[GitHub] [lucenenet] NightOwl888 commented on issue #256: Port ConditionalWeakTable from .NET Core 3.x to .NET Standard 2.0

[GitBox <gi...@apache.org>]

NightOwl888 commented on issue #256:
URL: https://github.com/apache/lucenenet/issues/256#issuecomment-705975452


   @shadowcaptain 
   
   Thanks. [An attempt](https://github.com/NightOwl888/J2N/tree/feature/conditional-weak-table/src/J2N/Runtime/CompilerServices) has already been made on this. The blocker is the fact that it depends on [DependentHandle](https://github.com/NightOwl888/J2N/blob/feature/conditional-weak-table/src/J2N/Runtime/CompilerServices/DependentHandle.cs) which has native resources.
   
   `DependentHandle` calls native methods using `[MethodImpl(MethodImplOptions.InternalCall)]`.
   
   ```c#
           [MethodImpl(MethodImplOptions.InternalCall)]
           private static extern IntPtr nInitialize(object primary, object? secondary);
   
           [MethodImpl(MethodImplOptions.InternalCall)]
           private static extern object? nGetPrimary(IntPtr dependentHandle);
   
           [MethodImpl(MethodImplOptions.InternalCall)]
           private static extern object? nGetPrimaryAndSecondary(IntPtr dependentHandle, out object? secondary);
   
           [MethodImpl(MethodImplOptions.InternalCall)]
           private static extern void nSetPrimary(IntPtr dependentHandle, object? primary);
   
           [MethodImpl(MethodImplOptions.InternalCall)]
           private static extern void nSetSecondary(IntPtr dependentHandle, object? secondary);
   
   
           [MethodImpl(MethodImplOptions.InternalCall)]
           private static extern void nFree(IntPtr dependentHandle);
   ```
   
    It is not currently known how to translate that into a call that can be done from a 3rd party library such as J2N. Some important questions to answer:
   
   - Can we assume the native method exists for the current platform, since .NET Standard should "just work"?
   - Do we need to bundle the native resources in J2N to call them?
   - If we need to bundle native resources, do they work on all platforms or do we need separate builds for specific platforms?
   
   Note that `[MethodImpl(MethodImplOptions.InternalCall)]` doesn't exist on .NET Standard 1.x, but it is probably time to drop support for that target, anyway.


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