Improve Alembic plugin to read assets with ArResolver to support othe…

…r sources except local files

pxr/usd/plugin/usdAbc/alembicReader.cpp

@@ -7,6 +7,9 @@
 /// \file alembicReader.cpp
 
 #include "pxr/pxr.h"
+#include "pxr/usd/ar/asset.h"
+#include "pxr/usd/ar/resolvedPath.h"
+#include "pxr/usd/ar/resolver.h"
 #include "pxr/usd/plugin/usdAbc/alembicReader.h"
 #include "pxr/usd/plugin/usdAbc/alembicUtil.h"
 #include "pxr/usd/usdGeom/hermiteCurves.h"
@@ -36,6 +39,7 @@
 #include <Alembic/AbcGeom/SchemaInfoDeclarations.h>
 #include <Alembic/AbcGeom/Visibility.h>
 #include <optional>
+#include <fstream>
 #include <functional>
 #include <memory>
 #include <mutex>
@@ -628,6 +632,34 @@ _ReaderSchema::GetPrimReaders(const std::string& schema) const
     return empty;
 }
 
+/// \class _ArAssetStreamContext
+/// \brief The context to save the associated std::istream
+/// std::filebuf, and pxr:ArAsset.
+///
+/// It's used by the Alembic reader to read from istreams.
+class _ArAssetStreamContext
+{
+public:
+    _ArAssetStreamContext(const std::shared_ptr<ArAsset> &asset) : _asset(asset)
+    {
+        if (asset && asset->GetFileUnsafe().first)
+        {
+            _fileBuf =
+                std::make_unique<std::filebuf>(asset->GetFileUnsafe().first);
+        }
+        // Note: Contructing std::istream with nullptr is allowed, but
+        // it returns a std::istream with invalid io state. 
+        _istream = std::make_unique<std::istream>(_fileBuf.get());
+    }
+
+    std::istream *GetIStream() const { return _istream.get(); }
+
+private:
+    std::unique_ptr<std::istream> _istream;
+    std::unique_ptr<std::filebuf> _fileBuf;
+    std::shared_ptr<ArAsset> _asset;
+};
+
 /// \class _ReaderContext
 /// \brief The Alembic to Usd writer context.
 ///
@@ -853,6 +885,7 @@ class _ReaderContext {
     _PrimMap _prims;
     Prim* _pseudoRoot;
     UsdAbc_TimeSamples _allTimeSamples;
+    std::vector<_ArAssetStreamContext> _allLayeredABCStreamContexts;
 };
 
 static
@@ -889,6 +922,16 @@ _ReaderContext::Open(const std::string& filePath, std::string* errorLog,
     }
     layeredABC.emplace_back(filePath);
 
+    std::vector<std::istream *> layeredABCStreams;
+    for (const std::string &path : layeredABC)
+    {
+        std::shared_ptr<ArAsset> asset =
+            ArGetResolver().OpenAsset(ArResolvedPath(path));
+        _ArAssetStreamContext context(asset);
+        layeredABCStreams.push_back(context.GetIStream());
+        _allLayeredABCStreamContexts.emplace_back(std::move(context));
+    }
+
 #if PXR_HDF5_SUPPORT_ENABLED && !H5_HAVE_THREADSAFE
     // HDF5 may not be thread-safe.
     using lock_guard = std::lock_guard<std::recursive_mutex>;
@@ -907,7 +950,7 @@ _ReaderContext::Open(const std::string& filePath, std::string* errorLog,
     }
 #endif
 
-    IArchive archive = factory.getArchive(layeredABC, abcType);
+    IArchive archive = factory.getArchive(layeredABCStreams, abcType);
 
 #if PXR_HDF5_SUPPORT_ENABLED && !H5_HAVE_THREADSAFE
     if (abcType == IFactory::kHDF5 || abcType == IFactory::kLayer) {