Feature/shared library refactor (#712)

* * Added ISlangSharedLibraryLoader and ISlangSharedLibrary
* Implemented default implementations
* Added slang API function to get/set the ISlangSharedLibraryLoader on the session
* Put function caching onto the Session - so that if the loader is chaged, its easy to reset the shared libraries, and functions

* Run premake.

* Fix problem with setting null, would cause an unnecessary function/shared lib flush.

* * Unload SharedLibrary when DefaultSharedLibrary is deleted.
* Make SharedLibrary handle unload safely if already unloaded.

* Refactor SharedLibrary, such that it becomes a utility class - simplifying it's semantics.

* Simplified ISlangSharedLibrary such that doesn't have unload and isLoaded so easier to implement.
Use updated SharedLibrary impl.

* Disable aarch64 on windows

* Premake windows files without aarch64 build.

* Moved slang-shared-library to core (so can be used in code outside of main slang)
Fixed problem in premake5 where on windows projects were incorrectly constructed

* Allowed RefObject to base class of com types
Added ConfigurableSharedLibraryLoader
Added -dxc-path -fxc-path -glslang-path
Fix problem with dxc-path not honoring it's path when loading dxil

* Added documentation for command line control of dll loading paths.

* Remove some tabbing issues.

* Change name of include guard.

1 files changed, 38 insertions, 18 deletions

diff --git a/source/core/platform.h b/source/core/platform.h
index fef698e6f..a545d139d 100644
--- a/source/core/platform.h
+++ b/source/core/platform.h
@@ -2,30 +2,50 @@
 #ifndef SLANG_CORE_PLATFORM_H_INCLUDED
 #define SLANG_CORE_PLATFORM_H_INCLUDED
 
+#include "../../slang.h"
+#include "../core/slang-string.h"
+
 namespace Slang
 {
 	// Interface for working with shared libraries
-	// in a platfomr-independent fashion.
+	// in a platform-independent fashion.
 	struct SharedLibrary
 	{
 		typedef struct SharedLibraryImpl* Handle;
-		Handle handle;
-
-		// Attempt to load a shared library for
-		// the current platform.
-		static SharedLibrary load(char const* name);
-
-		// If this refers to a valid loaded library,
-		// then attempt to unload it
-		void unload();
-
-		typedef void (*FuncPtr)(void);
-
-		FuncPtr findFuncByName(char const* name);
-
-
-		operator Handle() { return handle; }
-	};
+        
+        typedef void(*FuncPtr)(void);
+
+            /// Load via an unadorned filename
+            /// 
+            /// @param the unadorned filename
+            /// @return Returns a non null handle for the shared library on success. nullptr indicated failure
+        static SlangResult load(const char* filename, Handle& handleOut);
+
+		    /// Attempt to load a shared library for
+		    /// the current platform. Returns null handle on failure
+            /// The platform specific filename can be generated from a call to appendPlatformFileName
+            ///
+            /// @param platformFileName the platform specific file name. 
+            /// @return Returns a non null handle for the shared library on success. nullptr indicated failure
+        static SlangResult loadWithPlatformFilename(char const* platformFileName, Handle& handleOut);
+
+            /// Unload the library that was returned from load as handle
+            /// @param The valid handle returned from load 
+        static void unload(Handle handle);
+
+            /// Given a shared library handle and a name, return the associated function
+            /// Return nullptr if function is not found
+            /// @param The shared library handle as returned by loadPlatformLibrary
+        static FuncPtr findFuncByName(Handle handle, char const* name);
+
+            /// Append to the end of dst, the name, with any platform specific additions
+            /// The input name should be unadorned with any 'lib' prefix or extension
+        static void appendPlatformFileName(const UnownedStringSlice& name, StringBuilder& dst);
+
+        private:
+            /// Not constructible!
+        SharedLibrary();
+    };
 
 #ifndef _MSC_VER
 	#define _fileno fileno