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Rolf Kalbermatter

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Rolf Kalbermatter last won the day on September 16

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About Rolf Kalbermatter

  • Birthday 06/28/1966

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    LabVIEW 2011
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  1. You really should learn a little C programming. Because that is what is required when trying to call DLLs. Or hire someone to make the LabVIEW bindings for you! Currently you are sticking around with a pole in a heap of hay to find the needles hidden in there, but having chosen to not only blindfold yourself to make it more "interesting" but also bind your hands on your back. DLL_START is the function pointer declaration and is basically documenting the parameters and return value the function takes. This is almost what you need to use for the import library wizard but not quite. A function pointer declaration is only similar to a function declaration but not the same. The Import Library Wizard however needs a function declaration and it needs to use the same name as what the DLL is exporting, otherwise the wizard can't match the declaration to a particular function. In your example you need to find what function pointer declaration is used for which function. Then you need to translate it to a function declaration. So you have determined that the DLL_START declaration is used for the function pointer for StartGenericDevice() typedef int (*DLL_START) ( DWORD *dwSamplerate ); will then have to be turned into following function declaration: int StartGenericDevice( DWORD *dwSamplerate ); With this the Import Library Wizard does have a function prototype to use for the function exported from the DLL. Now you need to do that also for your other functions in the DLL.
  2. Well, if you have the source code for the GenericDevice_DLL_DEMODlg program you may be able to verify that which function pointer is assigned which DLL function. Without that it is simply assuming and things and there is "ass" in the word assuming, which is where assumptions usually bite you in! 😀
  3. That's because the GenericDeviceInterface.h doesn't declare the functions. And the other two DEMO header files don't really do either but are rather header files for an application to use this DLL with (and declare C++ classes, which the Import Library Wizard can't do anything with). There are some function pointer declarations in GenericDevice_DLL_DEMODlg.h that the according sample code most likely dynamically imports from the DLL on initialization but the naming is only partly similar to the function names the DLL seems to export, so it is a bit tricky and there is no function pointer declaration for the GetRequestKey() export but two function pointers for a DLL_TEST and DLL_ShowData function that the DLL doesn't seem to export anything similar for.
  4. Sometimes you may be forced to develop in 64-bit (image acquisition, large data processing or similar requirements) but also need to interface to a driver whose manufacturer never made the move to 64-bit and possibly never will. The opposite may also be possible: that you develop in 32-bit because the majority of your drivers are only available in 32-bit but one specific driver is only available in 64-bit. If the device protocol is documented and going over a standard bus like GPIB, serial or TCP/IP I would always recommend to implement the driver for at least the oddball device in LabVIEW instead of trying to mix and match bitnesses. If that is not an option, the only feasible solution is to create a separate executable and communicate to it through some IPC (RPC) mechanisme.
  5. Sometimes you don't really have a choice. But I agree, if at all possible, don't try to do it! In my case it is usually about my own DLLs/shared libraries, so this particular problem doesn't really present itself for me. I just recompile the DLL/shared library in whatever bitness is needed. Tidbit: While there is indeed thunking, and Windows internally uses it in the SysWOW64 layer that makes the 64-bit kernel API available to 32-bit application, this mechanism was very carefully shielded by Microsoft to not be available to anything outside of the SysWOW64 layer and therefore not provide any thunking facilities for user code between 32-bit and 64-bit code. It generally also only works from 32-bit code calling into 64-bit code and not the opposite at all. I suppose Microsoft wanted to avoid the situation when they went from the segmented 16-bit Windows memory model to the 32-bit flat memory model and just documented how the thunking can be done and everybody was starting to develop all kinds of mechanisms in weird to horrible assembly code to do just that. There was a lot of low level assembly involved in doing so, it had many restrictions and difficulties and once almost everybody had moved to 32-bit, really everybody tried to forget as quickly as possible about this episode. So when going to 64-bit model they carefully avoided this mistake and simply stated from the start that there was no in-process 32-bit to 64-bit translation layer at all (which is technically incorrect since SysWOW64 is just that, but you can't use its services from application code other than indirectly through calling the official Windows APIs). The method used here with executing the different bitness code in a separate process and communicate with it through network communication (or possibly some other Inter-Process Communication method) is not really thunking but rather out of process invocation. There is no officially sanctioned way of thunking between 32-bit and 64-bit code although I'm pretty sure that with enough determination, time and grey matter, there have been people developing their own thunking solutions in assembly. But it would require deep study of the Intel microcode documentation about how 32-bit and 64-bit code execution can interact together and it would probably result in individual assembly thunking wrappers for every single function that you want to call. Definitely not something most people could or would want to do. And to make matters worse, you would never be sure that there are not some CPU models that somehow do something just a little bit different than what you interpreted the specification to be and catastrophically fail on your assembly code thunk.
