#pointers #buffer #produced #devices #safe #ai-m #xrk

xdrk

Library to open XRK and DRK files, produced by AiM devices

1 stable release

1.0.0 Sep 19, 2022

#3 in #produced

Apache-2.0

14MB
1.5K SLoC

Contains (ELF lib, 5.5MB) aim/libxdrk-x86_64.so, (ELF lib, 5.5MB) aim/libmatlabxrk.so.0, (Windows DLL, 2.5MB) aim/libxdrk-x86_64.dll, (static library, 10KB) aim/libxdrk-x86_64.lib

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xdrk

a library to access files produced by AiM devices

Or rather, a Rust wrapper for the shared library provided by AiM which is written in C/C++ and provides an unsafe interface. This wrapper does its best to make the interface safe, which it does - but it still contains one pain point, which is having to work with write buffers (or, as you'd call them in C, pointers to head-allocated arrays). However also this is wrapped as tight as it can be.

Executive summary: safely use the AiM access library for XRK/DRK files.

Build and test it

Building is canonical Rust style:

cargo build

It works on both Linux and Windows 64bit; on Windows, you'll need to use the x86_64-pc-windows-msvc target which in turn required you to install a few GB of MSVC build tools.

Testing is the same, but the Drop implementation test has to be run separately since, well, the AiM library does some on-disk file I/O and that can't happen when running tests concurrently:

cargo test
cargo test -- --ignored

If you have a peak into the coverage.sh file, which is what the continuous integration environment runs, you'll notice that here, we run the tests single threaded:

cargo test -- --test-threads=1
cargo test -- --ignored

This is done because with the flags required by grcov, somehow tests are run in separate processes (I guess?) or something like that - the result is that it f%cks with the globals needed to wrap the AiM library in a thread safe way, and very strange errors occur, so we can't run tests in parallel in CI. Should you find yourself running into issues, I suggest you run the tests single threaded just like CI does, and see what happens.

On our machines, tests run in a reasonable, sub 60 seconds timeframe. So if you are on something vaguely modern, you are not on Windows and you're seeing excessive run times there is probably something wrong. On Windows, tests run 10x longer since the AiM DLL spends between 10 and 20 seconds opening any XRK/DRK file, a process which takes nothing close to a second on Linux.

Using it

Best is to declare it as a dependency of your project via git.

Caveats if you're working on this on Windows

MSVC won't link against a .dll and then later load it dynamically, but it also won't "blindly" link against a shared object and check if everything is dandy at runtime. Well, sort of, because the resource it needs to "link" is just a file containing a bunch of obfuscated symbol names and then they still check again at runtime (because, well, there really isn't any other way).

It is what it is. The good news is that if you have the .dll, you can actually just generate this obfuscated-symbols-file using Microsoft's own tooling.

To link against the AiM library on Windows, you need a .lib file corresponding to the .dll file they provide. There is one included in the aim directory, but if for whatever reason you need a newer one, read on.

You should already have the MSVC build tools installed to work with Rust's x86_64-pc-windows-msvc target. Go ahead and fire up your Visual Studio installer again and install the C++ CLI tools, or the Windows Foundational tools, or whatever your version of Visual Studio calls this stuff; if unsure just Google "visual studio dumpbin" or some similar combination of terms and go from there.

Now that you've installed another 2GB of stuff™, do the following:

  1. From Start menu run "Visual Studio Command Prompt".
  2. Navigate to where/you/put/xdrk/aim
  3. Execute command: dumpbin /exports libxdrk-x86_64.dll > libxdrk-x86_64.def This command prints some information about given DLL library in textual form to its standard output. We redirect it to a text file with DEF extension. But to make it real DEF file, we need to edit it.
  4. Open libxdrk-x86_64.def in some text editor and edit it to contain only the names of exported functions in form of:
    EXPORTS
    function_1_name
    function_2_name
    function_3_name
    
    At this point you may also want to compare the DEF file with the one that is provided in the aim directory of this repo.
  5. Execute another command:
    lib /def:libxdrk-x86_64.def /out:libxdrk-x86_64.lib /machine:x64
    

And there you have it! The so much required LIB file generated from DLL library.

I stole this guide from the internet. As always, thank you, internet!

Dependencies

~7.5MB
~135K SLoC