[Gambas-user] Working with .so library
Admin
admin at ...3661...
Wed May 31 11:59:46 CEST 2017
Hi, Caveat.
Yes, ofcourse, this is basically the only article outthere that explains
at least something. But I still can't understand why arguments are not
sent to my lib and what do I do wrong if it's not the Gambas issue.
31.05.2017 16:35, Caveat пишет:
> 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.
>>
>>
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>
>
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