Is there a way to do 2-way linking?

[Benjamin Thaut]

Am 05.02.2014 18:33, schrieb Jeroen Bollen:
> On Wednesday, 5 February 2014 at 16:27:10 UTC, Benjamin Thaut wrote:
>> Am 05.02.2014 16:36, schrieb Jeroen Bollen:
>>> On Wednesday, 5 February 2014 at 13:52:10 UTC, Benjamin Thaut wrote:
>>>> Am 05.02.2014 14:21, schrieb Jeroen Bollen:
>>>>> Is it possible to load in a dynamic library in D, and have the library
>>>>> you just loaded call your own functions? Imagine having a plugin
>>>>> loader
>>>>> and the plugins call methods like 'addButton()' from the host
>>>>> application.
>>>>
>>>> Yes, thats what core.runtime.loadLibrary is for.
>>>> http://dlang.org/phobos/core_runtime.html#.Runtime.loadLibrary
>>>>
>>>> You can also always fall back to operating system functions like,
>>>> LoadLibrary and GetProcAddress for windows.
>>>>
>>>> Kind Regards
>>>> Benjamin Thaut
>>>
>>> How exactly does that work 2 ways? Can I just define the functions and
>>> not implement them in the library?
>>
>> You don't define functions, just function pointers. You could also do
>> it oop style:
>>
>> // The loader
>> import core.sys.windows.windows;
>>
>> interface IPlugin
>> {
>>   void pluginMethod1();
>>   void pluginMethod2();
>> }
>>
>> // function pointer definition for the entry function
>> extern(C) alias IPlugin function() pluginEntry;
>>
>> IPlugin loadPlugin(const(char)[] path)
>> {
>>   auto handle = cast(HMODULE)runtime.loadLibrary(path);
>>   //use dlsym on linux
>>   auto entry = cast(pluginEntry)GetProcAddress(handle,
>> "pluginEntry".ptr);
>>   return entry(); // get the plugin interface
>> }
>>
>>
>> // The plugin
>> interface IPlugin
>> {
>>   void pluginMethod1();
>>   void pluginMethod2();
>> }
>>
>> class PluginImpl : IPlugin
>> {
>>   override void pluginMethod1() { ... }
>>   override void pluginMethod2() { ... }
>> }
>>
>> export extern(C) IPlugin pluginEntry()
>> {
>>   return new PluginImpl();
>> }
>>
>> This however will have issues on windows, because the runtime is not
>> shared. On Linux it should work just fine if you remember to link
>> against the shared runtime.
>>
>> You might also want to watch this talk from D-conf 2013:
>> http://dconf.org/2013/talks/nowak.html
>>
>> Kind Regards
>> Benjamin Thaut
>
> That example seems to only let the loader call the plugin, and not the
> other way around.

Well as I already said, for the other way around just pass 
function-pointers / interfaces to the plugin as soon as you established 
the one-way connection.