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gh-51067: Extract _read_local_file_header() as a module-level function #152139

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Merged
StanFromIreland merged 1 commit into from
Jun 25, 2026
+12 −17
Merged

gh-51067: Extract _read_local_file_header() as a module-level function #152139

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29 changes: 12 additions & 17 deletions Lib/zipfile/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -418,6 +418,15 @@ def _sanitize_filename(filename):
filename = filename.replace(os.altsep, "/")
return filename

def _read_local_file_header(fp):
fheader = fp.read(sizeFileHeader)
if len(fheader) != sizeFileHeader:
raise BadZipFile("Truncated file header")
fheader = struct.unpack(structFileHeader, fheader)
if fheader[_FH_SIGNATURE] != stringFileHeader:
raise BadZipFile("Bad magic number for file header")
return fheader


class ZipInfo:
"""Class with attributes describing each file in the ZIP archive."""
Expand Down Expand Up @@ -1648,7 +1657,7 @@ def _validate_local_file_entry_sequence(self, fp, start_offset, end_offset, chec
def _validate_local_file_entry(self, fp, offset, end_offset):
fp.seek(offset)
try:
fheader = self._read_local_file_header(fp)
fheader = _read_local_file_header(fp)
except BadZipFile:
return None

Expand Down Expand Up @@ -1714,15 +1723,6 @@ def _validate_local_file_entry(self, fp, offset, end_offset):

return entry_size

def _read_local_file_header(self, fp):
fheader = fp.read(sizeFileHeader)
if len(fheader) != sizeFileHeader:
raise BadZipFile("Truncated file header")
fheader = struct.unpack(structFileHeader, fheader)
if fheader[_FH_SIGNATURE] != stringFileHeader:
raise BadZipFile("Bad magic number for file header")
return fheader

def _scan_data_descriptor(self, fp, offset, end_offset, zip64):
dd_fmt = '<LLQQ' if zip64 else '<LLLL'
dd_size = struct.calcsize(dd_fmt)
Expand Down Expand Up @@ -1825,7 +1825,7 @@ def _trace_compressed_block_end(self, fp, offset, end_offset, decompressor,

def _calc_local_file_entry_size(self, fp, zinfo):
fp.seek(zinfo.header_offset)
fheader = self._read_local_file_header(fp)
fheader = _read_local_file_header(fp)

if zinfo.flag_bits & _MASK_USE_DATA_DESCRIPTOR:
zip64 = fheader[_FH_UNCOMPRESSED_SIZE] == 0xffffffff
Expand Down Expand Up @@ -2215,12 +2215,7 @@ def open(self, name, mode="r", pwd=None, *, force_zip64=False):
self._fpclose, self._lock, lambda: self._writing)
try:
# Skip the file header:
fheader = zef_file.read(sizeFileHeader)
if len(fheader) != sizeFileHeader:
raise BadZipFile("Truncated file header")
fheader = struct.unpack(structFileHeader, fheader)
if fheader[_FH_SIGNATURE] != stringFileHeader:
raise BadZipFile("Bad magic number for file header")
fheader = _read_local_file_header(zef_file)

fname = zef_file.read(fheader[_FH_FILENAME_LENGTH])
if fheader[_FH_EXTRA_FIELD_LENGTH]:
Expand Down
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