Issue #16350, part 2: Set unused_data (and unconsumed_tail) correctly in decompressobj().flush().

Additionally, fix a bug where a MemoryError in allocating a bytes object could
leave the decompressor object in an invalid state (with its unconsumed_tail
member being NULL).

Patch by Serhiy Storchaka.

1 files changed, 21 insertions, 9 deletions

diff --git a/Lib/test/test_zlib.py b/Lib/test/test_zlib.py
index eb3dd6e..eed8164 100644
--- a/Lib/test/test_zlib.py
+++ b/Lib/test/test_zlib.py
@@ -429,15 +429,27 @@ class CompressObjectTestCase(BaseCompressTestCase, unittest.TestCase):
     def test_decompress_unused_data(self):
         # Repeated calls to decompress() after EOF should accumulate data in
         # dco.unused_data, instead of just storing the arg to the last call.
-        x = zlib.compress(HAMLET_SCENE) + HAMLET_SCENE
-        for step in 1, 2, 100:
-            dco = zlib.decompressobj()
-            data = b''.join(dco.decompress(x[i : i + step])
-                            for i in range(0, len(x), step))
-            data += dco.flush()
-
-            self.assertEqual(data, HAMLET_SCENE)
-            self.assertEqual(dco.unused_data, HAMLET_SCENE)
+        source = b'abcdefghijklmnopqrstuvwxyz'
+        remainder = b'0123456789'
+        y = zlib.compress(source)
+        x = y + remainder
+        for maxlen in 0, 1000:
+            for step in 1, 2, len(y), len(x):
+                dco = zlib.decompressobj()
+                data = b''
+                for i in range(0, len(x), step):
+                    if i < len(y):
+                        self.assertEqual(dco.unused_data, b'')
+                    if maxlen == 0:
+                        data += dco.decompress(x[i : i + step])
+                        self.assertEqual(dco.unconsumed_tail, b'')
+                    else:
+                        data += dco.decompress(
+                                dco.unconsumed_tail + x[i : i + step], maxlen)
+                data += dco.flush()
+                self.assertEqual(data, source)
+                self.assertEqual(dco.unconsumed_tail, b'')
+                self.assertEqual(dco.unused_data, remainder)
 
     if hasattr(zlib.decompressobj(), "copy"):
         def test_decompresscopy(self):