I am having trouble figuring out how to pass a buffer address from C# to C. I have checked several references. One seems to explain how (passing pointers referencing memory allocated in managed code to unmanaged) but when I mimic it I can't get it to work.
The output should be "This is data" but what comes out is "buffer=System.Char[]".
If I use the debugger I can see that the string "This is data" is in fact being copied properly but the address of 'buffer' in the C function is different than the address of 'buffer' in the C# code. So I'm thinking the referenced link above is assuming some other knowledge of C# which is not explained. Or maybe I just don't understand the additional answers.
Here is my code:
XBaseNamespace.cs
-----------------
// XBase functions
using System;
using System.Runtime.InteropServices;
namespace XBaseNamespace.SecondNamespace
{
class XBaseFunctions
{
[DllImport("W:\\C_sharp\\Call_C\\Debug\\C_dll.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
public static extern void ProcessBigBuffer([MarshalAs(UnmanagedType.LPArray)] char[] buffer);
}
}
Program.cs
----------
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using XBaseNamespace.SecondNamespace;
namespace Call_C
{
class Program
{
static void Main()
{
char[] buffer = new char[1000];
// initialize the buffer
// and then process it
XBaseFunctions.ProcessBigBuffer(buffer);
Console.WriteLine("buffer={0}\n", buffer);
Console.WriteLine("Press any key to exit...");
Console.ReadKey();
}
}
}
c_dll.c
-------
// C DLL experiment
#include <stdio.h>
#include <string.h>
#define DSI_DLL __declspec(dllexport)
#define CALL_TYPE //__stdcall
DSI_DLL void CALL_TYPE ProcessBigBuffer( char* buffer )
{
strcpy( buffer, "This is data" );
}
I realize I had used 'char' because I'm so used to C. I should have used 'byte'. Now the buffer displays as I would expect. Here is how I did it:
XBaseNamespace.cs
-----------------
[DllImport("W:\\Dropbox\\DSI (His)\\Windows Apps\\Debug\\DsiLibrary_CSharp.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
public static extern int XBaseRead(UIntPtr pDefineFile, [MarshalAs(UnmanagedType.LPArray)] byte[] buffer, long bytes, bool reverse, O_FLAG oflag);
Program.c
---------
byte[] buffer = new byte[160];
XBaseFunctions.XBaseRead(df2500VENDR, buffer, 160, false, XBaseFunctions.O_FLAG._O_BINARY);
foreach (byte i in buffer)
{
Console.Write("{0:X2} ", i);
}
Related
I have a .NET 6 aspcore app that loads an unmanaged dll. The dll returns C strings encoded as ISO8859-1.
Everything works fine with the Windows version but on Linux, any accented characters that come back are not translated into Unicode.
I've re-created the issue using a minimal dll & .NET console app.
The shared library code is a simple C file
#include <stdio.h>
#include <string.h>
//file is ansi encoded 8859-1 é = xE9
static char* msg = "Montréal";
extern int Test(char* buf, int buf_size)
{
if (buf != NULL && buf_size > (int)strlen(msg)) {
strcpy(buf, msg);
return ((int)strlen(buf));
}
return -1;
}
This is the .NET console app code. Note that I used StringBuilder to handle the char* buffer. I believe this is the typical way to do this.
using System.Runtime.InteropServices;
using System.Text;
Console.WriteLine($"Hello,Montréal"); //utf8 encoded source file
var buf = new StringBuilder(512);
int ret = TestImport.Test(buf, 500);
Console.WriteLine($"Hello again, {buf.ToString()}");
public static class TestImport
{
public const string _dll = "libTestLib.so";
[DllImport(_dll, CharSet = CharSet.Ansi)]
public static extern int Test( StringBuilder buf, int buf_size);
}
I'm running the app from WSL (Ubuntu 20.04) as:
$ dotnet run -c Debug -r linux-x64 --no-self-contained
Output shows as:
Hello, Montréal
Hello again, Montr�al
So how do I tell DllImport what the source encoding is? (ie CharSet = CharSet.Ansi)
Is there some .NET environment setting I'm missing?
Is there something I need to set up in the Linux environment? (I've tried changing the locale to LANG=en_US.iso88591 - which doesn't seem to do anything)
I do have build ownership over the unmanaged dll, but it isn't going to return utf-8.
