Fall back to read for unimplemented readinto adapters

soundfile.py

@@ -1325,7 +1325,7 @@ def vio_read(ptr, count, user_data):
             try:
                 buf = _ffi.buffer(ptr, count)
                 data_read = file.readinto(buf)
-            except AttributeError:
+            except (AttributeError, NotImplementedError):
                 data = file.read(count)
                 data_read = len(data)
                 buf = _ffi.buffer(ptr, data_read)

tests/test_read_fallback.py

@@ -0,0 +1,65 @@
+import io
+
+import numpy as np
+import pytest
+from numpy.testing import assert_array_equal
+
+import soundfile as sf
+
+
+class ReadAdapter(io.RawIOBase):
+    def __init__(self, contents):
+        self.source = io.BytesIO(contents)
+        self.read_calls = 0
+
+    def readinto(self, buffer):
+        # PyPy does not expose RawIOBase's stub; exercise the same capability failure.
+        raise NotImplementedError
+
+    def read(self, size=-1):
+        self.read_calls += 1
+        return self.source.read(size)
+
+    def seek(self, offset, whence=0):
+        return self.source.seek(offset, whence)
+
+    def tell(self):
+        return self.source.tell()
+
+    def readable(self):
+        return True
+
+    def seekable(self):
+        return True
+
+
+@pytest.mark.parametrize('format', ['WAV', 'FLAC'])
+@pytest.mark.parametrize('channels', [1, 2])
+def test_virtual_io_read_adapter_with_unimplemented_readinto(format, channels):
+    values = np.array([1, 256, -2345, 42], dtype='int16')
+    if channels == 2:
+        values = np.column_stack((values, -values))
+    encoded = io.BytesIO()
+    sf.write(encoded, values, 8000, format=format, subtype='PCM_16')
+    adapter = ReadAdapter(encoded.getvalue())
+    # The method exists, but is deliberately not implemented by this adapter.
+    with pytest.raises(NotImplementedError):
+        adapter.readinto(bytearray(1))
+    decoded, rate = sf.read(adapter, dtype='int16')
+    assert rate == 8000
+    assert_array_equal(decoded, values)
+    assert adapter.read_calls > 0
+
+
+def test_virtual_io_prefers_working_readinto():
+    class ReadIntoAdapter(ReadAdapter):
+        def readinto(self, buffer):
+            return self.source.readinto(buffer)
+
+    values = np.array([1, 256, -2345, 42], dtype='int16')
+    encoded = io.BytesIO()
+    sf.write(encoded, values, 8000, format='WAV', subtype='PCM_16')
+    adapter = ReadIntoAdapter(encoded.getvalue())
+    decoded, _ = sf.read(adapter, dtype='int16')
+    assert_array_equal(decoded, values)
+    assert adapter.read_calls == 0