Patch #1435422: zlib's compress and decompress objects now have a

copy() method.

Doc/lib/libzlib.tex

@@ -123,6 +123,12 @@ prevents compressing any more data.  After calling
 action is to delete the object.  
 \end{methoddesc}
 
+\begin{methoddesc}[Compress]{copy}{}
+Returns a copy of the compression object.  This can be used to efficiently
+compress a set of data that share a common initial prefix.
+\versionadded{2.5}
+\end{methoddesc}
+
 Decompression objects support the following methods, and two attributes:
 
 \begin{memberdesc}{unused_data}
@@ -176,6 +182,13 @@ The optional parameter \var{length} sets the initial size of the
 output buffer.
 \end{methoddesc}
 
+\begin{methoddesc}[Decompress]{copy}{}
+Returns a copy of the decompression object.  This can be used to save the
+state of the decompressor midway through the data stream in order to speed up
+random seeks into the stream at a future point.
+\versionadded{2.5}
+\end{methoddesc}
+
 \begin{seealso}
   \seemodule{gzip}{Reading and writing \program{gzip}-format files.}
   \seeurl{http://www.zlib.net}{The zlib library home page.}