ENH: Optimize getting of named destinations in readers

Author: larsga

pypdf/_reader.py

@@ -71,6 +71,7 @@
     ArrayObject,
     ContentStream,
     DecodedStreamObject,
+    Destination,
     DictionaryObject,
     EncodedStreamObject,
     IndirectObject,
@@ -80,6 +81,7 @@
     PdfObject,
     StreamObject,
     TextStringObject,
+    TreeObject,
     is_null_or_none,
     read_object,
 )
@@ -143,6 +145,9 @@ def __init__(
         elif password is not None:
             raise PdfReadError("Not an encrypted file")
 
+        # cache so we don't have to parse this over and over
+        self._named_destinations: Optional[Dict[str, Destination]] = None
+
     def _initialize_stream(self, stream: Union[StrByteType, Path]) -> None:
         if hasattr(stream, "mode") and "b" not in stream.mode:
             logger_warning(
@@ -1273,3 +1278,17 @@ def _repr_mimebundle_(
             data = {k: v for k, v in data.items() if k not in exclude}
 
         return data
+
+    def _get_named_destinations(
+        self,
+        tree: Union[TreeObject, None] = None,
+        retval: Optional[Dict[str, Destination]] = None,
+    ) -> Dict[str, Destination]:
+        '''Override from PdfDocCommon. In the reader we can assume this is
+        static, but not in the writer.'''
+        if tree or retval:
+            return PdfDocCommon._get_named_destinations(self, tree, retval)
+
+        if self._named_destinations is None:
+            self._named_destinations = PdfDocCommon._get_named_destinations(self)
+        return self._named_destinations