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bpo-44129: Add descriptive global variables for general purpose bit flags (GH-26118) 

Replace hex flag masks with named global variables to improve
readability.

eg.
    if flags & 0x800
becomes:
    if flags & _MASK_UTF_FILENAME
This commit is contained in:
Daniel Hillier 2021-07-04 00:37:57 +10:00 committed by GitHub
parent a79e2b6497
commit 556d5ad11f
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 39 additions and 13 deletions
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2
Lib/test/test_zipfile.py
View File

@ -1545,7 +1545,7 @@ class OtherTests(unittest.TestCase):
with zipfile.ZipFile(TESTFN2, 'w') as orig_zip:
for data in 'abcdefghijklmnop':
zinfo = zipfile.ZipInfo(data)
zinfo.flag_bits |= 0x08 # Include an extended local header.
zinfo.flag_bits |= zipfile._MASK_USE_DATA_DESCRIPTOR # Include an extended local header.
orig_zip.writestr(zinfo, data)
def test_close(self):

50
Lib/zipfile.py
View File

@ -123,6 +123,32 @@ _CD_INTERNAL_FILE_ATTRIBUTES = 16
_CD_EXTERNAL_FILE_ATTRIBUTES = 17
_CD_LOCAL_HEADER_OFFSET = 18
# General purpose bit flags
# Zip Appnote: 4.4.4 general purpose bit flag: (2 bytes)
_MASK_ENCRYPTED = 1 << 0
# Bits 1 and 2 have different meanings depending on the compression used.
_MASK_COMPRESS_OPTION_1 = 1 << 1
# _MASK_COMPRESS_OPTION_2 = 1 << 2
# _MASK_USE_DATA_DESCRIPTOR: If set, crc-32, compressed size and uncompressed
# size are zero in the local header and the real values are written in the data
# descriptor immediately following the compressed data.
_MASK_USE_DATA_DESCRIPTOR = 1 << 3
# Bit 4: Reserved for use with compression method 8, for enhanced deflating.
# _MASK_RESERVED_BIT_4 = 1 << 4
_MASK_COMPRESSED_PATCH = 1 << 5
_MASK_STRONG_ENCRYPTION = 1 << 6
# _MASK_UNUSED_BIT_7 = 1 << 7
# _MASK_UNUSED_BIT_8 = 1 << 8
# _MASK_UNUSED_BIT_9 = 1 << 9
# _MASK_UNUSED_BIT_10 = 1 << 10
_MASK_UTF_FILENAME = 1 << 11
# Bit 12: Reserved by PKWARE for enhanced compression.
# _MASK_RESERVED_BIT_12 = 1 << 12
# _MASK_ENCRYPTED_CENTRAL_DIR = 1 << 13
# Bit 14, 15: Reserved by PKWARE
# _MASK_RESERVED_BIT_14 = 1 << 14
# _MASK_RESERVED_BIT_15 = 1 << 15
# The "local file header" structure, magic number, size, and indices
# (section V.A in the format document)
structFileHeader = "<4s2B4HL2L2H"
@ -411,7 +437,7 @@ class ZipInfo (object):
dt = self.date_time
dosdate = (dt[0] - 1980) << 9 | dt[1] << 5 | dt[2]
dostime = dt[3] << 11 | dt[4] << 5 | (dt[5] // 2)
if self.flag_bits & 0x08:
if self.flag_bits & _MASK_USE_DATA_DESCRIPTOR:
# Set these to zero because we write them after the file data
CRC = compress_size = file_size = 0
else:
@ -456,7 +482,7 @@ class ZipInfo (object):
try:
return self.filename.encode('ascii'), self.flag_bits
except UnicodeEncodeError:
return self.filename.encode('utf-8'), self.flag_bits | 0x800
return self.filename.encode('utf-8'), self.flag_bits | _MASK_UTF_FILENAME
def _decodeExtra(self):
# Try to decode the extra field.
@ -825,7 +851,7 @@ class ZipExtFile(io.BufferedIOBase):
self._decrypter = None
if pwd:
if zipinfo.flag_bits & 0x8:
if zipinfo.flag_bits & _MASK_USE_DATA_DESCRIPTOR:
# compare against the file type from extended local headers
check_byte = (zipinfo._raw_time >> 8) & 0xff
else:
@ -1147,7 +1173,7 @@ class _ZipWriteFile(io.BufferedIOBase):
self._zinfo.file_size = self._file_size
# Write updated header info
if self._zinfo.flag_bits & 0x08:
if self._zinfo.flag_bits & _MASK_USE_DATA_DESCRIPTOR:
# Write CRC and file sizes after the file data
fmt = '<LLQQ' if self._zip64 else '<LLLL'
self._fileobj.write(struct.pack(fmt, _DD_SIGNATURE, self._zinfo.CRC,
@ -1355,7 +1381,7 @@ class ZipFile:
print(centdir)
filename = fp.read(centdir[_CD_FILENAME_LENGTH])
flags = centdir[5]
if flags & 0x800:
if flags & _MASK_UTF_FILENAME:
# UTF-8 file names extension
filename = filename.decode('utf-8')
else:
@ -1527,15 +1553,15 @@ class ZipFile:
if fheader[_FH_EXTRA_FIELD_LENGTH]:
zef_file.read(fheader[_FH_EXTRA_FIELD_LENGTH])
if zinfo.flag_bits & 0x20:
if zinfo.flag_bits & _MASK_COMPRESSED_PATCH:
# Zip 2.7: compressed patched data
raise NotImplementedError("compressed patched data (flag bit 5)")
if zinfo.flag_bits & 0x40:
if zinfo.flag_bits & _MASK_STRONG_ENCRYPTION:
# strong encryption
raise NotImplementedError("strong encryption (flag bit 6)")
if fheader[_FH_GENERAL_PURPOSE_FLAG_BITS] & 0x800:
if fheader[_FH_GENERAL_PURPOSE_FLAG_BITS] & _MASK_UTF_FILENAME:
# UTF-8 filename
fname_str = fname.decode("utf-8")
else:
@ -1547,7 +1573,7 @@ class ZipFile:
% (zinfo.orig_filename, fname))
# check for encrypted flag & handle password
is_encrypted = zinfo.flag_bits & 0x1
is_encrypted = zinfo.flag_bits & _MASK_ENCRYPTED
if is_encrypted:
if not pwd:
pwd = self.pwd
@ -1580,9 +1606,9 @@ class ZipFile:
zinfo.flag_bits = 0x00
if zinfo.compress_type == ZIP_LZMA:
# Compressed data includes an end-of-stream (EOS) marker
zinfo.flag_bits |= 0x02
zinfo.flag_bits |= _MASK_COMPRESS_OPTION_1
if not self._seekable:
zinfo.flag_bits |= 0x08
zinfo.flag_bits |= _MASK_USE_DATA_DESCRIPTOR
if not zinfo.external_attr:
zinfo.external_attr = 0o600 << 16 # permissions: ?rw-------
@ -1749,7 +1775,7 @@ class ZipFile:
zinfo.header_offset = self.fp.tell() # Start of header bytes
if zinfo.compress_type == ZIP_LZMA:
# Compressed data includes an end-of-stream (EOS) marker
zinfo.flag_bits |= 0x02
zinfo.flag_bits |= _MASK_COMPRESS_OPTION_1
self._writecheck(zinfo)
self._didModify = True