Well taking #JeroenMostert's advice I'm going to marshal the params myself using a Byte[] buffer. Perhaps a custom marshaler would work - if I could figure it out.
using System.Runtime.InteropServices;
using System.Text;
Console.WriteLine($"Hello,Montréal"); //utf8 encoded source file
var buf = new Byte(512);
int ret = TestImport.Test(buf, 500);
var s = Encoding.Latin1.GetString(buf); // Latin1 = 8859-1
Console.WriteLine($"Hello again, {s}");
public static class TestImport
{
public const string _dll = "libTestLib.so";
[DllImport(_dll, CharSet = CharSet.Ansi)]
public static extern int Test( Byte[] buf, int buf_size);
}
output looks like
Hello,Montréal
Hello again, Montréal
I want to use functions from DLL in C++ with C#.
I store string data in a vector.
My C++ file contains:
#include "stdafx.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
extern "C" __declspec(dllexport) std::vector<std::string> GetProduct();
std::vector<std::string> GetProduct()
{
std::vector<std::string> vectProduct;
vectProduct.push_back("Citroen");
vectProduct.push_back("C5");
vectProduct.push_back("MOP-C5");
return vectProduct;
}
In C#
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Runtime.InteropServices;
namespace ConsoleApplication
{
class Program
{
[DllImport("ProductLibrary.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern StringBuilder GetProduct();
static void Main(string[] args)
{
StringBuilder vectProduct_impl = GetProduct();
}
}
}
I don't know how to continue to browse the array in c#.
I don't know if the use of vector is optimal. if you have other solution I'm ready.
Please help.
My favourite way for passing an array of strings C++-->C# is by using a delegate.
C#:
// If possible use UnmanagedType.LPUTF8Str
// or under Windows rewrite everything to use
// wchar_t, std::wstring and UnmanagedType.LPWStr
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
public delegate void AddAnsi([MarshalAs(UnmanagedType.LPStr)] string str);
[DllImport("CPlusPlusSide.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern void TestReturnArrayStrings(AddAnsi add);
and then
var lst = new List<string>();
TestReturnArrayStrings(lst.Add);
foreach (string str in lst)
{
Console.WriteLine(str);
}
And C++:
#include <string>
#include <vector>
extern "C"
{
__declspec(dllexport) void TestReturnArrayStrings(void (add)(const char* pstr))
{
std::string str1 = "Hello";
std::string str2 = "World";
add(str1.data());
add(str2.data());
// Example with std::vector
add("--separator--"); // You can even use C strings
std::vector<std::string> v = { "Foo", "Bar" };
// for (std::vector<std::string>::iterator it = v.begin(); it != v.end(); ++it)
for (std::vector<std::string>::const_iterator it = v.begin(); it != v.end(); ++it)
{
add(it->data());
}
add("--separator--"); // You can even use C strings
// With C++ 11
// for (auto& it: v)
for (const auto& it: v)
{
add(it.data());
}
}
}
Here the "trick" is that C# passes to C++ a delegate to the List<string>.Add() method, and C++ "fills" directly the C# List<>. The memory managed by C++ remains in the C++ side, the memory managed by the C# remains in the C# side. No problems of cross-memory ownership. As you can imagine, it is quite easy to expand the "trick" to any other .Add() method, like HashSet<string>, or Dictionary<string, string>.
As a sidenote, I've created a github with many examples about marshaling between C/C++ and C# (both .NET Framework and .NET Core/5.0).
One way to do it is to use COM's SAFEARRAY structure as it's supported by .NET (the .NET Allocator used by P/Invoke is the COM allocator), including most of associated sub types, like BSTR.
So, in C/C++, you can define this:
extern "C" __declspec(dllexport) LPSAFEARRAY GetProduct();
LPSAFEARRAY GetProduct()
{
LPSAFEARRAY psa = SafeArrayCreateVector(VT_BSTR, 0, 3);
LONG index = 0;
// _bstr_t is a smart class that frees allocated memory automatically
// it needs #include <comdef.h>
// but you can also use raw methods like SysAllocString / SysFreeString
_bstr_t s0(L"Citroen"); // could use "Citroen" if you really want ANSI strings
// note SafeArrayPutElement does a copy internally
SafeArrayPutElement(psa, &index, s0.GetBSTR());
index++;
_bstr_t s1(L"C5");
SafeArrayPutElement(psa, &index, s1.GetBSTR());
index++;
_bstr_t s2(L"MOP - C5");
SafeArrayPutElement(psa, &index, s2.GetBSTR());
index++;
return psa;
}
And in C#, you can define this:
[DllImport("ProductLibrary.dll", CharSet = CharSet.Unicode)]
[return: MarshalAs(UnmanagedType.SafeArray)]
public static extern string[] GetProduct();
I have a very large string in my c++ dll file , I need to pass it to C# as a byte array and I have no idea how to do that !