  6. Error handling is always a heated discussion topic. You could argue about the same for timeout errors on network and VISA nodes. And some people get in their frillies about the VISA Read returning a warning when it reads as many characters as you have specified it to read. A warning wouldn't be better as you still would have to read both the status=FALSE and code==4 to detect it. Also I never really work with the EOF error status as I don't read a file until it errors out but until I reach its size. And if you want to work with the EOF status there is a very easy thing. Using the Clear Errors.vi for error 4 you actually get a boolean status if this error was removed from the error cluster if you need that. Otherwise just terminate the loop on the error cluster anyways, clear error 4 in all cases and go on.
  7. That does take some time as LabVIEW has to enumerate the directory contents for all files to get the size which is the number of files in the directory.
  8. Most likely because the original code originates from pre LabVIEW 8.0. There all LabVIEW Read and Write nodes had explicit file offset input and output. When you upgrade these VIs, LabVIEW mutates them by adding explicit file offset calls before and after the File Read and File Write. It's the only safe way as LabVIEW can't easily know if the original file offset handling was unnecessary because the access is fully sequential or not. Obviously for trivial cases like this the analyzer could be made smart enough to decide that it is not needed, but there are corner cases where this is not easily decided. Rather than try to think up of all such corner cases and make sure that analyzer won't decide wrong by removing one file offset call to much, the easier thing is to simply maintain the original functionality and risk some performance loss (which is minimal in comparison to the old situation where this offset handling was always done anyways). The "example scrubber" for that code probably cleaned it up but didn't dare to remove the file offset calls, obviously not to familiar with LabVIEW internas.
  9. You can remove the Set and Get File Offset inside the loop. The LabVIEW file IO nodes maintain internally a file offset (actually it's the underlying OS file IO functions which do and advance that pointer along as you read). As long as you do pure sequential access there is no need to set the file offset explicitly setting. It's even so that when you open a file for anything but append mode, the file offset will be automatically set to 0. Only when you do random access will you need to do explicit file offset setting. I don't expect this to save a lot of time but why do it if it is not necessary? That would seem very strange. The Get File Size directly translates to a Windows API call on the underlying file handle. Why that would be so slow is a miracle to me.
  10. One obvious discrepancy: create uses a pointer sized integer and destroy uses an Adapt to type. This will result in passing the pointer as an u64 passed by reference (Adapt to Type are always passed by reference if they are not handles, arrays or ActiveX references). What you want to configure it to is Numeric, Pointer sized Integer, Pass by Value. Yes you want to pass it by value, the value returned from the create function is already a pointer and destroy expects this pointer.
  11. Since you don't access the internal elements in the struct at all from LabVIEW you just can treat it all as a pointer sized integer. In fact since OpenSSL 1.0.0 all those structs are considered opaque in terms of external users of the API and should never be referenced in any way other than through published OpenSSL functions. In terms of an external API user these contexts are meant to be simply a handle (a pointer to private data whose contents is unknown). EVP_MD_CTX_create() creates the context -> just configure it to return a pointer sized integer. Then pass this to all other EVP functions again as pointer sized integer. And of course don't forget to call the EVP_MD_CTX_free() function at the end to avoid memory leaks.
  12. It's essentially the same as what QueueYueue posted. And it has the same problem, it won't work at runtime. "LVClass.Open" is not available in Runtime and Realtime (Library: Get Ref by Qualified Name is available but not remote executable, but typecasting to LVClass won't work since the Runtime and Realtime does not support that VI server class). "ChildrenInMemory" is not available in Runtime and Realtime All LVClass properties and methods are not available in Runtime and Realtime
  13. Actually, the Widechar functions supported it since at least Windows 2000 but only with the special prefix. That registry hack and application manifest is needed to not have to use this prefix, so yes porting to Widechar functions is in either case needed to support long file paths. My library adds the special prefix and didn't have to go through manifests and registry settings to use the feature.
