I just want to know if there is any way to call a c++ class into our nsis script ?
Thanks.
NSIS can call functions in DLLs but the calling convention is somewhat limited and there's no direct support for classes. You will not be able to easily call class function.
You might be able to "hack" it by making extern "C" wrapper functions for every class member function, along with function that create and destroy instances of the class as necessary. You'd have to somehow passes something that represents the newly created instances back to NSIS, which then would pass it into the wrapper functions along with any necessary parameters/arguments.
Sounds like more trouble than it's worth...
In my opinion the easiest way to call your function will be to export it to dll and then call them from nsis using System::Call function.
Related
In file gperftools-2.2.1/src/gperftools/malloc_extension.h, it reads:
// Extra extensions exported by some malloc implementations. These
// extensions are accessed through a virtual base class so an
// application can link against a malloc that does not implement these
// extensions, and it will get default versions that do nothing.
//
// NOTE FOR C USERS: If you wish to use this functionality from within
// a C program, see malloc_extension_c.h.
My question is how exactly can I access these extensions through a virtual base class?
Usually to load a class from a dynamic library, I would need to write a base class which allows me to get an instance of the wanted class and its functions through polymorphism, as described here.
However to do so there must be some class factory functions available in the API, but there are no such functions in any tcmalloc files. Moreover I would also need to load the tcmalloc library with dlopen(), which is not recommended according to the install note:
...loading a malloc-replacement library via dlopen is
asking for trouble in any case: some data will be allocated with one malloc, some with another.
So clearly accessing the extensions through the typical way as mentioned above is not an option. I can get away with using the C versions as declared in malloc_extensions_c.h but just wonder if there is any better solution.
I managed to load the malloc extensions via some 'hack', which is not as clean as I would prefer, but it gets the job done. Here is the (temporary) solution for those who are interested in.
First, most of these malloc extension functions are similar to static functions in a way that they are mostly called on the current instance only, e.g. to call the GetMemoryReleaseRate() function on the current process you just call MallocExtension::instance()->GetMemoryReleaseRate(). Therefore we don't need to create a base class and get an instance of MallocExtension class to call these functions.
For the example above, I'd just create a standalone function getMemoryReleaseRate() which simply calls the required function when it gets called, as below:
getMemoryReleaseRate()
{
MallocExtension::instance()->GetMemoryReleaseRate();
}
This function can be inserted directly to a source file, e.g. tcmalloc.cc, or, if you prefer not to edit the tcmalloc source every time there is a new version, added to your makefile, to be attached to the source file when it is compiled.
Now in your code, you can call the MallocExtension function via the 'facade' function you have created via dlsym(), e.g. as below:
typedef void (*getMemoryReleaseRate)();
((getMemoryReleaseRate)dlsym(RTLD_DEFAULT, "getMemoryReleaseRate"))();
Simply including this header and doing MallocExtension::instance()->GetMemoryReleaseRate(); would work too. No need to modify tcmalloc for that.
I'm implementing a class named FilesWorkFlow. It's task is to open a file dialog and then if the file's extention is geotiff, some other member functions will be implemented to work with it. As you know before working with GDAL files , you have to call GDALAllRegister() so I need to call this function somewhere in the class that all of the member functions will suppose GDAL drivers as registered. Where should I call it?
The documentation for GDALAllRegister states:
This function should generally be called once at the beginning of the application.
Given that requirement I assume there's nothing wrong with calling it from your CWinApp::InitInstance override.
As an alternative you can encapsulate the GDAL functionality into a Singleton and use Lazy Initialization.
I finally got into a problem that I can't find a solution here. I'm using a Lua Wrapper Class found in here http://lua-users.org/wiki/CppConvenientLuaWrapperClass. We've been able to expose a complete API plus more other funcionalities like serial communication and on.
The concept behind this Lua Wrapper is that you expose every method before compiling so when you're running your programm all methods will be added to the Lua Stack and in that way you can execute them. The idea now is to build kind of a Dll in order to complete this process of exposing methods. This way you won't needed to release a version with all exposed methods instead you load them trough multiple dll files.
I've tried to create another table and register other methods in that table, but with that, previous exposed methods stop working.
The other way around I can think of, is to create a dll but in C that contains all desirable methods and load it directly to Lua. But I think the other way would be better.
Have you been able to do something similar ? Am I having some wrong concept?
