add support for linux

[clouds56]

By using https://github.com/McSimp/linoodle, we could load oo2core_8_win64.dll on linux

[ividyon]

Should this still have the ".dll" ending, given that it was removed from the other instances of DllImport?

[clouds56]

Since there's no kernel32.dll in linux, this line is just fine.
Actually, we use public static class Libdl in linux instead.

I'm not sure if netstandard could use the latest NativeLibrary.Load and/or LibraryImport, if so, we could simplify some code here.

[ividyon]

Looks interesting. We've kept compatibility to netstandard and netcore for the sake of having cross-platform capability, and this seems to move us closer to that goal.

Have you personally tested it? How would you suggest to test it?

[clouds56]

Yes, I've test on my wsl ubuntu.
But it's tricky for dlopen to find library.
This relies on linoodle library, I suggest use my fork (https://github.com/clouds56-contrib/linoodle/tree/path), or wait McSimp/linoodle#6 to check in. (to summarize, my fork add necessary API that SoulsFormats relies on, could find library in more path, and support both oo2core_6_win64 and oo2core_8_win64)

1. build linoode with mkdir build && cd build && cmake .. && make
2. copy output liboodle_26.so and liboodle_28.so to dotnet output folder
   • should be renamed as liboo2core_6_win64.so and liboo2core_8_win64.so since DllImport would find exact this name
   • should copy oo2core_6_win64.dll from game folder to the same folder liboo2core_6_win64.so
   • if you would like not to copy or encountered any error, add the path of liboo2core_6_win64.so and oo2core_6_win64.dll to LD_LIBRARY_PATH

~/workspace/linoodle % ls build
CMakeCache.txt  CMakeFiles  Makefile  cmake_install.cmake  liblinoodle.so  liboodle_26.so  liboodle_28.so  oo2core_6_win64.dll  pe-parse  testlinoodle
# test
~/workspace/linoodle % cp /path/to/game/oo2core_6_win64.dll bin/Debug/net8.0/ && ./build/testlinoodle ./build/liboodle_26.so
Test succeeded!
~/workspace/MyProject % dotnet build
...
~/workspace/MyProject % cp ../linoodle/liboodle_26.so bin/Debug/net8.0/liboo2core_6_win64.so
~/workspace/MyProject % cp /path/to/game/oo2core_6_win64.dll bin/Debug/net8.0/
# if this doesn't work, you might need set LD_LIBRARY_PATH
~/workspace/MyProject % export LD_LIBRARY_PATH="$PWD/bin/Debug/net8.0:$LD_LIBRARY_PATH"

[clouds56]

Some note here:

On linux we import liboo2core_6_win64.so twice from our SoulsFormats library

1. first time in public static IOodleCompressor GetOodleCompressor(), we called NativeLibrary.LoadLibrary("oo2core_6_win64"), which finally calls dlopen("liboo2core_6_win64.so") which would find lib in LD_LIBRARY_PATH (behavior of dlopen)
2. second time on first time calling new Oodle26(), the attribute of [DllImport("oo2core_6_win64", CallingConvention = CallingConvention.StdCall)] would find liboo2core_6_win64.so in LD_LIBRARY_PATH plus "dotnet output folder" (behavior of dotnet, see also Using the LD LIBRARY PATH to load local libraries does not work on Linux dotnet/runtime#34711)

Then when liboo2core_6_win64.so initialize, it would found oo2core_6_win64.dll in LD_LIBRAY_PATH plus where executable_path (just like exe in windows do), plus the location of liboo2core_6_win64.so, (the behavior is written in code of linoodle)