Passing source to Downstream compilation as artifacts (#2382)

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

* Make DownstreamCompileOptions use POD types.

* CharSliceAllocator -> SliceAllocator
Added SliceConverter
CharSliceCaster -> SliceCaster

* First attempt at zero terminating around blobs.

* Fix clang warning.

* Add SlangTerminatedChars
Make Blob implementations support it.
Make most blobs 'terminated'.

* Fix bug setting up sourceFiles for CommandLineDownstreamCompiler.

* Traffic in TerminatedCharSlice for sourceFiles.
Use ArtifactDesc to generate temporary file names for source.

* Fix typo in testing for shared library/C++.

* Working with source being passed as artifacts to DownstreamCompiler.

* Use artifacts in SourceManager/SourceFile.

* Support infering extension from the original file extension.

1 files changed, 38 insertions, 8 deletions

diff --git a/source/compiler-core/slang-slice-allocator.cpp b/source/compiler-core/slang-slice-allocator.cpp
index 9985f6b19..9a0620ced 100644
--- a/source/compiler-core/slang-slice-allocator.cpp
+++ b/source/compiler-core/slang-slice-allocator.cpp
@@ -5,9 +5,9 @@
 
 namespace Slang {
 
-/* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! SliceConverter !!!!!!!!!!!!!!!!!!!!!!!!!!! */
+/* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! SliceUtil !!!!!!!!!!!!!!!!!!!!!!!!!!! */
 
-/* static */ List<String> SliceConverter::toList(const Slice<TerminatedCharSlice>& in)
+/* static */ List<String> SliceUtil::toList(const Slice<TerminatedCharSlice>& in)
 {
     List<String> list;
     const auto count = in.count;
@@ -20,20 +20,21 @@ namespace Slang {
     return list;
 }
 
-/* static */TerminatedCharSlice SliceConverter::toTerminatedCharSlice(SliceAllocator& allocator, ISlangBlob* blob)
+/* static */const char* SliceUtil::getTerminated(ISlangBlob* blob, TerminatedCharSlice& outSlice)
 {
     const auto size = blob->getBufferSize();
-
     if (size == 0)
     {
-        return TerminatedCharSlice();
+        outSlice = TerminatedCharSlice();
+        return outSlice.begin();
     }
 
     // If there is a 0 at the end byte, we are zero terminated 
     const char* chars = (const char*)blob->getBufferPointer();
     if (chars[size - 1] == 0)
     {
-        return TerminatedCharSlice(chars, Count(size - 1));
+        outSlice = TerminatedCharSlice(chars, Count(size - 1));
+        return chars;
     }
 
     // See if it has a castable interface
@@ -42,15 +43,44 @@ namespace Slang {
     {
         if (castable->castAs(SlangTerminatedChars::getTypeGuid()))
         {
-            return TerminatedCharSlice(chars, Count(size));
+            outSlice = TerminatedCharSlice(chars, Count(size));
+            return chars;
         }
     }
 
+    return nullptr;
+}
+
+/* static */TerminatedCharSlice SliceUtil::toTerminatedCharSlice(SliceAllocator& allocator, ISlangBlob* blob)
+{
+    TerminatedCharSlice slice;
+    if (SliceUtil::getTerminated(blob, slice))
+    {
+        return slice;
+    }
+    const auto size = blob->getBufferSize();
     // We are out of options, we just have to allocate with zero termination which allocateString does
-    auto dst = allocator.getArena().allocateString(chars, Count(size));
+    auto dst = allocator.getArena().allocateString((const char*)blob->getBufferPointer(), Count(size));
     return TerminatedCharSlice(dst, Count(size));
 }
 
+/* static */TerminatedCharSlice SliceUtil::toTerminatedCharSlice(StringBuilder& storage, ISlangBlob* blob)
+{
+    TerminatedCharSlice slice;
+    if (SliceUtil::getTerminated(blob, slice))
+    {
+        return slice;
+    }
+    
+    const auto size = blob->getBufferSize();
+    auto chars = (const char*)blob->getBufferPointer();
+
+    storage.Clear();
+    storage.append(UnownedStringSlice(chars, size));
+   
+    return TerminatedCharSlice(storage.getBuffer(), Count(size));
+}
+
 /* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! SliceAllocator !!!!!!!!!!!!!!!!!!!!!!!!!!! */
 
 TerminatedCharSlice SliceAllocator::allocate(const char* in)