[Gambas-user] Working with .so library

[Caveat]

Hallo Dmitry

Did you already look at:

http://gambaswiki.org/wiki/howto/extern ?

Kind regards,
Caveat

On 31-05-17 06:48, Admin wrote:
> So, I am writing a programm for my business that would basically be a 
> cash register. Don't know for other countries but here in Russia the 
> tax law works like this: you have to form a check for a customer in a 
> spicific way spicified by the law, so some hardware manufacturers are 
> making certified cash registers/check printers that simply form the 
> check needed and automatically send tax info to authorities, very 
> simple and easy to integrate with ERP systems. The only problem is 
> that most of accounting software that is compatible with those 
> registers is written for Windows. Now that Windows becomes more and 
> more monstrous, many businesses turn to Linux, at least on those 
> computers that are only a cashier's workstation that does not need to 
> do much in terms of performance power. But the problem is, there's 
> only one or two cashier's programms for linux exist for now, that are 
> compatible with that certified hardware, and it's not open source or 
> free.
>
>
> First of all I want to make my own for myself, and second - I want to 
> share it. Gambas is a great language in this case because of many 
> aspects. In small buisnesses usually there are not a lot of qualified 
> programmers to make some apps in C or C++, but instead there usually 
> is just a single sysadmin, who is servicing the IT stuff wich usually 
> is just one or two PCs and a router/switch. So, Gambas is much more 
> accessible to those people as I see it. Programs written on it are 
> easy to understand and modify to the needs of a small business.
>
>
> And what is great - the manufacturers of that certified hardware are 
> willing to help: ofcourse they mostly do business with Windows stuff, 
> they only work directly with big businesses and they don't produce 
> accounting software themselves, but they are kind enough to provide at 
> least a binary libraries (they call those - drivers, but i'm not shure 
> if it's technically correct) for their hardware even for Linux as a 
> x86 and x64 .so files. What those binary libraries do is simple 
> conversion of easy commands to hex codes that are then passed to a 
> hardware via USB or RS232 or Ethernet. It is MUCH easier to work with 
> those commands then implement the whole communication protocol from 
> scratch. Ofcourse I am not the only one who is interested in those 
> devices to work under linux, and as I can tell from different forums 
> in the internet - programmers successfully use this libraries and 
> thank the developers. There's not a lot of documentation out there, 
> but yeah, on paper it seems to be simple enough... if you write your 
> code in C or C++.
>
>
> Things get much different when you try to use the library in Gambas. 
> What I was able to understand from the documentation is that you need 
> to "initialize the interface" with the library, which will create a 
> "virtual class" and than you can pass your data to it. So, in C (using 
> QT) that would look something like this:
>
>
>  typedef IFptr * (*_CreateFptrInterface)(int ver);
>
>     bool init() {
>         QLibrary *lib = new QLibrary("fptr");
>         lib->load();
>         if(lib->isLoaded()) {
>             _CreateFptrInterface CreateFptrInterface = 
> (_CreateFptrInterface)lib->resolve("CreateFptrInterface");
>             if(CreateFptrInterface) {
>                 IFptr * iface = CreateFptrInterface(12);
>                 iface->put_DeviceEnabled(true);
>                 int result = 0;
>                 iface->get_ResultCode(&result);
>                 qDebug() << result;
>                 wchar_t bfr[1000];
>                 int length = iface->get_ResultDescription(bfr,1000);
>                 qDebug() << QString::fromWCharArray(bfr,length);
>             }
>         }
>     }
>
>
> So, as I understand we create a pointer called IFptr by calling 
> CreateFptrInterface() and then we pass any other pointer through this 
> one. Pardon my terminology, I am new to this stuff.
>
> I wrote some simple code that basically initializes this driver just 
> so I can see some output in the driver logs which are kindly created 
> in ~/.atol. It also sends some data to driver which must change just 
> one setting:
>
> -----
>
> Library "~/ATOL/linux-x64/libfptr"
>
> Extern CreateFptrInterface(ver As Integer) As Pointer
> Extern put_DeviceSingleSettingAsInt(p As Pointer, s1 As String, s2 As 
> Integer) As Integer
> Extern ApplySingleSettings(p As Pointer) As Pointer
>
> [...]
>
> Public Sub Button1_Click()
> Dim IFptr As Pointer
>
> IFptr = CreateFptrInterface(12)
> put_DeviceSingleSettingAsInt(IFptr, "Model", 63)
>
> ApplySingleSettings(IFptr)
>
> End
>
> -----
>
> When I click Button1, the driver surely initializes, I see in logs 
> that IFptr object is created. If I provide the wrong version in 
> CreateFptrInterface it fails, saying in logs that there's missmatch in 
> interface version, so no doubt the argument is passed correctly. I 
> also can see that put_DeviceSingleSetting is being called, but the 
> configuration does not actually change. The commercial software that 
> uses this very same driver and works fine - leaves mostly the same 
> trace in driver's log except that I see what arguments are passed to 
> DeviceSingleSetting. And in my case I only see that the procedure is 
> envoked but with no arguments. I was trying to use many other 
> procedures (or methods, or pointers, or what are they?) with the same 
> effect - they surely are called and executed, but I can't pass any 
> arguments to them. I was experimenting with variable types I send 
> them, and if I, for example, send an integer as an argument when the 
> library expects a string - it crashes. If I do not use IFptr pointer - 
> it crashes. So I think I figured out the syntax correctly, but I still 
> can't get the desired result.
>
>
> My question is basically this: Should I continue experimenting, or is 
> it simply impossible to work with this kind of library from Gambas?
>
>
> Here is the link to the library and some other libraries it uses 
> itself: http://allunix.ru/back/atol.tar.gz - there's also a binary 
> executable that is a test program, unfortunately it's in Russian, but 
> it still shows what logs must look like when everything is correct, 
> just for a comparison.
>
>
> There's simple experiment you can make: it has a pointer 
> ShowProperties() which must show a window with driver's settings using 
> it's own library libgui_engine.so. When I call ShowProperties(IFptr) 
> it prints to log that it can't find this lib, which is expectable, 
> because first I must provide the path to it using 
> put_DeviceSingleSettingAsBuff(IFptr, "SearchDir", 
> "/home/bocha/ATOL/linux-x64/") and AplySingleSettings(IFptr), but when 
> I pass this setting, I, as always, see that it passes no arguments, so 
> the result stays the same.
>
> I do understand that I ask a lot of invovement, there's no simple way 
> to understand what's needed to be done to make this whole thing work 
> so not many people would even read this message to the end, but I 
> still hope for some answers, they would be much appriciated. Thank you!
>
> Best Regards.
>
> Dmitry Bachilo.
>
>
> ------------------------------------------------------------------------------ 
>
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
> Gambas-user mailing list
> Gambas-user at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/gambas-user
>
>