Unmanaged method member being used as a delegate in managed class - callback

I have a project where I am expanding existing native C++ compatible code functionality for a customer-facing library by integrating a driver from a managed DLL, which seems like the opposite direction for most marshaling questions. Since there can be multiple devices using this one driver, each device needs to be its own object, with its own callback methods. This integration will take the form of a native wrapper DLL that exposes the native class interface to the customer-facing library, which will pass an instance of a member method callback function pointer to the DLL. I need to pass a native method member instance (non-static) as a delegate to the managed wrapper class. The managed wrapper class uses GetDelegateForFunctionPointer, which works to marshal static native pointers to a delegate, but I can't find any information if it works with instances. GetDelegateForFunctionPointer also takes a System::IntPtr argument for the function pointer, but I'm also not sure if System::IntPtr works for instances, and when compiling in VC++2008 I'm being presented an error C3867 for attempting this.
Managed wrapper header:
//somemanagedclass.hpp
#pragma once
using namespace System;
using namespace ExternalManagedLibrary;
namespace SomeNameSpace
{
public ref class SomeManagedClass
{
public:
SomeManagedClass();
~SomeManagedClass();
delegate void CallbackHandler(const wchar_t*, int);
CallbackHandler^ CallbackEvent;
void RegisterCallback(IntPtr callbackEvent);
private:
ExternalManagedClass^ externalManagedClass;
void OnCallback(Object^ sender, ValueEventArgs<String^>^ e);
};
}
Managed wrapper source:
//somemanagedclass.cpp
#include "somemanagedclass.hpp"
#include <vcclr.h>
using namespace System;
using namespace Runtime::InteropServices;
namespace SomeNameSpace
{
SomeManagedClass::SomeManagedClass()
{
externalManagedClass = gcnew ExternalManagedClass();
externalManagedClass->CallbackEvent += gcnew EventHandler<ValueEventArgs<String^>^>(this, &SomeManagedClass::OnCallback);
}
SomeManagedClass::~SomeManagedClass()
{
externalManagedClass->CallbackEvent -= gcnew EventHandler<ValueEventArgs<String^>^>(this, &SomeManagedClass::OnCallback);
}
void SomeManagedClass::OnCallback(Object^ sender, ValueEventArgs<String^>^ e)
{
String^ some_string = String::Copy(e->Value);
cli::pin_ptr<const wchar_t> pinned_string = &PtrToStringChars(some_string)[0];
const wchar_t* p = pinned_string;
CallbackEvent(pinned_string, some_string->Length);
}
void SomeManagedClass::RegisterCallback(IntPtr callbackEvent)
{
CallbackEvent = (CallbackHandler^)(Marshal::GetDelegateForFunctionPointer(callbackEvent, CallbackHandler::typeid));
}
}
Native wrapper interface:
//somenativeinterface.hpp
#ifdef DLL_EXPORT
#define IMPORT_EXPORT __declspec(dllexport)
#else
#define IMPORT_EXPORT __declspec(dllimport)
#endif //DLL_EXPORT
typedef void (*NativeCallback)(const unsigned char*, unsigned long);
class IMPORT_EXPORT SomeNativeInterface
{
public:
//class factory
static SomeNativeInterface* Create(void);
static void Destroy(SomeNativeInterface* clInterface);
virtual void CallbackInit(NativeCallback fnNativeCallbackInit);
};
Native wrapper header:
//somenativeclass.hpp
#pragma once
#include "somenativeinterface.hpp"
#include "somemanagedclass.hpp"
#include <vcclr.h>
using namespace SomeNameSpace;
class IMPORT_EXPORT SomeNativeClass : public SomeNativeInterface
{
public:
SomeNativeClass();
~SomeNativeClass();
void CallbackInit(NativeCallback fnNativeCallbackInit); //can this take an instance?
private:
NativeCallback fnNativeCallback;
void OnNativeCallback(const wchar_t* cString, int iSize);
gcroot<SomeManagedClass^> wrapper; //warning C4251
};
Native wrapper source:
//somenativeclass.cpp
#include "somenativeclass.hpp"
#include <vcclr.h>
#include <string.h>
using namespace System;
using namespace Runtime::InteropServices;
SomeNativeInterface* SomeNativeInterface::Create()
{
return ((SomeNativeInterface*) new SomeNativeClass());
}
void SomeNativeInterface::Destroy(SomeNativeInterface* instance)
{
delete instance;
}
SomeNativeClass::SomeNativeClass()
{
wrapper = gcnew SomeManagedClass();
}
SomeNativeClass::OnNativeCallback(const wchar_t* cString, int iSize)
{
std::auto_ptr<char> pcConvertedString(new char[iSize+1]);
size_t iCharsConverted;
if (wcstombs_s(&iCharsConverted, (char*)*pcConvertedString, iSize+1, cString, iSize) == 0)
{
if (iCharsConverted > 0xFFFFFFFF)
iCharsConverted = 0xFFFFFFFF; //truncate
fnNativeCallback((const unsigned char*)*pcConvertedString, (unsigned long)(iCharsConverted));
}
}
SomeNativeClass::CallbackInit(NativeCallback fnNativeCallbackInit)
{
fnNativeCallback = fnNativeCallbackInit;
wrapper->RegisterCallback(System::IntPtr(this->OnNativeCallback)); //error C3867
}

