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gh-117716: Fix wave RIFF padding for data chunks #145237

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gh-117716: Fix wave RIFF padding for data chunks #145237

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24 changes: 24 additions & 0 deletions Lib/test/test_wave.py
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Original file line number Diff line number Diff line change
Expand Up @@ -207,6 +207,30 @@ def test_open_in_write_raises(self):
support.gc_collect()
self.assertIsNone(cm.unraisable)

def test_write_odd_data_chunk_pads_and_updates_riff_size(self):
# gh-117716: odd-sized data chunks must be padded with one zero byte.
with io.BytesIO() as output:
with wave.open(output, mode='wb') as w:
w.setnchannels(1)
w.setsampwidth(1)
w.setframerate(48000)
w.writeframes(b'\x80')

value = output.getvalue()

self.assertEqual(value[-1], 0)
self.assertEqual(
int.from_bytes(value[4:8], byteorder='little'),
38,
)

with wave.open(io.BytesIO(value), mode='rb') as r:
self.assertEqual(r.getnchannels(), 1)
self.assertEqual(r.getsampwidth(), 1)
self.assertEqual(r.getframerate(), 48000)
self.assertEqual(r.getnframes(), 1)
self.assertEqual(r.readframes(-1), b'\x80')


class WaveOpen(unittest.TestCase):
def test_open_pathlike(self):
Expand Down
6 changes: 4 additions & 2 deletions Lib/wave.py
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Original file line number Diff line number Diff line change
Expand Up @@ -565,6 +565,8 @@ def close(self):
try:
if self._file:
self._ensure_header_written(0)
if self._datawritten & 1:
self._file.write(b'\x00')
if self._datalength != self._datawritten:
self._patchheader()
self._file.flush()
Expand Down Expand Up @@ -600,7 +602,7 @@ def _write_header(self, initlength):
except (AttributeError, OSError):
self._form_length_pos = None
self._file.write(struct.pack('<L4s4sLHHLLHH4s',
36 + self._datalength, b'WAVE', b'fmt ', 16,
36 + self._datalength + (self._datalength & 1), b'WAVE', b'fmt ', 16,
WAVE_FORMAT_PCM, self._nchannels, self._framerate,
self._nchannels * self._framerate * self._sampwidth,
self._nchannels * self._sampwidth,
Expand All @@ -616,7 +618,7 @@ def _patchheader(self):
return
curpos = self._file.tell()
self._file.seek(self._form_length_pos, 0)
self._file.write(struct.pack('<L', 36 + self._datawritten))
self._file.write(struct.pack('<L', 36 + self._datawritten + (self._datawritten & 1)))
self._file.seek(self._data_length_pos, 0)
self._file.write(struct.pack('<L', self._datawritten))
self._file.seek(curpos, 0)
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2026-02-25-22-20-00.gh-issue-117716.w6kYp9.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fix :mod:`wave` writing of odd-sized ``data`` chunks by appending the required RIFF pad byte and correcting the RIFF chunk size field accordingly.
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