from the call back function of sys.settrace how to pass frame object to a c++ which accepts void *
Limitations (in a given situation):
Forced to use sys.settrace (can not use PyEval_SetTrace)
Also c++ function can not accept PyObject* or PyFrameObject*
C++ code (using SWIG python bindings are generated for this):
class TEST_DECLS InterpPython{
static int TraceHook(void *frame, hwString what, void * arg);
}
Python code:
sys.settrace(_trace_hook)
def _trace_hook(frame, event, arg):
InterpPython_TraceHook(frame,event, arg)
Results:
TypeError: in method 'InterpPython_TraceHook', argument 1 of type 'void *'
Try a typemap to convert the Python input object to a void* when it is a void* frame parameter. You could also add a check that the object is actually a PyFrameObject.
%typemap(in) void* frame %{
$1 = (void*)$input;
%}
Related
Hello I am using dart:ffi to build an interface with my native c/c++ library.
and I needed a way to get a callback from c to dart as an example in sqlite:
int sqlite3_exec(
sqlite3*, /* An open database */
const char *sql, /* SQL to be evaluated */
int (*callback)(void*,int,char**,char**), /* Callback function */
void *, /* 1st argument to callback */
char **errmsg /* Error msg written here */
);
the third parameter in sqlite3_exec is function pointer to a callback.
so if I called this function in dart using ffi I need to pass a function pointer: and in dart:ffi Pointer class there is a function named fromFunction witch accepts a dart static function and an exceptionalReturn; but just by calling this function to get the function pointer of a dart managed function: a (sigterm) is raised and the dart code no long work in the process.
So My Question: Is there any way to get a native callback in dart, as in Python, c#, ..
Extra:
Is there any way to include dartino in a flutter project, since this ForeignDartFunction covers what I need.
I got an example to work. Hopefully you can adapt this to your case.
Example C function
EXTERNC int32_t foo(
int32_t bar,
int32_t (*callback)(void*, int32_t)
) {
return callback(nullptr, bar);
}
Dart code
First the typedefs. We need two for the native function foo and one for the Dart callback.
typedef example_foo = Int32 Function(
Int32 bar, Pointer<NativeFunction<example_callback>>);
typedef ExampleFoo = int Function(
int bar, Pointer<NativeFunction<example_callback>>);
typedef example_callback = Int32 Function(Pointer<Void>, Int32);
and the code for the callback
static int callback(Pointer<Void> ptr, int i) {
print('in callback i=$i');
return i + 1;
}
and the lookup
ExampleFoo nativeFoo =
nativeLib.lookup<NativeFunction<example_foo>>('foo').asFunction();
and, finally, use it like this:
int foo(int i) {
return nativeFoo(
i,
Pointer.fromFunction<example_callback>(callback, except),
);
}
as expected, foo(123) prints flutter: in callback i=123 and returns 124
I am creating a class that needs a reference to the test bench's configuration object. Since the configuration must be intact throughout the simulation, I pass it as a const ref object. Here is a sudo code that I want to run:
class tb_config;
int unsigned rate;
int unsigned chnls[];
const int unsigned nb_chnls;
function new (int unsigned rate, int unsigned nb_chnls);
this.rate = rate;
this.nb_chnls = nb_chnls;
chnls = new[nb_chnls];
endfunction
endclass
class tx_phy;
static int phy_id;
tb_config cfg;
function new (int unsigned phy_id, const ref tb_config cfg);
this.phy_id = phy_id;
this.cfg = cfg;
endfunction
endclass
module test;
tb_config cfg = new(100, 4);
tx_phy phy = new( 1234, cfg);
endmodule
The code above works perfectly fine and it meets my expectation. But if I change the arguments in tx_phy::new to function new (const ref tb_config cfg, int unsigned phy_id); and pass the values to the constructor accordingly I get the following error in Cadence Incisive:
invalid ref argument usage because actual argument is not a variable.
Also same thing happens when I test it with Aldec in edaplayground: https://www.edaplayground.com/x/5PWV
I assume this is a language limitation, but is there any other reason for that??
The reason for this is because the argument kind is implicit if not specified. You specified const ref for the first argument, but nothing for the second argument, so it is also implicitly const ref. Adding input to the second argument declaration fixes this.
function new (const ref tb_config cfg, input int unsigned phy_id);
I also want to add const ref tb_config cfg is equivalent to writing
function new (tb_config cfg, int unsigned phy_id);
Both of these arguments are implicitly input arguments, which means they are copied upon entry.
A class variable is already a reference. Passing a class variable by ref means that you can update the handle the class variable has from within the function. Making the argument a const ref means you will not be able to update the class variable, but you can still update members of the class the variable references. There is no mechanism to prevent updating members of class object if you have a handle to it other than by declaring them protected or local.
The only place it makes sense to pass function arguments by ref in SystemVerilog is as an optimization when the arguments are large data structures like an array, and you only need to access a few of the elements of the array. You can use task ref arguments when the arguments need to be updated during the lifetime of the task (i.e. passing a clock as an argument).
I am trying to register a keyboard callback function to a 3D viewer using the Point Cloud Library API.
Todo this I do:
viewer->registerKeyboardCallback(&(RailExtraction::keyboard_callback), (void*)(>_data));
But I get the following error message:
note: no known conversion for argument 1 from 'void (RailExtraction< pcl::PointXYZI >::*)
(const pcl::visualization::KeyboardEvent&, void*)' to 'void (*)(const pcl::visualization::KeyboardEvent&, void*)'
I am trying to understand the error message. I understand what void and void * mean but what does void(*)(...) or void(RailExtraction< pcl::PointXYZI >::*>(...) mean ??
