Adding a DllImport resolver for netcoreapp3.1

sources/LLVMSharp/Interop.Extensions/LLVM.ResolveLibrary.cs

@@ -0,0 +1,78 @@
+// Copyright (c) Microsoft and Contributors. All rights reserved. Licensed under the University of Illinois/NCSA Open Source License. See LICENSE.txt in the project root for license information.
+
+using System;
+using System.Reflection;
+using System.Runtime.InteropServices;
+
+namespace LLVMSharp.Interop
+{
+    public static unsafe partial class LLVM
+    {
+        public static event DllImportResolver ResolveLibrary;
+
+        static LLVM()
+        {
+            NativeLibrary.SetDllImportResolver(Assembly.GetExecutingAssembly(), OnDllImport);
+        }
+
+        private static IntPtr OnDllImport(string libraryName, Assembly assembly, DllImportSearchPath? searchPath)
+        {
+            IntPtr nativeLibrary;
+
+            if (TryResolveLibrary(libraryName, assembly, searchPath, out nativeLibrary))
+            {
+                return nativeLibrary;
+            }
+
+            if (libraryName.Equals("libLLVM") && TryResolveLLVM(assembly, searchPath, out nativeLibrary))
+            {
+                return nativeLibrary;
+            }
+
+            return IntPtr.Zero;
+        }
+
+        private static bool TryResolveLLVM(Assembly assembly, DllImportSearchPath? searchPath, out IntPtr nativeLibrary)
+        {
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux) && NativeLibrary.TryLoad("libLLVM-10.so", assembly, searchPath, out nativeLibrary))
+            {
+                return true;
+            }
+
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && NativeLibrary.TryLoad("LLVM-C.dll", assembly, searchPath, out nativeLibrary))
+            {
+                return true;
+            }
+
+            if (NativeLibrary.TryLoad("libLLVM", assembly, searchPath, out nativeLibrary))
+            {
+                return true;
+            }
+
+            return false;
+        }
+
+        private static bool TryResolveLibrary(string libraryName, Assembly assembly, DllImportSearchPath? searchPath, out IntPtr nativeLibrary)
+        {
+            var resolveLibrary = ResolveLibrary;
+
+            if (resolveLibrary != null)
+            {
+                var resolvers = resolveLibrary.GetInvocationList();
+
+                foreach (DllImportResolver resolver in resolvers)
+                {
+                    nativeLibrary = resolver(libraryName, assembly, searchPath);
+
+                    if (nativeLibrary != IntPtr.Zero)
+                    {
+                        return true;
+                    }
+                }
+            }
+
+            nativeLibrary = IntPtr.Zero;
+            return false;
+        }
+    }
+}

sources/LLVMSharp/LLVMSharp.csproj

@@ -6,6 +6,10 @@
     <TargetFrameworks>netcoreapp3.1;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
 
+  <ItemGroup>
+    <Compile Remove="Interop.Extensions/LLVM.ResolveLibrary.cs" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="libLLVM" />
     <PackageReference Include="System.Memory" />