gh-102956: Fix returning of empty byte strings after seek in zipfile … (#103565)

gh-102956: Fix returning of empty byte strings after seek in zipfile module. This was a regression in 3.12.0 due to a performance enhancement.

1 files changed, 5 insertions, 5 deletions

diff --git a/Lib/zipfile/__init__.py b/Lib/zipfile/__init__.py
index 995d267..2b28a07 100644
--- a/Lib/zipfile/__init__.py
+++ b/Lib/zipfile/__init__.py
@@ -1136,8 +1136,12 @@ class ZipExtFile(io.BufferedIOBase):
         read_offset = new_pos - curr_pos
         buff_offset = read_offset + self._offset
 
+        if buff_offset >= 0 and buff_offset < len(self._readbuffer):
+            # Just move the _offset index if the new position is in the _readbuffer
+            self._offset = buff_offset
+            read_offset = 0
         # Fast seek uncompressed unencrypted file
-        if self._compress_type == ZIP_STORED and self._decrypter is None and read_offset > 0:
+        elif self._compress_type == ZIP_STORED and self._decrypter is None and read_offset > 0:
             # disable CRC checking after first seeking - it would be invalid
             self._expected_crc = None
             # seek actual file taking already buffered data into account
@@ -1148,10 +1152,6 @@ class ZipExtFile(io.BufferedIOBase):
             # flush read buffer
             self._readbuffer = b''
             self._offset = 0
-        elif buff_offset >= 0 and buff_offset < len(self._readbuffer):
-            # Just move the _offset index if the new position is in the _readbuffer
-            self._offset = buff_offset
-            read_offset = 0
         elif read_offset < 0:
             # Position is before the current position. Reset the ZipExtFile
             self._fileobj.seek(self._orig_compress_start)