Make ISlangFileSystem derive from ICastable (#2386)

* #include an absolute path didn't work - because paths were taken to always be relative.

* Make ISlangFileSystem derive from ICastable.

* Make ArchiveFileSystem into an interface
Make file systems atomically reference counted.

* Small fix.

* Some small fixes to work around issues of ICastable on ISlangFileSystem

* Use ISlangFileSystem derived type instead of IArchiveFileSystem. Can always get other interface with castAs.

* Some small fixes around change of interface returned from archive type functions.

* Remove CacheFileSystem member from linkage. Can access easily from m_fileSystemExt if necessary with as cast.

* Fix RiffFileSystem casting issue.

* Add a check around CacheFileSystem.

1 files changed, 29 insertions, 2 deletions

diff --git a/source/core/slang-riff-file-system.cpp b/source/core/slang-riff-file-system.cpp
index e916cf689..a8e0f2073 100644
--- a/source/core/slang-riff-file-system.cpp
+++ b/source/core/slang-riff-file-system.cpp
@@ -21,9 +21,36 @@ RiffFileSystem::RiffFileSystem(ICompressionSystem* compressionSystem):
 {
 }
 
-ISlangMutableFileSystem* RiffFileSystem::getInterface(const Guid& guid)
+void* RiffFileSystem::getInterface(const Guid& guid)
 {
-    return (guid == ISlangUnknown::getTypeGuid() || guid == ISlangFileSystem::getTypeGuid() || guid == ISlangFileSystemExt::getTypeGuid() || guid == ISlangMutableFileSystem::getTypeGuid()) ? static_cast<ISlangMutableFileSystem*>(this) : nullptr;
+    if  (   guid == ISlangUnknown::getTypeGuid() || 
+            guid == ISlangCastable::getTypeGuid() || 
+            guid == ISlangFileSystem::getTypeGuid() || 
+            guid == ISlangFileSystemExt::getTypeGuid() || 
+            guid == ISlangMutableFileSystem::getTypeGuid())
+    {
+        return static_cast<ISlangMutableFileSystem*>(this);
+    }
+    else if (guid == IArchiveFileSystem::getTypeGuid())
+    {
+        return static_cast<IArchiveFileSystem*>(this);
+    }
+    return nullptr;
+}
+
+void* RiffFileSystem::getObject(const Guid& guid)
+{
+    SLANG_UNUSED(guid);
+    return nullptr;
+}
+
+void* RiffFileSystem::castAs(const Guid& guid)
+{
+    if (auto ptr = getInterface(guid))
+    {
+        return ptr;
+    }
+    return getObject(guid);
 }
 
 SlangResult RiffFileSystem::_calcCanonicalPath(const char* path, StringBuilder& out)