Related

ESP8266 Scheduler. Tasks in separate files arduino IDE

I want to create simple weather station with esp8266 but with scheduler to updating data and GUI more simultaneously. I've downloaded scheduler from here but there is information:
Tasks must be declared globally on the stack (not a pointer). Failure to do so will crash your device
Does that mean that I have to write all task classes in *.ino file? Can I save them in separate files and call to sketch file? How to do that? I've tried few times but the code won't compile.
Simpliest example of sketch:
#include <Scheduler.h>
#include <Arduino.h>
class SimpleTask : public Task {
protected:
void setup() {
Serial.println("Setup func");
}
void loop() {
Serial.println("Loop func");
delay(600);
}
} simple_task;
void setup() {
Serial.begin(115200);
Scheduler.start(&simple_task);
Scheduler.begin();
}
void loop() { }
Tasks must be declared globally on the stack (not a pointer).
I think strictly this means that Tasks must not be created on the heap and need to be global, static objects.
This can be done by creating the object in a separate file and declaring the object using the extern keyword.
e.g. an example mysimpletask.h:
#ifndef __MySIMPLETASK_H__
#define __MySIMPLETASK_H__
#include <Scheduler.h>
class MySimpleTask : public Task {
protected:
void setup();
void loop();
};
extern MySimpleTask my_simple_task;
#endif
The implementation in mysimpletask.cpp:
#include "mysimpletask.h"
void MySimpleTask::setup() {
Serial.println("Setup func");
}
void MySimpleTask::loop() {
Serial.println("Loop func");
delay(600);
}
MySimpleTask my_simple_task;
And the sketch:
#include <Scheduler.h>
#include <Arduino.h>
#include "mysimpletask.h"
void setup() {
Serial.begin(115200);
Scheduler.start(&my_simple_task);
Scheduler.begin();
}
void loop() { }

boost.python MSVC12 linker errors when exposing classes with docstring_options

I regularly expose c++ classes to python using boost.python & MSVC 12 (dynamic linking). Recently I have been trying to include documentation using the "docstring_options" class. The documentation examples work fine:
http://www.boost.org/doc/libs/1_54_0/libs/python/doc/v2/docstring_options.html
However, when I include a class and expose it I get linker errors:
error LNK2019: unresolved external symbol "void __cdecl boost::throw_exception(class std::exception const &)" (?throw_exception#boost##YAXABVexception#std###Z) referenced in function "public: __thiscall boost::detail::shared_count::shared_count(void *,struct boost::python::converter::shared_ptr_deleter)"
I'm sure there is probably something simple I'm missing but I can't figure it out.
Many thanks in advance!
sample code spliced from the boost examples that gives this error for me.
#include <string>
#include <boost/python/module.hpp>
#include <boost/python/def.hpp>
#include <boost/python/args.hpp>
#include <boost/python/docstring_options.hpp>
#include <boost/python.hpp>
struct World
{
void set(std::string msg) { this->msg = msg; }
std::string greet() { return msg; }
std::string msg;
};
int foo1(int i) { return i; }
int foo2(long l) { return static_cast<int>(l); }
int bar1(int i) { return i; }
int bar2(long l) { return static_cast<int>(l); }
namespace {
void wrap_foos()
{
using namespace boost::python;
def("foo1", foo1, arg("i"), "foo1 doc");
def("foo2", foo2, arg("l"), "foo2 doc");
}
void wrap_bars()
{
using namespace boost::python;
bool show_user_defined = true;
bool show_signatures = false;
docstring_options doc_options(show_user_defined, show_signatures);
def("bar1", bar1, arg("i"), "bar1 doc");
def("bar2", bar2, arg("l"), "bar2 doc");
class_<World>("World")
.def("greet", &World::greet)
.def("set", &World::set)
;
}
}
BOOST_PYTHON_MODULE(boost_py_doc_demo)
{
boost::python::docstring_options doc_options(false);
wrap_foos();
wrap_bars();
}
I compiled the latest version of boost (1.63) and now the problem has gone. I guess my old libraries were incomplete in some way.