  14. As Shaun already more or less explained it is a multilayered problem. 1) The LabVIEW path control has internally following limitations: - a path element (single directory level or filename) can be at most 255 characters. - the path can have at most 65535 levels The only practical limit that is even remotely ever reachable is the 255 character limit per path level, but I think we all agree that if you get that long path level names you have probably other problems to tackle first. 😀 (such as getting out of the straightjacket they for sure have put you in already). 2) Traditionally Windows only supported long path names when you used the Widechar file IO functions and also only when you prepended the path string with a special character sequence. LabVIEWs lack of native support for Unicode made that basically impossible. Long path names are limited to 32000 something characters. 3) Somewhere along the line of Windows versions (7, 8?) the requirement for the special character sequence prepending seems to have relaxed. 4) Since Windows 10 you can enable a registry setting that also allows the ANSI functions to support long path names. So while theoretically there is now a way to support long path names in LabVIEW on Windows 10 this is hampered by a tiny little snag. The path conversion routines between LabVIEW paths and native paths never had to deal with such names since Windows until recently didn't support it for the ANSI functions, and there are some assumptions that paths can't get more than MAX_PATH name characters. This is simply for performance. With a maximum fixed size you don't need to preflight the path to determine a maximum size to allocate a dynamic buffer for, that you then have to properly deallocate afterwards. Instead you simply declare a buffer on the stack, which is basically nothing more than a constant offset added to the stack pointer and all is well. Very fast and very limiting! This is where it is currently still going wrong. Now reviewing the path manager code paths to all properly use dynamically allocated buffers would be possible but quite tedious. And it doesn't really solve the problem fully since you still need to go and change an obscure registry setting to enable it to work on a specific computer. And it doesn't solve another big problem, that of localized path names. Any character outside the standard 7-bit ASCII code will NOT transfer well between systems with different locales. To solve this LabVIEW will need some more involved path manager changes. First the path needs to support Unicode. That is actually doable since the Path data type is a private data type so how LabVIEW stores path data inside the handle is completely private and it could easily change that format to use whatever is the native prefered Unicode char for the current platform. On Windows this would be a 16 bit WCHAR, on other platforms it would be either a wchar or an UTF8 char. It wouldn't really matter since the only other relevant platforms are all Linux or Mac BSD based and use by default UTF8 for filenames. When the path needs to be externalized (LabVIEW speak is flattened) it always would be converted to and from UTF8 to the native format. Now LabVIEW can convert its Path to whatever is the native path type (WCHAR string on Windows, UTF8 string on other platforms) and it support long path names and international paths all in one go. The UTF8 format of externalized paths wouldn't be strictly compatible with the current paths, but for all practical purposes it would be not really worse than it is now. The only special case would be when saving VIs for previous versions where it would have to change paths from UTF8 to ASCII at a certain version. I kind of did attempt to do something like that for the OpenG ZIP library but it is hacky and error prone since I can't really go and change the LabVIEW internal data types, so I had to define my own data type that represents a Unicode capable path and then create functions for every single file function that I wanted to use to use this new path, basically rewriting a large part of the LabVIEW Path and File Manager component. It's ugly and really took away most of my motivation to work on that package anymore. I have another private library that I used in a grey past to create the LLB Viewer File Explorer extension before NI made one themselves, and I have modified that to support this type of file paths. Works quite well in fact but it is all very legacy by now. But it did have long file name and local independent file name support some 15 years ago already with an API that looked almost exactly like the LabVIEW File and Path Managers.
  15. We usually use discrete ones and just use a few digital IO ports in our E cabinet for them. The digital IO to use depends on the hardware in the E cabinet. That could be cRIO digital IOs, or a Beckhoff PLC IO or Beckhoff BusCoupler IOs, usually accessed through the ADS protocol over Ethernet. USB controlled devices don't work well for non-Windows controllers at all, since you always run into trouble to get drivers.
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