[Gambas-user] Working with .so library

[Admin]

31.05.2017 16:58, Benoît Minisini пишет:
> Le 31/05/2017 à 06:48, Admin a écrit :
>> 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.
>>
>
> Apparently all that black box is written in C++ with QT, and without 
> the header of the library interface , I can't tell you if it is 
> possible to use the library with Gambas, and how.
>
> Regards,
>
I was lucky enough to find the header file shared by developers and an 
example program in C++ that utilizes this lib.

Here they are: http://allunix.ru/back/atol-header.tar.gz