bpo-22908: Add seek and tell functionality to ZipExtFile (GH-4966)
This allows for nested zip files, tar files within zip files, zip files within tar files, etc.
Contributed by: John Jolly
diff --git a/Lib/zipfile.py b/Lib/zipfile.py
index f9db45f..5df7b1b 100644
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -696,6 +696,18 @@
self._close = close
self._lock = lock
self._writing = writing
+ self.seekable = file.seekable
+ self.tell = file.tell
+
+ def seek(self, offset, whence=0):
+ with self._lock:
+ if self.writing():
+ raise ValueError("Can't reposition in the ZIP file while "
+ "there is an open writing handle on it. "
+ "Close the writing handle before trying to read.")
+ self._file.seek(self._pos)
+ self._pos = self._file.tell()
+ return self._pos
def read(self, n=-1):
with self._lock:
@@ -746,6 +758,9 @@
# Read from compressed files in 4k blocks.
MIN_READ_SIZE = 4096
+ # Chunk size to read during seek
+ MAX_SEEK_READ = 1 << 24
+
def __init__(self, fileobj, mode, zipinfo, decrypter=None,
close_fileobj=False):
self._fileobj = fileobj
@@ -778,6 +793,17 @@
else:
self._expected_crc = None
+ self._seekable = False
+ try:
+ if fileobj.seekable():
+ self._orig_compress_start = fileobj.tell()
+ self._orig_compress_size = zipinfo.compress_size
+ self._orig_file_size = zipinfo.file_size
+ self._orig_start_crc = self._running_crc
+ self._seekable = True
+ except AttributeError:
+ pass
+
def __repr__(self):
result = ['<%s.%s' % (self.__class__.__module__,
self.__class__.__qualname__)]
@@ -963,6 +989,62 @@
finally:
super().close()
+ def seekable(self):
+ return self._seekable
+
+ def seek(self, offset, whence=0):
+ if not self._seekable:
+ raise io.UnsupportedOperation("underlying stream is not seekable")
+ curr_pos = self.tell()
+ if whence == 0: # Seek from start of file
+ new_pos = offset
+ elif whence == 1: # Seek from current position
+ new_pos = curr_pos + offset
+ elif whence == 2: # Seek from EOF
+ new_pos = self._orig_file_size + offset
+ else:
+ raise ValueError("whence must be os.SEEK_SET (0), "
+ "os.SEEK_CUR (1), or os.SEEK_END (2)")
+
+ if new_pos > self._orig_file_size:
+ new_pos = self._orig_file_size
+
+ if new_pos < 0:
+ new_pos = 0
+
+ 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
+ elif read_offset < 0:
+ # Position is before the current position. Reset the ZipExtFile
+
+ self._fileobj.seek(self._orig_compress_start)
+ self._running_crc = self._orig_start_crc
+ self._compress_left = self._orig_compress_size
+ self._left = self._orig_file_size
+ self._readbuffer = b''
+ self._offset = 0
+ self._decompressor = zipfile._get_decompressor(self._compress_type)
+ self._eof = False
+ read_offset = new_pos
+
+ while read_offset > 0:
+ read_len = min(self.MAX_SEEK_READ, read_offset)
+ self.read(read_len)
+ read_offset -= read_len
+
+ return self.tell()
+
+ def tell(self):
+ if not self._seekable:
+ raise io.UnsupportedOperation("underlying stream is not seekable")
+ filepos = self._orig_file_size - self._left - len(self._readbuffer) + self._offset
+ return filepos
+
class _ZipWriteFile(io.BufferedIOBase):
def __init__(self, zf, zinfo, zip64):