How can i convert interoperatability between a c++/CLI Array and a native c++ array AND VICE VERSA.
array^ Cpluspluss_CLI_ManagedArray;
unsigned char* UnmanagedArray;
I found the System::Runtime::InteropServices::Marshal; (IntPtr) there is so much of information for a first timer like me (to CLI) So I'm not sure about which one to use.
Thank you
Raj
// unmanaged to managed...
IntPtr ptr((unsigned char*)UnmanagedArray);
array< Byte>^Cpluspluss_CLI_ManagedArray = gcnew array(UnmanagedArrayLength);
Marshal::Copy(ptr, Cpluspluss_CLI_ManagedArray, 0, UnmanagedArrayLength);
// unmanaged to managed...
See this Post
Related
I haven't seen C++ code in more than 10 years and now I'm in the need of developing a very small DLL to use the Ping class (System::Net::NetworkInformation) to make a ping to some remoteAddress.
The argument where I'm receiving the remoteAddress is a FREObject which then needs to be transformed into a const uint8_t *. The previous is mandatory and I can't change anything from it. The remoteAddress has to be received as a FREObject and later be transformed in a const uint8_t *.
The problem I'm having is that I have to pass a String^ to the Ping class and not a const uint8_t * and I have no clue of how to convert my const uint8_t * to a String^. Do you have any ideas?
Next is part of my code:
// argv[ARG_IP_ADDRESS_ARGUMENT holds the remoteAddress value.
uint32_t nativeCharArrayLength = 0;
const uint8_t * nativeCharArray = NULL;
FREResult status = FREGetObjectAsUTF8(argv[ARG_IP_ADDRESS_ARGUMENT], &nativeCharArrayLength, &nativeCharArray);
Basically the FREGetObjectAsUTF8 function fills the nativeCharArray array with the value of argv[ARG_IP_ADDRESS_ARGUMENT] and returns the array's length in nativeCharArrayLength. Also, the string uses UTF-8 encoding terminates with the null character.
My next problem would be to convert a String^ back to a const uint8_t *. If you can help with this as well I would really appreciate it.
As I said before, non of this is changeable and I have no idea of how to change nativeCharArray to a String^. Any advice will help.
PS: Also, the purpose of this DLL is to use it as an ANE (Air Native Extension) for my Adobe Air app.
You'll need UTF8Encoding to convert the bytes to characters. It has methods that take pointers, you'll want to take advantage of that. You first need to count the number of characters in the converted string, then allocate an array to store the converted characters, then you can turn it into System::String. Like this:
auto converter = gcnew System::Text::UTF8Encoding;
auto chars = converter->GetCharCount((Byte*)nativeCharArray, nativeCharArrayLength-1);
auto buffer = gcnew array<Char>(chars);
pin_ptr<Char> pbuffer = &buffer[0];
converter->GetChars((Byte*)nativeCharArray, nativeCharArrayLength-1, pbuffer, chars);
String^ result = gcnew String(buffer);
Note that the -1 on nativeCharArrayLength compensates for the zero terminator being included in the value.
We have an out of process COM application that was written in C++ that implements are networking protocol. When a packet of data is received a callback is invoked into the application that registered for the packet.
The callback interface is defined as such:
[helpstring("method MessageHandler")] HRESULT MessageHandler([in,size_is(nSize)] char * szBuf, int nSize, DWORD dwTransCode, DWORD dwSenderID, BSTR bstrFromIP);
Using this in C++ has not been an issue. We now have a case where we have a C++/CLI application that needs to receive callbacks. After hacking away until the compiler was happy, I arrived at the following implementation:
ref class MessageHandlerClass : public MessageRouterCallback
{
public:
virtual void MessageHandler(signed char %buffer, int size, unsigned int msgId, unsigned int fromId, System::String^ fromIp)
{
switch (msgId)
{
case MaintenanceMsgs::maintenance_event_message::ID:
{
SomeStructure msg;
myHandler->HandleMaintenanceEvent(&msg);
}
}
}
This is my first foray into C++/CLI.
First Question: What they heck does '%' mean in 'signed char %buffer'?
Second Question: I can place a breakpoint and see that the callback is getting called. I can look at the 'buffer' argument in the memory debugger and it contains the data I expect. I have been VERY unsuccessful at pulling that data out and placing it into the variable 'msg'. I know I can't do a cast like in C++, but every example I've been tried (Mostly InteropServices::Marshal and some pin_ptr stuff) doesn't seem to get me anywhere.
SomeStructure is declared in a header file and is included by both the C++ and the C++/CLI application. SomeStructure contains 2 unsigned shorts followed by three character arrays.
Any direction on where to go from here would be greatly appreciated.
Ok. It just 'clicked'... So I'll answer my own question here.
First Question: What they heck does '%' mean in 'signed char %buffer'?
