diff --git a/Lib/zipfile.py b/Lib/zipfile.py
index d99c0d76977750..ebeb6100c1887d 100644
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -787,19 +787,12 @@ class ZipExtFile(io.BufferedIOBase):
def __init__(self, fileobj, mode, zipinfo, pwd=None,
close_fileobj=False):
+ self._zinfo = zipinfo
self._fileobj = fileobj
self._pwd = pwd
self._close_fileobj = close_fileobj
self._compress_type = zipinfo.compress_type
- self._compress_left = zipinfo.compress_size
- self._left = zipinfo.file_size
-
- self._decompressor = _get_decompressor(self._compress_type)
-
- self._eof = False
- self._readbuffer = b''
- self._offset = 0
self.newlines = None
@@ -808,33 +801,37 @@ def __init__(self, fileobj, mode, zipinfo, pwd=None,
if hasattr(zipinfo, 'CRC'):
self._expected_crc = zipinfo.CRC
- self._running_crc = crc32(b'')
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
self._decrypter = None
- if pwd:
- if zipinfo.flag_bits & 0x8:
- # compare against the file type from extended local headers
- check_byte = (zipinfo._raw_time >> 8) & 0xff
- else:
- # compare against the CRC otherwise
- check_byte = (zipinfo.CRC >> 24) & 0xff
- h = self._init_decrypter()
- if h != check_byte:
- raise RuntimeError("Bad password for file %r" % zipinfo.orig_filename)
+ # Compress start is the byte after the 'local file header' ie. the
+ # start of 'encryption header' section, if present, or
+ # 'file data' otherwise.
+ self._compress_start = fileobj.tell()
+ self.read_init()
+
+ def read_init(self):
+ """Set or reset this ZipExtFile to read from the start of the file"""
+ self._running_crc = crc32(b'')
+ self._compress_left = self._zinfo.compress_size
+ self._left = self._zinfo.file_size
+ self._eof = False
+ self._readbuffer = b''
+ self._offset = 0
+
+ if self._pwd:
+ self._init_decrypter()
+ self._decompressor = _get_decompressor(self._compress_type)
def _init_decrypter(self):
self._decrypter = _ZipDecrypter(self._pwd)
@@ -845,7 +842,17 @@ def _init_decrypter(self):
# and is used to check the correctness of the password.
header = self._fileobj.read(12)
self._compress_left -= 12
- return self._decrypter(header)[11]
+ computed_check_byte = self._decrypter(header)[11]
+
+ if self._zinfo.flag_bits & 0x8:
+ # compare against the file type from extended local headers
+ check_byte = (self._zinfo._raw_time >> 8) & 0xff
+ else:
+ # compare against the CRC otherwise
+ check_byte = (self._zinfo.CRC >> 24) & 0xff
+
+ if computed_check_byte != check_byte:
+ raise RuntimeError("Bad password for file %r" % self._zinfo.orig_filename)
def __repr__(self):
result = ['<%s.%s' % (self.__class__.__module__,
@@ -1072,17 +1079,8 @@ def seek(self, offset, whence=0):
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 = _get_decompressor(self._compress_type)
- self._eof = False
- read_offset = new_pos
- if self._decrypter is not None:
- self._init_decrypter()
+ self._fileobj.seek(self._compress_start)
+ self.read_init()
while read_offset > 0:
read_len = min(self.MAX_SEEK_READ, read_offset)
diff --git a/Misc/NEWS.d/next/Library/2021-05-14-04-37-51.bpo-44128.cxicgo.rst b/Misc/NEWS.d/next/Library/2021-05-14-04-37-51.bpo-44128.cxicgo.rst
new file mode 100644
index 00000000000000..b6da75e9c0a198
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-05-14-04-37-51.bpo-44128.cxicgo.rst
@@ -0,0 +1 @@
+Minor refactor of zipfile.ZipExtFile
\ No newline at end of file
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