I know I can use this function in C# :
string result = System.Text.Encoding.UTF8.GetString(bytearray);
My large string is a std::string in C++
I need to know how can I convert my string to A utf8 array and send it to C# and how to get string back in C# application :)
More about the question:
I don't know how to pars byte arrays from C++ to C# like swprintf to StringBuilder .
Here's an example code for my question :
C++ Code:
#include "stdafx.h"
#include <iostream>
#include <cstdio>
#include <fstream>
BOOL APIENTRY DllMain( HMODULE hModule,
DWORD ul_reason_for_call,
LPVOID lpReserved
)
{
switch (ul_reason_for_call)
{
case DLL_PROCESS_ATTACH:
case DLL_THREAD_ATTACH:
case DLL_THREAD_DETACH:
case DLL_PROCESS_DETACH:
break;
}
return TRUE;
}
extern "C" __declspec(dllexport) void __stdcall sendasbyte(char* byte_to_send)
{
std::ifstream file_t("testfile.txt");
std::string Read_test_file((std::istreambuf_iterator<char>(file_t)),
std::istreambuf_iterator<char>());
///// NEED TO SEND Read_test_file as byte array to C# HERE :
// <-------- CODE AREA --------->
}
Here's C# Code :
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;
namespace minimal_project_testapp
{
class Program
{
[DllImport("minimal_project_test.dll", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Unicode)]
private static extern void sendasbyte(byte[] get_String_Byte);
private static byte[] data_from_cpp;
static void Main(string[] args)
{
sendasbyte(data_from_cpp);
string result = System.Text.Encoding.UTF8.GetString(data_from_cpp);
Console.WriteLine(result);
Console.ReadLine();
}
}
}
And the testfile.txt : https://textuploader.com/dvvbb
Here's how to Do That clear and perfectly :D
1 > Change your c++ function to this :
extern "C" __declspec(dllexport) char* __stdcall test_int()
{
std::ifstream file_t("testfile.txt");
std::string Read_test_file((std::istreambuf_iterator<char>(file_t)),
std::istreambuf_iterator<char>());
int size_of_st = Read_test_file.length();
std::string test1 = std::to_string(size_of_st);
char* cstr = new char [size_of_st];
std::strcpy(cstr, Read_test_file.c_str());
return cstr;
}
2 > Don't forgot to add #define _CRT_SECURE_NO_WARNINGS
3 > Add Dllimport to your C# application
[DllImport("minimal_project_test.dll", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Unicode)]
private static extern IntPtr test_int();
4 > And finally use it everywhere you need like this :
IntPtr _test_from_Cpp = test_int();
int _test_char_count = <Enter Length of your string>;
byte[] _out_char_value = new byte[_test_char_count];
Marshal.Copy(_test_from_Cpp, _out_char_value, 0, _test_char_count);
string final_string = System.Text.Encoding.UTF8.GetString(_out_char_value);
Boom! it Works !!! ;)
I am trying to import a driver dll for a piece of equipment my company uses, but I can't seem to get this to work. I am new to c# so please go easy on me. This is related to a post I made yesterday, I am attempting to convert a C program over to C#.
I wrote this code so that I could start to understand PInvoke
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
namespace PInvokeTest {
class Program {
static void Main(string[] args) {
Int32 session_handle = 0;
Byte state_buffer = 0;
Int16 result = 1, PortNum = 1, PortType = 1;
session_handle = TMExtendedStartSession(PortNum, PortType);
result = TMSearch(session_handle, state_buffer, 1, 1, 0xEC);
if (result == 1)
Console.WriteLine("Device Found");
if (result == -201)
Console.WriteLine("Hardware Driver Not Found");
else
Console.WriteLine("Network Error");
Console.ReadKey();
}
[DllImport("IBFS32.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.Cdecl)]
public static extern Int32 TMExtendedStartSession(Int16 PortNum, Int16 PortType);
[DllImport("IBFS32.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.Cdecl)]
public static extern Int16 TMSearch(Int32 session_handle, Byte state_buffer, int p1, int p2, int p3);
}
}
I am trying to use these 2 functions
TMExthendedStartSession http://files.maximintegrated.com/sia_bu/licensed/docs/1-wire_sdk_win/TMEX/exst8l9q.html
and TMSearch
http://files.maximintegrated.com/sia_bu/licensed/docs/1-wire_sdk_win/TMEX/sear1ezy.html
When I run TMExthendedStartSession I get System.AccessViolationException, but when I run TMSearch alone I get a message
"Managed Debugging Assistant 'PInvokeStackImbalance' has detected a problem in 'C:\PInvokeTest\Debug\PInvokeTest.vshost.exe'."
