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dynarithmic / twain_library

Dynarithmic TWAIN Library, Version 5.x
Apache License 2.0
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Java DTWAIN_EnumSources returns bad values in array #20

Closed MichaelHurd closed 3 years ago

MichaelHurd commented 3 years ago

Note: this error only seems to occur when using the 64-bit dll's: dtwain64(u).dll and dtwainjni64(u).dll.

When selecting a scanner using DTWAIN_SelectSource(), I get a long value that I can use to interact with the scanner. If I attempt to enumerate the sources through DTWAIN_EnumSources(), the array has a long value that does not accurately correspond to an installed scanner. This means I must select a scanner using the built-in TWAIN dialogs instead of using my program's scanner dialogs.

dynarithmic commented 3 years ago

I will take a look and let you know what I find (with time permitting). The JNI layer is being reworked, so it won't be surprising if this is an existing bug or oversight, given that the Java binding hasn't been updated in over a year and has not kept up with the various changes done to DTWAIN in that time.

If you have a 32-bit TWAIN driver, does the issue happen for 32-bit also?

MichaelHurd commented 3 years ago

Thanks for the fast response! I tried the 32-bit TWAIN versions, and they were able to list my installed scanners correctly. We already have 32-bit scanner support in our application, though, and are trying to get 64-bit scanning through DTwain so we can handle very large image files.

I'm glad to hear about the JNI rework; hope it's going well. :)

dynarithmic commented 3 years ago

I identified the problem. The JNI layer was marshalling over 32-bit pointer values to the Java layer in 64-bit mode in the DTWAIN_EnumSources function.

I attached an updated dtwainapi.jar, and for now just the dtwainjni64u.dll. Please use these and check if the problem is solved. dtwain_java.zip

I had to change the Java source as well as the JNI source code, so right now I haven't updated the repo with the latest changes. The jar file basically has the src directory, and you can probably see the Java changes anyway by loading into Eclipse and browsing it. But the C++ source code hasn't been posted (when the next update of DTWAIN comes out, then the JNI source will be updated).

MichaelHurd commented 3 years ago

Yes, that fixed it! Thank you so much!

dynarithmic commented 3 years ago

I updated the master branch with the Java changes. You should be able to get all the adjusted jar files by downloading the master branch.

In addition, the JNI source code was posted, along with the Visual Studio project file, so if you have the capabilities to do so, you can set up a recompilation of the JNI DLL's.

dynarithmic commented 3 years ago

Closing this ticket.