Fixing blocks read with overlap for files shorter than block size

soundfile.py

@@ -1103,10 +1103,12 @@ def blocks(self, blocksize=None, overlap=0, frames=-1, dtype='float64',
         if 'r' not in self.mode and '+' not in self.mode:
             raise SoundFileRuntimeError("blocks() is not allowed in write-only mode")
 
+        frames = self._check_frames(frames, fill_value)
         if out is None:
             if blocksize is None:
                 raise TypeError("One of {blocksize, out} must be specified")
-            out = self._create_empty_array(blocksize, always_2d, dtype)
+            out_size = min(blocksize, frames)
+            out = self._create_empty_array(out_size, always_2d, dtype)
             copy_out = True
         else:
             if blocksize is not None:
@@ -1116,7 +1118,6 @@ def blocks(self, blocksize=None, overlap=0, frames=-1, dtype='float64',
             copy_out = False
 
         overlap_memory = None
-        frames = self._check_frames(frames, fill_value)
         while frames > 0:
             if overlap_memory is None:
                 output_offset = 0

tests/test_soundfile.py

@@ -408,6 +408,12 @@ def test_blocks_mono():
     assert_equal_list_of_arrays(blocks, [[0, 1, 2], [-2, -1, 0]])
 
 
+def test_block_longer_than_file_with_overlap_mono():
+    blocks = list(sf.blocks(filename_mono, blocksize=20, dtype='int16',
+                            overlap=2))
+    assert_equal_list_of_arrays(blocks, [[0, 1, 2, -2, -1]])
+
+
 def test_blocks_rplus(sf_stereo_rplus):
     blocks = list(sf_stereo_rplus.blocks(blocksize=2))
     assert_equal_list_of_arrays(blocks, [data_stereo[0:2], data_stereo[2:4]])