Reject block sizes and overlaps that prevent audio progress

soundfile.py

@@ -402,9 +402,10 @@ def blocks(file: FileDescriptorOrPath, blocksize: int | None = None,
         The file to read from.  See `SoundFile` for details.
     blocksize : int
         The number of frames to read per block.
-        Either this or *out* must be given.
+        Either this or *out* must be given. Must be greater than zero.
     overlap : int, optional
-        The number of frames to rewind between each block.
+        The number of frames to rewind between each block. Must be
+        non-negative and smaller than *blocksize* (or the length of *out*).
 
     Yields
     ------
@@ -1132,9 +1133,10 @@ def blocks(self, blocksize: int | None = None, overlap: int = 0,
         ----------
         blocksize : int
             The number of frames to read per block. Either this or *out*
-            must be given.
+            must be given. Must be greater than zero.
         overlap : int, optional
-            The number of frames to rewind between each block.
+            The number of frames to rewind between each block. Must be
+            non-negative and smaller than *blocksize* (or the length of *out*).
         frames : int, optional
             The number of frames to read.
             If ``frames < 0``, the file is read until the end.
@@ -1189,6 +1191,11 @@ def blocks(self, blocksize: int | None = None, overlap: int = 0,
             blocksize = len(out)
             copy_out = False
 
+        if blocksize <= 0:
+            raise ValueError("blocksize must be greater than zero")
+        if overlap < 0 or overlap >= blocksize:
+            raise ValueError("overlap must be non-negative and smaller than blocksize")
+
         overlap_memory = None
         while frames > 0:
             if overlap_memory is None:

tests/test_soundfile.py

@@ -373,6 +373,23 @@ def test_blocks_without_blocksize():
         list(sf.blocks(filename_stereo))
 
 
+@pytest.mark.parametrize('blocksize, overlap', [(0, 0), (3, -1), (3, 3), (3, 4)])
+@pytest.mark.parametrize('use_out', [False, True])
+@pytest.mark.parametrize('use_method', [False, True])
+def test_blocks_invalid_size_or_overlap(blocksize, overlap, use_out, use_method):
+    kwargs = {'out': np.empty((blocksize, 2))} if use_out else {'blocksize': blocksize}
+    with sf.SoundFile(filename_stereo) as f:
+        generator = (f.blocks(overlap=overlap, **kwargs) if use_method else
+                     sf.blocks(filename_stereo, overlap=overlap, **kwargs))
+        try:
+            with pytest.raises(ValueError, match='blocksize|overlap'):
+                next(generator)
+            if use_method:
+                assert f.tell() == 0
+        finally:
+            generator.close()
+
+
 def test_blocks_full_last_block(file_stereo_r):
     blocks = list(sf.blocks(file_stereo_r, blocksize=2))
     assert_equal_list_of_arrays(blocks, [data_stereo[0:2], data_stereo[2:4]])