I figured out the problem I am using the wrong version of registerKeyBoardCallBack. I am currently trying to use this signature:
registerKeyboardCallback (void (*callback) (const pcl::visualization::KeyboardEvent&, void*), void* cookie = NULL)
But I should be using this signature:
registerKeyboardCallback (void (T::*callback) (const pcl::visualization::KeyboardEvent&, void*), T& instance, void* cookie = NULL)
This is because my keyboard_callback function is part of a class and therefore I need to specify the instance of the class so that the compiler can figure out which instance the keyboard_callback function to use. Therefore my new call to registerKeyboardCallBack looks like this:
viewer->registerKeyboardCallback(&RailExtraction::keyboard_callback, *this, (void*)>_data);
I'm working on finishing up my server for my first iPhone application, and I want to implement a simple little feature.
I would like to run a function (perhaps method as well), if another function returns a certain value after a certain waiting period. Fairly simple concept.... right?
Here's my basic foundation.
template <typename T,class TYP>
struct funcpar{
T (*function)(TYP);
TYP parameter;
funcpar(T (*func)(TYP),TYP param);
funcpar& operator=(const funcpar& fp);
};
The goal here is to be able to call funcpar::function(funcpar::parameter) to run the stored function and parameter, and not have to worry about anything else...
When I attempted to use a void* parameter instead of the template, I couldn't copy the memory as an object (because I didn't know what the end object was going to be, or the beginning for that matter) and when I tried multiple timers, every single object's parameter would change to the new parameter passed to the new timer... With the previous struct I have a
question:
Is it possible to make an all-inclusive pointer to this type of object inside a method of a class? Can I templatize a method, and not the whole class? Would it work exactly like a function template?
I have a managing class that holds a vector of these "jobs" and takes care of everything fairly well. I just don't know how to use a templatized function with the struct, or how to utilize templates on a single method in a class..
I'm also utilizing this in my custom simple threadpool, and that's working fairly well, and has the same problems...
I have another question:
Can I possibly store a function with a parameter before it's run? Something like toRun = dontrunmeyet(withThisParameter);? Is my struct even necessary?
Am I going about this whole thing incorrectly?
If this is overly ambiguous, I can set you up with my whole code for context
In order to create a class method that takes a template parameter, yes, it would work almost exactly like a function template. For example:
class A
{
public:
template<typename T>
void my_function(const T& value) { }
};
int main()
{
A test;
test.my_function(5);
return 0;
}
Secondly, for your structure, you can actually turn that into a functor-object that by overloading operator(), lets you call the structure as-if it were a function rather than having to actually call the specific function pointer members inside the structure. For instance, your structure could be re-written to look like this:
#include <iostream>
template <class ReturnType, class ParameterType>
class funcpar
{
private:
ReturnType (*function)(ParameterType);
ParameterType parameter;
public:
funcpar(ReturnType (*func)(ParameterType),ParameterType param):
function(func), parameter(param) {}
funcpar& operator=(const funcpar& fp);
//operator() overloaded to be a function that takes no arguments
//and returns type ReturnType
ReturnType operator() ()
{
return function(parameter);
}
};
int sample_func(int value)
{
return value + 1;
}
int main()
{
funcpar<int, int> test_functor(sample_func, 5);
//you can call any instance of funcpar just like a normal function
std::cout << test_functor() << std::endl;
return 0;
}
BTW, you do need the functor object (or your structure, etc.) in order to bind a dynamic parameter to a function before the function is called in C/C++ ... you can't "store" a parameter with an actual function. Binding a parameter to a function is actually called a closure, and in C/C++, creating a closure requires a structure/class or some type of associated data-structure you can use to bind a function with a specific parameter stored in memory that is used only for a specific instance of that function call.
I'm currently start using boost::program_options for parsing command line options as well as configuration files.
Is it possible to use own template classes as option arguments? That means, something like
#include <iostream>
#include "boost/program_options.hpp"
namespace po = boost::program_options;
template <typename T>
class MyClass
{
private:
T* m_data;
size_t m_size;
public:
MyClass( size_t size) : m_size(size) { m_data = new T[size]; }
~MyClass() { delete[] m_data; }
T get( size_t i ) { return m_data[i]; }
void set( size_t i, T value ) { m_data[i] = value; }
};
int main (int argc, const char * argv[])
{
po::options_description generic("General options");
generic.add_options() ("myclass", po::value< MyClass<int>(2) >(),
"Read MyClass");
return 0;
}
Trying to compile this I get an Semantic Issue (No matching function for call to 'value'). I guess I need to provide some casting to an generalized type but I have no real idea.
Can anybody help?
Thanks
Aeon512
I wouldn't know if boost::program_options allows the use-case you are trying, but the error you are getting is because your are trying to pass an object as a template type to po::value<>. If the size is known at compile-time, you could have the size be passed in as a template parameter.
template< typename T, size_t size >
class MyClass {
T m_data[size];
public:
// ...
};
And then use it like so:
po::value< MyClass<int, 2> >()
You should also look into using Boost.Array instead that I guess fulfills what you are trying to implement.
I would write it like this:
MyClass<int> mine(2);
generic.add_options() ("myclass", po::value(&mine), "Read MyClass");
Then all that needs to be done is to define an input stream operator like this:
std::istream& operator >>(std::istream& source, MyClass& target);
Then Boost Program Options will invoke this stream operator when the myclass option is used, and your object will be automatically populated according to that operator's implementation, rather than having to later call one of the Program Options functions to extract the value.
If you don't prefer the above syntax, something like should work too:
generic.add_options() ("myclass", po::value<MyClass<int> >()->default_value(MyClass<int>(2)), "Read MyClass");
This way you would be creating the instance of your class directly with your desired constructor argument outside of the template part where runtime behavior isn't allowed. I do not prefer this way because it's verbose and you end up needing to call more functions later to convert the value.