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index fdc8e11..d7a8576 100644
--- a/Lib/test/test_lzma.py
+++ b/Lib/test/test_lzma.py@@ -137,6 +137,21 @@ class CompressorDecompressorTestCase(unittest.TestCase):
self.assertTrue(lzd.eof)
self.assertEqual(lzd.unused_data, b"")
+ def test_decompressor_chunks_empty(self):
+ lzd = LZMADecompressor()
+ out = []
+ for i in range(0, len(COMPRESSED_XZ), 10):
+ self.assertFalse(lzd.eof)
+ out.append(lzd.decompress(b''))
+ out.append(lzd.decompress(b''))
+ out.append(lzd.decompress(b''))
+ out.append(lzd.decompress(COMPRESSED_XZ[i:i+10]))
+ out = b"".join(out)
+ self.assertEqual(out, INPUT)
+ self.assertEqual(lzd.check, lzma.CHECK_CRC64)
+ self.assertTrue(lzd.eof)
+ self.assertEqual(lzd.unused_data, b"")
+
def test_decompressor_chunks_maxsize(self):
lzd = LZMADecompressor()
max_length = 100
@@ -274,6 +289,16 @@ class CompressorDecompressorTestCase(unittest.TestCase):
lzd = LZMADecompressor(lzma.FORMAT_RAW, filters=FILTERS_RAW_4)
self._test_decompressor(lzd, cdata, lzma.CHECK_NONE)
+ def test_roundtrip_raw_empty(self):
+ lzc = LZMACompressor(lzma.FORMAT_RAW, filters=FILTERS_RAW_4)
+ cdata = lzc.compress(INPUT)
+ cdata += lzc.compress(b'')
+ cdata += lzc.compress(b'')
+ cdata += lzc.compress(b'')
+ cdata += lzc.flush()
+ lzd = LZMADecompressor(lzma.FORMAT_RAW, filters=FILTERS_RAW_4)
+ self._test_decompressor(lzd, cdata, lzma.CHECK_NONE)
+
def test_roundtrip_chunks(self):
lzc = LZMACompressor()
cdata = []
@@ -284,6 +309,19 @@ class CompressorDecompressorTestCase(unittest.TestCase):
lzd = LZMADecompressor()
self._test_decompressor(lzd, cdata, lzma.CHECK_CRC64)
+ def test_roundtrip_empty_chunks(self):
+ lzc = LZMACompressor()
+ cdata = []
+ for i in range(0, len(INPUT), 10):
+ cdata.append(lzc.compress(INPUT[i:i+10]))
+ cdata.append(lzc.compress(b''))
+ cdata.append(lzc.compress(b''))
+ cdata.append(lzc.compress(b''))
+ cdata.append(lzc.flush())
+ cdata = b"".join(cdata)
+ lzd = LZMADecompressor()
+ self._test_decompressor(lzd, cdata, lzma.CHECK_CRC64)
+
# LZMADecompressor intentionally does not handle concatenated streams.
def test_decompressor_multistream(self):
diff --git a/Misc/ACKS b/Misc/ACKS
index 7711152..0cf1802 100644
--- a/
Misc/ACKS+++ b/
Misc/ACKS@@ -452,6 +452,7 @@ Frederik Fix
Tom Flanagan
Matt Fleming
Hernán Martínez Foffani
+Benjamin Fogle
Artem Fokin
Arnaud Fontaine
Michael Foord
diff --git a/Misc/NEWS b/Misc/NEWS
index 2d832a7..a621be3 100644
--- a/
Misc/NEWS+++ b/
Misc/NEWS@@ -30,6 +30,9 @@ Core and Builtins
Library
-------
+- Issue #27517: LZMA compressor and decompressor no longer raise exceptions if
+ given empty data twice. Patch by Benjamin Fogle.
+
- Issue #28549: Fixed segfault in curses's addch() with ncurses6.
- Issue #28449: tarfile.open() with mode "r" or "r:" now tries to open a tar
@@ -521,6 +521,8 @@ compress(Compressor *c, uint8_t *data, size_t len, lzma_action action)
Py_BEGIN_ALLOW_THREADS
lzret = lzma_code(&c->lzs, action);
data_size = (char *)c->lzs.next_out - PyBytes_AS_STRING(result);
+ if (lzret == LZMA_BUF_ERROR && len == 0 && c->lzs.avail_out > 0)
+ lzret = LZMA_OK; /* That wasn't a real error */
Py_END_ALLOW_THREADS
if (catch_lzma_error(lzret))
goto error;
@@ -896,6 +898,9 @@ decompress_buf(Decompressor *d, Py_ssize_t max_length)
PyObject *result;
lzma_stream *lzs = &d->lzs;
+ if (lzs->avail_in == 0)
+ return PyBytes_FromStringAndSize(NULL, 0);
+
if (max_length < 0 || max_length >= INITIAL_BUFFER_SIZE)
result = PyBytes_FromStringAndSize(NULL, INITIAL_BUFFER_SIZE);
else