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pythongh-127847: Fix position in the special-cased zipfile seek (pyth…
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…onGH-127856)

---------
(cherry picked from commit 7ed6c5c)

Co-authored-by: Dima Ryazanov <[email protected]>
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Peter Bierma <[email protected]>
Co-authored-by: Jason R. Coombs <[email protected]>
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4 people authored and miss-islington committed Dec 24, 2024
1 parent e7f8ba7 commit 63c113f
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Showing 3 changed files with 17 additions and 1 deletion.
12 changes: 12 additions & 0 deletions Lib/test/test_zipfile/test_core.py
Original file line number Diff line number Diff line change
Expand Up @@ -2324,6 +2324,18 @@ def test_read_after_seek(self):
fp.seek(1, os.SEEK_CUR)
self.assertEqual(fp.read(-1), b'men!')

def test_uncompressed_interleaved_seek_read(self):
# gh-127847: Make sure the position in the archive is correct
# in the special case of seeking in a ZIP_STORED entry.
with zipfile.ZipFile(TESTFN, "w") as zipf:
zipf.writestr("a.txt", "123")
zipf.writestr("b.txt", "456")
with zipfile.ZipFile(TESTFN, "r") as zipf:
with zipf.open("a.txt", "r") as a, zipf.open("b.txt", "r") as b:
self.assertEqual(a.read(1), b"1")
self.assertEqual(b.seek(1), 1)
self.assertEqual(b.read(1), b"5")

@requires_bz2()
def test_decompress_without_3rd_party_library(self):
data = b'PK\x05\x06\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
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5 changes: 4 additions & 1 deletion Lib/zipfile/__init__.py
Original file line number Diff line number Diff line change
Expand Up @@ -794,7 +794,10 @@ def seek(self, offset, whence=0):
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(offset, whence)
if whence == os.SEEK_CUR:
self._file.seek(self._pos + offset)
else:
self._file.seek(offset, whence)
self._pos = self._file.tell()
return self._pos

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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fix the position when doing interleaved seeks and reads in uncompressed, unencrypted zip files returned by :meth:`zipfile.ZipFile.open`.

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