1 files changed, 11 insertions, 1 deletions
diff --git a/org/ocda_functions.org b/org/ocda_functions.org
index 71d1b97..0e42cfb 100644
--- a/org/ocda_functions.org
+++ b/org/ocda_functions.org
@@ -3430,7 +3430,16 @@ SHA_256_Hashes_ obj_digest(M)(
   M                    manifested,
 ) {
   ST_file_name_hash_size_ safeComputeHashAndSize(N,P)(N filename, P file_path) @trusted {
-    auto file_with_path = file_path ~ filename;
+    string file_with_path = (file_path ~ filename).to!string;
+    /+ ↓ read & hash each image file once: an image referenced from several
+       objects (or from several documents sharing an image directory) was
+       otherwise re-read and re-hashed for every reference. static is
+       thread-local in D, so the cache needs no synchronisation
+    +/
+    static ST_file_name_hash_size_[string] _image_file_info_cache;
+    if (auto _cached = file_with_path in _image_file_info_cache) {
+      return *_cached;
+    }
     ST_file_name_hash_size_ _file_info;
     _file_info.fileName = filename;
     /+ ↓ a referenced image that is absent or unreadable is recorded as
@@ -3466,6 +3475,7 @@ SHA_256_Hashes_ obj_digest(M)(
         }
       }
     }
+    _image_file_info_cache[file_with_path] = _file_info;
     return _file_info;
   }
   obj.metainfo.sha256.text = obj.text.sha256Of;