The '%' just means its 'tracked' and will be garbage collected, or at least that's what I think it means :)
Second Question: How to marshal.
First I had to get to the 'internal pointer' and C++/CLI provides the & operator for that. Then I was able to simply memcpy the data over.
pin_ptr<signed char> p = &buffer;
MaintenanceMsgs::maintenance_event_message msg;
memcpy((void*)&msg, (void*)p, sizeof(msg));
myHandler->HandleMaintenanceEvent(&msg);
Is this safe?
I need to marshal an array of String^ to call a unmanaged function that expects an array of BSTRs.
On MSDN I found the article
How to: Marshal COM Strings Using C++ Interop
with this code sample:
// MarshalBSTR1.cpp
// compile with: /clr
#define WINVER 0x0502
#define _AFXDLL
#include <afxwin.h>
#include <iostream>
using namespace std;
using namespace System;
using namespace System::Runtime::InteropServices;
#pragma unmanaged
void NativeTakesAString(BSTR bstr) {
printf_s("%S", bstr);
}
#pragma managed
int main() {
String^ s = "test string";
IntPtr ip = Marshal::StringToBSTR(s);
BSTR bs = static_cast<BSTR>(ip.ToPointer());
pin_ptr<BSTR> b = &bs;
NativeTakesAString( bs );
Marshal::FreeBSTR(ip);
}
So I created a new BSTRs' array and called the Marshal::StringToBSTR() for every String of the array.
Then I created a managed pin_ptr array.
array<pin_ptr<BSTR> >^ gcDummyParameters = gcnew array<pin_ptr<BSTR> >(asParameters->Length);
but I receved the error:
Error 2 error C2691: 'cli::pin_ptr<Type>' : a managed array cannot have this element type
I tried also with a native array:
pin_ptr<BSTR> dummyParameters[100000];
but even in this case I got an error:
Error 1 error C2728: 'cli::pin_ptr<Type>' : a native array cannot contain this managed type
What else can I do?
Microsoft sample looks strange: there is no need to pin BSTR type because it is unmanaged. Just create BSTR array and fill every member using Marshal::StringToBSTR. Don't use pin_ptr.
pin_ptr should be removed from this sample. bs is a local variable and will not be moved by the garbage collector, also it is passed to the native function by value so there would be no problem if it did move.
The BSTR content to which it points is natively allocated by the system's BSTR allocator, it also will not be moved by the garbage collector.
I'm developing an app in C++/CLI and have a csv file writing library in unmanaged code that I want to use from the managed portion. So my function looks something like this:
bool CSVWriter::Write(const char* stringToWrite);
...but I'm really struggling to convert my shiny System::String^ into something compatible. Basically I was hoping to call by doing something like:
if( m_myWriter->Write(String::Format("{0}",someValueIWantToSave)) )
{
// report success
}
using namespace System::Runtime::InteropServices;
const char* str = (const char*) (Marshal::StringToHGlobalAnsi(managedString)).ToPointer();
From Dev Shed.
As mcandre mentions, Marshal::StringToHGlobalAnsi() is correct. But don't forget to free the newly allocated resource with Marshal::FreeHGlobal(), when the string is no longer in use.
Alternatively, you can use the msclr::interop::marshal_as template to create the string resource and automatically release it when the call exits the resource's scope.
There's a list of what types need which conversion in the overview of marshalling in C++.
can any body tell How to convert System::IntPtr to char* in managed c++
this is my main function
int main(void)
{
String* strMessage = "Hello world";
CManagedClass* pCManagedClass = new CManagedClass();//working
pCManagedClass->ShowMessage(strMessage);//working
****above said error here***
char* szMessage = (char*)Marshal::StringToHGlobalAnsi(strMessage);
CUnmanagedClass cUnmanagedClass; cUnmanagedClass.ShowMessageBox(szMessage);
Marshal::FreeHGlobal((int)szMessage);
return 0;
}
thanks in advance
I'm not a huge C++/CLI programmer, but the following should work just fine.
IntPtr p = GetTheIntPtr();
char* pChar = reinterpret_cast<char*>(p.ToPointer());
The IntPtr class has a method called ToPointer which returns the address as a void* type. That will be convertible to char* in C++/CLI.
EDIT
Verified this works on VS2008 and VS2015
Instead of
char* szMessage = (char*)Marshal::StringToHGlobalAnsi(strMessage).ToPointer();
Marshal::FreeHGlobal((int)szMessage);
Use
marshal_context conversions.
const char* szMessage = conversions.marshal_as<const char*>(strMessage);
It cleans itself up, the magic of C++ RAII.
Attention!
I want to add something to JaredPar answer.I don't know where your IntPtr is coming from but you should also use pin_ptr in order to prevent the garbage collector from messing up your memory. I did lot of CLR/Native inter op in the past and using pin_ptr is one of those things that I learnt to do in the hard way.
read the following:
click me