Hi, that's great !
Would you be able to provide instructions here for building TRX c++ library and how you made it work with mrtrix to see if I can reproduce (and leave a trace in case this information should make its way into the README.md).

Sure! On my mac I do

WD=${PWD}
brew install libzip nlohmann-json spdlog
# homebrew's eigen is too new. I downloaded 3.4.0 elsewhere
export EIGEN_CFLAGS="-isystem /path/to/eigen-3.4.0"

git clone [email protected]:tee-ar-ex/trx-cpp.git
cmake -S trx-cpp -B trx-build
cmake --build trx-build

git clone [email protected]:mrtrix3/mrtrix3.git
cd mrtrix3
gh pr checkout 3262
export TRX_CFLAGS="-I${WD}/trx-cpp/third_party/mio/include -I${WD}/trx-cpp/third_party/json11 -I/opt/homebrew/include -I${WD}/trx-cpp/include"
export TRX_LINKFLAGS="-L${WD}/trx-build -ltrx \
  -L/opt/homebrew/opt/libzip/lib -lzip \
  -L/opt/homebrew/opt/fmt/lib -lfmt"

export EIGEN_CFLAGS="-isystem $HOME/deps/eigen-3.4.0"
./configure -nogui
./build bin/tckconvert

Cross-linking to #2241

Thanks for the contribution, @mattcieslak! We've been meaning to look into implementing TRX, but bandwidth is seriously limited these days...

Any chance you could rebase this onto our dev branch? It should be relatively easy to make the changes - the main difference is that code now lives in the cpp folder. But it may take a bit of work to figure out the changes required for CMake to pick up the TRX library - @daljit46 can hopefully help with that bit.

Also: any reason you're not using a std::unique_ptr to handle the trxmmap::TrxFile objects?

Another thing worth mentioning is that the dev branch uses C++17 as the default standard, so changes like tee-ar-ex/trx-cpp#11 shouldn't be required.

Thanks @jdtournier and @daljit46! Wow, I missed some very nicely documented info about your development methods. I think I will close this PR and open a new one after switching trx-cpp to target c++17 as well.