The function TMSearch does return a value of -201 though.
Any help is appreciated.
In 32 bit Windows, the pascal calling convention maps to stdcall. There is a #define near the top of WinDef.h (or minwindef.h in more modern SDKs) that maps pascal to __stdcall.
On top of that, your parameters are all wrong. It should be like this:
[DllImport("IBFS32.dll")]
public static extern int TMExtendedStartSession(
short PortNum,
short PortType,
IntPtr EnhancedOptions
);
[DllImport("IBFS32.dll")]
public static extern short TMSearch(
int session_handle,
IntPtr state_buffer,
short p1,
short p2,
short p3
);
The state_buffer parameter might perhaps be better declared as byte[]. It's hard to tell from here what the semantics are.
What is the best practice to share memory of a struct from a C# program to a C++ win32 DLL?
I've used structs in managed shared memory using Boost between two C++ programs and it worked great. I'm lost on the best way to accomplish this between where the struct gets populated in the C# program and the C++ DLL that is an SNMP subagent.
Here's the C++ DLL:
//==================== Code Excerpt from the main cpp file ======================
#include "stdafx.h"
//================= Here we are setting up the shared memory area =====================
#pragma data_seg (".SHAREDMEMORY")
struct sharedData {
int sharedA;
int sharedB;
};
static sharedData A;
#pragma data_seg()
#pragma comment(linker,"/SECTION:.SHAREDMEMORY,RWS")
BOOL APIENTRY DllMain( HANDLE hModule, DWORD ul_reason_for_call, LPVOID lpReserved )
{
return TRUE;
}
//=============================================================================================
//====================== Here we are writing wrappers to the shared memory area ===========================
//=You must declare it as an Extern "C" to prevent name mangling. This is absolutely necessary in order to import it into c# =
//=============================================================================================
extern "C" __declspec(dllexport) sharedData __stdcall getMyData()
{
A.sharedA = 1237;
A.sharedB = 31337;
//return gshared_nTest;
return A;
}
extern "C" __declspec(dllexport) void __stdcall setMyData( sharedData buff )
{
A = buff;
}
Here's the calling C# function:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
namespace sharedMemTestCS
{
public partial class frmSharedMemTestCS : Form
{
struct sharedData {
int sharedA;
int sharedB;
};
static sharedData A;
//============== here we are importing the methods from the win32 dll into the c# console application =================
[DllImport(#"C:\Documents and Settings\My Documents\Visual Studio 2010\Projects\sharedMemTestCPP\Debug\sharedMemTestCPP.dll")]
public static extern sharedData getMyData();
[DllImport(#"C:\Documents and Settings\My Documents\Visual Studio 2010\Projects\sharedMemTestCPP\Debug\sharedMemTestCPP.dll")]
public static extern void setMyData(int data);
public frmSharedMemTestCS()
{
InitializeComponent();
//============== here i am incrementing the value =================
//== i use a message box so that i can have multiple console applications running at once and it will pause at the messagebox (if i don't click ok)
//== i do this so i can see the values changing in the shared memory.
//MessageBox.Show( getMyData().ToString() );
getMyData();
//txtBoxA.Text = (getMyData().ToString() );
}
private void btnAdd_Click(object sender, EventArgs e)
{
//setMyData( getMyData() + 100 );
//txtBoxA.Text = (getMyData().ToString() );
}
}
}
The error message I get is:
Error 1 Inconsistent accessibility: return type
'sharedMemTestCS.frmSharedMemTestCS.sharedData' is less accessible
than method
'sharedMemTestCS.frmSharedMemTestCS.getMyData()' c:\documents and
settings\mconrad\my documents\visual studio
2010\Projects\sharedMemTestCS\sharedMemTestCS\Form1.cs 23 37 sharedMemTestCS
The best practice for sharing memory would be to use the MemoryMappedFile class in C# and CreateFileMapping/MapViewOfFile in C++.
First thing, you cannot straightway use Boost for data sharing. You need to have some well-defined data-structures that you share between the managed and unmanaged worlds.
You may start here
Well your actual problem is your p/invoke expression is public but your struct is private, which is what the error is telling you. Making your p/invoke expression private or your struct public will resolve the immediate issue.
As for the actual data sharing, I've never tried doing it quite like that so I can't tell you if it will or won't work. All the pieces I've worked with are marshalled back and forth. Looking at your example code, it's quite possible it could work. You'll probably want to either copy the data to a new struct for c# or pin your struct that you get back so the GC won't move it around in memory.