Refactor stream filtering logic for empty streams

Introduced explicit checks for empty streams and refined filtering conditions for improved clarity and correctness.

Refactor stream filtering logic for empty streams
Introduced explicit checks for empty streams and refined filtering conditions for improved clarity and correctness.
m-holger
1 parent 3470c5f1
Showing 2 changed files with 17 additions and 1 deletions
libqpdf/QPDF_Stream.cc
manual/release-notes.rst
@@ -432,7 +432,16 @@ Stream::pipeStreamData(
         filterp = &ignored;
     }
     bool& filter = *filterp;
-    filter = encode_flags || decode_level != qpdf_dl_none;
+
+    const bool empty_stream = !s->stream_provider && !s->stream_data && s->length == 0;
+    const bool empty_stream_data = s->stream_data && s->stream_data->getSize() == 0;
+    const bool empty = empty_stream || empty_stream_data;
+
+    if(empty_stream || empty_stream_data) {
+        filter = true;
+    }
+
+    filter = empty || encode_flags || decode_level != qpdf_dl_none;
     if (filter) {
         filter = filterable(decode_level, filters);
     }
@@ -23,6 +23,13 @@ more detail.
       not work on some older Linux distributions. If you need support
       for an older distribution, please use version 12.2.0 or below.
+  - Other enhancements
+
+    - ``QPDFWriter`` will no longer add filters when writing empty streams.
+
+    - More sanity checks have been added when files with damaged xref tables
+      are recovered.
+
 12.2.0: May 4, 2025
   - Upcoming C++ Version Change