Disallow empty blobs from being read

[wimlib] / include / wimlib / blob_table.h

diff --git a/include/wimlib/blob_table.h b/include/wimlib/blob_table.h
index dcf6af7ffaa2c2a44870b1e3d8eb6bb55e8caf6b..0ccccfbbbbb0f876e4172016d7e2fc60d864834e 100644 (file)
--- a/include/wimlib/blob_table.h
+++ b/include/wimlib/blob_table.h
@@ -74,7 +74,20 @@ struct blob_descriptor {
        /* List node for a hash bucket of the blob table  */
        struct hlist_node hash_list;
 
-       /* Uncompressed size of this blob  */
+       /*
+        * Uncompressed size of this blob.
+        *
+        * In most cases we are now enforcing that this is nonzero; i.e. an
+        * empty stream will have "no blob" rather than "an empty blob".  The
+        * exceptions are:
+        *
+        *      - blob descriptors with 'blob_location == BLOB_NONEXISTENT',
+        *        e.g. placeholder entries for new metadata resources or for
+        *        blobs required for pipable WIM extraction.  In these cases the
+        *        size is not meaningful information anyway.
+        *      - blob descriptors with 'blob_location == BLOB_IN_STAGING_FILE'
+        *        can vary their size over time, including to 0.
+        */
        u64 size;
 
        union {