1 files changed, 77 insertions, 0 deletions
diff --git a/src/silx/io/h5link_utils.py b/src/silx/io/h5link_utils.py
new file mode 100644
index 0000000..39f9ae4
--- /dev/null
+++ b/src/silx/io/h5link_utils.py
@@ -0,0 +1,77 @@
+import os
+from typing import NamedTuple, Optional
+from .utils import is_dataset
+
+
+class ExternalDatasetInfo(NamedTuple):
+    type: str
+    nfiles: int
+    first_file_path: str
+    first_data_path: Optional[str] = None
+
+    @property
+    def first_source_url(self):
+        if self.first_data_path:
+            if self.first_data_path.startswith("/"):
+                return self.first_file_path + "::" + self.first_data_path
+            else:
+                return self.first_file_path + "::/" + self.first_data_path
+        return self.first_file_path
+
+
+def external_dataset_info(hdf5obj) -> Optional[ExternalDatasetInfo]:
+    """When the object is a virtual dataset or an external dataset,
+    return information on the external files. Return `None` otherwise.
+
+    Note that this has nothing to do with external HDF5 links."""
+    if not is_dataset(hdf5obj):
+        return
+    if hasattr(hdf5obj, "is_virtual") and hdf5obj.is_virtual:
+        sources = hdf5obj.virtual_sources()
+        if not sources:
+            return ExternalDatasetInfo(
+                type="Virtual",
+                nfiles=0,
+                first_file_path="",
+            )
+
+        first_source = sources[0]
+        first_file_path = first_source.file_name
+        if first_file_path == ".":
+            first_file_path = hdf5obj.file.filename
+        elif not os.path.isabs(first_file_path):
+            dirname = os.path.dirname(hdf5obj.file.filename)
+            first_file_path = os.path.normpath(
+                os.path.join(
+                    dirname,
+                    first_file_path,
+                )
+            )
+
+        return ExternalDatasetInfo(
+            type="Virtual",
+            nfiles=len(sources),
+            first_file_path=first_file_path,
+            first_data_path=first_source.dset_name,
+        )
+    if hasattr(hdf5obj, "external"):
+        sources = hdf5obj.external
+        if not sources:
+            return
+
+        first_source = sources[0]
+        first_file_path = first_source[0]
+        if not os.path.isabs(first_file_path):
+            dirname = os.path.dirname(hdf5obj.file.filename)
+            first_file_path = os.path.normpath(
+                os.path.join(
+                    dirname,
+                    first_file_path,
+                )
+            )
+
+        return ExternalDatasetInfo(
+            type="Raw",
+            nfiles=len(sources),
+            first_file_path=first_file_path,
+        )