pthread to invoke member func by wrapping it externally

I'm trying to invoke a member function by pthread by using an external wrapper but it doesn't quite work for me, I get a seg fault. Why is this?
Here's a little test program that displays the problem:
#include <iostream>
#include <pthread.h>
class test {
public:
test();
~test();
void RunTh(void);
private:
pthread_t *pid;
};
void *Run_wrp(void *context);
void test::RunTh(void)
{
while(1);
}
test::test()
{
pthread_create(pid,NULL,&Run_wrp,this);
}
test::~test(){}
int main(void) {
test tmp;
std::cin.get();
}
void *Run_wrp(void *context)
{
((test*)context)->RunTh();
}
Your pid member variable is just a pointer, not an actual pthread_t object.
Change it to:
private:
pthread_t pid;
Then create the new thread with:
pthread_create(&pid,NULL,&Run_wrp,this);
Also, if you want to keep everything contained in the class, you can make your Run_wrp() function a static member function of test, as long as you keep the same signature (return value/arguments). It needs to be static, as non-static functions take the this pointer to the class as a hidden argument, and thus end up with a different signature than what you need for pthread_create().

Access to the same class instance from qml

I'm using Qt 5.1.0 and QtQuick 2.0.
I've just learned how to exchange data and method between qml and C++. In detail, I want to expose a (nested) structure, so I created classes which contains the required properties and methods.
It works, but I cannot share the very same instance between C++ and qml. Changing something from C++ side leads to no changes in qml side.
A short example:
main.cpp
#include <QtGui/QGuiApplication>
#include <QtQml>
#include "qtquick2applicationviewer.h"
#include "myclass.h"
int main(int argc, char *argv[]) {
QGuiApplication app(argc, argv);
qmlRegisterType<MyClass>("MyLibrary", 1, 0, "MyClass");
MyClass *myclass = new MyClass();
Category *cat = new Category();
cat->setName("foo");
myclass->append(cat);
qDebug() << myclass->categoriesCount(); // returns 1 OK!
QtQuick2ApplicationViewer viewer;
viewer.setMainQmlFile(QStringLiteral("qml/main.qml"));
viewer.show();
return app.exec();
}
myclass.h
#include <QObject>
class Category : public QObject {
Q_OBJECT
Q_PROPERTY(QString name READ name WRITE setName)
public:
Category() {}
QString name() const { return m_name; }
void setName(QString name) { m_name = name; }
private:
QString m_name;
};
class MyClass : public QObject {
Q_OBJECT
Q_PROPERTY(QList<QObject*> categories READ categories NOTIFY categoriesChanged)
Q_PROPERTY(int categoriesCount READ categoriesCount)
public:
QList<QObject*> categories() const { return m_categories; }
void clear() { m_categories.clear(); }
void append(Category *category) { m_categories.append(category); }
int categoriesCount() const { return m_categories.count(); }
private:
QList<QObject*> m_categories;
signals:
void categoriesChanged();
};
main.qml
import QtQuick 2.0
import MyLibrary 1.0
Item {
id: root
width: 360
height: 360
Text {
id: foo
text: myclass.categoriesCount // writes 0 -> should be 1
}
MyClass {
id: myclass
}
}
I'm afraid the qml engine accesses to a different instance of the class myclass created in the main file.

Is it possible to point a Typedef function pointer to a class member?

I am working with an executable that includes a DLL. For my testcase, I combined the code into a single executable. I am working with Visual Studio 2008 and Boost 1.43. I've tried researching this, but haven't found any clear answer. Thanks for the help.
In my main.h:
#include <string>
//These are normally defined in a seperate DLL
typedef std::string Typedef_func(const std::string & title);
void Register_My_Typedef(Typedef_func*);
//-------------------------------------------
class myClass
{
public:
std::string func_one(const std::string & title);
Typedef_func _test;
void run();
};
In my main.cpp:
#include "main.h"
#include <boost/bind.hpp>
std::string workingFunc(const std::string & title)
{
return "";
}
int main(int argc, char* argv[])
{
myclass* example;
example->run();
Register_My_Typedef(&workingFunc);//This works.
return 0;
}
void myClass::run()
{
//I want to point a Typedef_func* in a DLL to call myclass::func_one
Typedef_func* tf = boost::bind(&myClass::func_one, this, "test"); //This does not.
Register_My_Typedef(tf);
}
std::string myClass::funcOne(const std::string & title)
{
return "";
}
void Register_My_Typedef(Typedef_func* passedIn)
{
//Points the pointer in the DLL to passedIn
}
The DLL logic works fine when Register_My_Typedef is called on a function not in a class, but is it possible to call it from within a class? When I try to compile this code it returns:
When I try and compile in Windows XP with VS2008 I get:
Error C2440: 'initializing' : cannot convert from
'boost::_bi::bind_t' to 'Typedef_func (__cdecl *)' with
[
R=std::string,
F=boost::_mfi::mf1,
L=boost::_bi::list2,boost::_bi::value>
]
No user-defined-conversion operator available that can perform this
conversion, or the operator cannot be called.
The Answer is Typedef itself is class member for a static member function & behave differently to non-static however works best reading rather class function of user defined class main.