Thanks
Humm... I really don't want to change our wrapper at this time. I think I could manage to do it, sort of. Instead of adding a new table for the plugin functions, I've added a new sub-table tha will contain the functions names and cClosures to be called from Lua.
So at the end we should have:
application.functionName()
application.plugin.functionName()
Even if it work this way it will do fine.
Now I wonder how can we reference the lua_settable when exposing the functions to be added to application[plugin][pluginFunction] instead of aplication[pluginFunction]?!
This is how the normal functions are exposed:
//mState is a pointer to a Lua_State
lua_pushstring( mState, functionName );
//methodDesc is a pointer to an object that describes the function arguments/returns
lua_pushlightuserdata( mState, methodDesc );
//exposeMethodProxy is the method that is responsible for conneting lua c-calls to the c-functions
lua_pushcclosure( mState, exposedMethodProxy, 1 );
//mMethodTableIndex is a member variable that contains the index of the table tha hold all exposed functions
lua_settable( mState, mMethodTableIndex );
Any ideas on how I could achieve adding the cclosures not to the main table(at mMethodTableIndex) as mainTable[functionName] but at maintable[plugin][functionNane].?
I'm not sure, you're clear on what you want to do. A typical way to extend lua is to write a DLL with a single method that uses the Lua API to register your C++ types and C functions. To conviniently bind C++ functions and classes, you could use LuaBridge. An example of such binding is here: https://github.com/d-led/xerceslua
The header for the DLL of the xerceslua module contains only one function:
#include <lua.hpp>
void register_xerceslua (lua_State* L);
inside the implementation LuaBridge is used to bind to C++:
#include "xerceslua_lib.h"
#include <lua.hpp>
#include <LuaBridge.h>
void register_xerceslua (lua_State* L) {
...
luabridge::getGlobalNamespace(L)
.beginNamespace("xerces")
.addVariable("version",&version,false)
...
in Lua you can then access the exposed C++ API:
assert(require 'xerceslua')
local parser=xerces.XercesDOMParser()
parser:loadGrammar("Employee.dtd",xerces.GrammarType.DTDGrammarType)
You can use Lua both as an embedded scripting language, where you can execute lua from within your software, or you could use it as an extensible scripting language, extending it using the method shown above. Both are valid, but you have to consider, what exactly you are trying to do.
So here's the situation: I'm using C++, SDL and GLConsole in conjunction. I have a class, SDLGame, which has the Init(), Loop(), Render() etc - essentially, it holds the logic for my game class.
GLConsole is a nice library so far - it lets me define CVars and such, even inside my SDL class. However, when defining commands, I have to specify a ConsoleFunc, which is typedef'd as
typedef bool (*ConsoleFunc)( std::vector<std::string> *args);
Simple enough. However, like I said, my functions are all in my class, and I know I can't pass pointer-to-class-functions as pointer-to-function arguments. I can't define static functions or make functions outside my class because some of these ConsoleFuncs must access class data members to be useful. I'd like to keep it OOP, since - well, OOP is nice.
Well, I actually have this problem "solved" - but it's extremely ugly. I just have an instance of SDLGame declared as an extern variable, and use that in my ConsoleFuncs/main class.
So, the question is: Is there a way to do this that isn't stupid and dumb like the way I am doing it? (Alternatively: is there a console library like GLConsole that supports SDL and can do what I'm describing?)
If the only interface you have is that function pointer, then you're screwed.
A member function needs a this pointer to be called, and if you have no way of passing that, you're out of luck (I guess the std::vector<std::string>* args pointer is what you get passed from the library).
In other words, even though that library uses C++ containers, it's not a good C++ library, because it relies on free functions for callbacks. A good C++ library would use boost::function or something similar, or would at the very least let you pass a void* user_data pointer that gets passed through to your callback. If you had that, you could pass the this pointer of your class, cast it back inside the callback, and call the appropriate member function.
How could I create a method in dll written in c++ which returns a class, and how could I use that dll in java?
If i am export that class the name of that class get changed. Could any body help me? Thanks in advance.
You can't export a C++ class from a DLL and use it from a different compiler. What you can, and should, do is to export a COM object.
You can't. You could use JNI, but that's pretty horrible, and you'll have to write the code to convert from a C++ object to a corresponding Java object.
You could also look at JNA, which tries to make this a little easier.