
pvData[3] = SysAllocString(L"FourthString");
pvData[4] = SysAllocString(L"FifthString");
*arr = myArray;
return true;
}
On the .NET side
The Calling convention needs to be specified otherwise you will have stack issues
You should set the SafeArraySubType
You can use out string[] to get the pointer to the SAFEARRAY
.NET Code
class Program
{
static void Main(string[] args)
{
string[] data;
bool b = GetStringArr(out data);
}
[DllImport("MyData.dll",
CallingConvention = CallingConvention.Cdecl)]
public static extern bool GetStringArr(
[MarshalAs(UnmanagedType.SafeArray, SafeArraySubType=VarEnum.VT_BSTR)]
out string[] strServerList);
}
Do you have access to the native DLL's source? If so you can enable unmanaged debugging in your Managed projects options, and step thru the unmanaged code (preferably Debug build) to see what's going on. If nothing else you can enable Exceptions in the debugger options, and debug to see where the native exception gets thrown.
I recommend you add a C++/CLI project (assembly) to your C# solution. That will enable you to write code that live in both managed and unmanaged land simultaneously. That means that your C++/CLI code can create a List<string^> instead and add managed strings to it before you return it to C#. :-)